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Ant example source code file (ScriptRunnerBase.java)

This example Ant source code file (ScriptRunnerBase.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

bufferedreader, buildexception, buildexception, classloader, classloader, filereader, hashmap, io, ioexception, map, object, object, project, string, string, util

The ScriptRunnerBase.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 java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;

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

import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;

/**
 * This is a common abstract base case for script runners.
 * These classes need to implement executeScript, evaluateScript
 * and supportsLanguage.
 * @since Ant 1.7.0
 */
public abstract class ScriptRunnerBase {
    /** Whether to keep the engine between calls to execute/eval */
    private boolean keepEngine = false;

    /** Script language */
    private String language;

    /** Script content */
    private String script = "";

    /** Project this runner is used in */
    private Project project;

    /** Classloader to be used when running the script. */
    private ClassLoader scriptLoader;

    /** Beans to be provided to the script */
    private Map beans = new HashMap();

    /**
     * Add a list of named objects to the list to be exported to the script
     *
     * @param dictionary a map of objects to be placed into the script context
     *        indexed by String names.
     */
    public void addBeans(Map dictionary) {
        for (Iterator i = dictionary.keySet().iterator(); i.hasNext();) {
            String key = (String) i.next();
            try {
                Object val = dictionary.get(key);
                addBean(key, val);
            } catch (BuildException ex) {
                // The key is in the dictionary but cannot be retrieved
                // This is usually due references that refer to tasks
                // that have not been taskdefed in the current run.
                // Ignore
            }
        }
    }

    /**
     * Add a single object into the script context.
     *
     * @param key the name in the context this object is to stored under.
     * @param bean the object to be stored in the script context.
     */
    public void addBean(String key, Object bean) {
        boolean isValid = key.length() > 0
            && Character.isJavaIdentifierStart(key.charAt(0));

        for (int i = 1; isValid && i < key.length(); i++) {
            isValid = Character.isJavaIdentifierPart(key.charAt(i));
        }

        if (isValid) {
            beans.put(key, bean);
        }
    }

    /**
     * Get the beans used for the script.
     * @return the map of beans.
     */
    protected Map getBeans() {
        return beans;
    }

    /**
     * Do the work.
     * @param execName the name that will be passed to BSF for this script
     *        execution.
     */
    public abstract void executeScript(String execName);

    /**
     * Evalulate the script.
     * @param execName the name that will be passed to BSF for this script
     *        execution.
     * @return the result of evalulating the script.
     */
    public abstract Object evaluateScript(String execName);

    /**
     * Check if a script engine can be created for
     * this language.
     * @return true if a script engine can be created, false
     *              otherwise.
     */
    public abstract boolean supportsLanguage();

    /**
     * Get the name of the manager prefix used for this
     * scriptrunner.
     * @return the prefix string.
     */
    public abstract String getManagerName();

    /**
     * Defines the language (required).
     * @param language the scripting language name for the script.
     */
    public void setLanguage(String language) {
        this.language = language;
    }

    /**
     * Get the script language
     * @return the script language
     */
    public String getLanguage() {
        return language;
    }

    /**
     * Set the script classloader.
     * @param classLoader the classloader to use.
     */
    public void setScriptClassLoader(ClassLoader classLoader) {
        this.scriptLoader = classLoader;
    }

    /**
     * Get the classloader used to load the script engine.
     * @return the classloader.
     */
    protected ClassLoader getScriptClassLoader() {
        return scriptLoader;
    }

    /**
     * Whether to keep the script engine between calls.
     * @param keepEngine if true, keep the engine.
     */
    public void setKeepEngine(boolean keepEngine) {
        this.keepEngine = keepEngine;
    }

    /**
     * Get the keep engine attribute.
     * @return the attribute.
     */
    public boolean getKeepEngine() {
        return keepEngine;
    }

    /**
     * Load the script from an external file; optional.
     * @param file the file containing the script source.
     */
    public void setSrc(File file) {
        if (!file.exists()) {
            throw new BuildException("file " + file.getPath() + " not found.");
        }
        BufferedReader in = null;
        try {
            in = new BufferedReader(new FileReader(file));
            script += FileUtils.readFully(in);
        } catch (IOException ex) {
            throw new BuildException(ex);
        } finally {
            FileUtils.close(in);
        }
    }

    /**
     * Set the script text.
     *
     * @param text a component of the script text to be added.
     */
    public void addText(String text) {
        this.script += text;
    }

    /**
     * Get the current script text content.
     * @return the script text.
     */
    public String getScript() {
        return script;
    }

    /**
     * Clear the current script text content.
     */
    public void clearScript() {
        this.script = "";
    }

    /**
     * Set the project for this runner.
     * @param project the project.
     */
    public void setProject(Project project) {
        this.project = project;
    }

    /**
     * Get the project for this runner.
     * @return the project.
     */
    public Project getProject() {
        return project;
    }

    /**
     * Bind the runner to a project component.
     * Properties, targets and references are all added as beans;
     * project is bound to project, and self to the component.
     * @param component to become <code>self
     */
    public void bindToComponent(ProjectComponent component) {
        project = component.getProject();
        addBeans(project.getProperties());
        addBeans(project.getUserProperties());
        addBeans(project.getTargets());
        addBeans(project.getReferences());
        addBean("project", project);
        addBean("self", component);
    }

    /**
     * Bind the runner to a project component.
     * The project and self are the only beans set.
     * @param component to become <code>self
     */
    public void bindToComponentMinimum(ProjectComponent component) {
        project = component.getProject();
        addBean("project", project);
        addBean("self", component);
    }

    /**
     * Check if the language attribute is set.
     * @throws BuildException if it is not.
     */
    protected void checkLanguage() {
        if (language == null) {
            throw new BuildException(
                "script language must be specified");
        }
    }

    /**
     * Replace the current context classloader with the
     * script context classloader.
     * @return the current context classloader.
     */
    protected ClassLoader replaceContextLoader() {
        ClassLoader origContextClassLoader =
            Thread.currentThread().getContextClassLoader();
        if (getScriptClassLoader() == null) {
            setScriptClassLoader(getClass().getClassLoader());
        }
        Thread.currentThread().setContextClassLoader(getScriptClassLoader());
        return origContextClassLoader;
    }

    /**
     * Restore the context loader with the original context classloader.
     *
     * script context loader.
     * @param origLoader the original context classloader.
     */
    protected void restoreContextLoader(ClassLoader origLoader) {
        Thread.currentThread().setContextClassLoader(
                 origLoader);
    }

}

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