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Ant example source code file (ScriptRunnerCreator.java)

This example Ant source code file (ScriptRunnerCreator.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

bsf_manager, bsf_runner, buildexception, buildexception, classloader, javax_manager, javax_manager, oatau, scriptrunnerbase, scriptrunnerbase, string, string, unable, util_opt

The ScriptRunnerCreator.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.util;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Project;

/**
 * This is a helper class used by ScriptRunnerHelper to
 * create a ScriptRunner based on a classloader and
 * on a language.
 */
public class ScriptRunnerCreator {
    private static final String AUTO = "auto";
    private static final String OATAU = "org.apache.tools.ant.util";
    private static final String UTIL_OPT = OATAU + ".optional";

    private static final String BSF = "bsf";
    private static final String BSF_PACK = "org.apache.bsf";
    private static final String BSF_MANAGER = BSF_PACK + ".BSFManager";
    private static final String BSF_RUNNER = UTIL_OPT + ".ScriptRunner";

    private static final String JAVAX = "javax";
    private static final String JAVAX_MANAGER = "javax.script.ScriptEngineManager";
    private static final String JAVAX_RUNNER = UTIL_OPT + ".JavaxScriptRunner";

    private Project     project;
    private String      manager;
    private String      language;
    private ClassLoader scriptLoader = null;

    /**
     * Constructor for creator.
     * @param project the current project.
     */
    public ScriptRunnerCreator(Project project) {
        this.project = project;
    }

    /**
     * Create a ScriptRunner.
     * @param manager      the script manager ("auto" | "bsf" | "javax")
     * @param language     the language.
     * @param classLoader  the classloader to use
     * @return the created script runner.
     * @throws BuildException if unable to create the ScriptRunner.
     */
    public ScriptRunnerBase createRunner(
        String manager, String language, ClassLoader classLoader) {
        this.manager      = manager;
        this.language     = language;
        this.scriptLoader = classLoader;

        if (language == null) {
            throw new BuildException("script language must be specified");
        }
        if (!manager.equals(AUTO) && !manager.equals(JAVAX) && !manager.equals(BSF)) {
                throw new BuildException(
                    "Unsupported language prefix " + manager);
        }

        // Check for bsf first then javax
        // This version does not check if the scriptManager
        // supports the language.

        ScriptRunnerBase ret = null;
        ret = createRunner(BSF, BSF_MANAGER, BSF_RUNNER);
        if (ret == null) {
            ret = createRunner(JAVAX, JAVAX_MANAGER, JAVAX_RUNNER);
        }
        if (ret != null) {
            return ret;
        }
        if (JAVAX.equals(manager)) {
            throw new BuildException(
                "Unable to load the script engine manager "
                + "(" + JAVAX_MANAGER + ")");
        } else if (BSF.equals(manager)) {
            throw new BuildException(
                "Unable to load the BSF script engine manager "
                + "(" + BSF_MANAGER + ")");
        } else {
            throw new BuildException(
                "Unable to load a script engine manager "
                + "(" + BSF_MANAGER + " or " + JAVAX_MANAGER + ")");
        }
    }

    /**
     * Create a script runner if the scriptManager matches the passed
     * in manager.
     * This checks if the script manager exists in the scriptLoader
     * classloader and if so it creates and returns the script runner.
     * @param checkManager check if the manager matchs this value.
     * @param mangagerClass the name of the script manager class.
     * @param runnerClass   the name of ant's script runner for this manager.
     * @return the script runner class.
     * @throws BuildException if there is a problem creating the runner class.
     */
    private ScriptRunnerBase createRunner(
        String checkManager, String managerClass, String runnerClass) {
        ScriptRunnerBase runner = null;
        if (!manager.equals(AUTO) && !manager.equals(checkManager)) {
            return null;
        }
        if (scriptLoader.getResource(
                LoaderUtils.classNameToResource(managerClass)) == null) {
            return null;
        }
        try {
            runner = (ScriptRunnerBase) Class.forName(
                runnerClass, true, scriptLoader).newInstance();
            runner.setProject(project);
        } catch (Exception ex) {
            ReflectUtil.throwBuildException(ex);
            // NotReached
        }

        runner.setLanguage(language);
        runner.setScriptClassLoader(scriptLoader);
        return runner;
    }
}

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