Ant example source code file (WhichResource.java)

This example Ant source code file (WhichResource.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

antclassloader, buildexception, buildexception, net, network, no, one, one, only, path, path, searching, string, string, task, whichresource

The WhichResource.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 org.apache.tools.ant.types.Path;
import org.apache.tools.ant.Task;
import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.AntClassLoader;

import java.net.URL;

/**
 * Find a class or resource on the supplied classpath, or the
 * system classpath if none is supplied. The named property is set if
 * the item can be found. For example
 * <pre>
 * <whichresource resource="/log4j.properties"
 *   property="log4j.url" >
 * </pre>
 * @since Ant 1.6
 * @ant.attribute.group name="oneof" description="Exactly one of these two"
 */
public class WhichResource extends Task {
    /**
     * our classpath
     */
    private Path classpath;

    /**
     * class to look for
     */
    private String classname;

    /**
     * resource to look for
     */
    private String resource;

    /**
     * property to set
     */
    private String property;


    /**
     * Set the classpath to be used for this compilation.
     * @param cp the classpath to be used.
     */
    public void setClasspath(Path cp) {
        if (classpath == null) {
            classpath = cp;
        } else {
            classpath.append(cp);
        }
    }

    /**
     * Adds a path to the classpath.
     * @return a classpath to be configured.
     */
    public Path createClasspath() {
        if (classpath == null) {
            classpath = new Path(getProject());
        }
        return classpath.createPath();
    }


    /**
     * validate
     */
    private void validate() {
        int setcount = 0;
        if (classname != null) {
            setcount++;
        }
        if (resource != null) {
            setcount++;
        }


        if (setcount == 0) {
            throw new BuildException(
                    "One of classname or resource must be specified");
        }
        if (setcount > 1) {
            throw new BuildException(
                    "Only one of classname or resource can be specified");
        }
        if (property == null) {
            throw new BuildException("No property defined");
        }
    }

    /**
     * execute it
     * @throws BuildException on error
     */
    public void execute() throws BuildException {
        validate();
        if (classpath != null) {
            getProject().log("using user supplied classpath: " + classpath,
                    Project.MSG_DEBUG);
            classpath = classpath.concatSystemClasspath("ignore");
        } else {
            classpath = new Path(getProject());
            classpath = classpath.concatSystemClasspath("only");
            getProject().log("using system classpath: " + classpath, Project.MSG_DEBUG);
        }
        AntClassLoader loader;
        loader = new AntClassLoader(getProject().getCoreLoader(),
                    getProject(),
                    classpath, false);
        String loc = null;
        if (classname != null) {
            //convert a class name into a resource
            resource = classname.replace('.', '/') + ".class";
        }

        if (resource == null) {
            throw new BuildException("One of class or resource is required");
        }

        if (resource.startsWith("/")) {
            resource = resource.substring(1);
        }

        log("Searching for " + resource, Project.MSG_VERBOSE);
        URL url;
        url = loader.getResource(resource);
        if (url != null) {
            //set the property
            loc = url.toExternalForm();
            getProject().setNewProperty(property, loc);
        }
    }

    /**
     * name the resource to look for
     * @param resource the name of the resource to look for.
     * @ant.attribute group="oneof"
     */
    public void setResource(String resource) {
        this.resource = resource;
    }

    /**
     * name the class to look for
     * @param classname the name of the class to look for.
     * @ant.attribute group="oneof"
     */
    public void setClass(String classname) {
        this.classname = classname;
    }

    /**
     * the property to fill with the URL of the resource or class
     * @param property the property to be set.
     * @ant.attribute group="required"
     */
    public void setProperty(String property) {
        this.property = property;
    }

}