Ant example source code file (BuildNumber.java)

This example Ant source code file (BuildNumber.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

buildexception, buildexception, default_filename, default_property_name, file, fileinputstream, fileoutputstream, io, ioexception, ioexception, properties, properties, string, string, unable, util

The BuildNumber.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 java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Properties;
import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Task;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.util.FileUtils;

/**
 * Read, increment, and write a build number in a file
 * It will first
 * attempt to read a build number from a file, then set the property
 * "build.number" to the value that was read in (or 0 if no such value). Then
 * it will increment the build number by one and write it back out into the
 * file.
 *
 * @since Ant 1.5
 * @ant.task name="buildnumber"
 */
public class BuildNumber
     extends Task {
    /**
     * The name of the property in which the build number is stored.
     */
    private static final String DEFAULT_PROPERTY_NAME = "build.number";

    /** The default filename to use if no file specified.  */
    private static final String DEFAULT_FILENAME = DEFAULT_PROPERTY_NAME;

    private static final FileUtils FILE_UTILS = FileUtils.getFileUtils();

    /** The File in which the build number is stored.  */
    private File myFile;


    /**
     * The file in which the build number is stored. Defaults to
     * "build.number" if not specified.
     *
     * @param file the file in which build number is stored.
     */
    public void setFile(final File file) {
        myFile = file;
    }


    /**
     * Run task.
     *
     * @exception BuildException if an error occurs
     */
    public void execute()
         throws BuildException {
        File savedFile = myFile; // may be altered in validate

        validate();

        final Properties properties = loadProperties();
        final int buildNumber = getBuildNumber(properties);

        properties.put(DEFAULT_PROPERTY_NAME,
            String.valueOf(buildNumber + 1));

        // Write the properties file back out
        FileOutputStream output = null;

        try {
            output = new FileOutputStream(myFile);

            final String header = "Build Number for ANT. Do not edit!";

            properties.store(output, header);
        } catch (final IOException ioe) {
            final String message = "Error while writing " + myFile;

            throw new BuildException(message, ioe);
        } finally {
            if (null != output) {
                try {
                    output.close();
                } catch (final IOException ioe) {
                    log("error closing output stream " + ioe, Project.MSG_ERR);
                }
            }
            myFile = savedFile;
        }

        //Finally set the property
        getProject().setNewProperty(DEFAULT_PROPERTY_NAME,
            String.valueOf(buildNumber));
    }


    /**
     * Utility method to retrieve build number from properties object.
     *
     * @param properties the properties to retrieve build number from
     * @return the build number or if no number in properties object
     * @throws BuildException if build.number property is not an integer
     */
    private int getBuildNumber(final Properties properties)
         throws BuildException {
        final String buildNumber =
            properties.getProperty(DEFAULT_PROPERTY_NAME, "0").trim();

        // Try parsing the line into an integer.
        try {
            return Integer.parseInt(buildNumber);
        } catch (final NumberFormatException nfe) {
            final String message =
                myFile + " contains a non integer build number: " + buildNumber;
            throw new BuildException(message, nfe);
        }
    }


    /**
     * Utility method to load properties from file.
     *
     * @return the loaded properties
     * @throws BuildException
     */
    private Properties loadProperties()
         throws BuildException {
        FileInputStream input = null;

        try {
            final Properties properties = new Properties();

            input = new FileInputStream(myFile);
            properties.load(input);
            return properties;
        } catch (final IOException ioe) {
            throw new BuildException(ioe);
        } finally {
            if (null != input) {
                try {
                    input.close();
                } catch (final IOException ioe) {
                    log("error closing input stream " + ioe, Project.MSG_ERR);
                }
            }
        }
    }


    /**
     * Validate that the task parameters are valid.
     *
     * @throws BuildException if parameters are invalid
     */
    private void validate()
         throws BuildException {
        if (null == myFile) {
            myFile = FILE_UTILS.resolveFile(getProject().getBaseDir(), DEFAULT_FILENAME);
        }

        if (!myFile.exists()) {
            try {
                FILE_UTILS.createNewFile(myFile);
            } catch (final IOException ioe) {
                final String message =
                    myFile + " doesn't exist and new file can't be created.";
                throw new BuildException(message, ioe);
            }
        }

        if (!myFile.canRead()) {
            final String message = "Unable to read from " + myFile + ".";
            throw new BuildException(message);
        }

        if (!myFile.canWrite()) {
            final String message = "Unable to write to " + myFile + ".";
            throw new BuildException(message);
        }
    }
}