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SpringMVC轻松学习-其他常用（四）

2024-07-02 02:00:46   219人阅读

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Spring MVC 3.0 深入

核心原理

1.      用户发送请求给服务器。url：user.do

2.      服务器收到请求。发现DispatchServlet可以处理。于是调用DispatchServlet。

3.      DispatchServlet内部，通过HandleMapping检查这个url有没有对应的Controller。如果有，则调用Controller。

4.      Controller开始执行。

5.      Controller执行完毕后，如果返回字符串，则ViewResolver将字符串转化成相应的视图对象；如果返回ModelAndView对象，该对象本身就包含了视图对象信息。

6.      DispatchServlet将执视图对象中的数据，输出给服务器。

7.      服务器将数据输出给客户端。

spring3.0中相关jar包的含义

org.springframework.aop-3.0.3.RELEASE.jar

spring的aop面向切面编程

org.springframework.asm-3.0.3.RELEASE.jar

spring独立的asm字节码生成程序

org.springframework.beans-3.0.3.RELEASE.jar

IOC的基础实现

org.springframework.context-3.0.3.RELEASE.jar

IOC基础上的扩展服务

org.springframework.core-3.0.3.RELEASE.jar

spring的核心包

org.springframework.expression-3.0.3.RELEASE.jar

spring的表达式语言

org.springframework.web-3.0.3.RELEASE.jar

web工具包

org.springframework.web.servlet-3.0.3.RELEASE.jar

mvc工具包

 

 

@Controller控制器定义

和Struts1一样，Spring的Controller是Singleton的。这就意味着会被多个请求线程共享。因此，我们将控制器设计成无状态类。

 

在spring 3.0中，通过@controller标注即可将class定义为一个controller类。为使spring能找到定义为controller的bean,需要在spring-context配置文件中增加如下定义：

 

<context:component-scan base-package="com.sxt.web"/>

 

         注：实际上，使用@component，也可以起到@Controller同样的作用。

 

@RequestMapping

 

    在类前面定义，则将url和类绑定。

       在方法前面定义，则将url和类的方法绑定，如下所示：

package com.sxt.web;

 

import javax.annotation.Resource;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

import com.sxt.service.UserService;

 

@Controller

@RequestMapping("/user.do")

public class UserController  {

 

    @Resource

    private UserService userService;

   

    //http://localhost:8080/springmvc02/user.do?method=reg&uname=zzzz

    @RequestMapping(params="method=reg")

    public String reg(String uname) {

       System.out.println("HelloController.handleRequest()");

       userService.add(uname);

       return "index";

    }

   

    public UserService getUserService() {

       return userService;

    }

    public void setUserService(UserService userService) {

       this.userService = userService;

    }

 

   

}

 

@RequestParam

         一般用于将指定的请求参数付给方法中形参。示例代码如下：

        

@RequestMapping(params="method=reg5")

    public String reg5(@RequestParam("name")String uname,ModelMap map) {

       System.out.println("HelloController.handleRequest()");

       System.out.println(uname);

       return "index";

    }

        

         这样，就会将name参数的值付给uname。当然，如果请求参数名称和形参名称保持一致，则不需要这种写法。

@SessionAttributes

    将ModelMap中指定的属性放到session中。示例代码如下：

   

@Controller

@RequestMapping("/user.do")

@SessionAttributes({"u","a"})   //将ModelMap中属性名字为u、a的再放入session中。这样，request和session中都有了。

public class UserController  {

    @RequestMapping(params="method=reg4")

    public String reg4(ModelMap map) {         System.out.println("HelloController.handleRequest()");

       map.addAttribute("u","uuuu");  //将u放入request作用域中，这样转发页面也可以取到这个数据。

       return "index";

    }

}

  <body>

   <h1>**********${requestScope.u.uname}</h1>

   <h1>**********${sessionScope.u.uname}</h1>

  </body>

   

    注：名字为”user”的属性再结合使用注解@SessionAttributes可能会报错。

 

@ModelAttribute

      这个注解可以跟@SessionAttributes配合在一起用。可以将ModelMap中属性的值通过该注解自动赋给指定变量。

    示例代码如下：

package com.sxt.web;

import javax.annotation.Resource;

import org.springframework.stereotype.Controller;

import org.springframework.ui.ModelMap;

import org.springframework.web.bind.annotation.ModelAttribute;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.SessionAttributes;

@Controller

@RequestMapping("/user.do")

