ServiceLoader<S> Dynamic Reloading on JEE7 Web Application

Introduction

We had a technical discussion about updating an application on the fly in Java EE. There were a couple of issues that we were trying to resolve. One was a simple way to add functionality to a web application while deployed, and update the running application. It could be functionality like a new module, or service, or something like, the classic example for the ServiceLoader, codecs.

Additionally, we needed to be able to add the functionality without adding another framework to make it happen. It needed to be something that was available in the existing Java SE/EE APIs. Again, the ServiceLoader seemed to be a possible solution.

I did a Proof of Concept (POC) for using a ServiceLoader to accomplish adding additional services to our application. That worked, but required a restart of the server, or a reload of the application at a minimum. This assumes that the application was NOT auto-deployed. It turns out that worked, but really was only a half-measure. I wanted to see if I could solve the dynamic reloading part, and I did.

Solution

Before we see the code, how does it work in general. We use the ServiceLoader which is part of the Service Provider Interface (SPI) functionality of Java. It is a hidden gem for those who need it, and framework creators can take advantage of this simple, easy to use technology. The ServiceLoader is managed by a Singleton that returns an instance of the ServiceLoader that will return our SPI implementations. In my example, I create an interface that is packaged separately in its own jar and is shared between the deployed web application and the service implementations. The ServiceLoader loads this interface and makes the implementations available. The cool part is that our Singleton class also has some cool NIO and NIO.2 help with the ZipFileSystemProvider to load the implementations from newly added jars. It also has some demo of how to use a URLClassLoader to add our new implementations and update the ServiceLoader.

The code for the project can be found here:

• serviceloader-web-example (code)
• example-log-spi-implementation (code)
  example-log-spi-implementation-1.0-SNAPSHOT.jar (bin)
• example-log-spi (code)
  example-log-spi-1.0-SNAPSHOT.jar (bin)

Log.java

Here is our interface that is common between the web service and the SPI implementations.

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LogImpl.java

This simple interface will allow me to demonstrate the power of the SPI. Here is an implementation of the API.

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LogService

This class is the magic behind the SPI and allows us to dyanmically reload the new implementations as we add them to the WEB-INF/lib directory.

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com.bluelotussoftware.service.spi.Log

The SPI file located in the META-INF/services directory of your jar file. This is one version, but each implementation would have its own. The file name is the same as the interface, and the listings on each line are concrete implementations.

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IndexBean.java

This bean has a cool NIO method of handling uploaded files. So I thought I would add it. Combined with PrimeFaces, it is functional and pretty.

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Conclusion

If you need to add some additional functionality to a web application, and reload it on the fly, Give the ServiceLoader a try. You might just be impressed.

JavaOne 2013 NetBeans Day: Cool NetBeans Tips and Tricks for Java EE 7 Development

I mentioned in my panel discussion for Cool NetBeans Tips and Tricks for Java EE 7 Development that I would publish my 6:30 demo for creating an application from nothing to PrimeFaces application on GlassFish 4.0.

Here is a link to the Mercurial project on BitBucket: JavaOneApp

JSF 2.x Tip of the Day: RichFaces 4.3.x Resource Mapping

I have a great opportunity to do different things at work. I get to help solve some really interesting issues around web development. This is particularly true with JSF. In the last few days we have been working on some issues with WebSphere using JSF. In particular, there is an issue with Drag-and-Drop (DnD) on RichFaces with MyFaces on WebSphere. We figured out that there is a possible fix we can implement by fixing the RichFaces DnD Javascript library.

So.... the question is how do we implement the changed library without having to compile a custom version of RichFaces, or modifying the files to load our changed script and prevent the bad script from loading, or implementing our own ResourceHandlerWrapper.

Well there are a number of alternative solutions, but if you are using RichFaces  there is a simple choice: using the Resource Mapping feature of RichFaces  This feature allows you to remap resources to point to alternative resources. This is a really helpful and convenient feature, and solves our problem of modified DnD JS for our RichFaces application.

