Log4j的使用教程

野性酷女 2022-07-14 23:13 164阅读 0赞

关于Log4J日志的配置详细解析请参考：[http://blog.csdn.net/qq\_32786873/article/details/51801116][http_blog.csdn.net_qq_32786873_article_details_51801116]

一.在java项目中使用Log4j

1.新建一个Java工程，导入包[log4j-1.2.17.jar][]，整个工程最终目录如下

![Center][]

2.src同级创建并设置log4j.properties

log4j.properties文件配置如下:

log4j.rootLogger=DEBUG, A1 ,R 
    log4j.appender.A1=org.apache.log4j.ConsoleAppender 
    log4j.appender.A1.layout=org.apache.log4j.PatternLayout 
    log4j.appender.A1.layout.ConversionPattern=%-d{yyyy-MM-dd HH\:mm\:ss} [%c]-[%p] %m%n
    log4j.appender.R=org.apache.log4j.RollingFileAppender 
    log4j.appender.R.File=D:\\Test_Log4j.log 
    log4j.appender.R.MaxFileSize=100KB log4j.appender.R.MaxBackupIndex=1
    log4j.appender.R.layout=org.apache.log4j.PatternLayout 
    log4j.appender.R.layout.ConversionPattern=%-d{yyyy-MM-dd HH\:mm\:ss} [%c]-[%p] %m%n

3、设置日志内容

package Solin;
    
    import org.apache.log4j.Logger;
    import org.apache.log4j.PropertyConfigurator;
    
    public class TestLog4J {
    	private static Logger log = Logger.getLogger(TestLog4J.class);
    	
    	public static void main(String[] args) {
    		PropertyConfigurator.configure(".\\src\\log4j.properties");
    		log.debug("This is debug message!");
    		log.info("This is info message!");
    		log.warn("This is warn message!");
    		log.error("This is error message!");
    	}
    }

4.输出结果  
     （1）首先是控制台的信息

![Center 1][]

（2）再来看输出的文件

![Center 2][]

以下内容来源于：[http://www.codeceo.com/article/log4j-usage.html][http_www.codeceo.com_article_log4j-usage.html]

二.Web项目中使用Log4j实例

上面代码描述了Log4j的简单应用，其实使用Log4j也就是这样简单方便。当然除了上面的配置方法，还有其它，比如做一个J2EE应用，在J2EE应用中使用Log4j，必须先在启动服务时加载Log4j的配置文件进行初始化，可以在web.xml中进行。  
  
1、web应用的log4j使用基本上都采用：新建一个servlet，这个servlet在init函数中为log4j执行配置。一般就是读入配置文件。所以需要在web.xml中为这个servlet配置，同时设定load-on-startup为1。  
  
2、这个servlet配置log4j就是读出配置文件，然后调用configure函数。这里有两个问题：一、需要知道文件在哪里；二、需要正确的文件类型  
  
3、配置文件位置在web.xml中配置一个param即可，路径一般是相对于web的root目录  
  
4、文件类型一般有两种，一个是Java的property文件，另一种是xml文件  
  
配置文件的大致内容：log4j可以指定输出的log级别的最低等级，以及log的输出配置格式，每个log可以指定多个输出方式

（1）创建Web工程，整个工程最后目录如下

![Center 3][]

（2）web.xml配置如下：

（3）配置文件log4j.properties

（4）web容器一来就初始化的servlet

Log4JInitServlet.java

package Solin;
    
    import java.io.File;
    import java.io.IOException;
    
    import javax.servlet.ServletConfig;
    import javax.servlet.ServletContext;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import org.apache.log4j.BasicConfigurator;
    import org.apache.log4j.PropertyConfigurator;
    
    @WebServlet("/Log4JInitServlet") 
    public class Log4JInitServlet extends HttpServlet {
    	private static final long serialVersionUID = -8587938407567965599L;
    
    	public Log4JInitServlet() {
    		super();
    	}
    
    	@Override
    	public void init(ServletConfig config) throws ServletException {
    		System.out.println("Log4JInitServlet 正在初始化 log4j日志设置信息");  
            String log4jLocation = config.getInitParameter("log4j-properties-location");  
    
            ServletContext sc = config.getServletContext();  
    
            if (log4jLocation == null) {  
                System.err.println("*** 没有 log4j-properties-location 初始化的文件, 所以使用 BasicConfigurator初始化");  
                BasicConfigurator.configure();  
            } else {  
                String webAppPath = sc.getRealPath("/");  
                String log4jProp = webAppPath + log4jLocation;  
                File file = new File(log4jProp);  
                if (file.exists()) {  
                    System.out.println("使用: " + log4jProp+"初始化日志设置信息");  
                    PropertyConfigurator.configure(log4jProp);  
                } else {  
                    System.err.println("*** " + log4jProp + " 文件没有找到， 所以使用 BasicConfigurator初始化");  
                    BasicConfigurator.configure();  
                }  
            }  
            super.init(config);  
    	}
    
