[Log4J]一个只打Console并且设有最高级别的Appender
/*
* Copyright 1999-2005 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.io.IOException;
import java.io.OutputStream;
import org.apache.log4j.Layout;
import org.apache.log4j.Level;
import org.apache.log4j.WriterAppender;
import org.apache.log4j.helpers.LogLog;
import org.apache.log4j.spi.LoggingEvent;
/**
* ConsoleAppender appends log events to <code>System.out</code> or
* <code>System.err</code> using a layout specified by the user. The default
* target is <code>System.out</code>.
*
* @author Ceki Gülcü
* @author Curt Arnold
* @since 1.1
*/
public class MyAppender extends WriterAppender {
public static final String SYSTEM_OUT = "System.out";
public static final String SYSTEM_ERR = "System.err";
protected String target = SYSTEM_OUT;
/**
* Determines if the appender honors reassignments of System.out or
* System.err made after configuration.
*/
private boolean follow = false;
/**
* Constructs an unconfigured appender.
*/
public MyAppender() {
}
/**
* Creates a configured appender.
*
* @param layout
* layout, may not be null.
*/
public MyAppender(Layout layout) {
this(layout, SYSTEM_OUT);
}
/**
* Creates a configured appender.
*
* @param layout
* layout, may not be null.
* @param targetStr
* target, either "System.err" or "System.out".
*/
public MyAppender(Layout layout, String target) {
setLayout(layout);
setTarget(target);
activateOptions();
}
/**
* Sets the value of the <b>Target</b> option. Recognized values are
* "System.out" and "System.err". Any other value will be ignored.
* */
public void setTarget(String value) {
String v = value.trim();
if (SYSTEM_OUT.equalsIgnoreCase(v)) {
target = SYSTEM_OUT;
} else if (SYSTEM_ERR.equalsIgnoreCase(v)) {
target = SYSTEM_ERR;
} else {
targetWarn(value);
}
}
/**
* Returns the current value of the <b>Target</b> property. The default
* value of the option is "System.out".
*
* See also {@link #setTarget}.
* */
public String getTarget() {
return target;
}
/**
* Sets whether the appender honors reassignments of System.out or
* System.err made after configuration.
*
* @param newValue
* if true, appender will use value of System.out or System.err
* in force at the time when logging events are appended.
* @since 1.2.13
*/
public final void setFollow(final boolean newValue) {
follow = newValue;
}
/**
* Gets whether the appender honors reassignments of System.out or
* System.err made after configuration.
*
* @return true if appender will use value of System.out or System.err in
* force at the time when logging events are appended.
* @since 1.2.13
*/
public final boolean getFollow() {
return follow;
}
@Override
public void append(LoggingEvent event) {
// Reminder: the nesting of calls is:
//
// doAppend()
// - check threshold
// - filter
// - append();
// - checkEntryConditions();
// - subAppend();
//[yangyh]
if (event.getLevel().isGreaterOrEqual(Level.WARN)) {
return;
}
if (!checkEntryConditions()) {
return;
}
subAppend(event);
}
void targetWarn(String val) {
LogLog.warn("[" + val + "] should be System.out or System.err.");
LogLog.warn("Using previously set target, System.out by default.");
}
/**
* Prepares the appender for use.
*/
@Override
public void activateOptions() {
if (follow) {
if (target.equals(SYSTEM_ERR)) {
setWriter(createWriter(new SystemErrStream()));
} else {
setWriter(createWriter(new SystemOutStream()));
}
} else {
if (target.equals(SYSTEM_ERR)) {
setWriter(createWriter(System.err));
} else {
setWriter(createWriter(System.out));
}
}
super.activateOptions();
}
/**
* {@inheritDoc}
*/
@Override
protected final void closeWriter() {
if (follow) {
super.closeWriter();
}
}
/**
* An implementation of OutputStream that redirects to the current
* System.err.
*
*/
private static class SystemErrStream extends OutputStream {
public SystemErrStream() {
}
@Override
public void close() {
}
@Override
public void flush() {
System.err.flush();
}
@Override
public void write(final byte[] b) throws IOException {
System.err.write(b);
}
@Override
public void write(final byte[] b, final int off, final int len) throws IOException {
System.err.write(b, off, len);
}
@Override
public void write(final int b) throws IOException {
System.err.write(b);
}
}
/**
* An implementation of OutputStream that redirects to the current
* System.out.
*
*/
private static class SystemOutStream extends OutputStream {
public SystemOutStream() {
}
@Override
public void close() {
}
@Override
public void flush() {
System.out.flush();
}
@Override
public void write(final byte[] b) throws IOException {
System.out.write(b);
}
@Override
public void write(final byte[] b, final int off, final int len) throws IOException {
System.out.write(b, off, len);
}
@Override
public void write(final int b) throws IOException {
System.out.write(b);
}
}
}
log4j.properties:
### set log levels ###
log4j.rootLogger = debug , stderr, D, A1
log4j.appender.stdout = org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target = System.out
log4j.appender.stdout.layout = org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern = %d{ABSOLUTE} %5p %c{1}:%L - %m%n
log4j.appender.stderr = org.apache.log4j.ConsoleAppender
log4j.appender.stderr.Target = System.err
log4j.appender.stderr.Threshold = WARN
log4j.appender.stderr.layout = org.apache.log4j.PatternLayout
log4j.appender.stderr.layout.ConversionPattern = %d{ABSOLUTE} %5p %c{1}:%L - %m%n
log4j.appender.A1 = com.baidu.tv.video.fetcher.log.MyAppender
log4j.appender.A1.Target = System.out
log4j.appender.A1.Threshold = DEBUG
log4j.appender.A1.layout = org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern = %d{ABSOLUTE} %5p %c{1}:%L - %m%n
log4j.appender.D = org.apache.log4j.DailyRollingFileAppender
log4j.appender.D.File = logs/error.log
log4j.appender.D.Append = true
log4j.appender.D.Threshold = WARN
log4j.appender.D.layout = org.apache.log4j.PatternLayout
log4j.appender.D.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss} [ %t:%r ] - [ %p ] %m%n
貌似现在的Appender只有最低级别：Threshold
这里重写了WriterAppander的append方法