@SessionAttributes({"u","a"}) 

public class UserController  {

   

    @RequestMapping(params="method=reg4")

    public String reg4(ModelMap map) {

       System.out.println("HelloController.handleRequest()");

       map.addAttribute("u","尚学堂高淇");

       return "index";

    }

   

    @RequestMapping(params="method=reg5")

public String reg5(@ModelAttribute("u")String uname[微软用户1] ,ModelMap map) {

       System.out.println("HelloController.handleRequest()");

       System.out.println(uname);

       return "index";

    }

   

}

 

先调用reg4方法，再调用reg5方法。我们发现控制台打印出来：尚学堂高淇

 

Controller类中方法参数的处理

 

Controller类中方法返回值的处理

1.      返回string(建议)

a)        根据返回值找对应的显示页面。路径规则为：prefix前缀+返回值+suffix后缀组成

b)        代码如下：

@RequestMapping(params="method=reg4")

    public String reg4(ModelMap map) {

       System.out.println("HelloController.handleRequest()");

       return "index";

    }

前缀为：/WEB-INF/jsp/    后缀是：.jsp

在转发到：/WEB-INF/jsp/index.jsp

 

2.      也可以返回ModelMap、ModelAndView、map、List、Set、Object、无返回值。一般建议返回字符串！

 

 

请求转发和重定向

         代码示例：

        

package com.sxt.web;

 

import javax.annotation.Resource;

import org.springframework.stereotype.Controller;

import org.springframework.ui.ModelMap;

import org.springframework.web.bind.annotation.ModelAttribute;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.SessionAttributes;

 

@Controller

@RequestMapping("/user.do")

public class UserController  {

   

    @RequestMapping(params="method=reg4")

    public String reg4(ModelMap map) {

       System.out.println("HelloController.handleRequest()");

//     return "forward:index.jsp";

//     return "forward:user.do?method=reg5"; //转发

//     return "redirect:user.do?method=reg5";  //重定向

       return "redirect:http://www.baidu.com";  //重定向

    }

   

    @RequestMapping(params="method=reg5")

    public String reg5(String uname,ModelMap map) {

       System.out.println("HelloController.handleRequest()");

       System.out.println(uname);

       return "index";

    }

   

}

        

         访问reg4方法，既可以看到效果。

 

 

 

获得request对象、session对象

普通的Controller类，示例代码如下：

@Controller

@RequestMapping("/user.do")

public class UserController  {

   

    @RequestMapping(params="method=reg2")

    public String reg2(String uname,HttpServletRequest req,ModelMap map){

       req.setAttribute("a", "aa");

       req.getSession().setAttribute("b", "bb");

       return "index";

    }

}

 

 

ModelMap

         是map的实现，可以在其中存放属性，作用域同request。下面这个示例，我们可以在modelMap中放入数据，然后在forward的页面上显示这些数据。通过el表达式、JSTL、java代码均可。代码如下：

        

package com.sxt.web;

 

import org.springframework.stereotype.Controller;

import org.springframework.ui.ModelMap;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.servlet.mvc.multiaction.MultiActionController;

 

@Controller

@RequestMapping("/user.do")

public class UserController extends MultiActionController  {

   

    @RequestMapping(params="method=reg")

    public String reg(String uname,ModelMap map){

       map.put("a", "aaa");

       return "index";

    }

}

<%@ page language="java"import="java.util.*" pageEncoding="gbk"%>

<%@ taglib prefix="c"uri="http://java.sun.com/jsp/jstl/core"%>

<!DOCTYPE HTMLPUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

  <head></head>

  <body>

       <h1>${requestScope.a}</h1>

       <c:out value="${requestScope.a}"></c:out>

  </body>

</html>

 

ModelAndView模型视图类

见名知意，从名字上我们可以知道ModelAndView中的Model代表模型，View代表视图。即，这个类把要显示的数据存储到了Model属性中，要跳转的视图信息存储到了view属性。我们看一下ModelAndView的部分源码，即可知其中关系：

public class ModelAndView {

 

    /** View instance or view name String */

    private Object view;

 

    /** Model Map */

    private ModelMap model;

 

    /**

     * Indicates whether or not this instance has been cleared with a call to {@link #clear()}.

     */

    private boolean cleared = false;

 

 

    /**

     * Default constructor for bean-style usage: populating bean

     * properties instead of passing in constructor arguments.

     * @see #setView(View)

     * @see #setViewName(String)

     */

    public ModelAndView() {

    }

 

    /**

     * Convenient constructor when there is no model data to expose.

