Spring MVC 3.x annotated controller的几点心得体会
最近拿Spring MVC 3.x做项目，用了最新的系列相关Annotation来做Controller，有几点心得体会值得分享。


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一、编写一个AbstractController.java，所有的Controller必须扩展

除了获得Template Design Pattern的好处之外，还能一点，那就是放置全局的@InitBinder：

public class AbstractController {...@InitBinderprotected void initBinder(WebDataBinder binder) {SimpleDateFormat dateFormat = new SimpleDateFormat("MM/dd/yyyy");dateFormat.setLenient(false);binder.registerCustomEditor(Date.class,new CustomDateEditor(dateFormat, false));}...}

二、每个域都应该有一个Controller，且做好URI规划

大家都知道Spring MVC 3.x是完全支持Restful的，我们把URI做好规划，对于诸如ACL的实现会有很大的帮助。建议的URI规划如下：{Domain}[/{SubDomain}]/{BusinessAction}/{ID}。比如：

hotels/bookings/cancel/{id} ——表示此URI匹配hotels域的bookings子域，将要进行的是取消某项booking的操作。代码如下：

@Controller@RequestMapping(value = "/hotels")public class HotelsController extends AbstractController {...@RequestMapping(value = "/bookings/cancel/{id}", method = RequestMethod.POST)public String deleteBooking(@PathVariable long id) {bookingService.cancelBooking(id);//use prefix 'redirect' to avoid duplicate submissionreturn "redirect:../../search";}...}

另外还有几个重要原因：


1、由于Spring的DefaultAnnotationHandlerMapping.java在做Mapping的时候，先做是否有类匹配，再找方法，把基本的mapping放在类上面，可以加速匹配效率；

2、后续可以通过更细腻的支持Ant path style的AntPathMatcher来规划URI Template资源，做ACL控制（请参考后面的心得体会）。




三、JSON/XML等ajax的支持很cool，可以尝试

JSON/XML/RSS等均可支持，当然有些denpendency，比如JSON的默认支持，需要jackson jar出现在lib中，POM的artifact如下：

<dependency><groupId>org.codehaus.jackson</groupId><artifactId>jackson-mapper-asl</artifactId><version>1.5.3</version></dependency>

这样，我们其实根本就不需要进行额外的JSON转换了，Spring MVC 3会根据请求的格式自行转换：

@ResponseBody@RequestMapping(value = "/ajax", method = RequestMethod.POST)public JsonDataWrapper<Hotel> ajax(WebRequest request, Hotel hotel, Model model) throws Exception {JsonDataWrapper<Hotel> jsonDataWrapper = this.getPaginatedGridData(request, hotel, hotelService);return jsonDataWrapper;}

注 ：我上面的JsonDataWrapper只是我自己做的一个简单的wrapper，目的是为jQuery Flexigrid plugin做数据准备的。还是贴出来吧：

/** * A wrapper class for jQuery Flexigrid plugin component. *  * The format must be like this: * <code> * {"total":2,"page":1,"rows":[ * {"personTitle":"Mr","partyName":"Test8325","personDateOfBirth":"1970-07-12"}, * {"personTitle":"Ms","partyName":"Ms Susan Jones","personDateOfBirth":"1955-11-27"} * ]} * </code> *  * @author bright_zheng * * @param <T>: the generic type of the specific domain */public class JsonDataWrapper<T> implements Serializable {private static final long serialVersionUID = -538629307783721872L;public JsonDataWrapper(int total, int page, List<T> rows){this.total = total;this.page = page;this.rows = rows;}private int total;private int page;private List<T> rows;public int getTotal() {return total;}public void setTotal(int total) {this.total = total;}public int getPage() {return page;}public void setPage(int page) {this.page = page;}public List<T> getRows() {return rows;}public void setRows(List<T> rows) {this.rows = rows;}}

四、Controller的单元测试变得很可为且简单

以前的项目从来不做controller层的测试，用了Spring MVC 3这一点就不再难为情，做吧：

public class HotelsControllerTest {private static HandlerMapping handlerMapping;private static HandlerAdapter handlerAdapter;private static MockServletContext msc;@BeforeClasspublic static void setUp() {String[] configs = {"file:src/main/resources/context-*.xml","file:src/main/webapp/WEB-INF/webapp-servlet.xml" };XmlWebApplicationContext context = new XmlWebApplicationContext();          context.setConfigLocations(configs);          msc = new MockServletContext();          context.setServletContext(msc);          context.refresh();          msc.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, context);        ApplicationContextManager manager = new ApplicationContextManager();manager.setApplicationContext(context);handlerMapping = (HandlerMapping) ApplicationContextManager.getContext().getBean(DefaultAnnotationHandlerMapping.class);handlerAdapter = (HandlerAdapter) ApplicationContextManager.getContext().getBean(ApplicationContextManager.getContext().getBeanNamesForType(AnnotationMethodHandlerAdapter.class)[0]);}@Testpublic void list() throws Exception {MockHttpServletRequest request = new MockHttpServletRequest();MockHttpServletResponse response = new MockHttpServletResponse();request.setRequestURI("/hotels");request.addParameter("booking.id", "1002");request.addParameter("hotel.name", "");request.setMethod("POST");//HandlerMappingHandlerExecutionChain chain = handlerMapping.getHandler(request);Assert.assertEquals(true, chain.getHandler() instanceof HotelsController);//HandlerAdapterfinal ModelAndView mav = handlerAdapter.handle(request, response, chain.getHandler());//Assert logicAssert.assertEquals("hotels/search", mav.getViewName());}}

