4.3 Creating Plans

Plans are similar to PARs in that they encapsulate the artifacts of an application as a single unit. As a consequence, they have similar benefits; for details of the benefits common to PARs and plans, see PARs.

Plans have the following additional benefits, which is why we recommend that you use plans rather than PARs when defining an application:

Plans always get their dependencies from the VTS repository. This means, for example, that if you drop one of the plan’s dependencies in the pickup directory rather than adding it to the repository, the plan will fail to deploy because it will not find the dependency.

Creating the Plan XML File

Plans are XML files that have a .plan file extension, such as multi-artifact.plan. The structure of the XML file is simple: the root element is <plan> with attributes specifying the name of the plan, the version, atomicity, and scoping. Then, for each artifact that makes up your application, you add a <artifact> element, using its attributes to specify the type of artifact and its name and version. The following is a simple example of a plan’s XML file:

<?xml version="1.0" encoding="UTF-8"?>
<plan name="multi-artifact.plan" version="1.0.0" scoped="true" atomic="true"
        xmlns="http://www.eclipse.org/virgo/schema/plan"
		xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
		xsi:schemaLocation="
		        http://www.eclipse.org/virgo/schema/plan
		        http://www.eclipse.org/virgo/schema/plan/eclipse-virgo-plan.xsd">

    <artifact type="configuration" name="app-properties" version="1.0.0"/>
    <artifact type="bundle" name="com.springsource.exciting.app" version="[2.0.0, 3.1.0)"/>

</plan>

In the preceding example, the name of the plan is multi-artifact.plan and its version is 1.0.0. The plan is both scoped and atomic. The plan contains two artifacts: one is a bundle called com.springsource.exciting.app and the other is a configuration file called app-properties.

The following table describes the attributes of the <plan> element.

Table 4.2. Attributes of the <plan> Element

AttributeDescriptionRequired?
nameSpecifies the name of this plan. Virgo Tomcat Server uses the name as one component of the unique identifier of this plan. Yes.
versionSpecifies the version of this plan. You must use OSGi version specification syntax, such as 2.1.0. Virgo Tomcat Server uses the version as one component of the unique identifier of this plan. Yes.
scopedSpecifies whether Virgo Tomcat Server should install the artifacts into plan-specific scope so that only the application described by this plan has access to the artifacts. If you disable scoping, then Virgo Tomcat Server installs the artifacts into the global scope, which means they are then available for access by all other deployed artifacts. Set the attribute to true to enable scoping or false to disable it.Yes.
atomicSpecifies whether you want to tie together the lifecycle of the artifacts in this plan. Making a plan atomic means that if you install, start, stop, or uninstall a single artifact in the plan, Virgo Tomcat Server escalates the event to all artifacts in the plan. Also, in an atomic plan, Virgo Tomcat Server prevents artifacts from being in inconsistent states. For example, if one artifact should fail to start, then Virgo Tomcat Server stops all artifacts in the plan. Set this attribute to true to enable atomicity or false to disable it. Yes.

The following table describes the attributes of the <artifact> element.

Table 4.3. Attributes of the <artifact> Element

AttributeDescriptionRequired?
typeSpecifies the type of the artifact. Valid values are:
  • bundle: Specifies an OSGi bundle. Use this artifact type for WAR files and Web application bundles.
  • configuration: Specifies that the artifact is a configuration file. Configuration files contain name/value pairs that set initial values for configuration properties of a bundle.
  • plan: Specifies that the artifact is a plan.
  • par: Specifies that the artifact is a PAR.
Yes.
nameSpecifies the name of the artifact.

See Artifact Names for guidelines for determining the name of an artifact.

Yes.
versionSpecifies the version or range of versions of this artifact that VTS should look up in its repositories and then install and deploy. You must use OSGi version specification syntax, such as [1.0.0, 2.0.0). No. If not specified, defaults to 0, which in OSGi means 0 to infinity, or any version.

Artifact Names

When you create a plan, you use the name attribute of the <artifact> element to specify the name of all the plan’s dependencies. This section describes how to determine the name of an artifact, which is not always obvious.

Use the following guidelines to determine the name of an artifact:

  • Bundle: In this context, a bundle refers to a standard OSGi bundle as well as a Web Application Bundle and a WAR file. The name of a bundle is the value of the Bundle-SymbolicName header in the META-INF/MANIFEST.MF file of the *.jar. If a WAR file has Bundle-SymbolicName header then it will be treated as a Web Application Bundle. The following MANIFEST.MF snippet shows a bundle with name com.springsource.exciting.app:

    Bundle-SymbolicName: org.eclispe.virgo.exciting.app

    If the bundle does not contain a META-INF/MANIFEST.MF file or the MANIFEST.MF doesn't contain a Bundle-SymbolicName header, then the name of the bundle is its filename minus the .jar or .war extension.

