Create Spring beans dynamically

Spring XML declared beans can be wired building your business structure. The problem with this approach is that these beans are loaded on the start up, when the Spring Context is created, which does not leave much of playground to modify or change beans at run time. How ever Spring offers opportunity to load beans in the Spring context on run time when beans are needed, and populate them at need.
For doing this, we need the Spring Application context. For this to accomplish, one can declare one dedicated Spring context bean, which will implement the ApplicationContextAware and BeanFactoryPostProcessor interfaces. This should look something like this:

  public class MyContextWrapper implements ApplicationContextAware,
                                           BeanFactoryPostProcessor {

   private ApplicationContext appContext;
   private ConfigurableListableBeanFactory factory;

   public void postProcessBeanFactory(ConfigurableListableBeanFactory factory)
                                                        throws BeansException {
         this.factory = factory;
   }
   public void setApplicationContext(ApplicationContext c)
                                                throws BeansException {
         this.appContext = c;   
   }

   //setters and getters

}

The postProcessBeanFactory will be executed after reading the configuration files of the spring context. Here one can do other configurations and bean loading, or save the factory for later use.
The Spring application context can be used for later dynamic bean retrieval or other purposes.

For this approach to work, one should let spring load this bean in to it's context by declaring the bean in the XML configuration file as follow:

Now this bean can be loaded in any other bean of the application via referencing it:

Now that we have the grip of the Spring context and it's factory, we can create beans dynamically. For this purpose, we can use the GenericBeanDefinition which allows to load bean definitions as follows:

      BeanDefinitionRegistry registry = ((BeanDefinitionRegistry )factory);
       
      GenericBeanDefinition beanDefinition = new GenericBeanDefinition();
      beanDefinition.setBeanClass(MyBeanClass.class);
      beanDefinition.setLazyInit(false);
      beanDefinition.setAbstract(false);
      beanDefinition.setAutowireCandidate(true);
      beanDefinition.setScope("session");
     
      registry.registerBeanDefinition("dynamicBean",beanDefinition);

As one can see, this bean is created in the session scope and will be stored in the session of the user. The property auto wire candidate tells spring if dependency's of the bean such as setter's or getter's or constructor argument's should be handled automatically by Spring. The property lay init tells Spring if this bean should be instantiated when needed.

To get a handle of Spring bean, one can use the Spring application context as follows:

Object bean= 
    getApplicationContext().getBean("dynamicBean");
 if(bean instanceof MyBeanClass){
    MyBeanClass myBean = (MyBeanClass) bean;

   // do with the bean what ever you have to do.
 } 

As you can see, the dynamic bean creation in Spring is no big deal.It is easy to use, an certainly handy in many situations.

JSR 286 IPC with JSF

In case you are portlets developer, you know what JSR 286 is. It is the holy grail for the portlets which should enable the portlets to communicate with each others. At least you would think it is the holy grail, until you read the specs and look upon the Suns minimalistic examples.
It seems to me, this spec is out for it's own sake, and forwards the developers in the ice age of pure html, which is unthinkable for someone who has got used to API's such as JSF or Struts. Vendors as JBoss or ICEFaces have yet to deliver a bridge which will support JSR 286 with an AJAX push.

The sad news is that JSR 286 works only with out AJAX push, and you have to do some work around to get the grips of it in JSF Portal environment.

The first thing to do is to define the event you want to publish. This is done in the portlet.xml. There are three declaration there:

1. One Global declaration of your event
2. Supported publishing event for your pulbishing portlet
3. Supported processing event for our consumer portlet

The global event declaration looks as follow:

x:EventName
    java.lang.String

In the Publishing portlet, put the following:

x:EventName

And atlast, in the consumer portlet:

x:EventName

Now that you have configured your event that it is only a simple String, you should set it. This can be done in two way's:

1. Either extend javax.portlet.faces.GenericFacesPortlet and override the
   

   
   public void processAction(ActionRequest request, ActionResponse);
   

2. Or set the event in one of your Faces action methods.

If you prefer the first way, than you have to think that your to pass your full class name in the portlet.xml for portlet instantiation which would look like this:

org.mycomp.IPCPublisher

If you prefer the JSF action method way, than your portlet.xml will look as usual:

javax.portlet.faces.GenericFacesPortlet
  

In you decide to override the method of the GenericFacesPortlet, than you will set the event similar to this:

public void processAction(ActionRequest request, ActionResponse response)
throws PortletException,IOException {