The details of how to use it are mentioned on the Resource Mapping page, but only from a very high level, and there is no example implementation. There is a blog post Re-routing JSF resource requests with RichFaces Resource Mapping from Lukas Fryc which details more functionality than the guide, but there is no complete example. I am going to rectify that with this post.

The code for the example that follows is located here: richfaces-resource-mapping.

The first thing you need is a static-resource-mappings.properties file. This tells the RichFaces ResourceServlet what the alternative mappings should be. In the example application above my mappings look like the following.


As you can see, I am remapping images to remote IP addresses, and the jquery.js file to an alternative location on the file system. This alternative remapping of jquery.js file allows us to replace the JQuery instance that comes with RichFaces with our own alternative version.

The static-resource-mappings.properties needs to be located in the META-INF/richfaces directory, or one of the other alternatives as noted in Resource Mapping guide. This can be easily accomplished in Maven using the code below:

This allows us to copy the files in the resources directory to META-INF/richfaces automatically while building.

That is pretty much it. How about that for being easy.

Here is what the output looks like in the example application: richfaces-resource-mapping.

RichFaces Resource Mapping

JSF 2.x Tip of the Day: RichFaces 4.3.x Charts in JSF using JSFlot, JFreeCharts, and PrimeFaces

Sexy PrimeFaces Charts in RichFaces

Introduction

I was asked to look at various charting solutions for JSF. Specifically, I was asked for some choices for use with RichFaces 4.3.1. I knew that PrimeFaces has really good chart components already so I knew it might be kind of fun to integrate them if possible. I was also aware of JFreeChart which will work, but produces some... rather ugly charts. Finally, someone had suggested that I look at jsflot. This was a very promising solution. This project is a proof of concept which demonstrates integration between projects, and technologies.

Requirements

• jsflot
• NetBeans This is required for the sample database, although you could create your own data.

The jsflot framework is currently not Mavenized, so if you are going to run my example code, you will need to download it from the link above, and install it in Maven using the command below.

Code

The code for this NetBeans Maven project can be found on BitBucket here: chart-demo

This is the bean that provides the data models for the charting solutions. There are a number of chart demos in the project. The two charts above are just examples.

ChartBean.java

JSF 2.x Tip of the Day: PrimeFaces Chart Coding Exam

PrimeFaces Pie Chart

Background

I have been asked to interview a number of engineers over the last couple of years. We were interested in hiring an engineer with a background in JSF specifically PrimeFaces, Java EE 6, and NetBeans.

Basically I wanted someone...like me.

I came into work one day, and I was told that I needed to interview someone in about an hour about a position. The person claimed experience in all of the aforementioned technologies. I needed to come up with a coding exam idea for them. Tick tock tick tock.

I decided to create a NetBeans project using the sample Java DB database, JPA, EJB facades, and a JSF front end using PrimeFaces with a pie chart. The whole process took about 7 minutes to create. When the engineer arrived, I showed him the result and said "I want to see the same results", and explained that I used the sample database from NetBeans.

The engineer was successful and created something similar in about 30 minutes, and additionally showed me up by adding percentage tags to the chart. We hired him after the interview. I am glad to say he is an integral part of our team today.

Coding Exam

What do I want?

Please create a JSF application using PrimeFaces that displays a pie chart using data provided. The application must be developed using NetBeans and Java EE 6 technologies. The example data is provided using the sample Java DB database in NetBeans  We would like to have a pie chart that shows sales totals by customer as a percentage of all sales. You have 1 hour to complete the code, and will be required to explain your design decisions, and results.

Note: I just showed them the pie chart that was generated in the browser and not the actual code. I don't want to sway the candidates decision making, or give them hints on how to solve the problem.

