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tomcat 启动时使用的是java.util.logger 日志框架

tomcat 实现类

package org.apache.juli.logging;

import java.util.logging.ConsoleHandler;
import java.util.logging.Formatter;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Hardcoded java.util.logging commons-logging implementation.
 */
class DirectJDKLog implements Log {

下面在启动类中定义了一个log 对象

package org.apache.catalina.startup;

import java.io.File;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.catalina.Globals;
import org.apache.catalina.security.SecurityClassLoad;
import org.apache.catalina.startup.ClassLoaderFactory.Repository;
import org.apache.catalina.startup.ClassLoaderFactory.RepositoryType;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;


/**
 * Bootstrap loader for Catalina.  This application constructs a class loader
 * for use in loading the Catalina internal classes (by accumulating all of the
 * JAR files found in the "server" directory under "catalina.home"), and
 * starts the regular execution of the container.  The purpose of this
 * roundabout approach is to keep the Catalina internal classes (and any
 * other classes they depend on, such as an XML parser) out of the system
 * class path and therefore not visible to application level classes.
 *
 * @author Craig R. McClanahan
 * @author Remy Maucherat
 */
public final class Bootstrap {

    private static final Log log = LogFactory.getLog(Bootstrap.class);

在main函数中我们打印一个debug日志

 /**
     * Main method and entry point when starting Tomcat via the provided
     * scripts.
     *
     * @param args Command line arguments to be processed
     */
    public static void main(String args[]) {
        String javaVersion = System.getProperty("java.version");
        log.debug("starting ..."+javaVersion);

该日志是打不出来的
为什么呢？
如何让这该日志打印出来呢？
第一修改tomcat_home/conf/logger.properties 文件日志级别
结果依然没有打印出来
为什么呢？
因此此刻tomcat 并没有启动，默认读的日志文件依然是java_home/jar/lig/logger.properties 文件
修改该文件日志级别后日志打印正常。

细心的朋友们可能会注意到,tomcat为什么会打印红色日志？
因为

   /**
     * Create a ConsoleHandler for System.err.
     * 
     * The ConsoleHandler is configured based on
     * LogManager properties (or their default values).
     *
     */
    public ConsoleHandler() {
        sealed = false;
        configure();
        setOutputStream(System.err);
        sealed = true;
    }

System.err 是打印红色字体的

结束...

tomcat 日志从这里开始，欢迎持续关注
跟着疯子从0 学计算机，从这里开始...
https://github.com/sparrowzoo