spring mvc 3.2 使用总结

时间 2019-11-06

标签 spring mvc 3.2 使用总结栏目 Spring 繁體版

原文原文链接

用spring mvc有一段时间了，今天有时间对这个框架的一些使用进行一些总结。

官网上面对spring mvc有一个很详细的demo，地址：

https://github.com/SpringSource/spring-mvc-showcase

就拿这个例子做为总结的代码。

1.首先介绍一下WebApplicationInitializer，能够经过下面的代码来实现对spring servlet的配置

public class MyWebApplicationInitializer implements WebApplicationInitializer { @Override public void onStartup(ServletContext container) { ServletRegistration.Dynamic registration = container.addServlet("dispatcher", new DispatcherServlet()); registration.setLoadOnStartup(1); registration.addMapping("/example/*"); } }

上面的代码功能等价于

<web-app>
    <servlet>
        <servlet-name>example</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>example</servlet-name>
        <url-pattern>/example/*</url-pattern>
    </servlet-mapping>
</web-app>

2.定义一个controller

@Controller
public class SimpleController {
 
    @RequestMapping("/simple")
    public @ResponseBody String simple() {
        return "Hello world!";
    }
 
}

这样就完成了一个controller，@RequestMapping( "/simple")定义访问的url，其中可使用一个参数“method”，取值能够是RequestMethod.POST，RequestMethod.GET, RequestMethod.DEL等，用来限定访问的方法

3.使用hibernate validation做为验证

定义一个JavaBean：

public class JavaBean { @NotNull @Max(5) private Integer number; @NotNull @Future @DateTimeFormat(iso=ISO.DATE) private Date date; public Integer getNumber() { return number; } public void setNumber(Integer number) { this.number = number; } public Date getDate() { return date; } public void setDate(Date date) { this.date = date; } }

定义一个controller：

@Controller
public class ValidationController {
 
    // enforcement of constraints on the JavaBean arg require a JSR-303 provider on the classpath
 
    @RequestMapping("/validate")
    public @ResponseBody String validate(@Valid JavaBean bean, BindingResult result) {
        if (result.hasErrors()) {
            return "Object has validation errors";
        } else {
            return "No errors";
        }
    }
 
}

@Valid说明须要对JavaBean这个参数进行验证，验证的规则由hibernate的validation限定，里面有最基本的@NotNull，@Max，@Min，@reg等等，强大的验证规则。其中BindingResult会返回验证的信息。

4.定义返回值类型：

@Controller
public class MappingController {
 
    @RequestMapping("/mapping/path")
    public @ResponseBody String byPath() {
        return "Mapped by path!";//最简单的，只定义了request的url
    }
 
    @RequestMapping(value="/mapping/path/*", method=RequestMethod.GET)
    public @ResponseBody String byPathPattern(HttpServletRequest request) {//拿到的HttpServletRequest基本上什么均可以作到了
        return "Mapped by path pattern ('" + request.getRequestURI() + "')";
    }
 
    @RequestMapping(value="/mapping/method", method=RequestMethod.GET)
    public @ResponseBody String byMethod() {
        return "Mapped by path + method";
    }
 
    @RequestMapping(value="/mapping/parameter", method=RequestMethod.GET, params="foo")
    public @ResponseBody String byParameter() {
        return "Mapped by path + method + presence of query parameter!";//定义了必须符合url+方法+参数三个规则的请求才能够被捕捉
    }
 
    @RequestMapping(value="/mapping/parameter", method=RequestMethod.GET, params="!foo")
    public @ResponseBody String byParameterNegation() {
        return "Mapped by path + method + not presence of query parameter!";//params="!foo"，不能有foo这个参数的url+方法的请求
    }
 
    @RequestMapping(value="/mapping/header", method=RequestMethod.GET, headers="FooHeader=foo")
    public @ResponseBody String byHeader() {
        return "Mapped by path + method + presence of header!";//附加header的规则
    }
 
