spring mvc 3.2 使用总结-白红宇

spring mvc 3.2 使用总结

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发布时间：2019-06-18

本文共 23265 字，大约阅读时间需要 77 分钟。

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：

就拿这个例子作为总结的代码。

1.首先介绍一下WebApplicationInitializer，可以通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


          
               
        
         example
                
        
         org.springframework.web.servlet.DispatcherServlet
                
        
         1
            
           
               
        
         example
                
        
         /example/*

2.定义一个controller

@Controllerpublic 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，其中可以使用一个参数“method”，取值可以是RequestMethod.POST，RequestMethod.GET, RequestMethod.DEL等，用来限定访问的方法

3.使用hibernate validation作为验证

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：

@Controllerpublic 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说明需要对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：

@Controllerpublic 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基本上什么都可以做到了        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可以被捕捉    }     @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 ，获得一个foo的参数，还可以指定参数的名字，例如下面的的    }     @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 ，参数需要在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) {//类似上面的，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 允许组合所有参数成为一个  public void findPet(        @MatrixVariable Map < String, String > matrixVars,        @MatrixVariable(pathVar = "petId" ) Map
        
          petMatrixVars) {    // matrixVars: [" q " : [11,22], " r " : 12, " s " : 23]    // petMatrixVars: [" q " : 11, " s " : 23] }/*Host                    localhost:8080Accept                  text/html,application/xhtml+xml,application/xml;q=0.9Accept-Language         fr,en-gb;q=0.7,en;q=0.3Accept-Encoding         gzip,deflateAccept-Charset          ISO-8859-1,utf-8;q=0.7,*;q=0.7Keep-Alive              300*/    @RequestMapping(value="header", method=RequestMethod.GET)    public @ResponseBody String withHeader(@RequestHeader String Accept) {//@RequestHeader 可以指定你想或者header中的哪个属性的信息        return "Obtained 'Accept' header '" + Accept + "'";//例如@RequestHeader("Keep-Alive") 获得 300     }     // cookie中有一个值openid_provider=415A4AC178C59DACE0B2C9CA727CDD84 ,也可以指定变量名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，一般是xml和json数据，可以使用consumes="application/json"指定接受的是json还是xml*spring可以把POST的数据转换成为一个bean*例如有个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，这种方式尽量少用*/    @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
         
           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来传递请求数据当然有一个返回应答的数据流类    @RequestMapping("/something")public ResponseEntity
          
            handle(HttpEntity
           
             requestEntity) throwsUnsupportedEncodingException {  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
            
             ("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来说，其他的方法的返回的jsp页面里面都会有一个people属性被返回，因为@ModelAttribute注解的方法会在这个controller的其他方法调用前被调用}

在jsp页面中可以访问${ people}这个属性，如果在 @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"%>
        Insert title here Edit Person
 
         
            
         
                                                     
             
              Id:
                                     
                                
                                            
             
              First Name:
                                     
                                
                                            
             
              Last Name
                                     
                                
                                            
             
              Money
                                     
                                
                                            
             
              Currency:

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，这里还获得了id这个信息}

controller代码

根据@ModelAttribute两种用法，可以这样子实现

@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，然后再执行add方法，其中person这个bean已经被new出来了，所以在add方法中可以被获得，这个有点像下面要说的convert，但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
       
         {     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) {        //操作accout类        return "accounts/edit";    }}

下面描述了convert的运作过程

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，可以允许我们使用，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可以指定变量名@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)@ResponseBodypublic 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 的主要工作流程大致如下：首先，Servlet 接收到请求之后，可能需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通常是最耗时的，这主要体现在数据库操作，以及其它的跨网络调用等，在此过程中，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，这有可能造成性能的瓶颈。对此，在以前通常是采用私有解决方案来提前结束 Servlet 线程，并及时释放资源

现在通过使用 Servlet 3.0 的异步处理支持，之前的 Servlet 处理流程可以调整为如下的过程：首先，Servlet 接收到请求之后，可能首先需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，线程本身返回至容器，此时 Servlet 还没有生成响应数据，异步线程处理完业务以后，可以直接生成响应数据（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 线程不再是一直处于阻塞状态以等待业务逻辑的处理，而是启动异步线程之后可以立即返回。

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
        
          callable(final @RequestParam(required=false, defaultValue="true") boolean handled) {         //进行一些与处理之后，把最耗时的业务逻辑部分放到Callable中，注意，如果你需要在new Callable中用到从页面传入的参数，需要在参数前加入final        return new Callable
         
          () {            @Override            public String call() throws Exception {                if(handled){                    Thread.sleep(2000);                }else{                    Thread.sleep(2000*2);                }                return "Callable result";            }        };    }

WebAsyncTask:

（一）对于Callable来说会默认使用SimpleAsyncTaskExecutor类来执行，这个类非常简单而且没有重用线程。而在实际中，你将可能会需要使用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但是实际上没有结束的异步请求来说，使用同一个request和response对象影响将无法估量。

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
        
          callableWithCustomTimeoutHandling() {         Callable
         
           callable = new Callable
          
           () {            @Override            public String call() throws Exception {                Thread.sleep(2000);                return "Callable result";            }        };         return new WebAsyncTask
           
            (1000, callable);//允许指定timeout时间    }

最后一个是DeferredResult<?> ，一个DeferredResult<?> 允许应用程序从一个线程中返回，而何时返回则由线程决定

@Controller@RequestMapping("/async")public class DeferredResultController {     private final Queue
        
         
          > responseBodyQueue = new ConcurrentLinkedQueue
          
           
            >();     private final Queue
            
             
              > mavQueue = new ConcurrentLinkedQueue
              
               
                >(); private final Queue
                
                 
                  > exceptionQueue = new ConcurrentLinkedQueue
                  
                   
                    >(); @RequestMapping("/deferred-result/response-body") public @ResponseBody DeferredResult
                    
                      deferredResult() { DeferredResult
                     
                       result = new DeferredResult
                      
                       (); this.responseBodyQueue.add(result); return result; } @RequestMapping("/deferred-result/model-and-view") public @ResponseBody DeferredResult
                       
                         deferredResultWithView() { DeferredResult
                        
                          result = new DeferredResult
                         
                          (); this.mavQueue.add(result); return result; } @RequestMapping("/deferred-result/exception") public @ResponseBody DeferredResult
                          
                            deferredResultWithException() { DeferredResult
                           
                             result = new DeferredResult
                            
                             (); this.exceptionQueue.add(result); return result; } //上面三个分别接受了请求之后就return了 // 这里允许我们在其他的线程中处理数据，并且无需实时返回 @RequestMapping("/deferred-result/timeout-value") public @ResponseBody DeferredResult
                             
                               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
                              
                               (1000L, "Deferred result after timeout"); } //创建一个计划任务，每2秒处理一次 @Scheduled(fixedRate=2000) public void processQueues() { for (DeferredResult
                               
                                 result : this.responseBodyQueue) { result.setResult("Deferred result"); this.responseBodyQueue.remove(result); } for (DeferredResult
                                
                                  result : this.exceptionQueue) { result.setErrorResult(new IllegalStateException("DeferredResult error")); this.exceptionQueue.remove(result); } for (DeferredResult
                                 
                                   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，通过继承HandlerInterceptor，实现preHandle(..)方法来定义一些列方法执行前后的动作

官方例子

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 里面有很多方法，下面是api的部分文档