  • Configuration File: The name of a configuration or PID (Persistent Identity) is its filename minus the .properties extension. The PID can also be specified within the properties file with the service.pid property.

  • Plan: The name of a plan is the value of the required name attribute of the <plan> element in the plan’s XML file. In the following XML snippet, the plan name is multi-artifact.plan:

    <?xml version="1.0" encoding="UTF-8"?>
    <plan name="multi-artifact.plan" version="1.0.0" scoped="true" atomic="true"
            xmlns="http://www.eclipse.org/virgo/schema/plan"
    ...
  • PAR: The name of a PAR is the value of the Application-SymbolicName header in the META-INF/MANIFEST.MF file of the *.par file. The following MANIFEST.MF snippet shows a PAR with name com.springsource.my.par:

    Application-SymbolicName: org.eclipse.virgo.my.par

    If the PAR does not contain a META-INF/MANIFEST.MF file, then the name of the PAR is its filename minus the .par extension.

Supplying Properties to Artifacts

It is possible to pass properties to an artifact specified in a plan. An example of this can be seen in the Admin Console plan where the context path to be used in the Admin console is passed from the plan.

    <artifact type="bundle" name="org.eclipse.virgo.apps.admin.web" version="[3.0, 4.0)">
        <property name="header:Web-ContextPath" value="/admin" />
    </artifact>
			

The only supported property is header which will overwrite the given manifest header with the supplied value. This should be used with care!

Using the Plan

Because a plan is a list of artifacts, rather than a physical file that contains the artifacts, there are a few additional steps you must perform before you deploy it to VTS.

  1. Copy the artifacts that make up the plan to the usr repository, which by default is the $SERVER_HOME/repository/usr directory, where $SERVER_HOME refers to the top-level installation directory of VTS. Note that you might have configured the server differently; in which case, copy the artifacts to your custom repository directory.

  2. Restart VTS if the repository used is not a watched repository.

  3. After the server has started, either use the Admin Console to deploy the plan, or manually deploy it by copying the plan’s XML file into the $SERVER_HOME/pickup directory.

    This results in VTS deploying the plan.

  4. To undeploy the plan, use the Admin Console, or simply delete it from the $SERVER_HOME/pickup directory.

Plans and Scoping

As described in previous sections, you can specify that a plan be scoped. This means that Virgo Tomcat Server installs the artifacts that make up the plan into a plan-specific scope so that only the application described by the plan has access to the artifacts. If you disable scoping, then Virgo Tomcat Server installs the artifacts into the global scope, which means they are available for access by all other deployed artifacts. This section describes scoping in a bit more detail. It also describes how you can change the default behavior of scoping, with respect to services, so that a service that is in a scope can be made globally available.

If a bundle in a given scope imports a package and a bundle in the same scope exports the package, then the import may only be satisfied by the bundle in the scope, and not by any bundles outside the scope, including the global scope. Similarly, package exports from bundles in a scope are not visible to bundles in the global scope.

If a bundle in a scope uses Spring DM (or the blueprint service) to obtain a service reference and a bundle in the same scope uses Spring DM (or the blueprint service) to publish a matching service, then the service reference may only bind to the service published in the scope (and not to any services outside the scope). Services published by bundles in a scope are not visible to bundles in the global scope.

However, sometimes it is useful to make a service in a scope globally available to artifacts outside the scope. To do this, publish the service with the org.eclipse.virgo.service.scope service property set to global. Use the <service-properties> child element of <service>, as shown in the following example:

<service id="publishIntoGlobal" interface="java.lang.CharSequence">
  <service-properties>
    <beans:entry key="org.eclipse.virgo.service.scope" value="global" />
  </service-properties>
  <beans:bean class="java.lang.String">
    <beans:constructor-arg value="foo"/>
  </beans:bean>
</service>

A scope forms a boundary for automatic propagation of load time weaving and bundle refresh. Additionally, a synthetic context bundle is generated for each scope. This bundle imports all the packages exported by other bundles in the scope. The class loader of the synthetic context bundle is used for thread context class loading. So, for example, hibernate will be able to load classes of any of the exported packages of the bundles in a scope using Class.forName() (or equivalent).

To ensure predictable class loading behaviour and avoid other issues associated with split packages (packages whose classes are split across more than one bundle), the synthetic context bundle has a restriction: no package may be exported by more than one bundle in the scope. If this restriction is broken, the scoped application will fail to deploy. This restriction can cause problems for substitutable exports.