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

1. package com.taobao.wuzhong.log;
3. import org.apache.commons.logging.Log;
4. import org.apache.commons.logging.LogFactory;
5. import org.junit.Test;
6. import org.slf4j.Logger;
7. import org.slf4j.LoggerFactory;
9. /**
10. * DESC:
11. *
12. * Copyright: Copyright 2011 m.taobao.com
13. *
14. * @author [e-mail]
15. * @time 2011-4-6 下午03:42:11
16. * @version 1.0
17. **/
18. public class LogTest {
20. // Logback tries to find a file called logback.groovy in the classpath.
21. // If no such file is found, logback tries to find a file called
22. // logback-test.xml in the classpath.
23. // If no such file is found, it checks for the file logback.xml in the
24. // classpath..
25. // If neither file is found, logback configures itself automatically using
26. // the BasicConfigurator which will cause logging output to be directed to
27. // the console.
28. @Test
29. public void test() {
30. //commons-logging的方式获取
31. Log log = LogFactory.getLog(LogTest.class);
32. //slf4j直接的方式获取，推荐用这个
33. Logger log2 = LoggerFactory.getLogger(LogTest.class);
34. log.debug("eeeeee {} {} {}");
35. log2.debug("{} {} {}", new String[] {"a", "b", "c" });
36. }
38. }

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 [e-mail] * @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.@Testpublic 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

1. Log instance = null;
2. // protect against concurrent access of loggerMap
3. synchronized (this) {
4. instance = (Log) loggerMap.get(name);
5. if (instance == null) {
6. Logger logger = LoggerFactory.getLogger(name); //slf4j的方式，代理过去了
7. if(logger instanceof LocationAwareLogger) {
8. instance = new SLF4JLocationAwareLog((LocationAwareLogger) logger);//包装了一层，做适配
9. } else {
10. instance = new SLF4JLog(logger);
11. }
12. loggerMap.put(name, instance);
13. }
14. }
15. 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

1. LoggerFactory.java
2. public static ILoggerFactory getILoggerFactory() {
3. if (INITIALIZATION_STATE == UNINITIALIZED) {
4. INITIALIZATION_STATE = ONGOING_INITILIZATION;
5. performInitialization();
7. }
8. switch (INITIALIZATION_STATE) {
9. case SUCCESSFUL_INITILIZATION:
10. return getSingleton().getLoggerFactory();
11. case FAILED_INITILIZATION:
12. throw new IllegalStateException(UNSUCCESSFUL_INIT_MSG);
13. case ONGOING_INITILIZATION:
14. // support re-entrant behavior.
15. // See also http://bugzilla.slf4j.org/show_bug.cgi?id=106
16. return TEMP_FACTORY;
17. }
18. throw new IllegalStateException("Unreachable code");
19. }
21. private final static void performInitialization() {
22. bind();
23. versionSanityCheck();
24. singleImplementationSanityCheck();
26. }

    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

1. static {
2. SINGLETON.init();
3. }
5. /**
6. * Package access for testing purposes.
7. */
8. void init() {
9. try {
10. try {
11. new ContextInitializer(defaultLoggerContext).autoConfig();
12. } catch (JoranException je) {
13. Util.reportFailure("Failed to auto configure default logger context",
14. je);
15. }
16. StatusPrinter.printInCaseOfErrorsOrWarnings(defaultLoggerContext);
17. contextSelectorBinder.init(defaultLoggerContext, KEY);
18. initialized = true;
19. } catch (Throwable t) {
20. // we should never get here
21. Util.reportFailure("Failed to instantiate ["
22. + LoggerContext.class.getName() + "]", t);
23. }
24. }

    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