1．我们已经搭建完了基本框架，接下来加入日志功能，只需修改原来的web.xml，增加一些配置信息：
<!--通知Spring Log4j配置文件的位置 -->
<context-param>
<param-name>log4jConfigLocation</param-name>
<param-value>/WEB-INF/log4j.properties</param-value>
</context-param>
<!--Spring默认刷新Log4j配置文件的间隔,单位为millisecond-->
<context-param>
<param-name>log4jRefreshInterval</param-name>
<param-value>60000</param-value>
</context-param>
<!--在应用启动时，由Spring负责加载Log4j-->
<listener>
<listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>
</listener>
2．接下来我们定义log4j.properties
# Global logging configuration
log4j.rootLogger=DEBUG,console,file
## APPENDERS ##
# define an appender named console, which is set to be a ConsoleAppender
log4j.appender.console=org.apache.log4j.ConsoleAppender
# define an appender named file, which is set to be a RollingFileAppender
log4j.appender.file=org.apache.log4j.RollingFileAppender
# replace <CATALINA_HOME> with your true path
log4j.appender.file.File=D:/eclipse/workspace/login/log.txt
## LAYOUTS ##
# assign a SimpleLayout to console appender
log4j.appender.console.layout=org.apache.log4j.SimpleLayout
# assign a PatternLayout to file appender
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%t%p-%m%n
在log4j.properties中，我们定义了日志级别是DEBUG,日志信息输出目的地是控制台（console）和文件（file）。
3．这样我们就可以在程序代码中进行日志操作了：
package test.register.action;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.log4j.LogManager;
import org.apache.log4j.Logger;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.DynaActionForm;
import test.register.entity.Register;
import test.register.service.RegisterService;
public class RegisterAction extends Action{
private static final Logger log = LogManager.getLogger(RegisterAction.class);
private RegisterService registerService;
public RegisterService getRegisterService() {
return registerService;
}
public void setRegisterService(RegisterService registerService) {
this.registerService = registerService;
}
public ActionForward execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
log.info("save register...");
Register r = (Register)((DynaActionForm)form).get("register");
getRegisterService().saveRegister(r);
return mapping.findForward("success");
}
}
4．在上面log4j.properties中，我们指定日志输入文件用了绝对路径，这在很多时候不方便，为此我们作如下修改：在web.xml中增加一个上下文参数
<context-param>
<param-name>webAppRootKey</param-name>
<param-value>webLogin.root</param-value>
</context-param>
增加系统变量，变量名为webAppRootKey，变量值可以指定应用部署的目录，这样就可以在log4j.properties对日志输出的文件路径作如下修改：
log4j.appender.file.File=${webLogin.root}/log.txt