Ant example source code file (JarLibResolveTask.java)

This example Ant source code file (JarLibResolveTask.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

arraylist, buildexception, buildexception, can, extension, extension, extensionresolver, file, file, io, jar, locationresolver, property, resolver, string, string, util

The JarLibResolveTask.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.optional.extension;

import java.io.File;
import java.util.ArrayList;
import java.util.jar.Manifest;
import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.Task;
import org.apache.tools.ant.taskdefs.optional.extension.resolvers.AntResolver;
import org.apache.tools.ant.taskdefs.optional.extension.resolvers.LocationResolver;
import org.apache.tools.ant.taskdefs.optional.extension.resolvers.URLResolver;

/**
 * Tries to locate a JAR to satisfy an extension and place
 * location of JAR into property.
 *
 * @ant.task name="jarlib-resolve"
 */
public class JarLibResolveTask extends Task {
    /**
     * The name of the property in which the location of
     * library is stored.
     */
    private String propertyName;

    /**
     * The extension that is required.
     */
    private Extension requiredExtension;

    /**
     * The set of resolvers to use to attempt to locate library.
     */
    private final ArrayList resolvers = new ArrayList();

    /**
     * Flag to indicate that you should check that
     * the librarys resolved actually contain
     * extension and if they don't then raise
     * an exception.
     */
    private boolean checkExtension = true;

    /**
     * Flag indicating whether or not you should
     * throw a BuildException if you cannot resolve
     * library.
     */
    private boolean failOnError = true;

    /**
     * The name of the property in which the location of
     * library is stored.
     *
     * @param property The name of the property in which the location of
     *                 library is stored.
     */
    public void setProperty(final String property) {
        this.propertyName = property;
    }

    /**
     * Check nested libraries for extensions
     *
     * @param checkExtension if true, libraries returned by nested
     * resolvers should be checked to see if they supply extension.
     */
    public void setCheckExtension(final boolean checkExtension) {
        this.checkExtension = checkExtension;
    }

    /**
     * Set whether to fail if error.
     *
     * @param failOnError if true, failure to locate library should fail build.
     */
    public void setFailOnError(final boolean failOnError) {
        this.failOnError = failOnError;
    }

    /**
     * Adds location resolver to look for a library in a location
     * relative to project directory.
     *
     * @param loc the resolver location to search.
     */
    public void addConfiguredLocation(final LocationResolver loc) {
        resolvers.add(loc);
    }

    /**
     * Adds a URL resolver to download a library from a URL
     * to a local file.
     *
     * @param url the URL resolver from which to download the library
     */
    public void addConfiguredUrl(final URLResolver url) {
        resolvers.add(url);
    }

    /**
     * Adds Ant resolver to run an Ant build file to generate a library.
     *
     * @param ant the AntResolver to generate the library.
     */
    public void addConfiguredAnt(final AntResolver ant) {
        resolvers.add(ant);
    }

    /**
     * Set the Extension looking for.
     *
     * @param extension Set the Extension looking for.
     */
    public void addConfiguredExtension(final ExtensionAdapter extension) {
        if (null != requiredExtension) {
            final String message = "Can not specify extension to "
                + "resolve multiple times.";
            throw new BuildException(message);
        }
        requiredExtension = extension.toExtension();
    }

    /**
     * Execute the task.
     *
     * @throws BuildException if the task fails.
     */
    public void execute() throws BuildException {
        validate();

        getProject().log("Resolving extension: " + requiredExtension,
                          Project.MSG_VERBOSE);

        String candidate =
            getProject().getProperty(propertyName);

        if (null != candidate) {
            final String message = "Property Already set to: " + candidate;
            if (failOnError) {
                throw new BuildException(message);
            }
            getProject().log(message, Project.MSG_ERR);
            return;
        }

        final int size = resolvers.size();
        for (int i = 0; i < size; i++) {
            final ExtensionResolver resolver =
                (ExtensionResolver) resolvers.get(i);

            getProject().log("Searching for extension using Resolver:" + resolver,
                              Project.MSG_VERBOSE);

            try {
                final File file =
                    resolver.resolve(requiredExtension, getProject());
                try {
                    checkExtension(file);
                    return;
                } catch (final BuildException be) {
                    final String message = "File " + file + " returned by "
                        + "resolver failed to satisfy extension due to: "
                        + be.getMessage();
                    getProject().log(message, Project.MSG_WARN);
                }
            } catch (final BuildException be) {
                final String message = "Failed to resolve extension to file "
                    + "using resolver " + resolver + " due to: " + be;
                getProject().log(message, Project.MSG_WARN);
            }
        }

        missingExtension();
    }

    /**
     * Utility method that will throw a {@link BuildException}
     * if {@link #failOnError} is true else it just displays
     * a warning.
     */
    private void missingExtension() {
        final String message =
            "Unable to resolve extension to a file";
        if (failOnError) {
            throw new BuildException(message);
        }
        getProject().log(message, Project.MSG_ERR);
    }

    /**
     * Check if specified file satisfies extension.
     * If it does then set the relevent property
     * else throw a BuildException.
     *
     * @param file the candidate library
     * @throws BuildException if library does not satisfy extension
     */
    private void checkExtension(final File file) {
        if (!file.exists()) {
            final String message =
                "File " + file + " does not exist";
            throw new BuildException(message);
        }
        if (!file.isFile()) {
            final String message =
                "File " + file + " is not a file";
            throw new BuildException(message);
        }

        if (!checkExtension) {
            final String message = "Setting property to " + file
                + " without verifying library satisfies extension";
            getProject().log(message, Project.MSG_VERBOSE);
            setLibraryProperty(file);
        } else {
            getProject().log("Checking file " + file
                + " to see if it satisfies extension", Project.MSG_VERBOSE);
            final Manifest manifest =
                ExtensionUtil.getManifest(file);
            final Extension[] extensions =
                Extension.getAvailable(manifest);
            for (int i = 0; i < extensions.length; i++) {
                final Extension extension = extensions[ i ];
                if (extension.isCompatibleWith(requiredExtension)) {
                    setLibraryProperty(file);
                    return;
                }
            }

            getProject().log("File " + file + " skipped as it "
                + "does not satisfy extension", Project.MSG_VERBOSE);

            final String message =
                "File " + file + " does not satisfy extension";
            throw new BuildException(message);
        }
    }

    /**
     * Utility method to set the appropriate property
     * to indicate that specified file satisfies library
     * requirements.
     *
     * @param file the library
     */
    private void setLibraryProperty(final File file) {
        getProject().setNewProperty(propertyName,
                                     file.getAbsolutePath());
    }

    /**
     * Validate the tasks parameters.
     *
     * @throws BuildException if invalid parameters found
     */
    private void validate() throws BuildException {
        if (null == propertyName) {
            final String message = "Property attribute must be specified.";
            throw new BuildException(message);
        }

        if (null == requiredExtension) {
            final String message = "Extension element must be specified.";
            throw new BuildException(message);
        }
    }
}