    @RequestMapping(value="/mapping/header", method=RequestMethod.GET, headers="!FooHeader")
    public @ResponseBody String byHeaderNegation() {
        return "Mapped by path + method + absence of header!";//没有FooHeader的headers
    }
 
    @RequestMapping(value="/mapping/consumes", method=RequestMethod.POST, consumes=MediaType.APPLICATION_JSON_VALUE)
    public @ResponseBody String byConsumes(@RequestBody JavaBean javaBean) {
        return "Mapped by path + method + consumable media type (javaBean '" + javaBean + "')";//这个在后面的convert再说
    }
 
    @RequestMapping(value="/mapping/produces", method=RequestMethod.GET, produces=MediaType.APPLICATION_JSON_VALUE)
    public @ResponseBody JavaBean byProducesJson() {//返回JavaBean的json数据
        return new JavaBean();
    }
 
    @RequestMapping(value="/mapping/produces", method=RequestMethod.GET, produces=MediaType.APPLICATION_XML_VALUE)
    public @ResponseBody JavaBean byProducesXml() {//返回JavaBean的xml数据
        return new JavaBean();
    }
}

5.请求参数的处理

@Controller
@RequestMapping("/data")
public class RequestDataController {
 
    @RequestMapping(value="param", method=RequestMethod.GET)
    public @ResponseBody String withParam(@RequestParam String foo) {
        return "Obtained 'foo' query parameter value '" + foo + "'";//RequestParam ，得到一个foo的参数，还能够指定参数的名字，例以下面的的
    }
 
    @RequestMapping(value="group", method=RequestMethod.GET)
    public @ResponseBody String withParamGroup(JavaBean bean) {
        return "Obtained parameter group " + bean;
    }
 
    @RequestMapping(value="path/{var}", method=RequestMethod.GET)
    public @ResponseBody String withPathVariable(@PathVariable String var) {//使用@PathVariable ，参数须要在url中出现例如  xxx/path/hello
        return "Obtained 'var' path variable value '" + var + "'";// "hello"这个参数就会被获取到
    }
 
    @RequestMapping(value="{path}/simple", method=RequestMethod.GET)// url=/pets;foo=11/simple
    public @ResponseBody String withMatrixVariable(@PathVariable String path, @MatrixVariable String foo) {
        //path=pets; foo=11
        return "Obtained matrix variable 'foo=" + foo + "' from path segment '" + path + "'";
    }
 
    @RequestMapping(value="{path1}/{path2}", method=RequestMethod.GET)// url = /42;foo1=11/21;foo2=22
    public @ResponseBody String withMatrixVariablesMultiple (
            @PathVariable String path1, @MatrixVariable(value="foo", pathVar="path1") String foo1,
            @PathVariable String path2, @MatrixVariable(value="foo", pathVar="path2") String foo2) {//相似上面的，分块分解参数
 
        return "Obtained matrix variable foo=" + foo1 + " from path segment '" + path1
                + "' and variable 'foo=" + foo2 + " from path segment '" + path2 + "'";
    }
    
@RequestMapping("/owners/{ownerId}")// 例如url：/owners/42/pets/21.
public class RelativePathUriTemplateController {
  @RequestMapping("/pets/{petId}")
  public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) {
    // implementation omitted
  }
}
 
// GET /owners/42;q=11/pets/21;q=22
@RequestMapping(value = "/owners/{ownerId}/pets/{petId}", method = RequestMethod.GET)
public void findPet(
    @MatrixVariable(value="q", pathVar="ownerId") int q1,
    @MatrixVariable(value="q", pathVar="petId") int q2) {
  // q1 == 11
  // q2 == 22
}
 
