increment task

[Stuart Barlow]

When undertaking nightly builds we have found the need for a build number.
And we also wanted this to live in a java propery file so that ANT could 
make
use of it during the build.

Below is a simple task that increments a numeric property in a java property
file.
Thanks,
Stuart.
/**
* Allows a particular property in a Java property file to be incremented by
* one. Useful for build numbers that increase by one with each build.
*
* @author Stuart Barlow <a 
href="mailto:[EMAIL PROTECTED]">[EMAIL PROTECTED]</a>
* @author <a href="mailto:[EMAIL PROTECTED]">Stuart Barlow</a>
*/
public class IncrementProperty extends Task {

  private File src = null;
  private String property = null;
  /**
   * Do the execution.
   */
  public void execute() throws BuildException {
      if (property == null) {
          throw new BuildException("replace token must not be null", 
location);
      }

      log("Incrementing " + property + " in file: " + src);
      if (src != null) {
          processFile(src);
      }
  }
  /**
   * Perform the increment of a property value on the given file.
   *
   * The replacement is performed on a temporary file which then 
replaces the original file.
   *
   * @param src the source file
   */
  private void processFile(File src) throws BuildException {
      if (!src.exists()) {
          throw new BuildException("Increment: source file " + 
src.getPath() + " doesn't exist", location);
      }

      File temp = new File(src.getPath() + ".temp");
      if (temp.exists()) {
          throw new BuildException("Replace: temporary file " + 
temp.getPath() + " already exists", location);
      }

      Properties propFile = new Properties();
      try {
          // load in the property file
          FileInputStream in = new FileInputStream(src);
          propFile.load(in);
          in.close();
      } catch (IOException ioe) {
          ioe.printStackTrace();
          throw new BuildException(ioe, location);
      }
      try {
          // get the old value and set the new one.
          String strValue = propFile.getProperty(property);
          long longValue = Long.parseLong(strValue);
          longValue++;
          Long newIncrementedValue = new Long(longValue);
          propFile.setProperty(property, newIncrementedValue.toString());
          // write out the property file
          FileOutputStream out = new FileOutputStream(src);
          propFile.store(out, "Ant - written out by the task: 
IncrementProperty");
          out.close();
      } catch (Exception ex) {
          ex.printStackTrace();
          throw new BuildException(ex, location);
      }
  }

  /**
   * Set the source file.
   */
  public void setFile(File file) {
      this.src = file;
  }
  /**
   * Set the string token to replace.
   */
  public void setProperty(String property) {
      this.property = property;
  }
}