Here is the code for the project: PrimeFacesCodingExam

Conclusion

Even if you don't use this in a coding exam, it is a good example of combining Java EE technologies using NetBeans  and PrimeFaces.

JSF 2.1.x Tip of the Day: Primefaces 3.5 <p:ring/> Drag-N-Drop Example

Camp Old Indian

I was trying to come up with an example to demonstrate <p:ring /> along with Drag-and-Drop (DnD). I had an idea of using a target to drop things on. I was sitting in my living room watching my youngest son creating a world on little big planet, and I remembered his first time shooting a bow. He had a perfect bullseye.

I decided that I would drag-n-drop arrows in honor of my son. I mentioned the idea to him, and he loved it. So here it is... a useful example that was fun to create. In this example, I will demonstrate the <p:ring />, and <p:fieldSet /> components primarily. I have added some effects to a <p:dialog /> if you select an arrow and dismiss it.

Requirements

• PrimeFaces 3.5
• Mojarra 2.1.20

I used NetBeans 7.3 to develop the Apache Maven based project. The Mercurial project can be found on BitBucket here: primefaces-ring-dnd.

Example

index.xhtml

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IndexBean.java

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Arrow.java

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Conclusion

This is a very simple example of what you can do with a Primefaces, Mojarra, and Netbeans.

Arrow Ring and Target

JSF Tip of the Day: PrimeFaces 3.0 Tree Drag and Drop Example

I worked on a proof of concept for a drag and drop enabled <p:tree /> for a project I was working on. At the time, PrimeFaces was just starting the path to 3.0, and I was working with a snapshot. The POC was part of a decision making process on which JSF framework, or combination of frameworks to use.

This drag and drop example was part of the the work Optimus Prime and his team created as a potential functionality for the <p:tree /> component. In the final release, this functionality was removed. I still have high hopes that in PrimeFaces 3.5.+ that it will be added back into the product. It was a cool idea and one that we had hoped to take advantage of in our products.

If you need this functionality currently, and don't mind using a 3.0-SNAPSHOT release, you can have a drag and drop <p:tree />. I published this since it was a good example, and I thought someone might need this specific functionality. Otherwise it is code lost in time.

The Mercurial project can be pulled from BitBucket and was developed using NetBeans and Apache Maven.

The code can be found here: primefaces-tree-dragdrop-demo

Example

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JSF 2.1 Tip of the Day: Using <iframe /> Elements with PrimeFaces

Carousel and LightBox

We have some requirements on a project I am working on to display <iframe /> elements which are connected to external pages within our JSF pages. Since JSF supports template language such as plain HTML, we could directly use an <iframe /> in the page. However, it would not match up with our existing page layouts.

PrimeFaces offers a component called a Light Box (<p:lightBox />) which supports <iframe /> elements directly. You can see an example from the PrimeFaces showcase for how to use it.

I thought I would share a more interesting approach using a <p:caraousel /> object to display multiple <iframe /> elements in a more "sexy" approach.

The cool thing is that the code is really easy to implement!

The code was developed using NetBeans 7.2 and Apache Maven. The code can be downloaded here: iframe-example.zip

code

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JSF 2.1 Tip of the Day: PrimeFaces 3.4 Advanced Table Example with JPA

PrimeFaces 3.4 Data Table

I was working on an example table to demonstrate some of the PrimeFaces data table capabilities. I think I may use it as an interview problem: "Create an advanced table with the layout seen in this picture using JPA".

The example was developed using Maven on NetBeans 7.2. The source code can be downloaded from here: advanced-table.zip.

Index.xhtml

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JSF 2.1 Tip of the Day: PrimeFaces Dialog <p:dialog/>

We have been doing a lot of work lately with PrimeFaces. A common set of questions comes up about displaying <p:dialog/> boxes on a page.

1. How do I update elements on the page outside of the dialog?
2. How do I include information from external pages?
3. Can I nest forms and dialogs?

