java/8 : java/util/logging/StreamHandler.java

StreamHandler
https://openjdk.java.net/
GPLv2 + Classpath Exception
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * particular file as subject to the "Classpath" exception as provided
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 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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package java.util.logging;

import java.io.*;

Stream based logging Handler.

This is primarily intended as a base class or support class to
be used in implementing other logging Handlers.

LogRecords are published to a given java.io.OutputStream.

Configuration:
By default each StreamHandler is initialized using the following
LogManager configuration properties where <handler-name>
refers to the fully-qualified class name of the handler.
If properties are not defined
(or have invalid values) then the specified default values are used.

   <handler-name>.level
       specifies the default level for the Handler
       (defaults to Level.INFO). 
   <handler-name>.filter
       specifies the name of a Filter class to use
        (defaults to no Filter). 
   <handler-name>.formatter
       specifies the name of a Formatter class to use
       (defaults to java.util.logging.SimpleFormatter). 
   <handler-name>.encoding
       the name of the character set encoding to use (defaults to
       the default platform encoding). 

 For example, the properties for StreamHandler would be: 

   java.util.logging.StreamHandler.level=INFO 
   java.util.logging.StreamHandler.formatter=java.util.logging.SimpleFormatter 


For a custom handler, e.g. com.foo.MyHandler, the properties would be:

   com.foo.MyHandler.level=INFO 
   com.foo.MyHandler.formatter=java.util.logging.SimpleFormatter 


Since: 1.4/**
 * 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 where <tt>&lt;handler-name&gt;</tt>
 * refers to the fully-qualified class name of the handler.
 * If properties are not defined
 * (or have invalid values) then the specified default values are used.
 * <ul>
 * <li>   &lt;handler-name&gt;.level
 *        specifies the default level for the <tt>Handler</tt>
 *        (defaults to <tt>Level.INFO</tt>). </li>
 * <li>   &lt;handler-name&gt;.filter
 *        specifies the name of a <tt>Filter</tt> class to use
 *         (defaults to no <tt>Filter</tt>). </li>
 * <li>   &lt;handler-name&gt;.formatter
 *        specifies the name of a <tt>Formatter</tt> class to use
 *        (defaults to <tt>java.util.logging.SimpleFormatter</tt>). </li>
 * <li>   &lt;handler-name&gt;.encoding
 *        the name of the character set encoding to use (defaults to
 *        the default platform encoding). </li>
 * </ul>
 * <p>
 * For example, the properties for {@code StreamHandler} would be:
 * <ul>
 * <li>   java.util.logging.StreamHandler.level=INFO </li>
 * <li>   java.util.logging.StreamHandler.formatter=java.util.logging.SimpleFormatter </li>
 * </ul>
 * <p>
 * For a custom handler, e.g. com.foo.MyHandler, the properties would be:
 * <ul>
 * <li>   com.foo.MyHandler.level=INFO </li>
 * <li>   com.foo.MyHandler.formatter=java.util.logging.SimpleFormatter </li>
 * </ul>
 * <p>
 * @since 1.4
 */

public class StreamHandler extends Handler {
    private OutputStream output;
    private boolean doneHeader;
    private volatile 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 = getClass().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 StreamHandler, with no current output stream.
/**
     * Create a <tt>StreamHandler</tt>, with no current output stream.
     */
    public StreamHandler() {
        sealed = false;
        configure();
        sealed = true;
    }

    Create a StreamHandler with a given Formatter
and output stream.

Params: out –         the target output stream
formatter –   Formatter to be used to format output/**
     * 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.

If there is a current output stream then the Formatter's
tail string is written and the stream is flushed and closed.
Then the output stream is replaced with the new output stream.
Params: out –   New output stream.  May not be null.
Throws: SecurityException –  if a security manager exists and if
            the caller does not have LoggingPermission("control")./**
     * 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 Handler.

The encoding should be set before any LogRecords are written
to the Handler.
Params: encoding –  The name of a supported character encoding.
       May be null, to indicate the default platform encoding.
Throws: SecurityException –  if a security manager exists and if
            the caller does not have LoggingPermission("control").
UnsupportedEncodingException – if the named encoding is
         not supported./**
     * 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.
     */
    @Override
    public synchronized 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 LogRecord.

The StreamHandler first checks if there is an OutputStream
and if the given LogRecord has at least the required log level.
If not it silently returns.  If so, it calls any associated
Filter to check if the record should be published.  If so,
it calls its Formatter to format the record and then writes
the result to the current output stream.

If this is the first LogRecord to be written to a given
OutputStream, the Formatter's "head" string is
written to the stream before the LogRecord is written.
Params: record –  description of the log event. A null record is
                silently ignored and is not published/**
     * 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. A null record is
     *                 silently ignored and is not published
     */
    @Override
    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 Handler would actually log a given LogRecord.

This method checks if the LogRecord has an appropriate level and
whether it satisfies any Filter.  It will also return false if
no output stream has been assigned yet or the LogRecord is null.

Params: record –  a LogRecord
Returns: true if the LogRecord would be logged./**
     * 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 or the LogRecord is null.
     * <p>
     * @param record  a <tt>LogRecord</tt>
     * @return true if the <tt>LogRecord</tt> would be logged.
     *
     */
    @Override
    public boolean isLoggable(LogRecord record) {
        if (writer == null || record == null) {
            return false;
        }
        return super.isLoggable(record);
    }

    Flush any buffered messages.
/**
     * Flush any buffered messages.
     */
    @Override
    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 {
        checkPermission();
        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.

The Formatter's "tail" string is written to the stream before it
is closed.  In addition, if the Formatter's "head" string has not
yet been written to the stream, it will be written before the
"tail" string.
Throws: SecurityException –  if a security manager exists and if
            the caller does not have LoggingPermission("control")./**
     * 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").
     */
    @Override
    public synchronized void close() throws SecurityException {
        flushAndClose();
    }
}
Params:	out – New output stream. May not be null.
Throws:	SecurityException – if a security manager exists and if the caller does not have `LoggingPermission("control")`.
Params:	encoding – The name of a supported character encoding. May be null, to indicate the default platform encoding.
Throws:	SecurityException – if a security manager exists and if the caller does not have `LoggingPermission("control")`. UnsupportedEncodingException – if the named encoding is not supported.
Params:	record – a `LogRecord`
Returns:	true if the `LogRecord` would be logged.
/

java/ 8/ java/util/logging/StreamHandler.java
