网上太多博客都讲不清楚…忍不住了,最恶心的是你转载copy过来好歹看一下格式吧,一半文件有格式一半文件没格式恶心谁啊

明确目的:只需要在控制台中输出即可

添加依赖

首先添加依赖,这里需要会使用maven

<dependency>
  	<groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.14</version>
</dependency>

配置文件

个人的配置,具体可以看下面的连接,可以根据不同情况来配置,如果要输出到文本还要修改…

log4j.rootLogger = debug, stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender  
log4j.appender.stdout.Target=System.out  
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout  
log4j.appender.stdout.layout.ConversionPattern=[%-5p] %d{yyyy-MM-dd HH:mm:ss,SSS} method:%l%n%m%n  

详解log4j配置文件〰

初始化配置文件

根据:log4j在javaWeb项目中的使用〰 我改了一下代码,写完之后需要在web.xml中配置

public class Log4JInitServlet extends HttpServlet {

    @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();

        String str= sc.getInitParameter("test");
        System.out.println("str:"+str);

        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 yoMamaYesThisSaysYoMama = new File(log4jProp);
            if (yoMamaYesThisSaysYoMama.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);
    }
}

	<servlet>
        <servlet-name>Log4JInitServlet</servlet-name>
        <servlet-class>top.sehnsucht.Log4JInitServlet</servlet-class>
        <init-param>
            <param-name>log4j-properties-location</param-name>
            <param-value>log4j.properties</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

之后在java文件中如何使用? 使用前输入 private Logger logger=Logger.getLogger(this.getClass());,看下示例就懂了

public class TestServlet extends HttpServlet {
    private Logger logger=Logger.getLogger(this.getClass());

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        logger.debug("你好啊");
        logger.info("我不好");
        logger.error("她和你都很好");
    }
    
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}