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<title>App Launching</title>
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<author email="bob@eng.werken.com">bob mcwhirter</author>
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<section name="Introduction">
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<subsection name="Purpose">
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In order to reduce the number of classloading projects,
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<code>classworlds</code> replaces <code>forehead</code>
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for application launching.
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The main problems to solve in application launching include
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locating all of application's JARs, configuring the initial
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classloaders, and invoking the <code>main</code> entry method.
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The launcher facilities of <code>classworlds</code> simplify
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the process of locating application jars. A common idiom is
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to have a script which starts the JVM with only the
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<code>classworlds.jar</code> in the classpath and a system
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property to specify the location of a launcher configuration.
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Additionally, typically a property specifying the installation
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location is passed on the command-line.
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-classpath $APP_HOME/lib/classworlds-1.0.jar \
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-Dclassworlds.conf=$APP_HOME/etc/classworlds.conf \
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-Dapp.home=$APP_HOME \
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org.codehaus.classworlds.Launcher \
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<section name="Configuration">
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<subsection name="Entry Definition">
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The entry-point class and realm must be specified
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using the <code>main is</code> directive before
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specifying realm definitions.
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main is com.werken.projectz.Server from app
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<subsection name="Realm Definitions">
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At least one <code>classworlds</code> realm must be defined
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within the configuration file. The syntax for starting a
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realm definition is <code>[realm.name]</code>. All lines
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following the realm header are considered directives for
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that realm. The realm definition continues either until
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another realm is defined or until the end of the file is
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Within a realm definition, two directives are available:
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<code>load</code> and <code>import</code>.
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directive specifies a class source to be used for loading
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classes in the realm. Any loaded source that ends with
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the <code>/</code> character is considered a directory
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hierarchy of classes and resources and all others are
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considered to be JAR files. System properties may be
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referred to using <code>${propname}</code> notation.
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The <code>load</code> directive is equivelent to the
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<code>addConstituent(..)</code> method of <code>ClassRealm</code>.
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load ${app.home}/lib/myapp.jar
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load ${app.home}/lib/xerces.jar
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The <code>import</code> directive specifies that certain
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packages should be imported and loaded by way of another
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realm. The <code>import</code> directive is equivelent
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to the <code>importFrom(..)</code> method of
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<code>ClassRealm</code>.
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import com.werken.projectz.Foo from [app]
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<subsection name="Entry point methods">
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<code>classworlds</code> can be used to invoke any existing
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application's <code>main()</code> method. Using the standard
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entry point does not allow for gaining access to the
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<code>ClassWorld</code> of the application, but not all
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applications will need it at run-time.
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For those applications that do require the <code>ClassWorld</code>
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instance, an alternative entry-point method signature can be
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provide. Simply add a <code>ClassWorld</code> parameter to
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the standard <code>main</code> parameter list.
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public static void main(String[] args,
added
removed
xdocs/launchusage.xml
