Myeclipse部署Web Project时如何输出日志

去官网下log4j-1.2.16.jar放在web项目的 WebRoot/WEB-INF/lib目录下， 然后再在MyEclipse右击属性里，添加到项目里，可能不添加也行。

建一个 log4j.properties文件，放在WebRoot/WEB-INF/classes目录下，内容可以参考如下：

log4j.rootCategory=INFO, stdout , R

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=[QC] %p [%t] %C.%M(%L) | %m%n

log4j.appender.R=org.apache.log4j.DailyRollingFileAppender
log4j.appender.R.File=dataservice.log
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%d-[TS] %p %t %c - %m%n

log4j.logger.com.neusoft=DEBUG
log4j.logger.com.opensymphony.oscache=ERROR
log4j.logger.net.sf.navigator=ERROR
log4j.logger.org.apache.commons=ERROR
log4j.logger.org.apache.struts=WARN
log4j.logger.org.displaytag=ERROR
log4j.logger.org.springframework=DEBUG
log4j.logger.com.ibatis.db=WARN
log4j.logger.org.apache.velocity=FATAL

log4j.logger.com.canoo.webtest=WARN

log4j.logger.org.hibernate.ps.PreparedStatementCache=WARN
log4j.logger.org.hibernate=DEBUG
log4j.logger.org.logicalcobwebs=WARN

在web.xml中，添加上：

<servlet>
<servlet-name>j2eelog4jdemo</servlet-name>
<servlet-class>lab.iel.logs.J2eeLog4jDemo</servlet-class>
<init-param>
<param-name>log4j</param-name>
<param-value>log4j.properties</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>

里面所提到的这个所谓的类 lab.iel.logs.J2eeLog4jDemo ，它内容如下：

package lab.iel.logs;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.PropertyConfigurator;

public class J2eeLog4jDemo extends HttpServlet {

public void destroy() {
super.destroy();
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
public void init() throws ServletException {
//通过web.xml来动态取得配置文件
String prefix = getServletContext().getRealPath("/");
String file = getInitParameter("log4j");

//如果没有给出相应的配置文件，则不进行初始化
if(file != null)
{
PropertyConfigurator.configure(prefix+file);
}
}

}

建一个LogHelper类，专门用于处理输出日志，代码如下：

import org.apache.log4j.*;
public class LogHelper {

private static Logger logger = null;
private static void init(){
logger = Logger.getLogger(lab.iel.logs.LogHelper.class);
}

public static Logger getLogger(){
if(null ==logger){
init();
}
return logger;
}
}

调用 ：

在jsp页面中

<%@ page language="java" import="lab.iel.logs.LogHelper"%>

然后写 LogHelper.getLogger().info("sth");

就可以输出了

如此，部署以后它就可以向，比如tomcat的文件夹里，写日志了。