web日志源码分析

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通过本图可以理清楚日志之间的关系，

commons-logging和slf4j都是日志的接口，供用户使用，而没有提供实现！

log4j,logback等等才是日志的真正实现。

目前的日志框架有jdk自带的logging，log4j1、log4j2、logback

目前用于实现日志统一的框架apache的commons-logging、slf4j

为了理清它们的关系，与繁杂的各种集成jar包，如下：

• log4j、log4j-api、log4j-core

• log4j-1.2-api、log4j-jcl、log4j-slf4j-impl、log4j-jul

• logback-core、logback-classic、logback-access

• commons-logging

• slf4j-api、slf4j-log4j12、slf4j-simple、jcl-over-slf4j、slf4j-jdk14、log4j-over-slf4j、slf4j-jcl

1.jdk 自带的log，

java.util.logging.Logger l = java.util.logging.Logger.getLogger(Deme.class.getName());

查看源码，主要是构建LoggerManage的时候读取配置文件

public static LogManager getLogManager() {    if (manager != null) {        manager.ensureLogManagerInitialized();    }    return manager;}final void ensureLogManagerInitialized() {    final LogManager owner = this;//省略   // Read configuration.   owner.readPrimordialConfiguration();}private void readPrimordialConfiguration() {  //省略  readConfiguration();}public void readConfiguration() throws IOException, SecurityException {//省略//默认是jre目录下的lib/logging.properties文件，也可以自定义修改系统属性"java.util.logging.config.file",源码如下：     String fname = System.getProperty("java.util.logging.config.file");        if (fname == null) {            fname = System.getProperty("java.home");            if (fname == null) {                throw new Error("Can't find java.home ??");            }            File f = new File(fname, "lib");            f = new File(f, "logging.properties");            fname = f.getCanonicalPath();        }        try (final InputStream in = new FileInputStream(fname)) {            final BufferedInputStream bin = new BufferedInputStream(in);            readConfiguration(bin);        }   }

2.1 log4j1 真正实现日志读写

//jar包引入    log4j    log4j    1.2.17//初始化，查看源码,org.apache.log4j.Logger logger1 = org.apache.log4j.Logger.getLogger("class or className");

public class Logger extends Category {  //可以看到 Logger继承了Category 类，这个类打印日志信息的时候有用。  Logger getLogger(String name) {    return LogManager.getLogger(name);  }}public class LogManager {  //主要是 LogManager 的getLogger方法  Logger getLogger(final String name) {     // Delegate the actual manufacturing of the logger to the logger repository.    return getLoggerRepository().getLogger(name);  }  //LogManager 类有个静态方法  static {    //初始化一个logger仓库Hierarchy，然后绑定到LoggerManager上，主要是通过getLoggerRepository()方法获取。    // By default we use a DefaultRepositorySelector which always returns 'h'.    Hierarchy h = new Hierarchy(new RootLogger((Level) Level.DEBUG));    repositorySelector = new DefaultRepositorySelector(h);    /** Search for the properties file log4j.properties in the CLASSPATH.  */    String override =OptionConverter.getSystemProperty(DEFAULT_INIT_OVERRIDE_KEY,                                                       null);    // if there is no default init override, then get the resource    // specified by the user or the default config file.    if(override == null || "false".equalsIgnoreCase(override)) {    String configurationOptionStr = OptionConverter.getSystemProperty(DEFAULT_CONFIGURATION_KEY ,null);  //省略代码  // 这里配置文件有个加载顺序  // log4j.defaultInitOverride > log4j.configuration > log4j.xml > log4j.properties  }  //通过查看Hierarchy这个类}public class Hierarchy implements LoggerRepository, RendererSupport, ThrowableRendererSupport {    private LoggerFactory defaultFactory;  //创建Logger工厂  Hashtable ht; //存放工厂创建的Logger  Logger root; //用于承载解析配置文件的结果，设置级别，同时存放appender  //省略    //构造方法  public Hierarchy(Logger root) {    ht = new Hashtable();    listeners = new Vector(1);    this.root = root;    // Enable all level levels by default.    setThreshold(Level.ALL);    this.root.setHierarchy(this);    rendererMap = new RendererMap();    defaultFactory = new DefaultCategoryFactory();  }}

