As we've just noticed, we've neglected so far to properly introduce the JVx Kitchensink, a (very) simple showcase application for JVx and its controls. We'd like to rectify that now.

A simple showcase, not a demo application

The JVx Kitchensink can be found on GitHub and is available under an Apache 2.0 License. It demonstrates nearly all controls and components of the JVx framework and simple and easy to digest examples.

As some of you might know, there is also the JVx Hello World Application. The Kitchensink does not intend to supersede the Hello World Application, quite the opposite, the intention is to complement it. The Hello World Application is demonstrating how to quickly and easily set up a complete JVx application and have it up and running in mere minutes, with focus on the lifecycle of the application. The Kitchensink on the other hand demonstrates each individual component and control of JVx, and completely neglects the "normal" lifecycle of a JVx application.

Samples

The button bar on the left allows you to quickly access each example, for example the one about databinding.

Newly added has been the feature that you can now see the source code of the selected sample right inside the Kitchensink, simply select the "Source" tab.

Here I have to mention the awesome RSyntaxTextArea, which is a Swing component and provides highlighting and editing functionalities for source code, and is obviously used by us.

Regarding the lifecycle

As said before, the Kitchensink as not a good example of the lifecycle of a JVx application, as outlined in JVx Reference, Application Basics.

Packaged and ready

The Kitchensink does already come as a ready to use Eclipse project with launchers, so all you have to do is import it into Eclipse and be ready to go. There is also an Ant build script and instructions on how to launch the readily compiled jars.

Last but not least, it does provide a nice test bed for most of the functionality of JVx and demonstrates most concepts in a neatly packaged manner. We've been using it excessively during the development of the JVx JavaFX frontend bindings and it can be as simply used to test new concepts and custom components.

Once again, the link to the KitchenSink GitHub repository

Let's talk about Resources and UIResources, and why they sound similar but are not the same.

The Basics

We've previously covered how the JVx GUI layer works, now we are going to have a better look at the Resources and UIResources. With "Resource" we do not mean images or similar, we mean the implementation at the technology layer which is encapsulated by a wrapper class (Bridge Pattern). An "UIResource" on the other hand is an encapsulated concrete implementation of one of the interfaces on the UI layer.

Let's do a short brush-up on how the JVx architecture looks like in regards to the GUI stack:

The UI Wrappers are the main UI classes which are used to create the GUI (f.e. UIButton). These are wrapping the Implementations (f.e. a SwingButton) which themselves are wrapping the Extension/Technology (f.e. a JVxButton/JButton). Only the UI and Implementation classes are implementing the interface required for the component (f.e. IButton). That also means that the Implementation is dependent on the Extension/Technology component, but the UI can use any object which implements the interface.

Now, with that knowledge we can start defining what is what:

The resource itself, accessed by calling <uiwrapper>.getResource(), is the Extension/Technology component. The uiresource can be accessed by calling <uiwrapper>.getUIResource(). The uicomponent can be accessed by calling <uiwrapper>.getUIComponent() and is usually the UI Wrapper itself. If we use our previous Swing example, the resource would be a JVxButton/JButton, the uiresource would be the SwingPanel and the uicomponent would be the UIButton.

As one can see, access to all objects which are comprising the GUI is at all times possible. We, of course, have the UI component, we can access the Implementation component and we can access the Extension/Technology component. Theoretically we could also swap them at runtime, but in JVx this is limited to the construction of the object to greatly reduce the error potential.

Creating custom components

Equipped with that knowledge, we can revisit the previous guide on how to create custom components, the part about the BeepComponent to be exact:

We are setting a new UIResource (an UIPanel) in the constructor (at line #5) which is to be used by the UIComponent. In this case it is not an Implementation, but another UI component, but that doesn't matter because the UIResource only must implement the expected interface. At line #15 we start using that custom UIResource.

Because UIComponent is an abstract component designed for exactly this usage, the example might not be the most exciting one, but it clearly illustrates the mechanic.

Bolting on functionality

Also from the previous guide on how to create custom components we can reuse the PostfixedLabel as example.

Now testLabel will be using the PostfixedLabel internally, but with no indication to the user of the object that this is the case. This allows to extend the functionality of a component completely transparently, especially in combination with functions which do return an UIComponent and similar.

An important note about the component hierarchy

If we create a simple component extensions, like the BeepComponent above, it is important to note that there is one other layer of indirection in regards to the hierarchy on the technology layer. If we create a simple frame with the BeepComponent in it, one might expect the following hierarchy:

         UI                   Technology
---------------------    ----------------------
 UIFrame                  Frame
   \-UIPanel                \-Panel
       \-BeepComponent          \-BeepComponent
                                    \-Panel
                                        |-Label
                                        |-Button
                                        \-Button

With the BeepComponent added and its sub-components as its children. However, the actual hierarchy looks like this:

         UI                   Technology
---------------------    ----------------------
 UIFrame                  Frame
   \-UIPanel                \-Panel
       \-BeepComponent          \-Panel
                                    |-Label
                                    |-Button
                                    \-Button

That is because such extended components are not "passed" to the Technology, they do only exist on the UI layer because they do not have a Technology component which could be used. That is done by adding the UIComponent to the UI parent, but for adding the actual Technology component the set UIResource is used.

The special case of containers

Another special case are containers. For example we could create a panel which does display an overlay in certain situations and we will need to use that throughout the whole application.

That means we do not want to build it every time anew, so one option would be to use a factory method to "wrap" the content, something like this:

And the wrap method itself:

Which is easy enough, but let's say we'd like to add logic to that wrapper, at that point it becomes more complicated. We can't use the same technique as for custom component from above, because in that case the "overlaying panel" would simply not be displayed. However, there is a similar mechanism for containers, setting the UIResourceContainer.

