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Overview

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This plugin

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Features

• GUI for bundle administration
• Web access to Felix Shell
• Application packages can be divided into bundles
• Supports Velocity and FreeMarker templates
• Supports Struts Spring integration
• Supports integration with the Convention plugin

Missing Features

• Probably can't access application classes from bundles, including Spring classes
• constant declarations in the bundled XML config files are ignored, these constants need to be set in the application XML config files (struts.xml)

About Run levels

Application bundles should go under /WEB-INF/classes/bundles. Bundles in this dir will be started in run level 2, the Apache Felix framework's bundles will be loaded in run level 1. Any other bundle under /WEB-INF/classes/bundles/other will be started in run level 3.

Simple Usage

Add these lines to MANIFEST.MF:

Struts2-Enabled: true
Export-Package: com.mycompany.myapp.actions
Bundle-Version: 1.0.0
Bundle-SymbolicName: foo.actions
Import-Package: com.opensymphony.xwork2

Now the jar is ready to be deployed. Drop the jar into the /WEB-INF/classes/bundles directory and it will automatically be installed when the application starts up.

Using Spring

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By default Spring OSGi loads its xml config files asynchronously, which causes the OSGi plugin to fail while starting. To fix this add this line to MANIFEST.MF:

Spring-Context:*;create-asynchronously:=false

Or if using The Apache Felix maven plugin (see below for details):

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<Spring-Context>*;create-asynchronously:=false</Spring-Context>

If you want to use the Spring as the object factory for your actions, then follow these steps:

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<constant name="struts.objectFactory" value="osgi" />
<constant name="struts.objectFactory.delegate" value="springOsgi" />

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<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_9" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

    <display-name>Struts Blank</display-name>

    <filter>
        <filter-name>struts2-prepare</filter-name>
        <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareFilter</filter-class>
    </filter>

    <filter>
        <filter-name>struts2-execute</filter-name>
        <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsExecuteFilter</filter-class>
    </filter>

     <filter-mapping>
        <filter-name>struts2-prepare</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <filter-mapping>
        <filter-name>struts2-execute</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <listener>
        <listener-class>org.apache.struts2.osgi.StrutsOsgiListener</listener-class>
    </listener>

    <listener>
        <listener-class>org.apache.struts2.dispatcher.ng.listener.StrutsListener</listener-class>
    </listener>

    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <context-param>
        <param-name>contextClass</param-name>
        <param-value>org.springframework.osgi.web.context.support.OsgiBundleXmlWebApplicationContext</param-value>
    </context-param>
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>osgibundle:/META-INF/spring/*.xml</param-value>
    </context-param>
    <context-param>
        <param-name>parentContextKey</param-name>
        <param-value>parent-context-bean</param-value>
    </context-param>
</web-app>

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<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-web</artifactId>
    <version>2.5.5</version>
</dependency>
<dependency>
     <groupId>org.springframework.osgi</groupId>
     <artifactId>spring-osgi-web</artifactId>
     <version>1.1.2</version>
</dependency>

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com.springsource.org.aopalliance-1.0.0.jar
com.springsource.org.apache.commons.logging-1.1.1.jar
org.springframework.aop-2.5.5.A.jar
org.springframework.beans-2.5.5.A.jar
org.springframework.context-2.5.5.A.jar
org.springframework.core-2.5.5.A.jar
org.springframework.osgi.core-1.1.2.A.jar
org.springframework.osgi.extender-1.1.2.A.jar
org.springframework.osgi.io-1.1.2.A.jar
org.springframework.osgi.web-1.1.2.A.jar
org.springframework.web-2.5.5.A.jar

Using Velocity

If you are going to use Velocity results, then add Velocity and Common Digester jars to your application. Using maven:

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<dependency>
    <groupId>velocity</groupId>
    <artifactId>velocity</artifactId>
    <version>1.5</version>
</dependency>

<dependency>
    <groupId>velocity-tools</groupId>
    <artifactId>velocity-tools</artifactId>
    <version>1.3</version>
</dependency>