2.2 log4j2 日志源码解析

//添加jar包，    org.apache.logging.log4j    log4j-api    2.2        org.apache.logging.log4j        log4j-core        2.2og4j2分成2个部分：log4j-api： 作为日志接口层，用于统一底层日志系统log4j-core : 作为上述日志接口的实现，是一个实际的日志框架web.xml 添加如下信息            org.apache.logging.log4j.web.Log4jServletFilter                log4jServletFilter        org.apache.logging.log4j.web.Log4jServletFilter                log4jServletFilter        /*        REQUEST        FORWARD        INCLUDE        ERROR    //创建对象Logger logger = LoggerFactory.getLogger(DemeMapping.class);

//LoggerFactory的getlogger方法public final class LoggerFactory {    public static Logger getLogger(Class clazz) {        Logger logger = getLogger(clazz.getName());        if (DETECT_LOGGER_NAME_MISMATCH) {            Class autoComputedCallingClass = Util.getCallingClass();            if (nonMatchingClasses(clazz, autoComputedCallingClass)) {                Util.report(String.format("Detected logger name mismatch. Given name: \"%s\"; computed name: \"%s\".", logger.getName(), autoComputedCallingClass.getName()));                Util.report("See http://www.slf4j.org/codes.html#loggerNameMismatch for an explanation");            }        }        return logger;    }    //获取logger对象    public static Logger getLogger(String name) {        //最终获取的是Log4jLoggerFactory对象实现了ILoggerFactory接口        ILoggerFactory iLoggerFactory = getILoggerFactory();        //调用的其实是Log4jLoggerFactory这个类        return iLoggerFactory.getLogger(name);    }    public static ILoggerFactory getILoggerFactory() {        //初始化，并且改变INITIALIZATION_STATE = 3        performInitialization();        case 3:            return StaticLoggerBinder.getSingleton().getLoggerFactory();    }    //主要看里面bind方法    private static final void bind() {        String msg;        try {            //这里通过类加载方式找到StaticLoggerBinder对象，            //代码里面定义路径："org/slf4j/impl/StaticLoggerBinder.class">

3 logback 日志解析

需要的jar包

• logback-core

• logback-classic

• slf4j-api

//添加maven依赖         ch.qos.logback         logback-core         1.1.3       ch.qos.logback     logback-classic     1.1.3         org.slf4j        slf4j-api        1.7.12//或者                  framework.pisces            pisces-log            1.2.3-beta                                                com.fasterxml.jackson.module                    jackson-module-jaxb-annotations                                                                        com.fasterxml.jackson.dataformat                    jackson-dataformat-xml                                                                        com.fasterxml.jackson.module                    jackson-module-jaxb-annotations                                                    com.fasterxml.jackson.jaxrs                    jackson-jaxrs-xml-provider                                                    slf4j-log4j12                    org.slf4j                                                    log4j                    log4j                                    

//申明变量org.slf4j.Logger logger2 = LoggerFactory.getLogger("");//用到的也是 LoggerFactory来创建public final class LoggerFactory {  public static Logger getLogger(String name) {    ILoggerFactory iLoggerFactory = getILoggerFactory();    return iLoggerFactory.getLogger(name);  }}//这里的调用和slf4j是一样getILoggerFactory()-> performInitialization(); -> bind(); -> findPossibleStaticLoggerBinderPathSet(); -> 返回LoggerContext对象//唯一不同是构造StaticLoggerBinder的地址是 "org/slf4j/impl/StaticLoggerBinder.class" ，在调用StaticLoggerBinder.getSingleton(); 用的是 logback-classic-0.9.21.jar包下的StaticLoggerBinder public class StaticLoggerBinder implements LoggerFactoryBinder {  //可以看到这里初始化并赋值 LoggerContext 对象  private LoggerContext defaultLoggerContext = new LoggerContext();  static {    SINGLETON.init();  }  void init() {    try {     //这里就是初始化并存储值defaultLoggerContext，看看autoConfig()方法，里面主要是findURLOfDefaultConfigurationFile(true); 方法在读取配置文件，      new ContextInitializer(defaultLoggerContext).autoConfig();   } private static StaticLoggerBinder SINGLETON = new StaticLoggerBinder();  public static StaticLoggerBinder getSingleton() {    return SINGLETON;  }  private StaticLoggerBinder() {    defaultLoggerContext.setName(CoreConstants.DEFAULT_CONTEXT_NAME);  }}

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