Spring Boot 整合 log4j 实现日志管理报错：java.lang.IllegalArgumentException: LoggerFactory is not a Logback

问题：

Caused by: java.lang.IllegalArgumentException: LoggerFactory is not a Logback LoggerContext but Logback is on the classpath. Either remove Logback or the competing implementation (class org.apache.logging.slf4j.Log4jLoggerFactory loaded from file:/C:/Users/fyk/.m2/repository/org/apache/logging/log4j/log4j-slf4j-impl/2.7/log4j-slf4j-impl-2.7.jar). If you are using WebLogic you will need to add 'org.slf4j' to prefer-application-packages in WEB-INF/weblogic.xml: org.apache.logging.slf4j.Log4jLoggerFactory
at org.springframework.util.Assert.instanceCheckFailed(Assert.java:389)
at org.springframework.util.Assert.isInstanceOf(Assert.java:327)
at org.springframework.boot.logging.logback.LogbackLoggingSystem.getLoggerContext(LogbackLoggingSystem.java:274)
at org.springframework.boot.logging.logback.LogbackLoggingSystem.beforeInitialize(LogbackLoggingSystem.java:98)
at org.springframework.boot.logging.LoggingApplicationListener.onApplicationStartingEvent(LoggingApplicationListener.java:230)
at org.springframework.boot.logging.LoggingApplicationListener.onApplicationEvent(LoggingApplicationListener.java:209)
at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)
at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:122)
at org.springframework.boot.context.event.EventPublishingRunListener.starting(EventPublishingRunListener.java:69)
at org.springframework.boot.SpringApplicationRunListeners.starting(SpringApplicationRunListeners.java:48)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:292)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107)
at com.light.SpringbootApplication.main(SpringbootApplication.java:32)
... 5 more

解决：

在 Spring Boot 中，程序默认使用 Logback 来记录日志并用 INFO 级别输出到控制台，某些情况下我们可能想用其他日志实现框架替换 Logback，在 Spring Boot 中，因为程序使用了自动配置，所以我们可以很方便地替换日志实现，下面以使用 log4j 替换 Logback 为例。

1. 去除对默认日志的依赖

    org.springframework.boot
    spring-boot-starter
    
        
            org.springframework.boot
            spring-boot-starter-logging
        
    

2. 添加对 log4j 的依赖

            org.springframework.boot
            spring-boot-starter-log4j
            1.3.8.RELEASE
        
        
            org.slf4j
            slf4j-api
        

到此，Spring Boot 项目的日志框架就已经替换成 log4j 了，如需要定义日志输出，只需添加 log4j.properties 文件并在该文件中添加相应配置即可。

3.log4j.properties配置文件 

# LOG4J配置
log4j.rootCategory=INFO, stdout, file

# 控制台输出
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:ss,SSS} %5p %c{1}:%L - %m%n

# root日志输出到文件
log4j.appender.file=org.apache.log4j.DailyRollingFileAppender
log4j.appender.file.file=/data/logs/springboot-log4j-all.log
log4j.appender.file.DatePattern='.'yyyy-MM-dd
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss,SSS} %5p %c{1}:%L - %m%n

# 按不同package进行输出
# com.micai包下的日志配置
log4j.category.com.micai=DEBUG, didifile

# com.micai下的日志输出
log4j.appender.didifile=org.apache.log4j.DailyRollingFileAppender
log4j.appender.didifile.file=/data/logs/springboot-log4j-my.log
log4j.appender.didifile.DatePattern='.'yyyy-MM-dd
log4j.appender.didifile.layout=org.apache.log4j.PatternLayout
log4j.appender.didifile.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss,SSS} %5p %c{1}:%L ---- %m%n

# ERROR级别输出到特定的日志文件中
log4j.logger.error=errorfile
# error日志输出
log4j.appender.errorfile=org.apache.log4j.DailyRollingFileAppender
log4j.appender.errorfile.file=/data/logs/springboot-log4j-error.log
log4j.appender.errorfile.DatePattern='.'yyyy-MM-dd
log4j.appender.errorfile.Threshold = ERROR
log4j.appender.errorfile.layout=org.apache.log4j.PatternLayout
log4j.appender.errorfile.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss,SSS} %5p %c{1}:%L - %m%n

4.代码如下：

package com.example.demo.controller;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

/**
 * @Auther: liang
 * @Date: 2018/12/26 15:08
 * @Description:
 */
@Controller
public class HelloController {
    private static final Logger logger = LoggerFactory.getLogger(HelloController.class);

    @ResponseBody
    @RequestMapping("/hello")
    public String hello(){
        logger.info("logger.info:::Hello World~");
        return "Hello World~";
    }
}

 5.控制台打印：