log4j 的使用

log4j 对于java 程序员费用重要，能够记录程序运行过程。

如果配置log4j 呢？

Step 1:添加log4j.jar文件

Step 2:创建log4j.properties文件
注意：文件名必须叫log4j.properties，位置必须在src下，两者缺一不可

Step 3: 编写log4j.properties 配置文件：

   例如（直接copy下面代码）：

###设置logger输出级别和输出目的地###

log4j.rootLogger=debug, stdout,logfile

### 把日志信息输出到控制台###

log4j.appender.stdout=org.apache.log4j.ConsoleAppender

log4j.appender.stdout.Target=System.err

log4j.appender.stdout.layout=org.apache.log4j.SimpleLayout
###把日志信息输出到文件：myfile.log###

log4j.appender.logfile=org.apache.log4j.FileAppender

log4j.appender.logfile.File=myfile.log

log4j.appender.logfile.layout=org.apache.log4j.PatternLayout

log4j.appender.logfile.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %l %F %p %m%n

Step 4：引进包和声明logger变量：

import org.apache.log4j.Logger;

private static Logger logger=Logger.getLogger(Father.class.getName());

Step 5：代码中给logger的属性赋值

package org.test.www;
import java.util.InputMismatchException;
import java.util.Scanner;
import org.apache.log4j.Logger;

public class Father {
private static Logger logger=Logger.getLogger(Father.class.getName());
public int  num;
public void Print() {
try {
Scanner scanner= new Scanner(System.in);

System.out.println("请输入被除数字：");
logger.debug("输入一个数");
int num1=scanner.nextInt();
logger.debug("这个数是"+num1);

System.out.println("请输入除数");

int num2=scanner.nextInt();

logger.debug("接收一个整数"+num2);
int result=num1/num2;
logger.debug("结果是"+result);
} catch (InputMismatchException e) {
logger.debug("输入的不是整数");
logger.debug(e.getMessage());
}catch(ArithmeticException e){
logger.info(e.getMessage());

}

}
}

运行结果如下：

1. 文档myfile.log

2013-07-28 11:09:51,703 %1 Father.java
DEBUG 输入一个数

2013-07-28 11:10:13 %1 Father.java DEBUG 输入一个数

2013-07-28 11:10:55 org.test.www.Father.Print(Father.java:13) Father.java DEBUG 输入一个数

2013-07-28 11:11:45 org.test.www.Father.Print(Father.java:13) Father.java DEBUG 输入一个数

2013-07-28 11:11:48 org.test.www.Father.Print(Father.java:15) Father.java DEBUG 接收一个整数

2013-07-28 11:14:11 org.test.www.Father.Print(Father.java:13) Father.java DEBUG 输入一个数

2013-07-28 11:14:15 org.test.www.Father.Print(Father.java:15) Father.java DEBUG 接收一个整数

2013-07-28 11:14:23 org.test.www.Father.Print(Father.java:13) Father.java DEBUG 输入一个数

2013-07-28 11:14:25 org.test.www.Father.Print(Father.java:15) Father.java DEBUG 接收一个整数

2013-07-28 11:21:09 org.test.www.Father.Print(Father.java:14) Father.java DEBUG 输入一个数

2013-07-28 11:32:15 org.test.www.Father.Print(Father.java:14) Father.java DEBUG 输入了一个数

2013-07-28 11:32:17 org.test.www.Father.Print(Father.java:16) Father.java DEBUG 这个数是1

2013-07-28 11:32:17 org.test.www.Father.Print(Father.java:18) Father.java DEBUG 接收一个整数1

2013-07-28 11:32:52 org.test.www.Father.Print(Father.java:14) Father.java DEBUG 输入了一个数

2013-07-28 11:32:55 org.test.www.Father.Print(Father.java:16) Father.java DEBUG 这个数是2

2013-07-28 11:33:00 org.test.www.Father.Print(Father.java:19) Father.java DEBUG 接收一个整数2

2013-07-28 11:33:37 org.test.www.Father.Print(Father.java:14) Father.java DEBUG 输入了一个数

2013-07-28 11:33:43 org.test.www.Father.Print(Father.java:16) Father.java DEBUG 这个数是1

2013-07-28 11:33:47 org.test.www.Father.Print(Father.java:19) Father.java DEBUG 接收一个整数2

2013-07-28 11:33:47 org.test.www.Father.Print(Father.java:21) Father.java DEBUG 0

2013-07-28 11:34:18 org.test.www.Father.Print(Father.java:14) Father.java DEBUG 输入一个数

2013-07-28 11:34:21 org.test.www.Father.Print(Father.java:23) Father.java DEBUG 输入的不是整数

2013-07-28 11:34:21 org.test.www.Father.Print(Father.java:24) Father.java DEBUG 

2013-07-28 11:44:48 org.test.www.Father.Print(Father.java:14) Father.java DEBUG 输入一个数

2013-07-28 11:47:56 org.test.www.Father.Print(Father.java:14) Father.java DEBUG 输入一个数

2013-07-28 11:47:58 org.test.www.Father.Print(Father.java:16) Father.java DEBUG 这个数是10

2013-07-28 11:48:00 org.test.www.Father.Print(Father.java:19) Father.java DEBUG 接收一个整数2

2013-07-28 11:48:00 org.test.www.Father.Print(Father.java:21) Father.java DEBUG 结果是5

2013-07-28 11:48:23 org.test.www.Father.Print(Father.java:14) Father.java DEBUG 输入一个数

2013-07-28 11:48:26 org.test.www.Father.Print(Father.java:16) Father.java DEBUG 这个数是20

2013-07-28 11:48:28 org.test.www.Father.Print(Father.java:19) Father.java DEBUG 接收一个整数0

2013-07-28 11:48:28 org.test.www.Father.Print(Father.java:26) Father.java INFO / by zero

2. 控制台结果为：