java.util.logging.Logger and log4j

Question

I am trying to compile the code from here: http://www.brackeen.com/javagamebook/#download (Chapter 6) and am having trouble. I don't understand how java.util.logging.Logger and log4j work together, but that seems to be the issue. The errors I get are all on the log.error() or log.warn() method calls.

Here is the output from NetBeans:

init:
deps-clean:
Deleting directory C:\JB\NetBeansProjects\WRServer\build
Deleting directory C:\JB\NetBeansProjects\WRServer\dist
clean:
init:
deps-jar:
Created dir: C:\JB\NetBeansProjects\WRServer\build\classes
Compiling 23 source files to C:\JB\NetBeansProjects\WRServer\build\classes
C:\JB\NetBeansProjects\WRServer\src\com\hypefiend\javagamebook\server\GameServer.java:110: cannot find symbol
symbol  : method error(java.lang.String,java.lang.Exception)
location: class java.util.logging.Logger
            log.error("error initializing ServerSocket", e);
               ^
C:\JB\NetBeansProjects\WRServer\src\com\hypefiend\javagamebook\server\GameServer.java:152: cannot find symbol
symbol  : method warn(java.lang.String)
location: class java.util.logging.Logger
                log.warn("error during serverSocket select(): " + ioe.getMessage());
                   ^
C:\JB\NetBeansProjects\WRServer\src\com\hypefiend\javagamebook\server\GameServer.java:155: cannot find symbol
symbol  : method error(java.lang.String,java.lang.Exception)
location: class java.util.logging.Logger
                log.error("exception in run()", e);
                   ^
C:\JB\NetBeansProjects\WRServer\src\com\hypefiend\javagamebook\server\GameServer.java:187: cannot find symbol
symbol  : method error(java.lang.String)
location: class java.util.logging.Logger
            log.error("no gamecontroller for gameNameHash: " + gameNameHash);
               ^
C:\JB\NetBeansProjects\WRServer\src\com\hypefiend\javagamebook\server\GameServer.java:203: cannot find symbol
symbol  : method error(java.lang.String)
location: class java.util.logging.Logger
            log.error("error getting GameController directory");
               ^
C:\JB\NetBeansProjects\WRServer\src\com\hypefiend\javagamebook\server\GameServer.java:223: cannot find symbol
symbol  : method warn(java.lang.String)
location: class java.util.logging.Logger
                    log.warn("class file does not extend GameController: " + file);
                       ^
C:\JB\NetBeansProjects\WRServer\src\com\hypefiend\javagamebook\server\GameServer.java:238: cannot find symbol
symbol  : method error(java.lang.String,java.lang.Exception)
location: class java.util.logging.Logger
                log.error("Error instantiating GameController from file: " + file, e);
                   ^
Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
7 errors
BUILD FAILED (total time: 0 seconds)

Here is the code straight from the book. I have not tried to edit it yet.

package com.hypefiend.javagamebook.server;

import com.hypefiend.javagamebook.common.*;
import com.hypefiend.javagamebook.server.controller.*;

import java.nio.channels.*;
import java.util.*;
import java.net.*;
import java.io.*;
import java.util.logging.Logger;
import org.apache.log4j.*;

/**
 * GameServer.java
 *
 * The heart of the framework, GameServer accepts
 * incoming client connections and hands them off to 
 * the SelectAndRead class.
 * GameServer also keeps track of the connected players
 * and the GameControllers.
 *
 * @author <a href="mailto:[email protected]">bret barker</a>
 * @version 1.0
 */
public class GameServer extends Thread {
/** log4j Logger */
private Logger log = Logger.getLogger("GameServer");

/** ServerSocketChannel for accepting client connections */
private ServerSocketChannel sSockChan;

/** selector for multiplexing ServerSocketChannels */
private Selector selector;

/** GameControllers keyed by GameName */
private Hashtable gameControllers;

/** classname prefix used for dynamically loading GameControllers */
private static final String CONTROLLER_CLASS_PREFIX = 
"com.hypefiend.javagamebook.server.controller.";

/** players keyed by playerId */
private static Hashtable playersByPlayerId;

/** players keyed by sessionId */
private static Hashtable playersBySessionId;

private boolean running;
private SelectAndRead selectAndRead;
private EventWriter eventWriter;

private static long nextSessionId = 0;

/**
 * main. 
 * setup log4j and fireup the GameServer
 */
public static void main(String args[]) {
BasicConfigurator.configure();
GameServer gs = new GameServer();
gs.start();
}

/**
 * constructor, just initialize our hashtables
 */
public GameServer() {
gameControllers = new Hashtable();
playersByPlayerId = new Hashtable();
playersBySessionId = new Hashtable();
}

/**
 * init the GameServer, startup our workers, etc.
 */ 
public void init() {
log.info("GameServer initializing");

loadGameControllers();
initServerSocket();

selectAndRead = new SelectAndRead(this);
selectAndRead.start();

eventWriter = new EventWriter(this, Globals.EVENT_WRITER_WORKERS); 
}

/**
 * GameServer specific initialization, bind to the server port,
 * setup the Selector, etc.
 */
private void initServerSocket() {
try {
    // open a non-blocking server socket channel
    sSockChan = ServerSocketChannel.open();
    sSockChan.configureBlocking(false);

    // bind to localhost on designated port
    InetAddress addr = InetAddress.getLocalHost();
    log.info("binding to address: " + addr.getHostAddress());
    sSockChan.socket().bind(new InetSocketAddress(addr, Globals.PORT));

    // get a selector
    selector = Selector.open();

    // register the channel with the selector to handle accepts
    SelectionKey acceptKey = sSockChan.register(selector, SelectionKey.OP_ACCEPT);
}
catch (Exception e) {
    log.error("error initializing ServerSocket", e);
    System.exit(1);
}
}