The last one is the easiest to answer: NO. You may get away with it in some cases, but the HTML specification does not allow <form> tags to be nested inside other forms. So your dialog can contain a form, but should be outside of the form that opens it.

Some components do not need to live inside a <form> to work. For example <h:button /> tags do not need to be inside a <form>. You can update <h:outputText /> elements outside a <form> with AJAX.

The second question is also easy. Using <ui:include /> you may add other JSF content to your dialog. You could also use a <ui:decorate />, <ui:component />, <ui:define />, or <ui:composition />. I personally like <ui:include />

The first question is best answered with some code. I have some interesting tidbits of code in here including using String concatenation in Expression Language (EL). The key to updating elements on the page comes from the update attribute on the <p:commandButton /> elements.

The project and code I have included below were developed using NetBeans 7.2 IDE on GlassFish 3.1.2.2, and PrimeFaces 3.3.1.

The code can be downloaded here: primefaces-dialog-examples.zip

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IndexBean.java

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JSF 2.1 Custom PrimeFaces 3.3 Tree Example

Custom PrimeFaces Tree

I was looking at the default implementation of PrimeFaces <p:tree /> and <p:treeNode />. The default looks nice, but I wanted a different look with different icons.

The icons I picked look more like "nodes" and "documents. The icons are by Yusuke Kamiyamane in his Fugue Icon set. These icons are released under a Creative Commons 3.0 Attribution License.

I also wanted a more flexible tree model with a custom TreeNode implementation that uses node types (node, leaf), and a data component which is represented by an Object.

The result is a nice looking tree that changes icons subtly on selection, or deselection of a node, and leaf nodes are displayed as document icons.


The Apache Maven project was developed using NetBeans 7, GlassFish 3.1.2, and PrimeFaces 3.3.1. 


The source code can be downloaded here: primefaces-custom-tree.zip

index.xhtml

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TreeNodeImpl.java

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TreeNodeType.java

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TreeBean.java

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PrimeFaces AJAX Enabled <p:selectOneMenu />

I saw a question posed on stackoverflow called Trouble with Primefaces 3.0.M2 SelectOneMenu Ajax behavior and I had just done an example a couple of months ago on a car trip so I decided to post my solution here, and reference it.

Essentially the problem is how to control the list of items in a second <p:selectOneMenu/< from the selection made in the first menu. The question comes up frequently enough that I decided to write up a demo application.

The application was developed using NetBeans 7.1.2 and PrimeFaces 3.2 originally. It has been updated to use PrimeFaces 3.3.1 which is the most current at the time of writing. I validated it on GlassFish 3.1.2.

 The Apache Maven project can be downloaded from here: primefaces-ajax-selectone.zip

This demo wants the user to pick a state, and then a city. A key problem is not just the update, but not displaying city values if a state is not selected. Also erasing the selected city, if the state has changed.

index.xhtml

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DataBean.java

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JSF Tip of the Day: JSF 2.1 AJAX Examples with PrimeFaces 3.3 and Mojarra 2.1

I have been working with my team at the office to bring them up to speed on using JSF and AJAX. I have been encouraging them to use PrimeFaces to reduce the amount of code required to "AJAXify" JSF components. PrimeFaces has AJAX functionality built in, or uses a simple <p:ajax/> tag to enable it.

However, I think that it is important to be able to use the default Mojarra JSF RI implementation along with its <f:ajax/> functionality both as a tag, and as JavaScript. The code examples below use a combination of PrimeFaces and Mojarra to demonstrate the ease with which you can develop fully functional AJAX applications with JSF.

The examples are done using Apache Maven on NetBeans 7.2 RC 1 and deployed to GlassFish 3.1.2. using JSF 2.1.0 and PrimeFaces 3.3.1.

The code for the project can be downloaded here: ajax-examples.zip

index.xhtml

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IndexBean.java

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The pictures below demonstrate the before and after of clicking the checkbox, and radio buttons.

Before

After