Ant example source code file (Antlib.java)

This example Ant source code file (Antlib.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Ant tags/keywords

antlib, antlib, antlibdefinition, antlibdefinition, buildexception, buildexception, classloader, io, net, network, object, projecthelper2, string, string, tag, unexpected, unknownelement, util

The Antlib.java source code

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */

package org.apache.tools.ant.taskdefs;

import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.apache.tools.ant.TaskContainer;
import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.ComponentHelper;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.Task;
import org.apache.tools.ant.helper.ProjectHelper2;
import org.apache.tools.ant.UnknownElement;


/**
 * Antlib task. It does not
 * occur in an ant build file. It is the root element
 * an antlib xml file.
 *
 * @since Ant 1.6
 */
public class Antlib extends Task implements TaskContainer {
    //
    // Static
    //

    /** The name of this task */
    public static final String TAG = "antlib";

    /**
     * Static method to read an ant lib definition from
     * a url.
     *
     * @param project   the current project
     * @param antlibUrl the url to read the definitions from
     * @param uri       the uri that the antlib is to be placed in
     * @return   the ant lib task
     */
    public static Antlib createAntlib(Project project, URL antlibUrl,
                                      String uri) {
        // Check if we can contact the URL
        try {
            antlibUrl.openConnection().connect();
        } catch (IOException ex) {
            throw new BuildException(
                "Unable to find " + antlibUrl, ex);
        }
        ComponentHelper helper =
            ComponentHelper.getComponentHelper(project);
        helper.enterAntLib(uri);
        try {
            // Should be safe to parse
            ProjectHelper2 parser = new ProjectHelper2();
            UnknownElement ue =
                parser.parseUnknownElement(project, antlibUrl);
            // Check name is "antlib"
            if (!(ue.getTag().equals(TAG))) {
                throw new BuildException(
                    "Unexpected tag " + ue.getTag() + " expecting "
                    + TAG, ue.getLocation());
            }
            Antlib antlib = new Antlib();
            antlib.setProject(project);
            antlib.setLocation(ue.getLocation());
            antlib.setTaskName("antlib");
            antlib.init();
            ue.configure(antlib);
            return antlib;
        } finally {
            helper.exitAntLib();
        }
    }


    //
    // Instance
    //
    private ClassLoader classLoader;
    private String      uri = "";
    private List  tasks = new ArrayList();

    /**
     * Set the class loader for this antlib.
     * This class loader is used for any tasks that
     * derive from Definer.
     *
     * @param classLoader the class loader
     */
    protected void setClassLoader(ClassLoader classLoader) {
        this.classLoader = classLoader;
    }

    /**
     * Set the URI for this antlib.
     * @param uri the namespace uri
     */
    protected void  setURI(String uri) {
        this.uri = uri;
    }

    private ClassLoader getClassLoader() {
        if (classLoader == null) {
            classLoader = Antlib.class.getClassLoader();
        }
        return classLoader;
    }

    /**
     * add a task to the list of tasks
     *
     * @param nestedTask Nested task to execute in antlib
     */
    public void addTask(Task nestedTask) {
        tasks.add(nestedTask);
    }

    /**
     * Execute the nested tasks, setting the classloader for
     * any tasks that derive from Definer.
     */
    public void execute() {
        for (Iterator i = tasks.iterator(); i.hasNext();) {
            UnknownElement ue = (UnknownElement) i.next();
            setLocation(ue.getLocation());
            ue.maybeConfigure();
            Object configuredObject = ue.getRealThing();
            if (configuredObject == null) {
                continue;
            }
            if (!(configuredObject instanceof AntlibDefinition)) {
                throw new BuildException(
                    "Invalid task in antlib " + ue.getTag()
                    + " " + configuredObject.getClass() + " does not "
                    + "extend org.apache.tools.ant.taskdefs.AntlibDefinition");
            }
            AntlibDefinition def = (AntlibDefinition) configuredObject;
            def.setURI(uri);
            def.setAntlibClassLoader(getClassLoader());
            def.init();
            def.execute();
        }
    }

}