// GET /owners/42;q=11;r=12/pets/21;q=22;s=23
@RequestMapping(value = "/owners/{ownerId}/pets/{petId}", method = RequestMethod.GET)//@MatrixVariable 容许组合全部参数成为一个
  public void findPet(
        @MatrixVariable Map < String, String > matrixVars,
        @MatrixVariable(pathVar = "petId" ) Map<String, String> petMatrixVars) {
    // matrixVars: [" q " : [11,22], " r " : 12, " s " : 23]
    // petMatrixVars: [" q " : 11, " s " : 23]
 }
/*
Host                    localhost:8080
Accept                  text/html,application/xhtml+xml,application/xml;q=0.9
Accept-Language         fr,en-gb;q=0.7,en;q=0.3
Accept-Encoding         gzip,deflate
Accept-Charset          ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive              300
*/
    @RequestMapping(value="header", method=RequestMethod.GET)
    public @ResponseBody String withHeader(@RequestHeader String Accept) {//@RequestHeader 能够指定你想或者header中的哪一个属性的信息
        return "Obtained 'Accept' header '" + Accept + "'";//例如@RequestHeader("Keep-Alive") 得到 300 
    }
 
    // cookie中有一个值openid_provider=415A4AC178C59DACE0B2C9CA727CDD84 ,也能够指定变量名withCookie(@CookieValue("openid_provider") param);
    @RequestMapping(value="cookie", method=RequestMethod.GET)
    public @ResponseBody String withCookie(@CookieValue String openid_provider) {
        return "Obtained 'openid_provider' cookie '" + openid_provider + "'";
    }
 
/**
*响应流媒体，通常是xml和json数据，可使用consumes="application/json"指定接受的是json仍是xml
*spring能够把POST的数据转换成为一个bean
*例若有个class JavaBean implements Serializable {
*                private Interger id;
*                private Stirng name;
*                private String status;
*                public JavaBean (){
*
*                }
*            }
*    @RequestMapping(value="body", method=RequestMethod.POST)
*    public @ResponseBody String withBody(@RequestBody JavaBean bean) {//响应流媒体
*        return "Posted request body '" + bean + "'";
*    }
*    $.post("/body",{'id':1, 'name': 'people', 'status': 'yes'},function(result){
*        alert(result);
*    });
*    spring 会把post过来的数据组成一个bean，这种方式尽可能少用
*/
    @RequestMapping(value="body", method=RequestMethod.POST)
    public @ResponseBody String withBody(@RequestBody String body) {//响应流媒体
        return "Posted request body '" + body + "'";
    }
 
    @RequestMapping(value="entity", method=RequestMethod.POST)
    public @ResponseBody String withEntity(HttpEntity<String> entity) {
        return "Posted request body '" + entity.getBody() + "'; headers = " + entity.getHeaders();
    }//这个就牛b了，把整个http请求的数据都给你了，有HttpEntity来传递请求数据固然有一个返回应答的数据流类
    
@RequestMapping("/something")
public ResponseEntity<String> handle(HttpEntity<byte[]> requestEntity) throws
UnsupportedEncodingException {
  String requestHeader = requestEntity.getHeaders().getFirst("MyRequestHeader"));
  byte[] requestBody = requestEntity.getBody();
  // do something with request header and body
  HttpHeaders responseHeaders = new HttpHeaders();
  responseHeaders.set("MyResponseHeader", "MyValue");//设置好header后和body-〉hello world组成ResponseEntity返回
  return new ResponseEntity<String>("Hello World", responseHeaders, HttpStatus.CREATED);
}
    /**
    *@RequestBody @ResponseBody分别是HttpEntity和ResponseEntity的去掉header的body部分
    */
 
}

在这里还有一种参数的形式@ModelAttribute，@ModelAttribute的定义有两种，一种是定义在方法上，另外一种是定义在参数里，当这个annotation定义在方法上，表示controller返回的是一个JavaBean，当annotation定义在参数里，表示post过来的数据会被转换成为JavaBean。