/**
 * Here's the meat, loop over the select() call to 
 * accept socket connections and hand them off to SelectAndRead
 */
public void run() {
init();
log.info("******** GameServer running ********");
running = true;
int numReady = 0;

while (running) {
    // note, since we only have one ServerSocket to listen to,
    // we don't need a Selector here, but we set it up for 
    // later additions such as listening on another port 
    // for administrative uses.
    try {
 // blocking select, will return when we get a new connection
 selector.select();

 // fetch the keys
 Set readyKeys = selector.selectedKeys();

 // run through the keys and process
 Iterator i = readyKeys.iterator();
 while (i.hasNext()) {
     SelectionKey key = (SelectionKey) i.next();
     i.remove();

     ServerSocketChannel ssChannel = (ServerSocketChannel) key.channel();
     SocketChannel clientChannel = ssChannel.accept();

     // add to the list in SelectAndRead for processing
     selectAndRead.addNewClient(clientChannel);
     log.info("got connection from: " + clientChannel.socket().getInetAddress());
 }  
    }
    catch (IOException ioe) {
 log.warn("error during serverSocket select(): " + ioe.getMessage());
    }
    catch (Exception e) {
 log.error("exception in run()", e);
    }
}
}

/** 
 * shutdown the GameServer
 */
public void shutdown() {
selector.wakeup();
}

/**
 * Return the next available sessionId
 */
public synchronized String nextSessionId() {
return "" + nextSessionId++;
}

/**
 * finds the GameController for a given GameName
 */
public GameController getGameController(String gameName) {
return getGameControllerByHash(gameName.hashCode());
}

/**
 * finds the GameController for a given GameName hash code
 */
public GameController getGameControllerByHash(int gameNameHash) {
GameController gc = (GameController) gameControllers.get("" + gameNameHash);
if (gc == null) 
    log.error("no gamecontroller for gameNameHash: " + gameNameHash);
return gc;
}

/**
 *  Dynamically loads GameControllers
 */
private void loadGameControllers() {
log.info("loading GameControllers");

// grab all class files in the same directory as GameController
String baseClass = "com/hypefiend/javagamebook/server/controller/GameController.class";
File f = new File( this.getClass( ).getClassLoader().getResource(baseClass).getPath());
File[] files = f.getParentFile().listFiles( );

if (files == null) {
    log.error("error getting GameController directory");
    return;
}

for( int i = 0; ( i < files.length); i++) {
    String file = files[i].getName( );
    if (file.indexOf( ".class") == -1)
 continue;
    if (file.equals("GameController.class"))
 continue;

    try {
 // grab the class
 String controllerClassName = CONTROLLER_CLASS_PREFIX + file.substring(0, file.indexOf(".class"));
 log.info("loading class: " + controllerClassName);

 Class cl = Class.forName(controllerClassName);

 // make sure it extends GameController
 if (!GameController.class.isAssignableFrom(cl)) {
     log.warn("class file does not extend GameController: " + file);
     continue;
 }

 // get an instance and initialize
 GameController gc = (GameController) cl.newInstance();
 String gameName = gc.getGameName();
 gc.init(this, getGameConfig(gameName));

 // add to our controllers hash
 gameControllers.put("" + gameName.hashCode(), gc);

 log.info("loaded controller for gameName: " + gameName + ", hash: " + gameName.hashCode());
    } 
    catch (Exception e) {
 log.error("Error instantiating GameController from file: " + file, e);
    }
}
}


/**
 * pass the event on to the EventWriter
 */
public void writeEvent(GameEvent e) {
eventWriter.handleEvent(e);
}

/**
 * returns the GameConfig object for the given gameName
 */
public GameConfig getGameConfig(String gameName) {
// todo: implement getGameConfig()
return null;
}

/**
 * fetches the Player for a given playerId
 */
public static Player getPlayerById( String id) {
return (Player) playersByPlayerId.get(id);
}

/**
 * fetches the Player for a given sessionId
 */
public static Player getPlayerBySessionId(String id) {
return (Player) playersBySessionId.get(id);
}

/** 
 * add a player to our lists
 */
public static void addPlayer(Player p) {
playersByPlayerId.put(p.getPlayerId(), p);
playersBySessionId.put(p.getSessionId(), p);
}

/**
 * remove a player from our lists
 */
public static void removePlayer(Player p) {
playersByPlayerId.remove(p.getPlayerId());
playersBySessionId.remove(p.getPlayerId());
}

}// GameServer

Answer 1

java.util.logging.Logger does not have a warn() method (although it does have a warning() method).

However, org.apache.log4j.Logger does indeed have a method named warn().

Are you sure you are importing the correct classes?

Answer 2

Could you please format your code ? Ti would be much more readable ...

You are trying to call the error(String, String) method on an instance of java.util.logger.Logger. There is no such method. You should use Logger.log(Level.SEVERE, "mesage") instead, or use an instance of a log4J Logger. Check the import section of your source file ...

Answer 3

The import of java.util.logging.Logger in your class seems to cause the problem (the compiler tries to compile against that one, altough it seems the intention was to use the log4j Logger class).

Try to remove the java.util.logging.Logger from the imports and recompile.

EDIT: Well, I just checked the original GameServer.java from the ZIP file linked in the page linked in the question. it does NOT contain any import of java.util.logging.Logger there. My guess is thus:

• You do not have log4j on the classpath of your project
• You or your IDE tried to somehow organize the imports automatically. This ended up adding java.util.logging.Logger to the imports because no other class of that name was found in project's classpath.

So, add log4j to the classpath first, then remove the java.util.logging.Logger from the imports.