Spring Mvc懒加载机制

• 在 web.xml中添加:

<!-- 解决懒加载问题 -->

   <filter>
       <filter-name>OpenEntityManagerInViewFilter</filter-name>
       <filter-class>org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter</filter-class>
       <init-param>
           <!-- 指定org.springframework.orm.jpa.LocalEntityManagerFactoryBean在spring配置文件中的名称,默认值为entityManagerFactory
               如果LocalEntityManagerFactoryBean在spring中的名称不是entityManagerFactory,该参数一定要指定,否则会出现找不到entityManagerFactory的例外 -->
           <param-name>entityManagerFactoryBeanName</param-name>
           <param-value>entityManagerFactory</param-value>
       </init-param>
   </filter>
   <filter-mapping>
       <filter-name>OpenEntityManagerInViewFilter</filter-name>
       <url-pattern>/*</url-pattern>
   </filter-mapping>

   <context-param>
       <param-name>contextConfigLocation</param-name>
       <param-value>/WEB-INF/mvc-dispatcher-servlet.xml</param-value>
   </context-param>

   <listener>
       <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
   </listener>
   <!-- 解决懒加载问题 -->

• 接下来最重要的是要在操作数据的函数上增加@Transactional注解（javax.transaction.Transactional），例如

public class CarController {
    private static final String TAG = CarController.class.getSimpleName();
    private static final Logger LOGGER = LoggerFactory.getLogger(CarController.class);
    @Autowired
    private CarRepository mCarRepository;


    @Transactional
    @RequestMapping(method = RequestMethod.GET)
    public Response<List<CarVo>> list() {
        LOGGER.info(TAG, " car data: list");

        Response<List<CarVo>> response = new Response<>();
        response.data = DomainCopyUtil.mapList(mCarRepository.findAll(), CarVo.class);
        LOGGER.info(" car data: " + response.data);
        if(response.data == null) {
            response.setStatusCode(ResponseCode.CODE_GOODS_GET_ALL_ERROR);
        }
        return response;
    }  
}