   QName qname = new QName("http://www.mycomp.com/myevent" , "EventName");
   response.setEvent(qname, "Hallo IPC Communication.");
}

If you decide you would like to publish this event from inside of your JSF action method, you can do that as follow:

  public void publishIPCEvent(ActionEvent event){
   Object response = FacesContext.getCurrentInstance()
            .getExternalContext()
           .getResponse();

   if(response instanceof ActionResponse){
     ActionResponse aResponse = (ActionResponse)response;
      QName qname = new QName("http://www.mycomp.com/myevent" , "EventName");
        aResponse.setEvent(qname, "Hallo IPC Communication.");
    }
}

This method will be called as usual in JSF:

What is left is to read out this event in the Consumer portlet.
You should extend the Generic Faces Portlet and override the processEvent method. By doing that, don't forget to put the class definition in the portlet.xml as follow:

   org.mycomp.IPCConsumer

Override the method as follow:

public void processEvent(EventRequest request, EventResponse response) {
   Event event = request.getEvent();
   if(event.getName().equals("EventName")){
     String ipc = event.getValue();
     response.getPortletSession().setAttribute("ipc",ipc);
   }
}

As you can see, I read out the event and compare it's name if it is my event I want to handle. Than I read it's value and set it in the portlet session as attribute.

To get this value inside of JSF, you should do something like this:

 Object ipc = FacesContext.getCurrentInstance()
  .getExternalContext().getSession(false)
   .getAttribute("ipc);

Some say that one can annotate the certain method, which should be responsible for processing the event. This should look something like this:

@ProcessEvent(qname="{http://www.mycomp.com/myevent}EventName")
 public void myEventProcessingMethod(EventRequest request, EventResponse response){
    Event event = request.getEvent();
   if(event.getName().equals("EventName")){
     String ipc = event.getValue();
     response.getPortletSession().setAttribute("ipc",ipc);
   }
}

But this method annotation did not work for me inside of JSF. The same should work with java.util.HashMap instead of java.lang.String as well.

Anyways, this IPC approach is not that straightforward as some would like it to be, but it fullfils it's purpose.

Create your JSF componenst with out JSP or Facelets Tags

It is personal reference. Some love XML Syntax, some try to save them from the XML Jungle. JSF is a framework that allows you to create components dynamically. The JSF Tags are only option.

If you prefer to create your compnents without JSP or Facelets, and you don't want to envent the weel again, you can define your JSF Panel Grid in your JSP or Facelet as follow:

Define the bean in Spring config file as follow:

This bean holds a instance of the JSF HtmlPanelGrid which renders the JSF Panel Grid for you. The JSF components should be added to the Panel Grid with it's public method getChildren().add(Object o);. Here is the example:

package org.mypackage;

import javax.faces.application.Application;
import javax.faces.component.html.HtmlOutputText;
import javax.faces.component.html.HtmlPanelGrid;
import javax.faces.context.FacesContext;


public class MyBean {

private HtmlPanelGrid panelGrid;

public MyBean(){

}
public void init(){

Application application = FacesContext.getCurrentInstance().getApplication();
setPanelGrid((HtmlPanelGrid) application.createComponent(HtmlPanelGrid.COMPONENT_TYPE));

HtmlOutputText text = (HtmlOutputText) application.createComponent(HtmlOutputText.COMPONENT_TYPE);

text.setValue("Hallo JSF with out Tags.");

getPanelGrid().getChildren().add(text);

}
public void setPanelGrid(HtmlPanelGrid panelGrid) {
this.panelGrid = panelGrid;
}
public HtmlPanelGrid getPanelGrid() {
return panelGrid;
}

}

1. In line 16 is the public method which will be ivoked by Spring after instantiation of the Bean.
2. Line 18 gets an instance of the current application.
3. On line 19 we create an instance of HtmlOutputText with the help of the method createComponent which takes String as argument. Every JSF Component defines public static field COMPONENT_TYPE which returns the type of the component to be created.
4. On line 21 a instance of HtmlOutputText is created in the same way as the HtmlOutputText.
5. In line 23 we set the value of the output text.
6. In line 25 we set the output text component as child of the Panel Grid.

On the end of the day, when JSF try's to render the Panel Grid with the ID dynamic in the JSP or Facelets, the Property panelGrid of the backing bean will be called and our instance would be copied and rendered.

In this way, we can create whole views or parts of it, as if we program in pure Java.