log4j 路径环境变量配置和log4j加载配置

1.lo4j日志路径从环境变量读取，log4j.xml配置如下：

具体配置如下：
log4j.appender.R.Encoding=UTF-8
log4j.appender.R=org.apache.log4j.DailyRollingFileAppender
log4j.appender.R.Append=true
#log4j.appender.R.Threshold=INFO
log4j.appender.R.File=${log4j.home}/logs/log.log
log4j.appender.R.DatePattern='.'yyyy-MM-dd
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%-d{yyyy-MM-dd HH\:mm\:ss} [%c]-[%p] %m%n

1.1 监听配置web.xml

  <listener>
      <listener-class>com.jumper.logview.servlet.Log4jlistener</listener-class>
  </listener>
  

1.2 监听代码

public class Log4jlistener implements ServletContextListener {
    final static String LOG4J_HOME = "log4j.home";
    final static String ENV_HOME = "LOG4J_HOME";

    public void contextDestroyed(ServletContextEvent servletcontextevent) {
        System.getProperties().remove(LOG4J_HOME);
    }

    public void contextInitialized(ServletContextEvent servletcontextevent) {
        String logsHome = System.getenv(ENV_HOME);
        if(logsHome == null){
            logsHome = System.getProperty("catalina.home")+"/log4j";
        }
System.out.println("*********log4j dir:"+logsHome);
        System.setProperty(LOG4J_HOME, logsHome);
    }
}

2.log4j　加载的两种方式

2.1采用spring加载配置

     <context-param>
        <param-name>log4jConfigLocation</param-name>
        <param-value>/WEB-INF/classes/config/log4j.properties</param-value>
    </context-param>
    <!-- Spring刷新Log4j配置文件变动的间隔,单位为毫秒 -->
    <context-param>
        <param-name>log4jRefreshInterval</param-name>
        <param-value>1000000</param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>
    </listener>

２.２采用serlvet加载

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import org.apache.log4j.PropertyConfigurator;
public class Log4jInit extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public void destroy() {
        super.destroy();
    }

    public Log4jInit() {
        super();
    }

    /**
     * Initialization of the servlet. <br>
     *
     * @throws ServletException
     *             if an error occurs
     */
    public void init() throws ServletException {
        String file = this.getInitParameter("log4j");// 从web.xml配置读取，名字一定要和web.xml配置一致
        if (file != null) {
            PropertyConfigurator.configure(this.getServletContext().getRealPath(file));
        }
    }
}

web.xml配置：
<servlet>
  <servlet-name>Log4jInit</servlet-name>
  <servlet-class>com.jumper.log4j.Log4jInit</servlet-class>
  <init-param>
   <param-name>log4j</param-name>//这个是名字是下边路径配置的标识（好像KEY一样）
   <param-value>/WEB-INF/classes/config/log4j.properties</param-value>//这是容器初始化时候加载log4j配置文件的路径（这好像一个value）;
  </init-param>
  <load-on-startup>1</load-on-startup>
 </servlet>