设置通过Maven创建的工程的JDK版本—一劳永逸

<profiles>
  	 <profile>
      <id>jdk-1.8</id>

      <activation>
      	<activationByDefault>true</activationByDefault>
        <jdk>jdk-1.8</jdk> 
      </activation>

      <repositories>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target> 
        <maven.compiler.compilerVersion>1.7</maven.compiler.compilerVersion>         
      </repositories>
    </profile>