The UIResourceContainer is another special mechanism which works similar to setting the UIResource, but it works exactly the other way round. While setting the UIResource does "hide" components from the Technology which are there in UI layer, setting the UIResourceContainer does hide components from the UI layer while there are added in the Technology. A little bit complicated, here is our example again using this technique:

What we've done is extend an UIPanel (line #1), setting it up and adding children and then we've declared one of its children as the UIResourceContainer (line #22). So all methods which are specific to IContainer (adding children, setting a layout, etc.) are now forwarding to the innerPanel and manipulating the contents of the OverlayedPanel directly is not directly available.

And here is how it is used:

Notice that we can use it is any other panel (line #5) and simply add it to the parent (line #18). For a user of the API it is transparent as to whether there are more components or not, this is also visible in the created component hierarchy:

         UI                   Technology
---------------------    ----------------------
 UIPanel                  Panel
   \-OverlayedPanel         \-Panel
       |-UILabel                |-Label
       |-UITextField                \-Panel
       |-UILabel                    |-Label
       |-UITextField                |-TextField
       |-UILabel                    |-Label
       |-UITextField                |-TextField
       |-UILabel                    |-Label
       |-UITextField                |-TextField
       |-UILabel                    |-Label
       \-UITextField                |-TextField
                                    |-Label
                                    \-TextField

This makes it very easy to have containers which add additional components without the actual GUI noticing or caring.

Conclusion

Because of the way the JVx framework is designed, it is easy to access all layers of the GUI framework and also facilitate the usage of these layers to create custom components and allow easy access to the wrapped components, no matter on what layer or of what kind they are.

With the preparations for the VisionX 2.4 Update 1 we've also created several simple but telling demo applications. Let's have a look at these.

Demo-AMLD

We start our short tour with the first demo, the "Aircraft Manufacturing Line Dashboard" which is emulating a dashboard as it can be found in various factories and manufacturing companies.

Its main frontend is a Swing based GUI which displays (randomly generated) data, additionally there is a Vaadin powered frontend which displays the raw data. The main highlights of this demo are:

• Capability to customize technology-specific components.
• Utilizing custom components in the VisionX designer.
• Usage of cell formatters.
• Making WorkScreens only available in certain environments.
• Data is generated with either the Random object or OpenSimplexNoise.

Demo-BIELS

This is a demo of a typical dashboard and master data forms of an ERP application, in this case a small company focused on import and export of chemical/biochemical materials and similar.

All WorkScreens are fully functional in Swing and Vaadin environments. The main highlights of this demo are:

• Demonstration of feature parity and interchangeability between Swing and Vaadin.
• Creation of custom controls for displaying data.
• Fully and easily editable with the VisionX designer.

Demo-CNASP

Next up is a demonstration of the ability to create end-user facing web portals with JVx and VisionX.

The whole application is designed to function on large and small displays alike, like those of smartphones. The main highlights are:

• Demonstration of extensive customization via CSS.
• Differing layouts depending on the environment (Desktop, Tablet, Smartphone).

Demo-DMARS

Accessing data and documents on the go is always kind of a hassle, but we can make it easier and more comfortable by providing easy to use GUIs for such occasions.

This simple document management system shows off a simple and easy to use GUI for accessing and manipulating documents in the storage. The highlights are:

• GUI designed to be used on small, touch-enabled displays.
• Extending the Table to allow checkbox based multi-row selection.
• Inserting and retrieving files from a database.
• The new Upload component available in ProjX.

Demo-Reports

Last but, not least, is the "big guide" of how to use reporting in VisionX.

This application will take you step by step through the capabilities and features of the VisionX reporting solution. Every WorkScreen demonstrates another feature complete with a description, example, access to the template and final report and of course the related documentation.

• A step-by-step introduction to the VisionX reporting solution.
• 12 examples with easy to read and documented source code.
• All parts easily accessible: Source code, Template, Data and Report.

Availability

All these applications are available in the VisionsX Solution Store, on demand. The source code is licensed under the permissive Apache License.

Let's talk about DataBooks, which allow access to data without any effort.

What is it?

DataBooks are an active model, which allow you to directly query and manipulate the data. Contrary to many other systems JVx does not map the data into objects, but instead allows you to directly access it in a table like fashion, exposing columns, rows and values.

One could say that it is like a three dimensional array, with these dimensions:

1. DataPages
2. DataRows
3. Columns/Values

With DataPages containing DataRows, which itself contain the values and everything is referencing the RowDefinition, which outlines how a row looks like.

RowDefinition

The RowDefinition defines what columns are available in the row and stores some additional information about them, like the names of the primary key columns. You can think of the RowDefinition as the headers of a table.

Its creation and usage is rather simple, and if you're working with RemoteDataBooks there is no need to create one at all, as it is automatically created when the DataBook is opened. A RowDefinition holds and manages ColumnDefinitions, which define the columns.

ColumnDefinition

The ColumnDefinition defines and provides all necessary information about the column, like its DataType, its size and if it is nullable or not. You can think of it as one column in a table.

MetaData

Most of the ColumnDefinition is additional information about the column, like if it is nullable, the label of the column, default values, allowed values and similar information.

DataType

Of course we must define what type the value in the column has, this is done by setting a DataType on the ColumnDefinition. The DataType defines what kind of values the column holds, like if it is a String, or a Number or something else. We do provide the widest used DataTypes out of the box:

• BigDecimal
• BinaryData
• Boolean
• Long
• Object
• String
• Timestamp

It is possible to add new DataTypes by simply implementing IDataType.

DataRow

The DataRow repesents a single row of data, it holds/references its own RowDefinition and of course provides access to the values of the row. Accessing the DataRow can be done either by column index or column name, and the methods do either return or accept Objects. Let's look at a simple usage example:

DataPage

The DataPage is basically a list of DataRows, it also holds its own RowDefinition which is shared with all the contained DataRows.

The main usage of DataPages is to allow paging in a master/detail relationship. If the master selects a different row, the detail databook does select the related DataPage.

DataBook

The DataBook is the main model of JVx, it provides direct access to its current DataPage and DataRow by extending from IDataRow and IDataPage.

By default, the DataBook holds one DataPage and only has multiple DataPages if it is the detail in a master/detail relationship.

