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253 lines
7.5 KiB
253 lines
7.5 KiB
# mybatis 日志源码
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- Author: [HuiFer](https://github.com/huifer)
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- Description: 该文介绍 mybatis 日志相关源码
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- 源码阅读工程: [huifer-mybatis](https://github.com/huifer/javaBook-src/tree/old/mybatis-3)
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## 核心类
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- `org.apache.ibatis.logging.Log`
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- `org.apache.ibatis.logging.LogFactory`
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- 多个日志实现
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- `org.apache.ibatis.logging.log4j2.Log4j2Impl`
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- `org.apache.ibatis.logging.slf4j.Slf4jLocationAwareLoggerImpl`
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- ...
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## 源码流程
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- mybatis 提供了一个日志接口,内容如下.
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```java
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/**
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* mybatis 的日志接口,提供日志级别
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* <ol>
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* <li>error</li>
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* <li>debug</li>
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* <li>trace</li>
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* <li>warn</li>
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* </ol>
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* <p>通过自己定义的接口来实现各大日志框架的内容达到高可用</p>
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* @author Clinton Begin
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*/
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public interface Log {
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boolean isDebugEnabled();
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boolean isTraceEnabled();
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void error(String s, Throwable e);
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void error(String s);
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void debug(String s);
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void trace(String s);
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void warn(String s);
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}
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```
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- 有了日志接口必然有实现类, mybatis 有`log4j2` 、 `slf4j` 等日志的相关实现 , 下面是`Slf4jImpl`的代码,其他代码也是一样的模式进行初始化就不再重复贴代码了.
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```java
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public class Slf4jImpl implements Log {
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private Log log;
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/**
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* 创建日志实例
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* @param clazz
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*/
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public Slf4jImpl(String clazz) {
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Logger logger = LoggerFactory.getLogger(clazz);
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if (logger instanceof LocationAwareLogger) {
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try {
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// check for slf4j >= 1.6 method signature
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logger.getClass().getMethod("log", Marker.class, String.class, int.class, String.class, Object[].class, Throwable.class);
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log = new Slf4jLocationAwareLoggerImpl((LocationAwareLogger) logger);
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return;
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} catch (SecurityException | NoSuchMethodException e) {
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// fail-back to Slf4jLoggerImpl
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}
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}
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// Logger is not LocationAwareLogger or slf4j version < 1.6
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log = new Slf4jLoggerImpl(logger);
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}
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@Override
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public boolean isDebugEnabled() {
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return log.isDebugEnabled();
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}
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@Override
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public boolean isTraceEnabled() {
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return log.isTraceEnabled();
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}
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@Override
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public void error(String s, Throwable e) {
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log.error(s, e);
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}
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@Override
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public void error(String s) {
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log.error(s);
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}
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@Override
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public void debug(String s) {
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log.debug(s);
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}
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@Override
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public void trace(String s) {
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log.trace(s);
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}
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@Override
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public void warn(String s) {
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log.warn(s);
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}
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}
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```
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- 通过上述方法来达到统一接口多个实现,这个在开发中也经常使用.多日志的实现方法有了还缺一个创建方法,创建方法由`org.apache.ibatis.logging.LogFactory`提供
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```java
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/**
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* <p>日志工厂，实现内容:</p>
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* <ol>
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* <li>org.slf4j.Logger 日志框架 slf4j</li>
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* <li>org.apache.commons.logging.Log 日志框架 apache</li>
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* <li>org.apache.logging.log4j.Logger 日志框架 log4j2</li>
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* <li>org.apache.log4j.Logger 日志框架 log4j </li>
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* <li>java.util.logging.Logger 日志框架,JDK的logger</li>
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*
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* </ol>
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* @author Clinton Begin
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* @author Eduardo Macarron
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*/
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public final class LogFactory {
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/**
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* Marker to be used by logging implementations that support markers.
