大家能够松一口气了,这个组件比較简单,这一节和前面几节想比,也简单的多。

Logger接口

Tomcat中的日志记录器都必须实现org.apache.catalina.Logger接口。

package org.apache.catalina;

import java.beans.PropertyChangeListener;

public interface Logger {
    
    public static final int FATAL = Integer.MIN_VALUE;
    public static final int ERROR = 1;
    public static final int WARNING = 2;
    public static final int INFORMATION = 3;
    public static final int DEBUG = 4;

    public Container getContainer();
    public void setContainer(Container container);
    public String getInfo();
    public int getVerbosity();
    public void setVerbosity(int verbosity);
    public void addPropertyChangeListener(PropertyChangeListener listener);

    public void log(String message);
    public void log(Exception exception, String msg);
    public void log(String message, Throwable throwable);
    public void log(String message, int verbosity);
    public void log(String message, Throwable throwable, int verbosity);
    public void removePropertyChangeListener(PropertyChangeListener listener);
}

Logger定义了五种日志记录基本,当我们在调用log(String message, int verbosity)方法记录日志的时候,仅仅有传进来的verbosity小于等于系统的默认值才会记录。话说大家知道Integer.MIN_VALUE等于多少吗?大概负的21亿左右吧。setVerbosity与getVerbosity是干什么的还须要我说么?

Tomcat的日志记录器

LoggerBase类(抽象类)

它实现了Logger接口中除log(String message)方法外的其余方法;
在类中默认了日志记录级别为
         protected int verbosity = ERROR;
可是我们能够通过setVerbosity(int verbosity)来又一次设置记录级别;
看看定义的接受日志级别的两个log方法

public void log(String message, int verbosity) {
    if (this.verbosity >= verbosity)
        log(message);
}
public void log(String message, Throwable throwable, int verbosity) {
    if (this.verbosity >= verbosity)
        log(message, throwable);
}

SystemOutLogger类

看名字就知道,信息最后输出到控制台。

SysteErrLogger类

看名字就知道,它是错误输出,信息仍在控制台,只是是红色的。

FileLogger类

看名字就知道,它是吧信息输出的文件中。
只是详细的来说,里面还是有点说头的,慢慢来。

首先FileLogger还实现了Lifecycle接口,因此它能够像其它组件一样被父组件所启动。
在本节中FileLogger的start与stop方法事实上仅仅是改变了布尔值started而已,没有做其它的,还有一方面,FileLogger的start与stop方法也并没有被调用!
如今我们就看看怎么给文件中写信息。

 

public void log(String msg) {

        // Construct the timestamp we will use, if requested
        Timestamp ts = new Timestamp(System.currentTimeMillis());
        String tsString = ts.toString().substring(0, 19);
        String tsDate = tsString.substring(0, 10);
        System.out.println("tsString   "+tsString); //tsString   2014-10-20 15:25:27
        System.out.println("ts   "+ts);            //ts   2014-10-20 15:25:27.406
        System.out.println("tsDate   "+tsDate);        //tsDate   2014-10-20

        // If the date has changed, switch log files
        if (!date.equals(tsDate)) {
            synchronized (this) {
                if (!date.equals(tsDate)) {
                    close();
                    date = tsDate;
                    open();
                }
            }
        }

        // Log this message, timestamped if necessary
        if (writer != null) {
            if (timestamp) {
                writer.println(tsString + " " + msg);
            } else {
                writer.println(msg);
            }
        }
    }

File默认是每一天一个新的文件,文件内格式就是日期+详细信息(假设timestamp为true的话);
那close(),open()方法和writer属性又是什么呢?
 

   private void open() {

        // Create the directory if necessary
        File dir = new File(directory);
        if (!dir.isAbsolute())
            dir = new File(System.getProperty("catalina.base"), directory);  //至于catalina.base是什么 一会再说
        dir.mkdirs();

        // Open the current log file
        try {
            String pathname = dir.getAbsolutePath() + File.separator +
                prefix + date + suffix;
            writer = new PrintWriter(new FileWriter(pathname, true), true);
        } catch (IOException e) {
            writer = null;
        }

    }

先检查给定的文件夹是否存在,假设不存在新建一个;接着依据前缀,时间,后缀设定文件名称;依据文件名称填充writer对象。

    private void close() {

        if (writer == null)
            return;
        writer.flush();
        writer.close();
        writer = null;
        date = "";
    }

FileLogger中的date代表的就是当前的时间,当然关闭后为空。

应用程序

Bootstrap类

...
    System.setProperty("catalina.base", System.getProperty("user.dir"));
    FileLogger logger = new FileLogger();
    logger.setPrefix("FileLog_");
    logger.setSuffix(".txt");
    logger.setTimestamp(true);
    logger.setDirectory("webroot");
    context.setLogger(logger);
....

SimpleContext类

public synchronized void start() throws LifecycleException {
    log("starting Context");
    ........
    lifecycle.fireLifecycleEvent(AFTER_START_EVENT, null);
    log("Context started");
  }
private void log(String message) {
    Logger logger = this.getLogger();
    if (logger!=null)
      logger.log(message);
  }

执行后在项目的webroot文件夹下就能够看到FileLog_2014-10-20.txt文件;
每次执行,在文件里都会多出例如以下的内容
2014-10-20 14:34:21 HttpConnector Opening server socket on all host IP addresses
2014-10-20 14:34:22 HttpConnector[8080] Starting background thread
2014-10-20 14:34:22 HttpProcessor[8080][0] Starting background thread
2014-10-20 14:34:22 HttpProcessor[8080][1] Starting background thread
2014-10-20 14:34:22 HttpProcessor[8080][2] Starting background thread
2014-10-20 14:34:22 HttpProcessor[8080][3] Starting background thread
2014-10-20 14:34:22 HttpProcessor[8080][4] Starting background thread
2014-10-20 14:34:22 starting Context
2014-10-20 14:34:22 Context started