Usage example

Here is a simple usage example of a MemDataBook, an IDataBook implementation which does only operate in memory:

Accessing the data with Strings

One of the major advantages of the DataBook concept is that there is no need to create new classes to represent each table, view or query result. One can always use the DataBook, directly and easily and model changes don't necessitate changes on the client side. The downside to this approach is that we lose compile time checks because we access the data dynamically. However, This can be mitigated by using EPlug, an Eclipse plugin which provides compile time checks and many more features.

No primitives, Objects only

We do not provide overloads to fetch primitives, that is because there are mainly three types of data inside a database:

1. Numbers
2. Text
3. Binary Data

Text and Binary Data are both objects (arrays of primitives are Objects after all) and Numbers are either primitives or Objects. Most of the time if we deal with numbers inside a database we want them to be of arbitrary precision, which means we must represent them as BigDecimal. Supporting double or float in these cases would be dangerously, because one might write a float into the database which might or might not end up with the correct value in the database. To completely eliminate such problems, we do only support Objects, which means that one is "limited" to the usage of Number extensions like BigLong and BigDecimal, which do not suffer from such problems.

Where are the DataPages?

What is not clear from this example is how and when DataPages are used. As a matter of fact, most of the time there is no need to think about DataPages because they are managed directly by the DataBook, and if used this like there is only one DataPage. Multiple DataPages will be used if there is a Master/Detail relationship defined in which case the DataBook does select the correct DataPage automatically.

Master/Detail

Master/Detail is something that occurs in nearly every data model. It means simply that there is one master dataset which is referenced by one or multiple detail datasets. Or to express it in SQL:

We can of course express a Master/Detail relationship when using DataBooks. For that we just create a ReferenceDefinition and assign it to the Detail DataBook:

Let's assume the following data for illustration purposes:

Now if we select the second row in the masterDataBook, the detailDataBook will just contain the rows with the corresponding MASTER_ID, so 3, 4 and 5.

The detailDataBook is automatically adjusted according to the selection in the masterDatabook. Of course this can have an arbitrary depth, too.

Conclusion

The DataBook is the backbone of JVx, it provides a clean and easy way to access and manipulate data. At the same time, it is flexible and can be customized to specific needs with ease.

Let's talk about the basics, how a JVx application starts, works and how the connection strings together the client and server side.

Multitier Architecture

JVx is designed to be Multitier by default. It allows a clean and easy separation of processes and makes it easy to build, maintain and extend applications by separating the client, server and data storage.

Launchers

The following method is a simplified way to launch a JVx application. Normally, you'd use the technology specific launcher to launch the application. These launchers do know exactly what is required to set it up and start the technology and the application. However, covering the launchers is out of scope for this post, so we will review them and their mechanics in a follow-up.

The simplest JVx application: Just the GUI

But first, we will start without anything. The most simple application you can create with JVx is an application which does open a single window and only works with in memory data (if at all). This can be easily achieved by "just starting" the application.

The JVx GUI is a simple layer on top of the Technology which implements the actual functionality. So if we want to have a GUI we'll need to initialize the factory before doing anything else:

With this little code we have initialized everything we need to create a simple Swing application. Now we can start to create and populate a window with something:

We can start to create and manipulate the GUI, in this case we are building a simple window with a label inside. Last but not least, we make sure that the JVM will exit when the window is closed.

A very good example and showcase for that is the JVx Kitchensink.

That's it. That is the most simple way to start a JVx application. We can use all controls and we can use MemDataBooks without any problem or limitation. And best of all, we can simply switch to another Technology by using another factory.

Anatomy of a remote JVx application

Of course JVx wouldn't be that useful if it would just provide static GUI components. Now, to explain what else is required for a remote JVx application I have to go far afield, so let's head down the rabbit hole.

What you are seeing here is a rough sketch of how the architecture of JVx looks like. Let's walk through the image step by step. We will look at each successive layer and work our way from the database on the server to the databook on the client.

DBAccess, accessing a database

Accessing a database is easy when using DBAccess. All we must do is to set the JDBC URL of the server and connect to it:

As a note, the instance returned by getDBAccess is the database specific DBAccess extension, which does know how to handle its database.

We can of course use DBAccess to directly access the database:

...or manipulate the database, or query information about the database or execute procedures or do anything else.

DBStorage, preparing the database access for databooks

The downside of using DBAccess is that everything must be database specific. To become database agnostic we must use DBStorage. DBStorage does not care which database it is connected to and can operate on any of them:

We can use this to insert, update, delete and fetch data. Additionally the DBStorage does retrieve and manage the metadata of the table we've set, which means that we can query all column names, what type they are, we can even access the indexes and the default values. Short, the DBStorage leaves little to be desired when it comes to operating on a database.

If we query data from the DBStorage we receive a List of rows. The rows are are either represented as Object array, IBean or a POJO and we can easily manipulate the data, like this:

As one can see, it looks quite familiar to the DataBook, which isn't a coincidence. The DBStorage "powers" the DataBooks on the server side, a DataBook will get its data from and will send its modified data to the DBStorage.

I've been using the DBStorage here as an example, but actually the Storage is not dependent on a database. IStorage can be implemented to provide any sort of data provider, like reading from an XML or JSON file, scraping data from a website, fetching data from a different process or reading it directly from a hardware sensor.

Life Cycle Objects, the business objects with all the logic

Life Cycle Objects, or LCOs, are the server side business objects which contain and provide the business logic. They are created and destroyed as is requested by the client-side and are used to provide specific functionality to the client, like providing functionality specific to one screen or workflow. This is done by RPC, Remote Procedure Calls, which means that the client is directly calling the methods defined in the LCOs, which includes getting the Storages for the DataBooks.

There is also a security aspect to these, as you can permit one client access to a certain LCO but lock out everyone else, which means that only that client can use the functionality provided by the LCO.

But let's not get ahead of our selves, there are three important "layers" of LCOs which we will look at.

Application

The LCO for the application represents the application itself and provides functionality on the application layer. It is created once for the lifetime of the application and this instance is shared by all sessions.

