使用log4j MDC记录操作员的信息
在记录日志的时候，我们可能有这种需求，对于每个记录除了知道日志信息外，也要当前登录用户的信息。
可以这样解决：使用log4j的MDC
在web.xml加入 Filter：
<filter>
<filter-name>set log4j MDC for log2userId</filter-name>
<filter-class>UserFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>set log4j MDC for log2userId</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
UserFilter的代码如下：
import org.apache.log4j.Logger;import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpSession;import org.apache.log4j.MDC;import org.springside.bookstore.domain.Customer;/** * 记录当前使用者的信息到log4j.MDC * @author frank * */public class UserFilter implements Filter { /** * Logger for this class */ private static final Logger logger = Logger.getLogger(UserFilter.class); private final static String DEFAULT_USERID="anonymous"; public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { HttpServletRequest req=(HttpServletRequest)request; HttpSession session= req.getSession(); if (session==null){ MDC.put("userId",DEFAULT_USERID); } else{ Customer customer=(Customer)session.getAttribute("customer"); if (customer==null){ MDC.put("userId",DEFAULT_USERID); } else { MDC.put("userId",customer.getLoginid()); } } logger.info("test for MDC."); chain.doFilter(request,response); } public void init(FilterConfig fc) throws ServletException { // do nothing } public void destroy() {// do nothing }}在log4j.properties中加入新配置，示例使用jdbc存储log4j.appender.db=org.apache.log4j.jdbc.JDBCAppender#log4j.appender.db.BufferSize=100log4j.appender.db.URL=jdbc:ulrlog4j.appender.db.driver=org.hsqldb.jdbcDriverlog4j.appender.db.user=salog4j.appender.db.password=log4j.appender.db.sql=INSERT INTO LOG4J_MSG (LOGINID,PRIORITY,LOGDATE,CLASS,METHOD,MSG) VALUES(‘%X{userId}’,’%p’,'%d{yyyy-MM-dd HH:mm:ss}’,'%C’,'%M’,'%m’)%X{userId}：就是取出MDC的代码了