Ant task to update the AIR application version number

/**
 * Copyright (C) 2010, Sandeep Gupta
 * http://www.sangupta.com
 * 
 * The file is licensed under the 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 com.sangupta.ant.tasks;
 
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;
 
import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Task;
 
/**
* A simple ANT task that takes in an Adobe AIR application's application descriptor
* XML file and replaces the <version> string with the given build number. The
* task comes handy when used in a continuous integration process. The task has been
* tested with AIR SDK version 1.0 to 2.0. Your mileage may vary.
* 
* <b>Note: The application descriptor file must be write-enabled before invoking the task.</b>
* 
* @author Sandeep Gupta <a href="mailto:[email protected]">[email]</a>
* @version 1.0
* @since 23 Oct 2010
*/
public class AIRVersionTask extends Task {
  
 /**
 * The location of the application descriptor XML file.
 */
 private String appDescriptor = null;
  
 /**
 * The build number to replace the version with.
 */
 private String buildNumber = null;
  
 /**
 * Constant represnting the platform dependent new-line character.
 */
 private static String newline = System.getProperty("line.separator");
  
 /**
 * Here goes the task execution code, pretty self-explanatory.
 */
 public void execute() throws BuildException {
  // check for build number
  if(this.buildNumber == null || "".equals(this.buildNumber.trim())) {
   throw new BuildException("Build number cannot be empty.");
  }
   
  // check the file has to be an XML file
  if(!(this.appDescriptor != null && this.appDescriptor.toLowerCase().endsWith(".xml"))) {
   throw new BuildException("The application descriptor must be an XML file.");
  }
   
  // check if the file is actually present
  File xml = new File(this.appDescriptor);
  if(!xml.exists()) {
   throw new BuildException("The provided application descriptor file does not exist.");
  }
   
  // read the file and modify the build number
  StringBuilder builder = new StringBuilder();
  BufferedReader reader = null;
  Writer output = null;
   
  try {
   reader =  new BufferedReader(new FileReader(xml));
   String line = null;
   while((line = reader.readLine()) != null) {
    String l = line.trim();
    if(l.startsWith("<version>") && l.endsWith("</version>")) {
     int index = line.indexOf(l);
     line = line.substring(0, index) + "<version>" + this.buildNumber + "</version>";
      
    }
    builder.append(line);
    builder.append(newline);
   }
 
   // gracefully close the reader
   reader.close();
 
   // now we have the contents in string builder
   // just replace the file in
   output = new BufferedWriter(new FileWriter(xml));
   output.write(builder.toString());
   output.close();
    
   // all done
  } catch(IOException e) {
   throw new BuildException("Unable to set version string.", e);
  } finally {
   if(reader != null) {
    try {
     reader.close();
    } catch(Exception ex) {
     // do nothing
    }
   }
    
   if(output != null) {
    try {
     output.close();
    } catch(Exception ex) {
     // do nothing
    }
   }
  }
 }
  
 // Usual accessor's follow
 
 public String getAppDescriptor() {
  return appDescriptor;
 }
 
 public void setAppDescriptor(String appDescriptor) {
  this.appDescriptor = appDescriptor;
 }
 
 public String getBuildNumber() {
  return buildNumber;
 }
 
 public void setBuildNumber(String buildNumber) {
  this.buildNumber = buildNumber;
 }
 
}