首先定义一个JavaBean的class：

import java.io.Serializable; public class Person implements Serializable { private static final long serialVersionUID = -8333984959652704635L; private Integer id; private String firstName; private String lastName; private String currency; private Double money; ......getter/setter }

有一个controller：

@Controller
@RequestMapping("EDIT")
public class PetSitesEditController {
 @ModelAttribute("people")
    public Person getPerson() {
        return this.person ;
    }//对于这个这个controller来讲，其余的方法的返回的jsp页面里面都会有一个people属性被返回，由于@ModelAttribute注解的方法会在这个controller的其余方法调用前被调用
}

在jsp页面中能够访问${ people}这个属性，若是在 @ModelAttribute没有指定属性的名字，那么默认就是person

看下面

有一个jsp页面

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://www.springframework.org/tags/form" prefix="form" %>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
 
<h1>Edit Person</h1>
 
<c:url var="saveUrl" value="/main/edit/${personAttribute.id}" />
 
<form:form modelAttribute="personAttribute" method="POST" action="${saveUrl}">
    <table>
        <tr>
            <td><form:label path="id">Id:</form:label></td>
            <td><form:input path="id" disabled="true"/></td>
        </tr>
 
        <tr>
            <td><form:label path="firstName">First Name:</form:label></td>
            <td><form:input path="firstName"/></td>
        </tr>
 
        <tr>
            <td><form:label path="lastName">Last Name</form:label></td>
            <td><form:input path="lastName"/></td>
        </tr>
 
        <tr>
            <td><form:label path="money">Money</form:label></td>
            <td><form:input path="money"/></td>
        </tr>
 
        <tr>
            <td><form:label path="currency">Currency:</form:label></td>
            <td><form:select path="currency"  items="${currencies}"/></td>
        </tr>
    </table>
 
    <input type="submit" value="Save" />
</form:form>
 
</body>
</html>

效果

post过来的数据

personAttribute.id = 1, personAttribute. firstName = John....

@RequestMapping(value = "/edit/{id}", method = RequestMethod.POST)
    public String saveEdit(@ModelAttribute("personAttribute") Person person,
      @PathVariable Integer id) {
      //spring会把post过来的person信息组合成为一个JavaBean，这里还得到了id这个信息
}

controller代码

根据@ModelAttribute两种用法，能够这样子实现

@Controller
    public class PersonController { 
 
        @ModelAttribute("person") 
        public Person getPerson() { 
           return new Person();
        } 
 
        @RequestMapping(value = "/new") 
        public String add(@ModelAttribute("person") Person person) { 
           return "add person";
        }
   }
/*
* 访问url  /new
* 首先会执行getPerson的方法，而后再执行add方法，其中person这个bean已经被new出来了，因此在add方法中能够被得到，这个有点像下面要说的convert，可是功能要稍微弱一些。
*/

6.convert，这是spring mvc最令我佩服的地方

首先定义一个convert

public class AccountConverter implements Converter<String, Account> { private AccountManager accountManager; @Autowired public AccountConverter(AccountManager accountManager) {//ioc一个accoutManager，用来根据id查出accout this.accountManager = accountManager; } @Override public Account convert(String id) { return this.accountManager.getAccount(id); } }

下面一个controller：

@Controller
@RequestMapping("/accounts")
public class AccountController {

    @RequestMapping(value="/{account}/edit", method = RequestMethod.GET)
    public String edit(@PathVariable Account account) {
        //操做accout类
        return "accounts/edit";
    }
}

下面描述了convert的运做过程

7.redirect，重点用法在return中

@Controller
@RequestMapping("/redirect")
public class RedirectController {
 
    private final ConversionService conversionService;
 
    @Inject
    public RedirectController(ConversionService conversionService) {
        this.conversionService = conversionService;
    }
 