Session

The LCO for the session represents one session, which most of the time also equals one client connection. It provides functionality which should be session-local, like providing the database connection which can be used.

Sub-Session aka Screen

The sub-session, also known as screen, LCO is the last in the chain. It provides functionality specific to a certain part of the application, like a single screen, and provides the storages required to power the databooks and other functionality.

Server, serving it up

There really isn't much to say about the server, it accepts connections and hands out sessions. Of course it is not that easy, but for this guide we will not go into any further detail.

Connection, connecting to a server

The connection which strings together the client and the server is used for the communication between them, obviously. It can be anything, from a simple direct connection which strings two objects together to a HTTP connection which talks with a server on the other side of the planet.

By default we provide different IConnection implementations, the DirectServerConnection, DirectObjectConnection, the HttpConnection and the VMConnection. The DirectServerConnection is a simple IConnection implementation which does simply forward method calls to known Objects - without serialization - and is used when the client and server reside inside the same JVM. The HttpConnection communicates with the server over a HTTP connection and is used whenever the client and server are not inside the same JVM. The DirectObjectConnection and VMConnection are used for unit tests.

As example we will use the DirectServerConnection, which serves as Server and Connection. It is used if the server and client reside in the same JVM.

Master- and SubConnections, client-side lifecycle management

The MasterConnection is the main connection which is used to access the server and its functionality. When a MasterConnection is established, a Session LCO on the server is created.

A SubConnection is a sub connection of the MasterConnection and allows to access specific functionality encapsulated in an LCO. When a SubConnection is established, the requested/specified LCO on the server is created and can be accessed through the SubConnection.

The SubConnection can now access the functionality provided by the Application, the Session and the LCO which was specified.

DataSource, preparing the connection for the databook

To provide data to the databooks we can use the connection which we've described earlier. However, the DataBook does not directly know about the connection, it expects an IDataSource, which is used as an intermediate:

Of course the RemoteDataSource is just one possible implementation of IDataSource which can be used to provide data to the DataBook.

DataBook, accessing data

And now we are at the other end of the chain, at the databook on the client side. We just need to tell our databook what datasource to use, and we are done.

The name of the DataBook is used to access the DBStorage object in the LCO provided by the datasource. The mechanism for that is a simple search for a getter with the set name.

Interactive Demo

Here is an interactive demo which allows you to explore the connections between the client and server side. The complement classes are always highlighted and you can click on the names of the objects to receive additional information about them.

The JVx application: Manual example

Now that we have seen all layers that make up the architecture of JVx, let us put all of that into code:

With this little example we have a completely working JVx application. We provide ways to create most of this out of the box and read most of it from configuration files, so there really is just little code to be written, see the JVx FirstApp as a perfect example for that. So there is rarely any need to write code like this, all you have to do is create a new application and start it.

Additionally, we could combine this long example with the simple one from before to initialize and create a GUI which could use our RemoteDataBook, like this:

Abstractions on every step

As you can see, you always have full control over the framework and can always tailor it to your needs. There is always the possibility to provide a custom implementation to fulfill your needs:

1. Accessing a not supported database can be achieved by extending DBAccess
2. Having a different service/way of providing data can be implemented on top of IStorage
3. Supporting a different connection can be implemented on top of IConnection
4. And a completely different way of providing data can be implemented on top of IDataSource

You can swap out every layer and provide custom and customized implementations which exactly work as you require it.

Just like that

Just like that we've walked through the whole stack of a JVx application, from the database which holds the data all the way to the client GUI. Of course there is much more going on in a full-blown JVx application, for example I've spared you here the details of the configuration, server, network and providing actual LCOs and similar. But all in all, this should get you going.

My third year at SIB Visions is now coming to an end, once more it is time to take a deep breath, sit down and have a look at everything that has happened so far.

My year has been filled with a lot of non-public work, so please forgive me if I cannot go into details on various fronts.

Prototypes

Quite a few customers approached us and asked if we could implement prototypes for their projects, for one reason or another they all ended up on my table, the prototypes, that is. I like working on prototypes, because they allow me to quickly and easily explore new concepts and they have a definitive, narrow scope. Also we can finally use and show off all these cool new features we have built, like the new client-side layouts which we've created for our Vaadin implementation.

In the course of the year I've worked on over half a dozen prototypes for different customers. They all came with their own set of requirements and goals, obviously, and so they were very different to work on. The most interesting part about these prototypes is the vast spectrum of different designs and ideas. I unfortunately can't go into much detail here, but we've created application frames ranging from simple Swing input forms to highly customized Vaadin dashboards and information screens. Further down I'll talk a little more about these concepts and ideas.

Improved MySQL Fetching

Our MySQL implementation did suffer from a major problem, it fetched all records, always. That is not just an inconvenience as you can imagine, it might also lead to OutOfMemoryExceptions and similar problems. So one fine day we sat down and did take a deep look at our possibilities to either mitigate or completely fix this problem. As it turned out, the fix was far simpler and easier to implement than we imagined.

To cut an already told long story short, we are now utilizing the MySQL support to limit the fetched datasets (the LIMIT keyword). Which means that we are not only able to display initial data faster, but also fetching of more rows is now working as one would expect.

As you can see, we can now display initial data a lot quicker than before.

Vaadin Client-Side Layouts

More work has been poured into the aforementioned new client-side layouts and they are now usable for testing and (limited) productive usage.

Since the beginning we had trouble to sculpt the Vaadin layouts into the necessary shape to support our ideas about layouts. Over a year ago we started to work an new layout implementations which would operate completely client-side, most of the work was based off earlier work to improve the FormLayout. These new layouts have no logic on the server-side, but instead operate completely client-side only using "hints" from the server. That means that one can implement quite complicated layout logic (like our FormLayout) with ease.

We've implemented a new component, the so called LayoutedPanel, which can have different layouts. It does provide the base component for the new layouts but does not provide any logic itself. Instead it delegates all the layouting logic to layout implementations, that means it basically works the same as the Panel from AWT/Swing. Performing the layout logic on the client has multiple upsides, for example that the actual size of the components is known and that you can do it with a lot less elements.

