SpringBoot集成log4j，解决log4j.properties不生效问题

Spring Boot集成log4j其实比较简单，maven的话，在xml中增加log4j依赖就行

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-log4j</artifactId>
    <version>1.3.8.RELEASE</version>
</dependency>

然后配置log4j.properties（每一行是啥意思，自行百度）

log4j.rootLogger=info,stdout, infofile
######################################################################
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - %m%n
######################################################################
log4j.appender.infofile=org.apache.log4j.DailyRollingFileAppender
log4j.appender.infofile.File=/log/infofile-log.log
log4j.appender.infofile.Append=true
log4j.appender.infofile.Threshold=info
log4j.appender.infofile.layout=org.apache.log4j.PatternLayout
log4j.appender.infofile.layout.ConversionPattern=%-d{yyyy-MM-dd HH:mm:ss}  [ %t:%r ] - [ %p ]  %m%n
log4j.appender.infofile.encoding=GBK

但是、启动项目后，我发现并没有生成 /log/infofile-log.log 文件

网上查了一下，大概原因是jar包冲突，因为 spring-boot-starter-web、spring-boot-starter-data-jpa、spring-boot-starter-jdbc等下面有一些logback、log4j、slf4j等相关的包，我用 dependency:tree命令查到具体是那些jar，然后一一排除，这样再启动时，就会发现 infofile-log.log文件创建成功了

这种方法比较繁琐，但是可以更理解jar包依赖关系

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.slf4j</groupId>
            <artifactId>*</artifactId>
        </exclusion>
    </exclusions>
</dependency>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <exclusions>
        <exclusion>
            <groupId>ch.qos.logback</groupId>
            <artifactId>*</artifactId>
        </exclusion>
        <exclusion>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>*</artifactId>
        </exclusion>
    </exclusions>
</dependency>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jdbc</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.slf4j</groupId>
            <artifactId>*</artifactId>
        </exclusion>
    </exclusions>
</dependency>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-log4j</artifactId>
    <version>1.3.8.RELEASE</version>
</dependency>

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看这里，更优雅一些： https://www.cnblogs.com/myfrank/p/14286815.html