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*/
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public static final String MARKER = "MYBATIS";
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private static Constructor<? extends Log> logConstructor;
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/**
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* 日志的实现类的具体选择
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*/
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static {
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// slf4j 日志
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tryImplementation(LogFactory::useSlf4jLogging);
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// apache 日志
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tryImplementation(LogFactory::useCommonsLogging);
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// log4j2 日志
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tryImplementation(LogFactory::useLog4J2Logging);
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// log4 日志
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tryImplementation(LogFactory::useLog4JLogging);
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// JDK 日志
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tryImplementation(LogFactory::useJdkLogging);
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// 空 日志
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tryImplementation(LogFactory::useNoLogging);
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}
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/**
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* 私有化构造方法,这是一个单例
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*/
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private LogFactory() {
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// disable construction
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}
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public static Log getLog(Class<?> aClass) {
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return getLog(aClass.getName());
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}
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public static Log getLog(String logger) {
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try {
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return logConstructor.newInstance(logger);
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} catch (Throwable t) {
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throw new LogException("Error creating logger for logger " + logger + ". Cause: " + t, t);
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}
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}
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public static synchronized void useCustomLogging(Class<? extends Log> clazz) {
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setImplementation(clazz);
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}
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public static synchronized void useSlf4jLogging() {
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setImplementation(org.apache.ibatis.logging.slf4j.Slf4jImpl.class);
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}
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public static synchronized void useCommonsLogging() {
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setImplementation(org.apache.ibatis.logging.commons.JakartaCommonsLoggingImpl.class);
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}
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public static synchronized void useLog4JLogging() {
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setImplementation(org.apache.ibatis.logging.log4j.Log4jImpl.class);
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}
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public static synchronized void useLog4J2Logging() {
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setImplementation(org.apache.ibatis.logging.log4j2.Log4j2Impl.class);
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}
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public static synchronized void useJdkLogging() {
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setImplementation(org.apache.ibatis.logging.jdk14.Jdk14LoggingImpl.class);
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}
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public static synchronized void useStdOutLogging() {
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setImplementation(org.apache.ibatis.logging.stdout.StdOutImpl.class);
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}
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public static synchronized void useNoLogging() {
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setImplementation(org.apache.ibatis.logging.nologging.NoLoggingImpl.class);
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}
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/**
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* 选择具体的日志实现
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*/
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private static void tryImplementation(Runnable runnable) {
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if (logConstructor == null) {
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try {
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// run()? 似乎违背了代码的语义, 看静态方法.静态方法多行同类型的操作我认为是一个多线程
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runnable.run();
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} catch (Throwable t) {
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// ignore
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}
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}
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}
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/**
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* 选择具体的日志实现
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*/
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private static void setImplementation(Class<? extends Log> implClass) {
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try {
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Constructor<? extends Log> candidate = implClass.getConstructor(String.class);
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Log log = candidate.newInstance(LogFactory.class.getName());
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if (log.isDebugEnabled()) {
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log.debug("Logging initialized using '" + implClass + "' adapter.");
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}
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logConstructor = candidate;
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} catch (Throwable t) {
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throw new LogException("Error setting Log implementation. Cause: " + t, t);
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}
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}
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}
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```
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- `LogFactory`是一个单例对象,对外公开`getLog`方法在使用时直接`private static final Log log = LogFactory.getLog(CglibProxyFactory.class);`即可
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- 在 `org.apache.ibatis.session.Configuration` 中可以看到下面这些注册方法
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```java
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// 日志实现类
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typeAliasRegistry.registerAlias("SLF4J", Slf4jImpl.class);
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typeAliasRegistry.registerAlias("COMMONS_LOGGING", JakartaCommonsLoggingImpl.class);
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typeAliasRegistry.registerAlias("LOG4J", Log4jImpl.class);
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typeAliasRegistry.registerAlias("LOG4J2", Log4j2Impl.class);
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typeAliasRegistry.registerAlias("JDK_LOGGING", Jdk14LoggingImpl.class);
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typeAliasRegistry.registerAlias("STDOUT_LOGGING", StdOutImpl.class);
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typeAliasRegistry.registerAlias("NO_LOGGING", NoLoggingImpl.class);
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```
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