Let's have a short look at how the usage of the LayoutedPanel looks like in pure Vaadin:

As you can see, it is quite easy to use and works nearly identical to our panel/layouts. Let's take a further look into what is happening on the server and what is happening on the client.

Server

On the server the LayoutedPanel manages the list of components which have been added, what layout is currently in use and the constraints of the added components. There are layout classes/implementations on the server, but they are mere placeholders (so that the LayoutedPanel on the client side knows which layout to use) and provide only limited logic (for example how to write the constraints into the state which is send to the client).

Client

On the client side there is the ClientSideLayoutedPanel, with some basic logic for adding the components to the DOM and layouting, but does otherwise delegate all the work to the current layout. The DOM structure created consists of two divs, the main element and the "canvas" element:

• panel
• canvas
• child
• child
• child
• child

As mentioned in my last years post, the panel must fulfill two seemingly contradicting properties:

1. It must resize itself to the size of/fill the parent container.
2. It must dictate its own size.

This is necessary because the panel always must fill the parent, but at the same time it must dictate its own size so that the parent does not collapse if it does not have a fixed size set. The next stumbling block on the road was that the children of that panel would be absolute positioned. That means that the panel itself would not have a size because absolute positioned children are skipped when it comes to calculating the size of an element. Quite complex, but there is a rather simple solution:

• panel (width: 100%, height: 100%)
• canvas (min-width: 100%, min-height: 100%)
• child (position: absolute)

Additionally, the size of the canvas is always set to the same size as the panel, to prevent the element from collapsing. There is of course more logic in place to make it all feasible and usable, but I won't go into any further detail here.

The layouts itself are simple to implement, they have a list of components and the size of the container, and they set the location and size of each component.

Summary

For everyone adventurous and daring enough, the source for the new layouts is available in the com.sibvisions.rad.ui.vaadin.ext.ui.panel and com.sibvisions.rad.ui.vaadin.ext.ui.client.panel packages in the JVx.Vaadin project.

For those who want to give these new layouts a spin in their application, you must simply set a property on the VaadinFactory to enable them:

Or if you don't want to import VaadinFactory:

From that moment on, every layout created will use the client-side layouts. Of course you can always set it to false or true inside your code, to get either new or old layouts.

Swing GridLayout improvements

We've also improved the GridLayout in Swing, previously the Swing GridLayout would show gaps every time it is resized. After some back and forth, we've managed to implement a new way to prevent/fill these gaps. That means that the Swing GridLayout is now distributing "left over space" through out its entirety, instead of just to the last column. This creates a very "organic" feel when it is resized and it is barely noticeable that some elements are a pixel wider than others.

More databases

Hurray! Over the course of the year we've added two new databases to JVx!

SQLite

The first one is SQLite. In case you don't know what SQLite is, it is a simple, lightweight and easy to use database which is embedded into the application which uses it. That means there is no server or connection, not even a different thread for the database engine, there is just the driver which does everything. This is interesting for many reasons, but the main one is to allow embedded applications to use a lightweight database. It also supports an in-memory mode, which means that it never must write the data to any kind of storage.

We've added support for it to allow JVx applications to use it as fast and easy database backend whenever there are either system constraints (little memory or CPU power) or if there is no network connection. It can be easily used, like any other database which is supported by JVx:

Because SQLite is designed to be used in embedded applications (or at least embedded in applications) it has quite limited functionality, like no triggers, functions or sequences. But nothing beats the minimal footprint and ease of use it has.

H2

Another database which we now support is H2. H2 is a database written completely in Java, which can be started as a server or embedded into an application directly. Last but not least, it does also support an in-memory mode and nearly most features you got used to when using databases. It can be easily used, like any other database which is supported by JVx:

Personally, I'm quite excited to support the H2, because it is a very easy to use and yet powerful and flexible database engine. I'm looking forward to use it in projects.

Intern

For the summer we actually had an intern which wanted to take a sneak peek into the world of software development. As it is with interns (at least around these parts), they are young, foolish and shy. What took me by surprise about this one was not only the eagerness with which he set to work, but also the will to learn new things as fast as possible. No matter how much information I threw at him (not literally, though, I was disallowed that, too) in the form of books and short lectures, he seemed to be able to digest and at least follow it, that impressed me very much. With very, very few exceptions ("Did you just fetch a Timestamp from a DataBook as String, parse that String to a Date and then convert it back to a Timestamp?") he was up to speed with Java and JVx in no time and wrote very good code. As I said, I am very impressed with how he held up.

Daniel, was a honor having you!

EPlug 1.2.5

Of course the year also brought more work on our Eclipse plugin, called EPlug, and the update to 1.2.5 was released in late summer.

Some of the highlights are:

• Better hover information/tooltips
• More and better ways to retrieve metadata
• More options to control the errors/warnings issued by EPlug
• QuickFixes for misspelled column names
• And various more improvements and bug fixes

The most important new feature in this release might be the extended and improved tooltips, which look like this:

For this to work we had to rewrite how tooltips were presented to the user. For those familiar with the Eclipse tooltip system, there is the IInformationControl interface which allows to display tooltips and similar. In previous versions we used an implementation which embedded a HTML renderer into the tooltip. That allowed the clients to have absolute control over the content, but it also meant that there were sever restrictions, for example autosizing the tooltip was tough.

With this version we used a new implementation which uses plain old SWT components and displays well prepared information, like this list of properties. This also has the upside that we now have absolute control over how images are treated, so they are now always fully displayed in the preview:

All that is accomplished by a rather simple system. It's nothing more than a control with an icon (top-left), a title (top) and the content, which can either be an object or an image. If it is an object there are just a few ifs which are determining how to display that information.

What I took away from that was a quite important lesson. The initial implementation tried to be as flexible as possible by using a HTML rendering engine, the new implementation is not as flexible, but has a clear and well defined behavior and does have definitive advantages. So my advice is one that has been repeated way too often: YAGNI, You Ain't Gonna Need It. Start out small, and start building up as the need arises.

