在<profiles>标签内添加如下配置：

<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>

方法二：不同的项目使用不同的jre，pom.xml里添加如下配置

导入项目可以这样配置然后进行maven project update：

<build>

    <plugins>

        <plugin>

            <groupId>org.apache.maven.plugins</groupId>

            <artifactId>maven-compiler-plugin</artifactId>

            <configuration>

                <source>1.8</source>

                <target>1.8</target>

            </configuration>

        </plugin>

    </plugins>

</build>

修正maven-dependency-plugin不支持m2e的问题：

<pluginManagement>  
    <plugins>  
        <!--This plugin's configuration is used to store Eclipse m2e settings only. It has no influence on the Maven build itself.-->  
        <plugin>  
            <groupId>org.eclipse.m2e</groupId>  
            <artifactId>lifecycle-mapping</artifactId>  
            <version>1.0.0</version>  
            <configuration>  
                <lifecycleMappingMetadata>  
                    <pluginExecutions>  
                        <pluginExecution>  
                            <pluginExecutionFilter>  
                                <groupId>  
                                    org.apache.maven.plugins  
                                </groupId>  
                                <artifactId>  
                                    maven-dependency-plugin  
                                </artifactId>  
                                <versionRange>  
                                    [2.0,)  
                                </versionRange>  
                                <goals>  
                                    <goal>unpack</goal>  
                                </goals>  
                            </pluginExecutionFilter>  
                            <action>  
                                <ignore></ignore>  
                            </action>  
                        </pluginExecution>  
                    </pluginExecutions>  
                </lifecycleMappingMetadata>  
            </configuration>  
        </plugin>  
    </plugins>  
</pluginManagement>  

maven配置文件中修改默认jre