projecthelper.java

Use the links below to download a source distribution of Ant from one of our mirrors. It is good pra

/*
 *  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;

import java.io.BufferedReader;
import java.io.File;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Hashtable;
import java.util.Locale;
import java.util.Vector;

import org.xml.sax.AttributeList;

import org.apache.tools.ant.helper.ProjectHelper2;
import org.apache.tools.ant.util.LoaderUtils;

/**
 * Configures a Project (complete with Targets and Tasks) based on
 * a XML build file. It'll rely on a plugin to do the actual processing
 * of the xml file.
 *
 * This class also provide static wrappers for common introspection.
 *
 * All helper plugins must provide backward compatibility with the
 * original ant patterns, unless a different behavior is explicitly
 * specified. For example, if namespace is used on the <project> tag
 * the helper can expect the entire build file to be namespace-enabled.
 * Namespaces or helper-specific tags can provide meta-information to
 * the helper, allowing it to use new ( or different policies ).
 *
 * However, if no namespace is used the behavior should be exactly
 * identical with the default helper.
 *
 */
public class ProjectHelper {
    /** The URI for ant name space */
    public static final String ANT_CORE_URI    = "antlib:org.apache.tools.ant";

    /** The URI for antlib current definitions */
    public static final String ANT_CURRENT_URI      = "ant:current";

    /** The URI for defined types/tasks - the format is antlib:<package> */
    public static final String ANTLIB_URI     = "antlib:";

    /** Polymorphic attribute  */
    public static final String ANT_TYPE = "ant-type";

    /**
     * Name of JVM system property which provides the name of the
     * ProjectHelper class to use.
     */
    public static final String HELPER_PROPERTY = MagicNames.PROJECT_HELPER_CLASS;

    /**
     * The service identifier in jars which provide Project Helper
     * implementations.
     */
    public static final String SERVICE_ID = MagicNames.PROJECT_HELPER_SERVICE;

    /**
     * name of project helper reference that we add to a project
     */
    public static final String PROJECTHELPER_REFERENCE = MagicNames.REFID_PROJECT_HELPER;

    /**
     * Configures the project with the contents of the specified XML file.
     *
     * @param project The project to configure. Must not be <code>null</code>.
     * @param buildFile An XML file giving the project's configuration.
     *                  Must not be <code>null</code>.
     *
     * @exception BuildException if the configuration is invalid or cannot be read
     */
    public static void configureProject(Project project, File buildFile) throws BuildException {
        ProjectHelper helper = ProjectHelper.getProjectHelper();
        project.addReference(PROJECTHELPER_REFERENCE, helper);
        helper.parse(project, buildFile);
    }

    /** Default constructor */
    public ProjectHelper() {
    }

    // -------------------- Common properties  --------------------
    // The following properties are required by import ( and other tasks
    // that read build files using ProjectHelper ).

    // A project helper may process multiple files. We'll keep track
    // of them - to avoid loops and to allow caching. The caching will
    // probably accelerate things like <antCall>.
    // The key is the absolute file, the value is a processed tree.
    // Since the tree is composed of UE and RC - it can be reused !
    // protected Hashtable processedFiles=new Hashtable();

    private Vector importStack = new Vector();

    // Temporary - until we figure a better API
    /** EXPERIMENTAL WILL_CHANGE
     *
     */
//    public Hashtable getProcessedFiles() {
//        return processedFiles;
//    }

    /** EXPERIMENTAL WILL_CHANGE
     *  Import stack.
     *  Used to keep track of imported files. Error reporting should
     *  display the import path.
     *
     * @return the stack of import source objects.
     */
    public Vector getImportStack() {
        return importStack;
    }

    // --------------------  Parse method  --------------------
    /**
     * Parses the project file, configuring the project as it goes.
     *
     * @param project The project for the resulting ProjectHelper to configure.
     *                Must not be <code>null</code>.
     * @param source The source for XML configuration. A helper must support
     *               at least File, for backward compatibility. Helpers may
     *               support URL, InputStream, etc or specialized types.
     *
     * @since Ant1.5
     * @exception BuildException if the configuration is invalid or cannot
     *                           be read
     */
    public void parse(Project project, Object source) throws BuildException {
        throw new BuildException("ProjectHelper.parse() must be implemented "
            + "in a helper plugin " + this.getClass().getName());
    }

    /**
     * Discovers a project helper instance. Uses the same patterns
     * as JAXP, commons-logging, etc: a system property, a JDK1.3
     * service discovery, default.
     *
     * @return a ProjectHelper, either a custom implementation
     * if one is available and configured, or the default implementation
     * otherwise.
     *
     * @exception BuildException if a specified helper class cannot
     * be loaded/instantiated.
     */
    public static ProjectHelper getProjectHelper() throws BuildException {
        // Identify the class loader we will be using. Ant may be
        // in a webapp or embedded in a different app
        ProjectHelper helper = null;

        // First, try the system property
        String helperClass = System.getProperty(HELPER_PROPERTY);
        try {
            if (helperClass != null) {
                helper = newHelper(helperClass);
            }
        } catch (SecurityException e) {
            System.out.println("Unable to load ProjectHelper class \""
                + helperClass + " specified in system property "
                + HELPER_PROPERTY);
        }

        // A JDK1.3 'service' ( like in JAXP ). That will plug a helper
        // automatically if in CLASSPATH, with the right META-INF/services.
        if (helper == null) {
            try {
                ClassLoader classLoader = LoaderUtils.getContextClassLoader();
                InputStream is = null;
                if (classLoader != null) {
                    is = classLoader.getResourceAsStream(SERVICE_ID);
                }
                if (is == null) {
                    is = ClassLoader.getSystemResourceAsStream(SERVICE_ID);
                }
                if (is != null) {
                    // This code is needed by EBCDIC and other strange systems.
                    // It's a fix for bugs reported in xerces
                    InputStreamReader isr;
                    try {
                        isr = new InputStreamReader(is, "UTF-8");
                    } catch (java.io.UnsupportedEncodingException e) {
                        isr = new InputStreamReader(is);
                    }
                    BufferedReader rd = new BufferedReader(isr);

                    String helperClassName = rd.readLine();
                    rd.close();

                    if (helperClassName != null && !"".equals(helperClassName)) {
                        helper = newHelper(helperClassName);
                    }
                }
            } catch (Exception ex) {
                System.out.println("Unable to load ProjectHelper from service " + SERVICE_ID);
            }
        }
        return helper == null ? new ProjectHelper2() : helper;
    }

    /**
     * Creates a new helper instance from the name of the class.
     * It'll first try the thread class loader, then Class.forName()
     * will load from the same loader that loaded this class.
     *
     * @param helperClass The name of the class to create an instance
     *                    of. Must not be <code>null</code>.
     *
     * @return a new instance of the specified class.
     *
     * @exception BuildException if the class cannot be found or
     * cannot be appropriate instantiated.
     */
    private static ProjectHelper newHelper(String helperClass)
        throws BuildException {
        ClassLoader classLoader = LoaderUtils.getContextClassLoader();
        try {
            Class clazz = null;
            if (classLoader != null) {
                try {
                    clazz = classLoader.loadClass(helperClass);
                } catch (ClassNotFoundException ex) {
                    // try next method
                }
            }
            if (clazz == null) {
                clazz = Class.forName(helperClass);
            }
            return ((ProjectHelper) clazz.newInstance());
        } catch (Exception e) {
            throw new BuildException(e);
        }
    }

    /**
     * JDK1.1 compatible access to the context class loader. Cut & paste from JAXP.
     *
     * @deprecated since 1.6.x.
     *             Use LoaderUtils.getContextClassLoader()
     *