Oracle Forms Importer Improvements

As some of you might remember, one of the first tasks I was assigned to was to create an Oracle Forms Importer, which we do offer to VisionX customers. It is a rather simple piece of software which allows to import Forms directly into VisionX.

In autumn we took another shot at it and improved the import system, so that it now recognizes and correctly imports an even more varied range of forms.

Some of the major changes are:

• Better recognition of bound controls
• Improved setup of cell editors
• Various other layout fixes (for example checkboxes are now correctly size)
• And other improvements (for example the table column order is now correct)

Importing a form is still quite because of the outlined differences between Forms and JVx, but I believe that we are on a very good track and the current solution works quite well for a wide variety of forms.

Kitchensink improvements

Our Kitchensink, a simple demo application with all components and controls, has seen some improvements throughout the last year:

• JVx has been updated
• There are now all libraries and starters in place to get it to run
• A new sample showing the FontAwesome icons
• Improved the StyledTableSample and StyledTreeSample
• Various minor improvements and more options

The Kitchensink is an Eclipse project, that means all you have to do is download or clone the source and import the project into Eclipse. With the included launchers you can now start it either with Swing or JavaFX frontend.

We are currently considering to embed a lightweight application server, so that testing the Vaadin frontend also becomes as easy as starting the Swing variant. That would mean that all three major frontends could be easily tested from the Kitchensink, which would be awesome.

Custom components

Some of our customers requested that we build custom components for them, these component should work in Swing and Vaadin in the same way. As I've outlined in a previous blog post, this is actually easily done depending on what your exact use-case is.

One of the most notable examples is a calendar which we've built on the technology layer. For Swing we've used the java-swing-calendar project and for Vaadin the Vaadin Calendar. Unfortunately, Vaadin has discontinued their Calendar for the time being. Anyway, we've implemented the calendar component and also added bindings for the databook to provide events, which was quite straight forward.

I do have to rant about the Vaadin Calendar, though. It does support two sources for the data, the Container interface and a calendar specific CalendarEventProvider interface. As we already had an implementation for a Container, I used that one and adjusted it so that it could be easily used with the Calendar. All fine and dandy, until I started to work with events, which are only providing a CalendarEvent as information on what event is affected. This CalendarEvent has zero information about the model, and I mean zero. There is no way to track the model from the CalendarEvent, you just don't know what event just was clicked or dragged. The only way is to not use a Container and instead use a CalendarEventProvider which returns custom CalendarEvent extensions which know about the model.

Otherwise implementing these components was very smooth.

EPlug 1.2.6

At the beginning of this year, we did some more work on EPlug and we could release EPlug 1.2.6 after a short time:

• Cleaned up context menu
• Resources (Images, etc.) are now also available from outside the source folders
• Even better handling of DataBooks
• Some bug fixes and other new features

The updates are available in the marketplace, so Eclipse can automatically update to it.

JVx References

For the last few months I have started to write a series of blog posts about various topics around JVx, the JVx Reference series. The goal is to provide a concise and easy to digest insight into JVx and various of its mechanics and techniques. There are currently three posts published:

• Events
• Of Technologies and Factories
• Custom Components

And there are more in the pipeline:

• About DataBooks
• An Overview of how JVx works
• What Resources and UIResources are in JVx

So stay tuned!

Demos

Out of the work on prototypes for our customers arose the idea to provide quite a few these new ideas to VisionX users in the form of demo projects. We've prepared these demo projects over the last few weeks and they will be released to the VisionX solution store within the next time.

Here is a sneak peek at those:

As said, these demo applications will be available in the VisionX Solution Store.

The look ahead

Wow, that has been an interesting year. A lot of things happened and we made a lot more happen, with even more stuff in the pipeline and yet even more stuff on the horizon. From where I'm sitting, the next year looks very interesting with a lot of new challenges, which we will for sure master.

Thanks to everyone at SIB Visions, it's been an awesome year and I'm looking forward to another one with all of you!

Let's talk about custom components, and how to create them.

The GUI of JVx

We've previously covered how the GUI of JVx works, and now we will have a look on how we can add custom components to the GUI.

In the terminology of JVx there are two different kinds of custom components:

1. UI based
2. Technology based

We will look at both, of course.

Custom components at the UI layer

The simplest way to create custom components is to extend and use already existing UI classes, like UIPanel or UIComponent. These custom components will be Technology independent because they use Technology independent components, there is no need to know about the underlying Technology. You can think of those as a "remix" of already existing components.

The upside is that you never have to deal with the underlying Technology, the downside is that you can only use already existing components (custom drawing is not possible, for example).

Let's look at a very simple example, we will extend the UILabel to always display a certain postfix along with the set text:

It will be treated just like another label, but every time a text is set, the postfix is appended to it.

Another example, we want a special type of component, one that always does the same but will be used in many different areas of the application, it should contain a label and two buttons. The best approach for a custom component which should not inherit any specific behavior is to extend UIComponent:

So we extend UIComponent and set a new UIPanel as UIResource on it, which we can use later and which is the base for our new component. After that we added a label and two buttons which will play beep sounds if pressed. This component does not expose any specific behavior as it extends UIComponent, it only inherits the most basic properties, like background color and font settings, yet it can easily be placed anywhere in the application and will perform its duty.

Custom controls at the Technology layer

The more complex option is to create a custom component at the Technology layer. That means that we have to go through a multiple steps process to create and use the component:

1. Create an interface for the functionality you'd like to expose
2. Extend the Technology component (if needed)
3. Implement the necessary interfaces for JVx
4. Extend the factory to return the new component
5. Create a UIComponent for the new component
6. Use the new factory

I will walk you through this process, step by step.

The upside is that we can use any component which is available to us in the Technology, the downside is that it is quite some work to build the correct chain, ideally for every technology.

Creating an interface

The first step is to think about what functionality the component should expose, we will use a progress bar as example. We don't want anything fancy for now, a simple progress bar on which we set a percent value should be more than enough:

Might not be the most sophisticated example (especially in regards to documentation) but it will do for now. This interface will be the foundation for our custom component.