<dependency>
    <groupId>commons-digester</groupId>
    <artifactId>commons-digester</artifactId>
    <version>1.8</version>
</dependency>

Using The Convention Plugin

The Convention plugin will discover actions in bundles in the same way that it discovers them in normal applications. The Convention plugin expects result templates to be (by default) stored under /WEB-INF/content. When packaging actions inside bundles, there won't be a WEB-INF folder, so you must let Convention know where the templates are located. There are two ways of doing so(assuming the templates are under /content):

1. Set the templates location constant in struts.xml (in the application struts.xml, not a bundled struts.xml)

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<constant name="struts.convention.result.path" value="/content/"/>

2. Using the ResultPath annotation

@ResultPath("/content")
public class HelloWorldAction extends ActionSupport
...
}

The OSGi interceptor

The OSGi plugins defines the osgi interceptor and osgiStack(defaultStack plus the osgi interceptor) in the package osgi-default. This interceptor will check the action and if it implements org.apache.struts2.osgi.interceptor.BundleContextAware, it will invoke setBundleContext(BundleContext bundleContext) on the action, passing the BundleContext of the OSGi container. The interceptor also checks if the class implements org.apache.struts2.osgi.interceptor.ServiceAware<T>, if it does, setServices(List<T> services) will be called, where T is the type of a service published in the OSGi container. For example, lets assume an installed bundle publishes a service with the interface BookPriceLookup, to get all the instances of this service, an action would look like:

public class BookPriceAction extends ActionSupport implements ServiceAware<BookPriceLookup> {
    private List<BookPriceLookup> services;

    public void setServices(List<BookPriceLookup> services) {
        this.services = services;
    }
}

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Keep in mind that the interceptor is not defined in the default struts package, so when using Convention, you need to specify the parent package as "osgi-default", either using annotations (@ParentPackage), or XML(this XML fragment must be in the struts XML config file in the application, not the bundle's, this is a current limitation of the OSGi plugin):

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<constant name="struts.convention.default.parent.package" value="osgi-default" />

Admin bundle

An admin bundle is distributed with struts, which provides a simple interface to list the installed bundles. Using this interface the bundles can be stopped, started and updated (reloaded from the file system). This interface also provides information on the installed bundles, like OSGi metadata, and a list of packages and actions loaded from each bundle. An interactive AJAX shell is also available, which is just a web interface to the Apache Felix Shell. To use this bundle, just copy the jar file to /bundles (same place where the application bundles are installed) and open http://localhost:PORT/CONTEXT/osgi/admin/^{Image Removed} (replace PORT and context)

About stopping/starting bundles

When a bundle is started, the OSGi plugin will check for the header Struts2-Enabled in it. If it is set to "true", the bundle will be scanned for XML config and Convention config. When a bundle is stopped, any actions that were loaded from it will be removed from the runtime configuration.

Settings

The following settings can be customized. See the developer guide.

The following setting must be set as context parameters in web.xml, because they are used by the StrutsOsgiListener, for example:

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<context-param>
    <param-name>struts.osgi.clearBundleCache</param-name>
    <param-value>false</param-value>
</context-param>

Building bundles with Maven

See the Maven Bundle Plugin documentation for more details.

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.felix</groupId>
            <artifactId>maven-bundle-plugin</artifactId>
            <extensions>true</extensions>
            <version>2.0.0</version>
            <configuration>
                <instructions>
                    <manifestLocation>META-INF</manifestLocation>
                    <Struts2-Enabled>true</Struts2-Enabled>
                    <Export-Package>org.apache.struts2.osgi.demo</Export-Package>
                    <Import-Package>*,com.opensymphony.xwork2</Import-Package>
                    <Bundle-Activator>org.apache.struts2.osgi.StrutsActivator</Bundle-Activator>
                    <Spring-Context>*;create-asynchronously:=false</Spring-Context>
                </instructions>
            </configuration>
        </plugin>
    </plugins>
</build>

Resources

• OSGi
• Apache Felix
• Spring OSGi

Version History

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