Maven：maven默认jdk版本是1.5，现在一般使用1.8，如何修改默认版本？

<build>   
        <plugins>  
            <plugin>  
                <groupId>org.apache.maven.plugins</groupId>  
                <artifactId>maven-compiler-plugin</artifactId>  
                <version>3.1</version>
                <!-- <version>3.7.0</version> -->  
                <configuration>  
                    <source>1.8</source>  
                    <target>1.8</target>  
                </configuration>  
            </plugin>  
        </plugins>  
</build>

<profile>    
      <id>jdk-1.8</id>    
      <activation>    
           <activeByDefault>true</activeByDefault>    
           <jdk>1.8</jdk>    
      </activation>    
      <properties>        
          <maven.compiler.source>1.8</maven.compiler.source>    
          <maven.compiler.target>1.8</maven.compiler.target>   
          <maven.compiler.compilerVersion>1.8</maven.compiler.compilerVersion>    
      </properties>    
</profile>