logger.java

编写程序

/*
 * @(#)Logger.java	1.5 03/01/23
 * 
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package jnlp.sample.servlet;
import java.text.MessageFormat;
import java.util.*;
import java.io.*;
import javax.servlet.*;

/* A loging object used by the servlets */
public class Logger {
    // Logging levels
    public final static int NONE           	 = 0; 
    public static final String NONE_KEY    	 = "NONE";
    public final static int FATAL          	 = 1; 
    public static final String FATAL_KEY   	 = "FATAL";
    public final static int WARNING        	 = 2; 
    public static final String WARNING_KEY       = "WARNING";
    public final static int INFORMATIONAL        = 3; 
    public static final String INFORMATIONAL_KEY = "INFORMATIONAL";
    public final static int DEBUG                = 4; 
    public static final String DEBUG_KEY         = "DEBUG";
    
    // Configuration parameters
    private final static String LOG_LEVEL = "logLevel";
    private final static String LOG_PATH  = "logPath";
    
    private int _loggingLevel = FATAL;
    private ServletContext _servletContext = null;
    private String _logFile = null;
    private String _servletName = null;
    
    // Localization
    ResourceBundle  _resources = null; 
    
    
    /** Initialize logging object. It reads the logLevel and pathLevel init parameters.
     *  Default is logging level FATAL, and logging using the ServletContext.log
     */
    public Logger(ServletConfig config, ResourceBundle resources) {        		
	_resources = resources;
	_servletContext = config.getServletContext();	
	_servletName = config.getServletName();
	_logFile = config.getInitParameter(LOG_PATH);
	if (_logFile != null) {
	    _logFile = _logFile.trim();
	    if (_logFile.length() == 0) _logFile = null;
	}
        String level = config.getInitParameter(LOG_LEVEL);
	if (level != null) {
	    level = level.trim().toUpperCase();
	    if (level.equals(NONE_KEY)) _loggingLevel = NONE;
	    if (level.equals(FATAL_KEY)) _loggingLevel = FATAL;
	    if (level.equals(WARNING_KEY)) _loggingLevel = WARNING;
	    if (level.equals(INFORMATIONAL_KEY)) _loggingLevel = INFORMATIONAL;
	    if (level.equals(DEBUG_KEY)) _loggingLevel = DEBUG;
	}
    }
    
    // Logging API. Fatal, Warning, and Informational are localized    
    public void addFatal(String key, Throwable throwable) { 
	logEvent(FATAL, getString(key), throwable); 
    }    
    
    public void addWarning(String key, String arg) { 
	logL10N(WARNING, key, arg, (Throwable)null); 
    }
    
    public void addWarning(String key, String arg, Throwable t) { 
	logL10N(WARNING, key, arg, t); 
    }
    
    public void addWarning(String key, String arg1, String arg2) { 
	logL10N(WARNING, key, arg1, arg2); 
    }
    
    public void addWarning(String key, String arg1, String arg2, String arg3) { 
	logL10N(WARNING, key, arg1, arg2, arg3); 
    }
    
    public void addInformational(String key) { 
	logEvent(INFORMATIONAL, getString(key), (Throwable)null); 
    }
    
    public void addInformational(String key, String arg) { 
	logL10N(INFORMATIONAL, key, arg, (Throwable)null); 
    }
    
    public void addInformational(String key, String arg1, String arg2, String arg3) { 
	logL10N(INFORMATIONAL, key, arg1, arg2, arg3); 
    }
    
    // Debug messages are not localized
    public void addDebug(String msg)   { logEvent(DEBUG, msg, null); }    
    
    public void addDebug(String msg, Throwable throwable) { 
	logEvent(DEBUG, msg, throwable); 
    }
    
    // Query to test for level
    boolean isNoneLevel() { return _loggingLevel >= NONE; }
    boolean isFatalevel() { return _loggingLevel >= FATAL; }
    boolean isWarningLevel() { return _loggingLevel >= WARNING; }
    boolean isInformationalLevel() { return _loggingLevel >= INFORMATIONAL; }
    boolean isDebugLevel() { return _loggingLevel >= DEBUG; }
    
    // Returns a string from the resources    
    private String getString(String key) {
        try {
	    return _resources.getString(key);
        } catch (MissingResourceException mre) {
	    return "Missing resource for: " + key;            
        }
    }
    
    private void logL10N(int level, String key, String arg, Throwable e) {	
	Object[] messageArguments = { arg };
        logEvent(level, applyPattern(key, messageArguments), e);    
    }
    
    private void logL10N(int level, String key, String arg1, String arg2) {	
	Object[] messageArguments = { arg1, arg2 };
        logEvent(level, applyPattern(key, messageArguments), null);
    }
    
    private void logL10N(int level, String key, String arg1, String arg2, String arg3) {	
	Object[] messageArguments = { arg1, arg2, arg3 };
        logEvent(level, applyPattern(key, messageArguments), null);
    }
    
    /** Helper function that applies the messageArguments to a message from the resource object */
    private String applyPattern(String key, Object[] messageArguments) {
        String message = getString(key);
        MessageFormat formatter = new MessageFormat(message);
        String output = formatter.format(message, messageArguments);
        return output;
    }
    
    // The method that actually does the logging */
    private synchronized void logEvent(int level, String string, Throwable throwable) {
	// Check if the event should be logged
	if (level > _loggingLevel) return;
	
	if (_logFile != null) {
	    // No logfile specified, log using servlet context
	    PrintWriter pw = null;
	    try {
		pw = new PrintWriter(new FileWriter(_logFile, true));
		pw.println(_servletName + "(" + level + "): " + string);	
		if (throwable != null) {		 
		    throwable.printStackTrace(pw);		    		    
		}		
		pw.close();
		// Do a return here. An exception will cause a fall through to
		// do _servletContex logging API
		return;
	    } catch (IOException ioe) {
		/* just ignore */
	    }    
	}
	
	// Otherwise, write to servlet context log	    
	if (throwable == null) {
	    _servletContext.log(string);
	} else {
	    _servletContext.log(string, throwable);
	}
    }	
}