Extending the component, if needed

We will be using Swing and the JProgressBar for this example, so the next step is to check if we must add additional functionality to the Technology component. In our case we don't, as we do not demand any behavior that is not provided by JProgressBar, but for the sake of the tutorial we will still create an extension on top of JProgressBar anyway.

Within this class we could now implement additional behavior independent of JVx. For example, we provide many extended components for Swing, JavaFX and Vaadin with additional features but without depending on JVx. The extension layer is the perfect place to extend already existing components with functionality which will be used by, but is not depending on, JVx.

Creating the Implementation

The next step is to create an Implementation class which allows us to bind our newly extended JProgressBar to the JVx interfaces. Luckily there is the complete Swing Implementation infrastructure which we can use:

That's it already. Again, in this case it is quite simple because we do not expect a lot of behavior. The implementation layer is the place to "glue" the component to the JVx interface, implementing missing functionality which is depending on JVx and "translating" and forwarding values and properties.

Extending the factory

Now we must extend the Factory to be aware of our new custom component, that is equally simple as our previous steps. First we extend the interface:

And afterwards we extend the SwingFactory:

Again, it is that easy.

Creating the UIComponent

So that we can use our new and shiny progress bar easily, and without having to call the factory directly, we wrap it one last time in a new UIComponent:

Nearly done, we can nearly use our new and shiny component in our project.

Using thecustom factory

Of course we have to tell JVx that we want to use our factory, and not the default one. Depending on the technology which is used, this has to be done at different places:

Swing and JavaFX

Add the factory setting to the application.xml of the application:

Vaadin

Add the following setting to the web.xml under the WebUI Servlet configuration:

Using our new component

And now we are done, from here we can use our custom component like any other.

Wrapping custom components with UICustomComponent

There is a third way to have Technology dependent custom components in JVx, you can wrap them within a UICustomComponent:

This has the upside of being fast and easy, but the downside is that your code has to know about the currently used Technology and is not easily portable anymore.

Conclusion

As you can see, there are multiple ways of extending the default set of components which are provided by JVx, depending on the use case and what custom components are required. It is very easy to extend JVx with all the components one does require.

We're happy to announce the release of EPlug 1.2.6. Again this small version bump does not only yield important bug fixes, but also new features which will make your life a lot easier.

Fixes

This release includes bug fixes along with new features. One of the most notable problems fixed was that compile time checks might not be run if the communication with VisionX was active.

Cleaner context menu with more actions

We have restructured our approach to the context menu entries and introduced a new menu item which holds all EPlug related actions:

As you can see we've also added new actions to jump to the configuration files.

Resources outside of source folders

We do support autocompletion and compile time checks for resources, like images. But we only supported resources inside of source folders, with this version we do now also support resources anywhere in the project.

Improved DataBook handling

DataBook handling has been improved once more. There are now additional checks which make sure that a RemoteDataBook receives the correct DataSource and there for if the MetaData can reliably be determined.

Additionally, the type of flag issued if no MetaData could be determined is now a configurable build option on the project.

An example:

This would have been flagged as warning, because no MetaData could be determined for pDataBook. Now the check determines that determining MetaData for this DataBook is impossible and flags it accordingly. You can configure whether you want to see this flag or not in the project settings.

EPlug does also recognize if a "foreign" datasource has been set:

Usernames for sessions

Last but not least, there is now a project setting which allows to set the username which is used by EPlug for the session it creates.

A little background, to acquire the MetaData (and some other information about the application) EPlug creates a session of the application and executes the server side code. It could be that projects do have checks and manipulations on the username somewhere in their code on the server. Previously EPlug would set null as username, but now it does either use the configured autologin username or the username configured in the project settings. That allows server side code which does operate on the username of the session to run without a problem, which means that there are no checks necessary if the session was initialized by EPlug or not.

How to get it?

Simply update EPlug via Eclipse!

Let's talk about the UI layer, the implementations and the factory that powers it all.

The basics

For everyone who does not know, JVx allows you to write code once and run it on different GUI frameworks, without changing your code. This is achieved by hiding the concrete GUI implementations behind our own classes, the UI classes, and providing "bindings" for different GUI frameworks behind the scenes. Such a "Single Sourcing" approach has many advantages, and just one of them is that migrating to a new GUI framework requires only the change of a single line, the one which controls which factory is created.

The Factory Pattern

The Factory Pattern is an important pattern in Object-Oriented-Programming, it empowers us to delegate the creation of Objects to another Object which must not be known at design and/or compile time. That allows us to use Objects which have not been created by us but merely "provided" to us by an, for us unknown, implementation.

Like an onion

JVx is separated into different layers, with the UI layer being at the top and of the most concern to users.

Technology

Obviously, the first one in the chain is the so called "technology" layer. It represents the UI technology, for example Swing, JavaFX or Vaadin, which is used to power the JVx application.

To put it into a more simple term:

Extension

Next comes the extension layer, components from the technology are extended to support needed features of JVx. This includes creating bindings for the databook, additional style options and changing of behavior if necessary. From time to time this also includes creating components from scratch if the provided ones do not meet the needs or there simply are none with the required functionality. For the most part, we do our best that these layers can be used without JVx, meaning that they represent a solitary extension to the technology. A very good example is our JavaFX implementation, which compiles into two separate jars, the first being the complete JVx/JavaFX stack, the second being stand-alone JavaFX extensions which can be used in any application and without JVx.

Theoretically one can skip this layer and directly jump to the Implementation layer, but so far it has proven necessary (for cleanliness of the code and object structure and sanity reasons) to create a separate extension layer.

Implementation

After that comes the implementation layer. The extended components are extended to implement JVx interfaces. This is some sort of "glue" layer, it binds the technology or extended components against the interfaces which are provided by JVx.

UI

Last but for sure not least is the UI layer, which wraps the implementations. It is completely Implementation independent, that means that one can swap out the stack underneath:

This is achieved because the UI layer is not extending the Implementation layer, but wrapping instances provided by the factory. It is oblivious to what Technology is actually underneath it.

