Package org.camunda.bpm.application.impl

Class ServletProcessApplication

java.lang.Object
org.camunda.bpm.application.AbstractProcessApplication
org.camunda.bpm.application.impl.AbstractServletProcessApplication
org.camunda.bpm.application.impl.ServletProcessApplication
All Implemented Interfaces:
EventListener, javax.servlet.ServletContextListener, ProcessApplicationInterface
Direct Known Subclasses:
InvoiceProcessApplication
public class ServletProcessApplication extends AbstractServletProcessApplication implements javax.servlet.ServletContextListener

A AbstractProcessApplication Implementation to be used in a Servlet container environment.

This class implements the ServletContextListener interface and can thus participate in the deployment lifecycle of your web application.

Usage

In a Servlet 3.0 container it is sufficient adding a custom subclass of ServletProcessApplication annotated with @ProcessApplication to your application: 

 @ProcessApplication("Loan Approval App")
 public class LoanApprovalApplication extends ServletProcessApplication {
 // empty implementation
 }
This, in combination with a META-INF/processes.xml file is sufficient for making sure that the process application class is picked up at runtime.

In a Servlet 2.5 container, the process application can be added as a web listener to your project's web.xml 

 <?xml version="1.0" encoding="UTF-8"?>
 <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://java.sun.com/xml/ns/javaee    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

 <listener>
   <listener-class>org.my.project.MyProcessApplication</listener-class>
 </listener>
</web-app>

Invocation Semantics

When the AbstractProcessApplication.execute(java.util.concurrent.Callable) method is invoked, the servlet process application modifies the context classloader of the current Thread to the classloader that loaded the application-provided subclass of this class. This allows

  • the process engine to resolve JavaDelegate implementations using the classloader of the process application
  • In apache tomcat this allows you to resolve Naming Resources (JNDI) form the naming context of the process application. JNDI name resolution is based on the TCCL in Apache Tomcat.

                        Set TCCL of Process Application
                                     |
                                     |  +--------------------+
                                     |  |Process Application |
                       invoke        v  |                    |
      ProcessEngine -----------------O--|--> Java Delegate   |
                                        |                    |
                                        |                    |
                                        +--------------------+

Process Application Reference

The process engine holds a WeakReference to the ServletProcessApplication and does not cache any classes loaded using the Process Application classloader.

Author:
Daniel Meyer, Thorben Lindhauer

  • Field Details

    • servletContext

      protected javax.servlet.ServletContext servletContext

  • Constructor Details

    • ServletProcessApplication

      public ServletProcessApplication()

  • Method Details

    • contextInitialized

      public void contextInitialized(javax.servlet.ServletContextEvent sce)
      Specified by:
      contextInitialized in interface javax.servlet.ServletContextListener

    • initProcessApplicationClassloader

      protected ClassLoader initProcessApplicationClassloader(javax.servlet.ServletContextEvent sce)

    • contextDestroyed

      public void contextDestroyed(javax.servlet.ServletContextEvent sce)
      Specified by:
      contextDestroyed in interface javax.servlet.ServletContextListener

    • getServletContext

      public javax.servlet.ServletContext getServletContext()