use -source 5 or higher to enable annotations

pom.xml中加入：

<build>
    <plugins>
       	<plugin>
            <groupId>org.apache.maven.plugins</groupId>
	    <artifactId>maven-compiler-plugin</artifactId>
	    <version>2.0.2</version>
	    <configuration>
	    <source>1.6</source>
	    <target>1.6</target>
	    </configuration>
	</plugin>
    </plugins> 
</build>