log日志框架和LocationAwareLogger问题

今天启动tomcat服务失败,碰到异常情况如下

java.lang.NoSuchMethodError: org.slf4j.spi.LocationAwareLogger.log(Lorg/slf4j/Marker;Ljava/lang/String;ILjava/lang/String;Ljava/lang/Throwable;)V

at org.apache.commons.logging.impl.SLF4JLocationAwareLog.info(SLF4JLocationAwareLog.java:159)

Commons-log + log4j 这黄金搭档一直以来都让我们很省心，很好的完成了日志的需求。但是随着技术的变更和对性能的追求，slf4j 和 logback 这对后起之秀的到来好像打破了原本很平静的日志系统，频繁的出现包冲突...

和平的日子不在了，让我们一起来看看究竟发生了什么...

首先看看这些个包，特别是slf4j引入后就引入了一大堆包之后就有点懵了。

为什么commons-logging和jcl-over-slf4j会有冲突呢？看一下它们的类结构

很清晰的可以看到jcl-over-slf4j 重写了 commons-logging...

还有slf4j-api的实现呢，同样看类：

其实就这么简单，往往看了代码之后才发现错误是这么显而易见。。。

顺着研究，继续看一下slf4j的源码及流程

1.测试类

Java代码







package com.taobao.wuzhong.log;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
* DESC:
*
* Copyright: Copyright 2011 m.taobao.com
*
* @author wuzhong@taobao.com
* @time 2011-4-6 下午03:42:11
* @version 1.0
**/
public class LogTest {

// Logback tries to find a file called logback.groovy in the classpath.

// If no such file is found, logback tries to find a file called

// logback-test.xml in the classpath.
// If no such file is found, it checks for the file logback.xml in the

// classpath..
// If neither file is found, logback configures itself automatically using

// the BasicConfigurator which will cause logging output to be directed to

// the console.
@Test
public void test() {

//commons-logging的方式获取
Log log = LogFactory.getLog(LogTest.class);
//slf4j直接的方式获取，推荐用这个
Logger log2 = LoggerFactory.getLogger(LogTest.class);

log.debug("eeeeee {} {} {}");
log2.debug("{} {} {}", new String[] {
"a", "b",
"c" });
}

}

package com.taobao.wuzhong.log;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
* DESC:
*
* Copyright: Copyright 2011 m.taobao.com
*
* @author wuzhong@taobao.com
* @time 2011-4-6 下午03:42:11
* @version 1.0
**/
public class LogTest {

// Logback tries to find a file called logback.groovy in the classpath.
// If no such file is found, logback tries to find a file called
// logback-test.xml in the classpath.
// If no such file is found, it checks for the file logback.xml in the
// classpath..
// If neither file is found, logback configures itself automatically using
// the BasicConfigurator which will cause logging output to be directed to
// the console.
@Test
public void test() {
//commons-logging的方式获取
Log log = LogFactory.getLog(LogTest.class);
//slf4j直接的方式获取，推荐用这个
Logger log2 = LoggerFactory.getLogger(LogTest.class);
log.debug("eeeeee {} {} {}");
log2.debug("{} {} {}", new String[] { "a", "b", "c" });
}

}

logFactory.getLog 会调用内部静态变量 Slf4jLogFactory.getInstance方法，如下：

public Log getInstance(String name) throws LogConfigurationException {

Java代码







Log instance = null;
// protect against concurrent access of loggerMap

synchronized (this) {

instance = (Log) loggerMap.get(name);
if (instance == null) {

Logger logger = LoggerFactory.getLogger(name); //slf4j的方式，代理过去了

if(logger instanceof LocationAwareLogger) {

instance = new SLF4JLocationAwareLog((LocationAwareLogger) logger);
//包装了一层，做适配
} else {
instance = new SLF4JLog(logger);
}
loggerMap.put(name, instance);
}
}
return (instance);

Log instance = null;
// protect against concurrent access of loggerMap
synchronized (this) {
instance = (Log) loggerMap.get(name);
if (instance == null) {
Logger logger = LoggerFactory.getLogger(name);   //slf4j的方式，代理过去了
if(logger instanceof LocationAwareLogger) {
instance = new SLF4JLocationAwareLog((LocationAwareLogger) logger);  //包装了一层，做适配
} else {
instance = new SLF4JLog(logger);
}
loggerMap.put(name, instance);
}
}
return (instance);

loggerFactory 会调用getILoggerFactory().getlOgger()

Java代码







LoggerFactory.java
public static ILoggerFactory getILoggerFactory() {

if (INITIALIZATION_STATE == UNINITIALIZED) {
INITIALIZATION_STATE = ONGOING_INITILIZATION;
performInitialization();

}
switch (INITIALIZATION_STATE) {
case SUCCESSFUL_INITILIZATION:
return getSingleton().getLoggerFactory();
case FAILED_INITILIZATION:
throw new IllegalStateException(UNSUCCESSFUL_INIT_MSG);

case ONGOING_INITILIZATION:
// support re-entrant behavior.
// See also http://bugzilla.slf4j.org/show_bug.cgi?id=106
return TEMP_FACTORY;
}
throw new IllegalStateException("Unreachable code");

}

private final
static void performInitialization() {
bind();
versionSanityCheck();
singleImplementationSanityCheck();

}

LoggerFactory.java
public static ILoggerFactory getILoggerFactory() {
if (INITIALIZATION_STATE == UNINITIALIZED) {
INITIALIZATION_STATE = ONGOING_INITILIZATION;
performInitialization();

}
switch (INITIALIZATION_STATE) {
case SUCCESSFUL_INITILIZATION:
return getSingleton().getLoggerFactory();
case FAILED_INITILIZATION:
throw new IllegalStateException(UNSUCCESSFUL_INIT_MSG);
case ONGOING_INITILIZATION:
// support re-entrant behavior.
// See also http://bugzilla.slf4j.org/show_bug.cgi?id=106 return TEMP_FACTORY;
}
throw new IllegalStateException("Unreachable code");
}

private final static void performInitialization() {
bind();
versionSanityCheck();
singleImplementationSanityCheck();

}

这里的bind很关键，这里动态的绑定了slf4j-api的实现机制

Java代码







static {
SINGLETON.init();
}

/**
* Package access for testing purposes.
*/
void init() {
try {
try {
new ContextInitializer(defaultLoggerContext).autoConfig();

} catch (JoranException je) {
Util.reportFailure("Failed to auto configure default logger context",

je);
}
StatusPrinter.printInCaseOfErrorsOrWarnings(defaultLoggerContext);
contextSelectorBinder.init(defaultLoggerContext, KEY);
initialized = true;
} catch (Throwable t) {
// we should never get here
Util.reportFailure("Failed to instantiate ["
+ LoggerContext.class.getName() +
"]", t);
}
}

static {
SINGLETON.init();
}

/**
* Package access for testing purposes.
*/
void init() {
try {
try {
new ContextInitializer(defaultLoggerContext).autoConfig();
} catch (JoranException je) {
Util.reportFailure("Failed to auto configure default logger context",
je);
}
StatusPrinter.printInCaseOfErrorsOrWarnings(defaultLoggerContext);
contextSelectorBinder.init(defaultLoggerContext, KEY);
initialized = true;
} catch (Throwable t) {
// we should never get here
Util.reportFailure("Failed to instantiate ["
+ LoggerContext.class.getName() + "]", t);
}
}

获取配置信息初始化