streamhandler.java

JAVA基本类源代码,大家可以学习学习!

/*
 * @(#)StreamHandler.java	1.13 03/01/27
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */


package java.util.logging;

import java.io.*;

/**
 * Stream based logging <tt>Handler</tt>.
 * <p>
 * This is primarily intended as a base class or support class to
 * be used in implementing other logging <tt>Handlers</tt>.
 * <p>
 * <tt>LogRecords</tt> are published to a given <tt>java.io.OutputStream</tt>.
 * <p>
 * <b>Configuration:</b>
 * By default each <tt>StreamHandler</tt> is initialized using the following
 * <tt>LogManager</tt> configuration properties.  If properties are not defined
 * (or have invalid values) then the specified default values are used.
 * <ul>
 * <li>   java.util.logging.StreamHandler.level
 *	  specifies the default level for the <tt>Handler</tt>
 *	  (defaults to <tt>Level.INFO</tt>).
 * <li>   java.util.logging.StreamHandler.filter
 *	  specifies the name of a <tt>Filter</tt> class to use
 *	   (defaults to no <tt>Filter</tt>).
 * <li>   java.util.logging.StreamHandler.formatter 
 *	  specifies the name of a <tt>Formatter</tt> class to use
 *  	  (defaults to <tt>java.util.logging.SimpleFormatter</tt>).
 * <li>   java.util.logging.StreamHandler.encoding 
 *	  the name of the character set encoding to use (defaults to
 *	  the default platform encoding).
 * </ul>
 *
 * @version 1.13, 01/27/03
 * @since 1.4
 */

public class StreamHandler extends Handler {
    private LogManager manager = LogManager.getLogManager();
    private OutputStream output;
    private boolean doneHeader;
    private Writer writer;

    // Private method to configure a StreamHandler from LogManager
    // properties and/or default values as specified in the class
    // javadoc.
    private void configure() {
        LogManager manager = LogManager.getLogManager();
	String cname = StreamHandler.class.getName();

	setLevel(manager.getLevelProperty(cname +".level", Level.INFO));
	setFilter(manager.getFilterProperty(cname +".filter", null));
	setFormatter(manager.getFormatterProperty(cname +".formatter", new SimpleFormatter()));
	try {
	    setEncoding(manager.getStringProperty(cname +".encoding", null));
	} catch (Exception ex) {
	    try {
	        setEncoding(null);
	    } catch (Exception ex2) {
		// doing a setEncoding with null should always work.
		// assert false;
	    }
	}
    }

    /**
     * Create a <tt>StreamHandler</tt>, with no current output stream.
     */
    public StreamHandler() {
	sealed = false;
	configure();
	sealed = true;
    }

    /**
     * Create a <tt>StreamHandler</tt> with a given <tt>Formatter</tt>
     * and output stream.
     * <p>
     * @param out         the target output stream
     * @param formatter   Formatter to be used to format output
     */
    public StreamHandler(OutputStream out, Formatter formatter) {
	sealed = false;
	configure();
	setFormatter(formatter);
	setOutputStream(out);
	sealed = true;
    }

    /**
     * Change the output stream.
     * <P>
     * If there is a current output stream then the <tt>Formatter</tt>'s 
     * tail string is written and the stream is flushed and closed.
     * Then the output stream is replaced with the new output stream.
     *
     * @param out   New output stream.  May not be null.
     * @exception  SecurityException  if a security manager exists and if
     *             the caller does not have <tt>LoggingPermission("control")</tt>.
     */
    protected synchronized void setOutputStream(OutputStream out) throws SecurityException {
	if (out == null) {
	    throw new NullPointerException();
	}
	flushAndClose();
	output = out;
	doneHeader = false;
	String encoding = getEncoding();
	if (encoding == null) {
	    writer = new OutputStreamWriter(output);
	} else {
	    try {
	        writer = new OutputStreamWriter(output, encoding);
	    } catch (UnsupportedEncodingException ex) {
		// This shouldn't happen.  The setEncoding method
		// should have validated that the encoding is OK.
		throw new Error("Unexpected exception " + ex);
	    }
	}
    }