Why is the UI layer necessary?

It isn't, not at all. The Implementations could be used directly without any problems, but having yet another layer has two key benefits:

1. It allows easier usage.
2. It allows to add Technology independent features.

By wrapping it one more time we gain a lot of freedom which we would not have otherwise, when it comes to features as when it comes to coding. The user does not need to call the factory directly and instead just needs to create a new object:

Internally, of course, the Factory is called and an implementation instance is created, but that is an implementation detail. If we would use the implementation layer directly, our code would either need to know about the implementations, which doesn't follow the Single-Sourcing principle:

It also would be possible to directly use the factory (but this isn't modern coding style):

Both can be avoided by using another layer which does the factory calls for us:

Additionally this layer allows us to implement features which can be technology independent, our naming scheme, which we created during stress testing of an Vaadin application, is a very good example of that. The names of the components are derived in the UI layer without any knowledge of the underlying Technology or Implementation.

Also it does provide us (and everyone else of course) with a layer which allows to rapidly and easily build compound components out of already existing ones, like this:

Of course that is not even close to sophisticated, or a good example for that matter. But it shows that one can build new components out of already existing ones without having to deal with the Technology or Implementation at all, creating truly cross-technology controls.

The Factory

The heart piece of the UI layer is the Factory, which is creating the Implemented classes. It's a rather simple system, a Singleton which is set at the beginning to the Technology specific factory which can be retrieved later:

The complexity of the implementation of the factory is technology dependent, but for the most part it is devoid of any logic:

It "just returns new objects" from the implementation layer. That's about it when it comes to the factory, it is as simple as that.

Piecing it together

With all this in mind, we know now that JVx has swappable implementations underneath its UI layer for each technology it utilizes:

Changing between them can be as easy as setting a different factory. I say "can", because that is only true for Swing, JavaFX and similar technologies, Vaadin, obviously, requires some more setup work. I mean, theoretically one could embed a complete application server and launch it when the factory for Vaadin is created, allowing the application to be basically stand-alone and be started as easily as a Swing application. That is possible.

What else?

That is how JVx works in regards to the UI layer. It depends on "technology specific stacks" which can be swapped out and implemented for pretty much every GUI framework out there. We currently provide support for Swing, JavaFX and Vaadin, but we also had implementations for GWT and Qt. Additionally we do support a "headless" implementation which allows to use lightweight objects which might be serialized and send over the wire without much effort.

Adding a new Technology

Adding support for a new Technology is as straightforward as one can imagine, simply creating the Extensions/Implementations layers and implementing the factory for that Technology. Giving a complete manual would be out for scope for this post, but the most simple approach to adding a new stack to JVx is to start with stubbing out the IFactory and implementing IWindow. Once that one window shows up, it's just implementing one interface after another in a quite straightforward manner. And in the end, your application can switch to yet another GUI framework without the need to change your code.

Let's talk about events and event handling in JVx.

What are events...

Events are an important mechanism no matter to what programming language or framework you turn to. It allows us to react on certain actions and "defer" actions until something triggered them. Such triggers can be anything, like a certain condition is hit in another thread, the user clicked a button or another action has finally finished. Long story short, you get notified that something happened, and that you can now do something.

...and why do I need to handle them?

Well, you can't skip events, they are a cornerstone of JVx. Theoretically, you could use JVx without using any of its events, but you would not only miss out on a lot of functionality but also be unable to do anything useful. But don't worry, understanding the event system is easy, using it even easier.

Terminology

For JVx the following terminology applies: An event is a property of an object, you can register listeners on that event which will get invoked if the event is dispatched (fired). Every event consists of the EventHandler class which allows to register, remove and manage the listeners and also dispatches the events, meaning invoking the listeners and notifying them that the event occurred. There is no single underlying listener interface.

Within the JVx framework, every event-property of an object does start with the prefix "event" to make it easily searchable and identifiable. But enough dry talk, let's get started.

Attaching listeners as class

The easiest way to get notified of events is to attach a class (which is implementing the listener interface) to an event as listener, like this:

Attaching listeners as inlined class

Of course we can inline this listener class:

Attaching listeners JVx style

So far, so normal. But in JVx we have support to attach listeners based on reflection, like this:

What is happening here is that, internally, a listener is created which references the given object and the named method. This allows to easily add and remove listeners from events and keeping the classes clean by allowing to have all related event listeners in one place and without additional class definitions.

Attaching listeners as lambdas

Yet there is more, we can of course attach lambdas to the events as listeners, too:

Attaching listeners as method references

And last but not least, thanks to the new capabilities of Java 1.8, we can also use method references:

Parameters or no parameters? To throw or not to throw?

By default we actually support two different classes of listeners, the specified event/listener interface itself, and (javax.rad.util.)IRunnable. Which means that you can also attach methods which do not have any parameters, like this:

Additionally, all listeners and IRunnable itself do support to throw Throwable, which is then handled inside the EventHandler. So you are very flexible when it comes to what methods you can attach and use as listeners.

Creating your own events

You can, of course, create your own EventHandlers and listeners to create your own events. All you need are two classes, an extension of EventHandler and a listener interface.

And that's it, from here on you can use it:

More methods!

You can also use an interface for listeners which has multiple methods, specifying in the constructor which method to invoke:

Now every time the event is dispatched, the somethingOtherHappened method will be invoked. Anyway, don't use this. The upside of having a "simple" listener interface with just one method (SAM-type) is that it allows to use lambdas with it. A listener interface with multiple methods won't allow this.

In JVx we reduced our listener interfaces to just one method (in a backward compatible way) to make sure all events can be used with lambdas.

Fire away!

That's it for this short reference sheet, that is how our event system can and should be used. Of course, there is much more to it under the hood, for example listeners being wrapped in proxy classes, reflection used for invoking methods and some more stuff. If you feel adventurous, be my guest and have a good look at the internals of EventHandler, it is quite an interesting read.