    @RequestMapping(value="/uriTemplate", method=RequestMethod.GET)
    public String uriTemplate(RedirectAttributes redirectAttrs) {
        redirectAttrs.addAttribute("account", "a123");  // Used as URI template variable
        redirectAttrs.addAttribute("date", new LocalDate(2011, 12, 31));  // Appended as a query parameter
        return "redirect:/redirect/{account}";
    }
 
    @RequestMapping(value="/uriComponentsBuilder", method=RequestMethod.GET)
    public String uriComponentsBuilder() {
        String date = this.conversionService.convert(new LocalDate(2011, 12, 31), String.class);
        UriComponents redirectUri = UriComponentsBuilder.fromPath("/redirect/{account}").queryParam("date", date)
                .build().expand("a123").encode();
        return "redirect:" + redirectUri.toUriString();
    }
 
    @RequestMapping(value="/{account}", method=RequestMethod.GET)
    public String show(@PathVariable String account, @RequestParam(required=false) LocalDate date) {
        return "redirect/redirectResults";
    }
 
}

8.org.springframework.ui.Model，Model这个类中有一些css的配置，能够容许咱们使用，有时可能会用到

@Controller
@RequestMapping("/views/*")
public class ViewsController {
 
    @RequestMapping(value="html", method=RequestMethod.GET)
    public String prepare(Model model) {
        model.addAttribute("foo", "bar");
        model.addAttribute("fruit", "apple");
        return "views/html";
    }
}

9.文件上传、下载：

上传代码

@Controller
@RequestMapping("/fileupload")
public class FileUploadController {
 
    @ModelAttribute
    public void ajaxAttribute(WebRequest request, Model model) {
        model.addAttribute("ajaxRequest", AjaxUtils.isAjaxRequest(request));
    }
 
    @RequestMapping(method=RequestMethod.GET)
    public void fileUploadForm() {
    }
 
    @RequestMapping(method=RequestMethod.POST)
    public void processUpload(@RequestParam MultipartFile file, Model model) throws IOException {//MultipartFile能够指定变量名@MultipartFile("file001") file
        //file.isEmpty()，file.getBytes();，file.getInputStream();
        model.addAttribute("message", "File '" + file.getOriginalFilename() + "' uploaded successfully");
    }
}

文件下载

@RequestMapping(value = "/files/{file_name}", method = RequestMethod.GET)
public void getFile(
    @PathVariable("file_name") String fileName,
    HttpServletResponse response) {
    try {
      // get your file as InputStream
      InputStream is = ...;
      // copy it to response's OutputStream
      IOUtils.copy(is, response.getOutputStream());
      response.flushBuffer();
    } catch (IOException ex) {
      log.info("Error writing file to output stream. Filename was '" + fileName + "'");
      throw new RuntimeException("IOError writing file to output stream");
    }
}//本人比较喜欢这个

@RequestMapping(value = "/files/{file_name}", method = RequestMethod.GET)
@ResponseBody
public FileSystemResource getFile(@PathVariable("file_name") String fileName) {
    return new FileSystemResource(myService.getFileFor(fileName));
}

10.ajax 部分，有关 Servlet 3 async processing feature：

首先说一下Servlet 3 的一些特性，一个普通 Servlet 的主要工做流程大体以下：首先，Servlet 接收到请求以后，可能须要对请求携带的数据进行一些预处理；接着，调用业务接口的某些方法，以完成业务处理；最后，根据处理的结果提交响应，Servlet 线程结束。其中第二步的业务处理一般是最耗时的，这主要体如今数据库操做，以及其它的跨网络调用等，在此过程当中，Servlet 线程一直处于阻塞状态，直到业务方法执行完毕。在处理业务的过程当中，Servlet 资源一直被占用而得不到释放，对于并发较大的应用，这有可能形成性能的瓶颈。对此，在之前一般是采用私有解决方案来提早结束 Servlet 线程，并及时释放资源