    /**
     * Set (or change) the character encoding used by this <tt>Handler</tt>.
     * <p>
     * The encoding should be set before any <tt>LogRecords</tt> are written
     * to the <tt>Handler</tt>.
     *
     * @param encoding  The name of a supported character encoding.
     *	      May be null, to indicate the default platform encoding.
     * @exception  SecurityException  if a security manager exists and if
     *             the caller does not have <tt>LoggingPermission("control")</tt>.
     * @exception  UnsupportedEncodingException if the named encoding is
     *		not supported.
     */
    public void setEncoding(String encoding) 
			throws SecurityException, java.io.UnsupportedEncodingException {
	super.setEncoding(encoding);
	if (output == null) {
	    return;
	}
	// Replace the current writer with a writer for the new encoding.
	flush();
	if (encoding == null) {
	    writer = new OutputStreamWriter(output);
	} else {
	    writer = new OutputStreamWriter(output, encoding);
	}
    }

    /**
     * Format and publish a <tt>LogRecord</tt>.
     * <p>
     * The <tt>StreamHandler</tt> first checks if there is an <tt>OutputStream</tt>
     * and if the given <tt>LogRecord</tt> has at least the required log level.
     * If not it silently returns.  If so, it calls any associated
     * <tt>Filter</tt> to check if the record should be published.  If so,
     * it calls its <tt>Formatter</tt> to format the record and then writes 
     * the result to the current output stream.
     * <p>
     * If this is the first <tt>LogRecord</tt> to be written to a given
     * <tt>OutputStream</tt>, the <tt>Formatter</tt>'s "head" string is 
     * written to the stream before the <tt>LogRecord</tt> is written.
     *
     * @param  record  description of the log event
     */
    public synchronized void publish(LogRecord record) {
	if (!isLoggable(record)) {
	    return;
	}
	String msg;
	try {
 	    msg = getFormatter().format(record);
	} catch (Exception ex) {
	    // We don't want to throw an exception here, but we
	    // report the exception to any registered ErrorManager.
	    reportError(null, ex, ErrorManager.FORMAT_FAILURE);
	    return;
	}

	try {
	    if (!doneHeader) {
	        writer.write(getFormatter().getHead(this));
		doneHeader = true;
	    }
	    writer.write(msg);
	} catch (Exception ex) {
	    // We don't want to throw an exception here, but we
	    // report the exception to any registered ErrorManager.
	    reportError(null, ex, ErrorManager.WRITE_FAILURE);
	}
    }


    /**
     * Check if this <tt>Handler</tt> would actually log a given <tt>LogRecord</tt>.
     * <p>
     * This method checks if the <tt>LogRecord</tt> has an appropriate level and 
     * whether it satisfies any <tt>Filter</tt>.  It will also return false if
     * no output stream has been assigned yet.
     * <p>
     * @param record  a <tt>LogRecord</tt>
     * @return true if the <tt>LogRecord</tt> would be logged.
     *
     */
    public boolean isLoggable(LogRecord record) {
	if (writer == null) {
	    return false;
	}
	return super.isLoggable(record);
    }

    /**
     * Flush any buffered messages.
     */
    public synchronized void flush() {
	if (writer != null) {
	    try {
	        writer.flush();
	    } catch (Exception ex) {	
	        // We don't want to throw an exception here, but we
	        // report the exception to any registered ErrorManager.
	        reportError(null, ex, ErrorManager.FLUSH_FAILURE);
	    }
	}
    }

    private synchronized void flushAndClose() throws SecurityException {
        checkAccess();
	if (writer != null) {
	    try {
	        if (!doneHeader) {
	            writer.write(getFormatter().getHead(this));
		    doneHeader = true;
	        }
		writer.write(getFormatter().getTail(this));
		writer.flush();
	        writer.close();
	    } catch (Exception ex) {
	        // We don't want to throw an exception here, but we
	        // report the exception to any registered ErrorManager.
	        reportError(null, ex, ErrorManager.CLOSE_FAILURE);
	    }
	    writer = null;
	    output = null;
	}
    }

    /**
     * Close the current output stream.
     * <p>
     * The <tt>Formatter</tt>'s "tail" string is written to the stream before it
     * is closed.  In addition, if the <tt>Formatter</tt>'s "head" string has not
     * yet been written to the stream, it will be written before the
     * "tail" string.
     *
     * @exception  SecurityException  if a security manager exists and if
     *             the caller does not have LoggingPermission("control").
     * @exception  SecurityException  if a security manager exists and if
     *             the caller does not have LoggingPermission("control").
     */
    public synchronized void close() throws SecurityException {
	flushAndClose();
    }
}