debug.java

SSD9 练习9

package org.gjt.mm.mysql;

import java.io.PrintStream;

import java.sql.DriverManager;

import java.util.Hashtable;
import java.util.StringTokenizer;

/**
 * The Debug class allows debug messages on a per-class
 * basis.
 * 
 * <p>
 * The user issues a trace() call, listing the classes
 * they wish to debug.
 */

public class Debug
{
    private static Hashtable _Classes     = new Hashtable();
    private static Object    _Mutex       = new Object();
    private static boolean   _watch_all   = false;

    /**
     * Set the classes to trace.
     *
     * @param ClassList the list of classes to trace, separated by colons
     *                  or the keyword &quot;ALL&quot; to trace
     *                  all classes that use the Debug class.
     */

    public static void trace(String ClassList)
    {
	StringTokenizer ST = new StringTokenizer(ClassList, ":");
	synchronized (_Mutex) {
	    _watch_all = false;

	    if (ClassList.equals("ALL")) {
		_watch_all = true;
	    }
	    else {
		_Classes = new Hashtable();

		while (ST.hasMoreTokens()) {
		    String ClassName = ST.nextToken();

		    if (!_Classes.contains(ClassName)) {
			_Classes.put(ClassName, ClassName);
		    }
		}
	    }
	}
    }

    /**
     * Trace a method call.
     *
     * <p>
     * If the user has registered in interest in the Class of Source, then 
     * the Source class can trace method calls through this method.
     *
     * @param Source the Object issuing the methodCall() method
     * @param Method the name of the Method
     * @param Args a list of arguments
     */

    public static void methodCall(Object Source, String Method, Object[] Args)
    {
	synchronized (_Mutex) {
	    if (_watch_all || _Classes.contains(Source.getClass().getName())) {
		// Print the message
		StringBuffer Mesg = new StringBuffer("\nTRACE: ");
		Mesg.append(Source.toString());
		Mesg.append(".");
		Mesg.append(Method);
		Mesg.append("( ");
		
		// Print the argument list
		for (int i = 0; i < Args.length - 1; i++) {
		    if (Args[i] == null) {
			Mesg.append("null");
		    }
		    else {
			if (Args[i] instanceof String) {
			    Mesg.append("\"");
			}
			Mesg.append(Args[i].toString());
			if (Args[i] instanceof String) {
			    Mesg.append("\"");
			}
		    }
		    Mesg.append(", ");
		}
		if (Args.length > 0) {
		    if (Args[Args.length - 1] instanceof String) {
			Mesg.append("\"");
		    }
		    Mesg.append(Args[Args.length - 1]);
		    if (Args[Args.length - 1] instanceof String) {
			Mesg.append("\"");
		    }
		}
		Mesg.append(" )\n");

		DriverManager.println(Mesg.toString());
	    }
	}
    }

    /**
     * Trace a method call.
     *
     * <p>
     * If the user has registered in interest in the Class of Source, then 
     * the Source class can trace return calls through this method.
     *
     * @param Source the Object issuing the returnValue() method
     * @param Method the name of the method
     * @param Value the return value
     */

    public static void returnValue(Object Source, String Method, Object Value)
    {
	synchronized (_Mutex) {
	    if (_watch_all || _Classes.contains(Source.getClass().getName())) {
		// Print the message
		StringBuffer Mesg = new StringBuffer("\nTRACE: ");
		Mesg.append(Source.toString());
		Mesg.append(".");
		Mesg.append(Method);
		Mesg.append(": Returning -> ");

		if (Value == null) {
		    Mesg.append("null");
		}
		else {
		    Mesg.append(Value.toString());
		}
		Mesg.append("\n");
		
		DriverManager.println(Mesg.toString());
	    }
	}
    }

      /**
     * Log a message.
     *
     * <p>
     * If the user has registered in interest in the Class of Source, then 
     * the Source class can trace return calls through this method.
     *
     * @param Source the Object issuing the msg() method
     * @param Method the name of the method
     * @param Value the return value
     */

    public static void msg(Object Source, String Message)
    {
	synchronized (_Mutex) {
	    if (_watch_all || _Classes.contains(Source.getClass().getName())) {
		// Print the message
		StringBuffer Mesg = new StringBuffer("\nTRACE: ");
		Mesg.append(Source.toString());
		Mesg.append(": ");
		Mesg.append(Message);
		Mesg.append("\n");
		
		DriverManager.println(Mesg.toString());
	    }
	}
    }
}