如今经过使用 Servlet 3.0 的异步处理支持，以前的 Servlet 处理流程能够调整为以下的过程：首先，Servlet 接收到请求以后，可能首先须要对请求携带的数据进行一些预处理；接着，Servlet 线程将请求转交给一个异步线程来执行业务处理，线程自己返回至容器，此时 Servlet 尚未生成响应数据，异步线程处理完业务之后，能够直接生成响应数据（异步线程拥有 ServletRequest 和 ServletResponse 对象的引用），或者将请求继续转发给其它 Servlet。如此一来， Servlet 线程再也不是一直处于阻塞状态以等待业务逻辑的处理，而是启动异步线程以后能够当即返回。

一个简单的demo

@WebServlet(urlPatterns = "/demo", asyncSupported = true)
public class AsyncDemoServlet extends HttpServlet {
    @Override
    public void doGet(HttpServletRequest req, HttpServletResponse resp)
    throws IOException, ServletException {
        resp.setContentType("text/html;charset=UTF-8");
        PrintWriter out = resp.getWriter();
        out.println("开始时间：" + new Date() + ".");
        out.flush();
 
        //在子线程中执行业务调用，并由其负责输出响应，主线程退出
        AsyncContext ctx = req.startAsync();
        new Thread(new Executor(ctx)).start();
 
        out.println("结束时间：" + new Date() + ".");
        out.flush();
    }
}
 
public class Executor implements Runnable {
    private AsyncContext ctx = null;
    public Executor(AsyncContext ctx){
        this.ctx = ctx;
    }
 
    public void run(){
        try {
            //等待十秒钟，以模拟业务方法的执行
            Thread.sleep(10000);
            PrintWriter out = ctx.getResponse().getWriter();
            out.println("业务处理完毕的时间：" + new Date() + ".");
            out.flush();
            ctx.complete();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

输出的结果：

开始时间：Thu Jul 27 09:49:30 CST 2013

业务处理完毕的时间: Thu Jul 27 09:49:40 CST 2013

下面是spring mvc 3.2 对其的支持。对于spring mvc 里面有三种方式的支持，分别是Callable，DeferredResult，WebAsyncTask

Callable：

@RequestMapping("/response-body")
    public @ResponseBody Callable<String> callable(final @RequestParam(required=false, defaultValue="true") boolean handled) {
         //进行一些与处理以后，把最耗时的业务逻辑部分放到Callable中，注意，若是你须要在new Callable中用到从页面传入的参数，须要在参数前加入final
        return new Callable<String>() {
            @Override
            public String call() throws Exception {
                if(handled){
                    Thread.sleep(2000);
                }else{
                    Thread.sleep(2000*2);
                }
                return "Callable result";
            }
        };
    }

WebAsyncTask:

（一）对于Callable来讲会默认使用SimpleAsyncTaskExecutor类来执行，这个类很是简单并且没有重用线程。而在实际中，你将可能会须要使用AsyncTaskExecutor类来针对你所处的环境进行适当的配置。

（二）在servlet中timeout是一个很重要的问题，servlet容器会尝试重用request和response对象，对于一个timeout可是实际上没有结束的异步请求来讲，使用同一个request和response对象影响将没法估量。

WebAsyncTask中有一个setTimeout的选项，其中他的核心原理是callable

@RequestMapping("/custom-timeout-handling")
    public @ResponseBody WebAsyncTask<String> callableWithCustomTimeoutHandling() {
 
        Callable<String> callable = new Callable<String>() {
            @Override
            public String call() throws Exception {
                Thread.sleep(2000);
                return "Callable result";
            }
        };
 
        return new WebAsyncTask<String>(1000, callable);//容许指定timeout时间
    }

最后一个是DeferredResult<?> ，一个DeferredResult<?> 容许应用程序从一个线程中返回，而什么时候返回则由线程决定

@Controller
@RequestMapping("/async")
public class DeferredResultController {
 
    private final Queue<DeferredResult<String>> responseBodyQueue = new ConcurrentLinkedQueue<DeferredResult<String>>();
 
    private final Queue<DeferredResult<ModelAndView>> mavQueue = new ConcurrentLinkedQueue<DeferredResult<ModelAndView>>();
 
    private final Queue<DeferredResult<String>> exceptionQueue = new ConcurrentLinkedQueue<DeferredResult<String>>();
 
