添加启动项。Edit Configurations->点击+号->Application添加一个启动项，然后填写如下内容

编辑启动项

在build.gradle中添加如下内容，其中2.12.0改为你使用的对应版本即可

dependencies {
    compile 'org.scala-lang:scala-library:2.12.0'
}

解决报错

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder"

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.

在build.gradle的子项目core中需要添加这两个依赖:

project(':core') {
  println "Building project 'core' with Scala version ${versions.scala}"
  ...

  dependencies {
    ...
    // 添加以下两个依赖
    // https://mvnrepository.com/artifact/org.slf4j/slf4j-api
    compile group: 'org.slf4j', name: 'slf4j-api', version: '1.7.25'
    // https://mvnrepository.com/artifact/org.slf4j/slf4j-log4j12
    compile group: 'org.slf4j', name: 'slf4j-log4j12', version: '1.7.25'
}

这两行首先要添加slf4j的依赖，还要添加基于slf4j的log4j12的依赖。注意这里一定要用compile而不是testCompile，因为后者的意思是只在test环境下编译.

我当时就是因为直接从Maven官网上拷贝了如下内容翻了车:

testCompile group: 'org.slf4j', name: 'slf4j-log4j12', version: '1.7.25'  // 不要这样写

log4j:WARN No appenders could be found for logger (LoggerMain).

log4j:WARN No appenders could be found for logger (LoggerMain).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.

创建src/main/resources文件夹，创建文件log4j.properties，并写入以下内容:

### 设置###
log4j.rootLogger = debug,stdout

### 输出信息到控制抬 ###
log4j.appender.stdout = org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target = System.out
log4j.appender.stdout.Threshold = INFO
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

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