随着业务的扩展，有时需要输出日志方便找出系统中的bug。同时好的日志也可以迅速定位问题，加快开发速度
参考文献：
1、https://www.yiibai.com/log4j log4j教程
2、https://www.cnblogs.com/v-weiwang/p/4814050.html springmvc+log4j 操作日志
依赖jar包
aopalliance-1.0.jar
commons-logging-1.2.jar
log4j-1.2.17.jar
spring-aop-4.3.8.RELEASE.jar
spring-beans-4.3.8.RELEASE.jar
spring-context-4.3.8.RELEASE.jar
spring-core-4.3.8.RELEASE.jar
spring-expression-4.3.8.RELEASE.jar
spring-web-4.3.8.RELEASE.jar
spring-webmvc-4.3.8.RELEASE.jar
操作步骤：
1、配置 web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>serverJsonTest</display-name>
<!-- 配置spring mvc-->
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<!-- 配置springmvc 的配置文件路径-->
<param-name>contextConfigLocation</param-name>
<param-value>classpath:springmvc.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>
<!-- 配置log4j -->
<context-param>
<param-name>log4jConfigLocation</param-name>
<param-value>/WEB-INF/log4j.properties</param-value>
</context-param>
<listener> <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class> </listener>
</web-app>
2、配置springmvc.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<!-- 配置扫描注解 -->
<!--需要和工程名匹配-->
<context:component-scan base-package="com.ccl.test.controller" />
</beans>
3、配置 log4j.properties
###设置###
log4j.rootLogger = debug,stdout,D,E
###输出信息到控制台##
log4j.appender.stdout = org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target = System.out
###格式化日志信息
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
### 输出ERROR 级别以上的日志到=E://logs/error.log ###
log4j.appender.E = org.apache.log4j.DailyRollingFileAppender
log4j.appender.E.File =E://logs/error.log
log4j.appender.E.Append = true
log4j.appender.E.Threshold = ERROR
log4j.appender.E.layout = org.apache.log4j.PatternLayout
log4j.appender.E.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss} [ %t:%r ] - [ %p ] %m%n
#close spring log out
log4j.logger.org.springframework=WARN
4、在java 中调用log4j
package com.ccl.test.controller;
import org.apache.log4j.Logger;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
@Controller
//method=RequestMethod.GET get方法
//默认情况是 get+post
@RequestMapping(value="/app")
public class apiController {
private static Logger logger = Logger.getLogger(apiController.class);
@RequestMapping(value="/welcome.do")
//直接输出返回内容@ResponseBody
@ResponseBody
public String hello() {
//输出日志
logger.debug("hello");
//建立json串
StringBuffer sb = new StringBuffer();
sb.append("{\"word\":\"hello\"}");
String json = sb.toString();
return json;
}
}
最后输入网址 http://localhost：8080/工程名/app/welcome.do 查看输出内容
