/*
* Copyright 1999-2005 The Apache Software Foundation.
*
* Licensed 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.log4j.net;
import java.io.*;
import java.net.*;
import java.util.*;
import org.apache.log4j.Layout;
import org.apache.log4j.spi.LoggingEvent;
import org.apache.log4j.AppenderSkeleton;
import org.apache.log4j.helpers.LogLog;
/**
<p>The TelnetAppender is a log4j appender that specializes in
writing to a read-only socket. The output is provided in a
telnet-friendly way so that a log can be monitored over TCP/IP.
Clients using telnet connect to the socket and receive log data.
This is handy for remote monitoring, especially when monitoring a
servlet.
<p>Here is a list of the available configuration options:
<table border=1>
<tr>
<th>Name</th>
<th>Requirement</th>
<th>Description</th>
<th>Sample Value</th>
</tr>
<tr>
<td>Port</td>
<td>optional</td>
<td>This parameter determines the port to use for announcing log events. The default port is 23 (telnet).</td>
<td>5875</td>
</table>
@author <a HREF="mailto:jay@v-wave.com">Jay Funnell</a>
*/
public class TelnetAppender extends AppenderSkeleton {
private SocketHandler sh;
private int port = 23;
/**
This appender requires a layout to format the text to the
attached client(s). */
public boolean requiresLayout() {
return true;
}
/** all of the options have been set, create the socket handler and
wait for connections. */
public void activateOptions() {
try {
sh = new SocketHandler(port);
sh.start();
}
catch(Exception e) {
e.printStackTrace();
}
}
public
int getPort() {
return port;
}
public
void setPort(int port) {
this.port = port;
}
/** shuts down the appender. */
public void close() {
sh.finalize();
}
/** Handles a log event. For this appender, that means writing the
message to each connected client. */
protected void append(LoggingEvent event) {
sh.send(this.layout.format(event));
if(layout.ignoresThrowable()) {
String[] s = event.getThrowableStrRep();
if (s != null) {
int len = s.length;
for(int i = 0; i < len; i++) {
sh.send(s[i]);
sh.send(Layout.LINE_SEP);
}
}
}
}
//---------------------------------------------------------- SocketHandler:
/** The SocketHandler class is used to accept connections from
clients. It is threaded so that clients can connect/disconnect
asynchronously. */
protected class SocketHandler extends Thread {
private boolean done = false;
private Vector writers = new Vector();
private Vector connections = new Vector();
private ServerSocket serverSocket;
private int MAX_CONNECTIONS = 20;
/** make sure we close all network connections when this handler is destroyed. */
public void finalize() {
for(Enumeration e = connections.elements();e.hasMoreElements();) {
try {
((Socket)e.nextElement()).close();
} catch(Exception ex) {
}
}
try {
serverSocket.close();
} catch(Exception ex) {
}
done = true;
}
/** sends a message to each of the clients in telnet-friendly output. */
public void send(String message) {
Enumeration ce = connections.elements();
for(Enumeration e = writers.elements();e.hasMoreElements();) {
Socket sock = (Socket)ce.nextElement();
PrintWriter writer = (PrintWriter)e.nextElement();
writer.print(message);
if(writer.checkError()) {
// The client has closed the connection, remove it from our list:
connections.remove(sock);
writers.remove(writer);
}
}
}
/**
Continually accepts client connections. Client connections
are refused when MAX_CONNECTIONS is reached.
*/
public void run() {
while(!done) {
try {
Socket newClient = serverSocket.accept();
PrintWriter pw = new PrintWriter(newClient.getOutputStream());
if(connections.size() < MAX_CONNECTIONS) {
connections.addElement(newClient);
writers.addElement(pw);
pw.print("TelnetAppender v1.0 (" + connections.size()
+ " active connections)\r\n\r\n");
pw.flush();
} else {
pw.print("Too many connections.\r\n");
pw.flush();
newClient.close();
}
} catch(Exception e) {
LogLog.error("Encountered error while in SocketHandler loop.", e);
}
}
}
public SocketHandler(int port) throws IOException {
serverSocket = new ServerSocket(port);
}
}
}