4.3 Creating Plans

Plans are similar to PARs in that they encapsulate the artifacts of an application as a single unit. However plans are XML files that refer to their artifacts, whereas PARs are JAR files that physically contain their artifacts. Plans, known as parent plans may refer to other plans, known as child plans.

Plans share several benefits with PARs:

Plans have the following additional benefits compared to PARs:

The artifacts of a plan are usually stored in Virgo's repository. This means, for example, that if you drop one of the plan’s artifacts in the pickup directory rather than adding it to the repository, the plan will fail to deploy because it will not find the artifact.

The artifacts of a plan may also be stored outside Virgo's repository, somewhere else on the file system and referenced from the plan using URIs. Such artifacts must be available on the file system when the plan is deployed and when Virgo restarts while the plan is deployed. If you delete any of these artifacts, deployment of the plan may fail, either when it is initially deployed or when Virgo restarts.

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 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 uses the version as one component of the unique identifier of this plan. Yes.
scopedSpecifies whether Virgo 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 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 start, stop, or uninstall a single artifact in the plan, Virgo escalates the operation to the whole plan. Also Virgo prevents artifacts of an atomic plan from being in inconsistent states. For example, if one artifact should fail to start, then Virgo stops all artifacts in the plan. Set this attribute to true to enable atomicity or false to disable it. Yes.
provisioning

Specifies whether Virgo installs bundles from the repository to attempt to satisfy any missing dependencies in the plan. Missing dependencies prevent one or more bundles in the plan from resolving. For example, a bundle which imports a package cannot resolve if the package is missing, that is, not exported by another bundle.

A value of auto instructs Virgo to install bundles from the repository to attempt to satisfy any missing dependencies in the plan. This is known as auto-provisioning.

A value of disabled prevents Virgo from installing bundles from the repository to attempt to satisfy any missing dependencies in the plan. This value can make the plan deploy faster, although if there are missing dependencies, deployment will fail.

A value of inherit, which is the default if no value is specified, inherits the parent plan's provisioning behaviour. If the plan does not have a parent, it inherits Virgo's auto-provisioning behaviour.

No. If not specified, defaults to inherit.

The following table describes the attributes of the <artifact> element. Note that you must either specify type, name, and (optionally) version, in which case Virgo's repository is searched for the artifact, or uri in which case the artifact is obtained directly from the file system. If you specify uri, you must not specify type, name, or version.

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, unless uri is specified in which case type must not be specified and is automatically determined from the artifact.
nameSpecifies the name of the artifact.

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

Yes, unless uri is specified in which case name must not be specified and is automatically determined from the artifact.
versionSpecifies the range of versions of this artifact that Virgo 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). Note that a single version number represents the range from that version number upwards. For example, 1.3 represents the range of versions greater than or equal to 1.3. No. If uri is specified, version must not be specified. If neither uri nor version are specified, version defaults to 0, which in OSGi means 0 to infinity, or any version.
uri Specifies an optional, absolute URI string beginning with file: that refers to the artifact on the file system. Such an artifact must be available on the file system when the plan is deployed and when Virgo restarts while the plan is deployed. If you delete such an artifact, deployment of the plan may fail, either when it is initially deployed or when Virgo restarts. This attribute is normally omitted so that the artifact is searched for in Virgo's repository. No. If not specified, Virgo searches for the artifact in its repository.

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 Virgo.

  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 Virgo. Note that you might have configured the server differently; in which case, copy the artifacts to your custom repository directory.

  2. Restart Virgo 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 Virgo 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 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 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 the thread context class loader.

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.

Web Applications and Scoping

A Web Application Bundle (WAB) or WAR has its bundle class loader set as the TCCL, even when the WAB or WAR belongs to a PAR or scoped plan. To enable the TCCL to load classes of other bundles in the same scope as a WAB or WAR, use a WAB which imports the necessary packages.

Also a WAB or WAR has its own per-application trace, independent of the per-application trace of any PAR or scoped plan to which the WAB or WAR belongs.