    	@Override
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    	}
    
    	@Override
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    	}
    
    }

（5）调用日志Log4JTestServlet.java

package Solin;
    
    import java.io.IOException;
    
    import javax.servlet.ServletConfig;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import org.apache.log4j.Logger;
    
    @WebServlet("/Log4JTestServlet")  
    public class Log4JTestServlet extends HttpServlet {
    	private static final long serialVersionUID = 6357686651026518299L;
    	private static Logger log = Logger.getLogger(Log4JTestServlet.class);
    	
    	public Log4JTestServlet() {
    		super();
    	}
    
    	@Override
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		// 记录debug级别的信息    
            log.debug("This is debug message!");    
            // 记录info级别的信息    
            log.info("This is info message!"); 
            // 记录warn级别的信息    
            log.warn("This is warn message!");
            // 记录error级别的信息    
            log.error("This is error message!"); 
    	}
    
    	@Override
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		doGet(req,resp);
    	}
    
    	@Override
    	public void init(ServletConfig config) throws ServletException {
    		// TODO Auto-generated method stub
    	}
    
    }

（6）控制台信息：

![Center 4][]![Center 5][]

（7）输出结果：

![Center 6][]

三、Spring中使用Log4j

这里要实现web项目中利用Spring来使用Log4j

（1）接上面的工程，然后再导入Spring的包  
（2）web.xml增加

<context-param>    
           <param-name>webAppRootKey</param-name>    
           <param-value>webapp.root</param-value>    
       </context-param>    
    
       <context-param>  
        <param-name>log4jConfigLocation</param-name>  
        <param-value>/WEB-INF/classes/log4j.properties</param-value>  
    </context-param>  
      
    <context-param>    
            <param-name>log4jRefreshInterval</param-name>    
            <param-value>3000</param-value>    
       </context-param>   
    <listener>  
        <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>  
    </listener>

整个内容如下：

<?xml version="1.0" encoding="UTF-8"?>  
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
        xmlns="http://java.sun.com/xml/ns/javaee"  
        xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"  
        id="WebApp_ID" version="3.0">  
        <display-name>TestLog4J</display-name>  
    
        <servlet>  
            <servlet-name>Log4JTestServlet</servlet-name>  
            <servlet-class>com.mucfc.Log4JTestServlet</servlet-class>  
        </servlet>  
    
          
      
    
        <servlet-mapping>  
            <servlet-name>Log4JTestServlet</servlet-name>  
            <url-pattern>/test</url-pattern>  
        </servlet-mapping>   
    
          
        <listener>  
            <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>  
        </listener>  
        <context-param>  
            <param-name>contextConfigLocation</param-name>  
            <param-value>classpath:applicationContext.xml</param-value>  
        </context-param>   
    
          
        <context-param>    
            <param-name>webAppRootKey</param-name>    
            <param-value>webapp.root</param-value>    
        </context-param>    
    
        <context-param>  
            <param-name>log4jConfigLocation</param-name>  
            <param-value>/WEB-INF/classes/log4j.properties</param-value>  
        </context-param>  
          
        <context-param>    
             <param-name>log4jRefreshInterval</param-name>    
             <param-value>3000</param-value>    
        </context-param>   
        <listener>  
            <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>  
        </listener>   
    
    </web-app>

这里Log4JInitServlet.java就相当于没用到了 。  
  
  
（3）applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>  
    <beans xmlns="http://www.springframework.org/schema/beans"  
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"  
        xmlns:aop="http://www.springframework.org/schema/aop"  
        xsi:schemaLocation="http://www.springframework.org/schema/beans
    						http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
    						http://www.springframework.org/schema/aop
    						http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
    						http://www.springframework.org/schema/context
    						http://www.springframework.org/schema/context/spring-context-3.2.xsd">  
    </beans>

（4）这样日志就跟随Spring窗口启动而启动了  
  程序一运行，就会自动把日志打印

![Center 7][]

Test\_Log4j.log

![Center 8][]

浏览器输入http://localhost:8080/TestLog4J/test

![Center 9][]

[http_blog.csdn.net_qq_32786873_article_details_51801116]: http://blog.csdn.net/qq_32786873/article/details/51801116
[log4j-1.2.17.jar]: http://download.csdn.net/detail/qq_32786873/9663405
[Center]: /images/20220715/6a308d9c526f478996ed283c3009cab4.png
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[http_www.codeceo.com_article_log4j-usage.html]: http://www.codeceo.com/article/log4j-usage.html
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