 
    @RequestMapping("/deferred-result/response-body")
    public @ResponseBody DeferredResult<String> deferredResult() {
        DeferredResult<String> result = new DeferredResult<String>();
        this.responseBodyQueue.add(result);
        return result;
    }
 
    @RequestMapping("/deferred-result/model-and-view")
    public @ResponseBody DeferredResult<ModelAndView> deferredResultWithView() {
        DeferredResult<ModelAndView> result = new DeferredResult<ModelAndView>();
        this.mavQueue.add(result);
        return result;
    }
 
    @RequestMapping("/deferred-result/exception")
    public @ResponseBody DeferredResult<String> deferredResultWithException() {
        DeferredResult<String> result = new DeferredResult<String>();
        this.exceptionQueue.add(result);
        return result;
    }
     //上面三个分别接受了请求以后就return了
    // 这里容许咱们在其余的线程中处理数据，而且无需实时返回
    @RequestMapping("/deferred-result/timeout-value")
    public @ResponseBody DeferredResult<String> deferredResultWithTimeoutValue() {
 
        // Provide a default result in case of timeout and override the timeout value
        // set in src/main/webapp/WEB-INF/spring/appServlet/servlet-context.xml
 
        return new DeferredResult<String>(1000L, "Deferred result after timeout");
    }
     //建立一个计划任务，每2秒处理一次
    @Scheduled(fixedRate=2000)
    public void processQueues() {
        for (DeferredResult<String> result : this.responseBodyQueue) {
            result.setResult("Deferred result");
            this.responseBodyQueue.remove(result);
        }
        for (DeferredResult<String> result : this.exceptionQueue) {
            result.setErrorResult(new IllegalStateException("DeferredResult error"));
            this.exceptionQueue.remove(result);
        }
        for (DeferredResult<ModelAndView> result : this.mavQueue) {
            result.setResult(new ModelAndView("views/html", "javaBean", new JavaBean("bar", "apple")));
            this.mavQueue.remove(result);
        }
    }
 
    @ExceptionHandler
    @ResponseBody
    public String handleException(IllegalStateException ex) {
        return "Handled exception: " + ex.getMessage();
    }
 
}

11. Interceptor，经过继承HandlerInterceptor，实现preHandle(..)方法来定义一些列方法执行先后的动做

官方例子

<mvc:interceptors>
    <ref bean="officeHoursInterceptor"/>
</mvc:interceptors>
<bean id="officeHoursInterceptor"
          class="samples.TimeBasedAccessInterceptor">
        <property name="openingTime" value="9"/>
        <property name="closingTime" value="18"/>
</bean>

package samples; public class TimeBasedAccessInterceptor extends HandlerInterceptorAdapter { private int openingTime; private int closingTime; public void setOpeningTime(int openingTime) { this.openingTime = openingTime; } public void setClosingTime(int closingTime) { this.closingTime = closingTime; } public boolean preHandle( HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { Calendar cal = Calendar.getInstance(); int hour = cal.get(HOUR_OF_DAY); if (openingTime <= hour && hour < closingTime) { return true; } else { response.sendRedirect("http://host.com/outsideOfficeHours.html"); return false; } } }

HandlerInterceptorAdapter 里面有不少方法，下面是api的部分文档

那些pre，after和post开头的方法基本能够知足interceptor的各类须要

这里基本结束了spring mvc 3.2的总结，在写这个文章的前几天spring已经出4.0了，看了一下，发现里面开始有websocket的支持了。

来自为知笔记(Wiz)