需要说明一下 ：由于当前最想版本的Spring(Test) 3.0.5还不支持@ContextConfiguration的注解式context file注入，所以还需要写个setUp处理下，否则类似于Tiles的加载过程会有错误，因为没有ServletContext。3.1的版本应该有更好的解决方案，参见：https://jira.springsource.org/browse/SPR-5243 。

Service等其他layer就没有这类问题，测试的写法将变得更加优雅，贴个出来：

@RunWith(SpringJUnit4ClassRunner.class)@ContextConfiguration(locations = {"file:src/main/resources/context-*.xml" })public class DefaultServiceImplTest {/** @Autowired works if we put @ContextConfiguration at junit type */@Autowired@Qualifier("hotelService")private HotelService<Hotel> hotelService;@Testpublic void insert() {Hotel hotel = new Hotel();hotel.setAddress("addr");hotel.setCity("Singapore");hotel.setCountry("Singapore");hotel.setName("Great Hotel");hotel.setPrice(new BigDecimal(200));hotel.setState("Harbarfront");hotel.setZip("010024");hotelService.insert(hotel);}}

五、ACL可以写一个HandlerInterceptorAdapter，在“事前”拦截。

由于Spring是Restful friendly的framework，做ACL就不要用过滤器了，用interceptor吧：

public class AclInterceptor extends HandlerInterceptorAdapter {private static final Logger logger = Logger.getLogger(AclInterceptor.class);/** default servlet prefix */private static final String DEFAULT_SERVLET_PREFIX = "/servlet";/** will be injected from context configuration file */private AclService service;@Overridepublic boolean preHandle(HttpServletRequest request,HttpServletResponse response, Object handler) throws Exception {String currentUri = request.getRequestURI();boolean isAccessible = true;//only intercept for annotated business controllersController c = AnnotationUtils.findAnnotation(handler.getClass(), Controller.class);if(c!=null){String[] grantedResource = getGrantedResource(request);if(grantedResource==null || grantedResource.length==0){throw new AccessDeniedException("No resource granted");}isAccessible = service.isAccessible(grantedResource, currentUri);if(logger.isDebugEnabled()){logger.debug("ACL interceptor excueted. Accessible for Uri[" + currentUri +"] = " + isAccessible);}//if isAccessible==true, throw custom AccessDeniedExceptionif(!isAccessible) throw new AccessDeniedException();}return isAccessible;}/** * transfer the original Uri to resource Uri * e.g.: * original Uri: /servlet/hotels/ajax * target Uri  : /hotels/ajax * @param originalUri * @return */protected String getUri(String originalUri){return originalUri.substring(DEFAULT_SERVLET_PREFIX.length());}/** * Get the granted resource from session * @param request * @return */protected String[] getGrantedResource(HttpServletRequest request){//get the resources from current session//String[] uriResourcePattern = (String[]) request.getSession().getAttribute("uriResourcePattern");//TODO: mock data hereString[] uriResourcePattern = new String[]{"/**"};return uriResourcePattern;}public void setService(AclService service) {this.service = service;}}

注 ：上面还有TODO部分，很简单，登录后把当然用户可访问的Ant path style的URI Resources放到session中，作为一个String[]，这里拿来出匹配即可，建议匹配就用org.springframework.util.AntPathMatcher。



六、对于Ajax Form Validation，正在寻求更佳的解禁方案。

Spring 3已经支持@Valid的注解式validation，又一个JSR，但通过我研究代码发现，默认的org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.java实现还是非常封闭，并不能很好的实现binding后执行业务代码前处理，所以目前的实现办法还不算优雅。

已经实现，大致的思路是：

1）发出ajax form post请求（用jQuery）；

2）正常mapping到controller的方法中处理；

3）做form validation；

4）不管怎样，forward到一个解析错误消息的JSP，叫ajaxFormValidatorResult.jsp；

5）再写一个jquery plugin，叫errorBinder.js，解析错误并自定binding为Tooltip，如果没错误就正常submit

贴个简单的demo效果，欢迎拍砖。

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