maven项目打包并指定main方法

如题：

pom.xml配置如下：

 <build>
        <plugins>
            <plugin>  
                <groupId>org.apache.maven.plugins</groupId>  
                <artifactId>maven-shade-plugin</artifactId>  
                <version>2.3</version>  
                <executions>  
                    <execution>  
                        <phase>package</phase>  
                        <goals>  
                            <goal>shade</goal>  
                        </goals>  
                        <configuration>  
                            <transformers>  
                                <transformer  
                                    implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">  
                                    <!--指定main方法-->
                                    <mainClass>com.liao.App</mainClass>  
                                </transformer>  
                            </transformers>  
                        </configuration>  
                    </execution>  
                </executions>  
            </plugin>  
        </plugins>
    </build>