ConsoleStreamAppender.java

/*
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 2 of the License, or (at your option) any later
 * version. You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

package org.aitools.programd.interfaces;

import java.io.OutputStream;

import org.aitools.programd.interfaces.shell.Shell;
import org.apache.log4j.Layout;
import org.apache.log4j.Level;
import org.apache.log4j.WriterAppender;
import org.apache.log4j.spi.LoggingEvent;
import org.apache.log4j.spi.ThrowableInformation;

/**
 * A <code>ConsoleStreamAppender</code> publishes any record it's passed to the given <code>stream</code>.
 * 
 * @author <a href="mailto:noel@aitools.org">Noel Bush</a>
 */
public class ConsoleStreamAppender extends WriterAppender {

  /** A Shell to watch. */
  private Shell shell;

  /** Whether to print stack traces for exceptions. */
  private boolean printStackTraces = false;

  /**
   * Creates a new ConsoleStreamAppender.
   */
  public ConsoleStreamAppender() {
    super();
    this.setImmediateFlush(true);
    this.setThreshold(Level.ALL);
  }

  /**
   * Publishes the given record, also to the shell if one is attached.
   * 
   * @param event
   */
  @Override
  public synchronized void doAppend(LoggingEvent event) {
    super.doAppend(event);
    if (this.shell != null) {
      this.shell.gotLine();
    }
  }

  /**
   * @return whether the writer has been set
   */
  public boolean isWriterSet() {
    return this.qw != null;
  }

  /**
   * Specifies whether or not to print stack traces for "caught" exceptions (for uncaught exceptions, see
   * {@link org.aitools.programd.CoreSettings}).
   * 
   * @param value whether or not to print stack traces for "caught" exceptions
   */
  public void setPrintStackTraces(boolean value) {
    this.printStackTraces = value;
  }

  /**
   * @param stream
   */
  public synchronized void setWriter(OutputStream stream) {
    super.setWriter(this.createWriter(stream));
  }

  /**
   * Overrides this method of the parent class so that it will not print stack traces if it isn't supposed to.
   * 
   * @see org.apache.log4j.WriterAppender#subAppend(org.apache.log4j.spi.LoggingEvent)
   */
  @Override
  protected void subAppend(LoggingEvent event) {
    this.qw.write(this.layout.format(event));

    // This if statement is the only addition.
    if (this.printStackTraces) {
      if (this.layout.ignoresThrowable()) {
        String[] s = event.getThrowableStrRep();
        if (s != null) {
          int len = s.length;
          for (int i = 0; i < len; i++) {
            this.qw.write(s[i]);
            this.qw.write(Layout.LINE_SEP);
          }
        }
      }
    }
    else {
      ThrowableInformation ti = event.getThrowableInformation();
      if (ti != null) {
        Throwable t = ti.getThrowable();
        if (t != null) {
          String message = t.getMessage();
          if (message != null) {
            this.qw.write(event.getThrowableInformation().getThrowable().getMessage());
            this.qw.write(Layout.LINE_SEP);
          }
        }
      }
    }

    if (this.immediateFlush) {
      this.qw.flush();
    }
  }

  /**
   * Assigns the given Shell to this handler, to watch it.
   * 
   * @param shellToWatch
   */
  public void watch(Shell shellToWatch) {
    this.shell = shellToWatch;
  }
}