代码已上传至Github，有兴趣的同学可以下载来看看：https://github.com/ylw-github/SpringBoot-Log4j-Demo
Log4j是Apache的一个开源项目，通过使用Log4j，我们可以控制日志信息输送的目的地是控制台、文件、GUI组件，甚至是套接口服务器、NT的事件记录器、UNIX Syslog守护进程等；我们也可以控制每一条日志的输出格式；通过定义每一条日志信息的级别，我们能够更加细致地控制日志的生成过程。最令人感兴趣的就是，这些可以通过一个配置文件来灵活地进行配置，而不需要修改应用的代码。
下面我们来讲解一下SpringBoot集成log4j。
1.1 添加Maven依赖
<parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.0.RELEASE</version> </parent> <dependencies> <!-- SpringBoot 核心组件 --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> </dependency> <dependency> <groupId>org.apache.tomcat.embed</groupId> <artifactId>tomcat-embed-jasper</artifactId> </dependency> <!-- spring boot start --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter</artifactId> <exclusions> <!-- 排除自带的logback依赖 --> <exclusion> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-logging</artifactId> </exclusion> </exclusions> </dependency> <!-- springboot-log4j --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-log4j</artifactId> <version>1.3.8.RELEASE</version> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-aop</artifactId> </dependency> </dependencies>
1.2在resources目录下新建log4j配置文件：
### set log levels ### log4j.rootLogger=info,error,info log4j.appender.stdout=org.apache.log4j.ConsoleAppender log4j.appender.stdout.layout=org.apache.log4j.PatternLayout log4j.appender.stdout.layout.ConversionPattern=%d{yyyy-MM-dd-HH-mm} [%t] [%c] [%p] - %m%n log4j.logger.info=info log4j.appender.info=org.apache.log4j.DailyRollingFileAppender log4j.appender.info.layout=org.apache.log4j.PatternLayout log4j.appender.info.layout.ConversionPattern=%d{yyyy-MM-dd-HH-mm} [%t] [%c] [%p] - %m%n log4j.appender.info.datePattern='.'yyyy-MM-dd log4j.appender.info.Threshold = INFO log4j.appender.info.append=false log4j.appender.info.File=info.log log4j.logger.error=error log4j.appender.error=org.apache.log4j.DailyRollingFileAppender log4j.appender.error.layout=org.apache.log4j.PatternLayout log4j.appender.error.layout.ConversionPattern=%d{yyyy-MM-dd-HH-mm} [%t] [%c] [%p] - %m%n log4j.appender.error.datePattern='.'yyyy-MM-dd log4j.appender.error.Threshold = ERROR log4j.appender.error.append=false log4j.appender.error.File=error.log
1.3 使用AOP统一处理Web请求日志
首先需要在maven新增AOP依赖：
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-aop</artifactId> </dependency>
切面类：WebLogAspect
package com.ylw.springboot.aspect; import org.aspectj.lang.JoinPoint; import org.aspectj.lang.annotation.AfterReturning; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Before; import org.aspectj.lang.annotation.Pointcut; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.stereotype.Component; import org.springframework.web.context.request.RequestContextHolder; import org.springframework.web.context.request.ServletRequestAttributes; import javax.servlet.http.HttpServletRequest; import java.util.Enumeration; @Aspect @Component public class WebLogAspect { private static final Logger logger = LoggerFactory.getLogger(WebLogAspect.class); @Pointcut("execution(public * com.ylw.springboot.controller.*.*(..))") public void webLog() { } @Before("webLog()") public void doBefore(JoinPoint joinPoint) throws Throwable { // 接收到请求，记录请求内容 ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes(); HttpServletRequest request = attributes.getRequest(); // 记录下请求内容 logger.info("URL : " + request.getRequestURL().toString()); logger.info("HTTP_METHOD : " + request.getMethod()); logger.info("IP : " + request.getRemoteAddr()); Enumeration<String> enu = request.getParameterNames(); while (enu.hasMoreElements()) { String name = (String) enu.nextElement(); logger.info("name:{},value:{}", name, request.getParameter(name)); } } @AfterReturning(returning = "ret", pointcut = "webLog()") public void doAfterReturning(Object ret) throws Throwable { // 处理完请求，返回内容 logger.info("RESPONSE : " + ret); } }
1.4 编写启动类和Controller
//启动类 @ComponentScan("com.ylw") @EnableAutoConfiguration public class App { public static void main(String[] args) { SpringApplication.run(App.class, args); } } //Controller @RestController public class LoginController { @RequestMapping(value = "/login",method = RequestMethod.GET) public String login(String userName, String passWord) { System.out.println("userName -> " + userName + "passWord ->" + passWord); return "success"; } }
1.5 测试
浏览器访问：http://localhost:8080/login?userName=Dumas&passWord=123456
访问之后，会发现项目的根目录生成了一个info.log 日志文件
里面都是info级别的日志：
总结