     * Can also be used in conjunction with <code>addObject</code>.

     * @param viewName name of the View to render, to be resolved

     * by the DispatcherServlet‘s ViewResolver

     * @see #addObject

     */

    public ModelAndView(String viewName) {

       this.view = viewName;

    }

 

    /**

     * Convenient constructor when there is no model data to expose.

     * Can also be used in conjunction with <code>addObject</code>.

     * @param view View object to render

     * @see #addObject

     */

    public ModelAndView(View view) {

       this.view = view;

    }

 

    /**

     * Creates new ModelAndView given a view name and a model.

     * @param viewName name of the View to render, to be resolved

     * by the DispatcherServlet‘s ViewResolver

     * @param model Map of model names (Strings) to model objects

     * (Objects). Model entries may not be <code>null</code>, but the

     * model Map may be <code>null</code> if there is no model data.

     */

    public ModelAndView(String viewName, Map<String, ?> model) {

       this.view = viewName;

       if (model != null) {

           getModelMap().addAllAttributes(model);

       }

    }

 

    /**

     * Creates new ModelAndView given a View object and a model.

     * <emphasis>Note: the supplied model data is copied into the internal

     * storage of this class. You should not consider to modify the supplied

     * Map after supplying it to this class</emphasis>

     * @param view View object to render

     * @param model Map of model names (Strings) to model objects

     * (Objects). Model entries may not be <code>null</code>, but the

     * model Map may be <code>null</code> if there is no model data.

     */

    public ModelAndView(View view, Map<String, ?> model) {

       this.view = view;

       if (model != null) {

           getModelMap().addAllAttributes(model);

       }

    }

 

    /**

     * Convenient constructor to take a single model object.

     * @param viewName name of the View to render, to be resolved

     * by the DispatcherServlet‘s ViewResolver

     * @param modelName name of the single entry in the model

     * @param modelObject the single model object

     */

    public ModelAndView(String viewName, String modelName, Object modelObject) {

       this.view = viewName;

       addObject(modelName, modelObject);

    }

 

    /**

     * Convenient constructor to take a single model object.

     * @param view View object to render

     * @param modelName name of the single entry in the model

     * @param modelObject the single model object

     */

    public ModelAndView(View view, String modelName, Object modelObject) {

       this.view = view;

       addObject(modelName, modelObject);

    }

 

 

    /**

     * Set a view name for this ModelAndView, to be resolved by the

     * DispatcherServlet via a ViewResolver. Will override any

     * pre-existing view name or View.

     */

    public void setViewName(String viewName) {

       this.view = viewName;

    }

 

    /**

     * Return the view name to be resolved by the DispatcherServlet

     * via a ViewResolver, or <code>null</code> if we are using a View object.

     */

    public String getViewName() {

       return (this.view instanceof String ? (String) this.view : null);

    }

 

    /**

     * Set a View object for this ModelAndView. Will override any

     * pre-existing view name or View.

     */

    public void setView(View view) {

       this.view = view;

    }

 

    /**

     * Return the View object, or <code>null</code> if we are using a view name

     * to be resolved by the DispatcherServlet via a ViewResolver.

     */

    public View getView() {

       return (this.view instanceof View ? (View) this.view : null);

    }

 

    /**

     * Indicate whether or not this <code>ModelAndView</code> has a view, either

     * as a view name or as a direct {@link View} instance.

     */

    public boolean hasView() {

       return (this.view != null);

    }

 

    /**

     * Return whether we use a view reference, i.e. <code>true</code>

     * if the view has been specified via a name to be resolved by the

     * DispatcherServlet via a ViewResolver.

     */

    public boolean isReference() {

       return (this.view instanceof String);

    }

 

    /**

     * Return the model map. May return <code>null</code>.

     * Called by DispatcherServlet for evaluation of the model.

     */

    protected Map<String, Object> getModelInternal() {

       return this.model;

    }

 

    /**

     * Return the underlying <code>ModelMap</code> instance (never <code>null</code>).

     */

    public ModelMap getModelMap() {

       if (this.model == null) {

           this.model = new ModelMap();

       }

       return this.model;

    }

 

    /**

     * Return the model map. Never returns <code>null</code>.

     * To be called by application code for modifying the model.

     */

    public Map<String, Object> getModel() {

       return getModelMap();

    }

 

 

    /**

     * Add an attribute to the model.

     * @param attributeName name of the object to add to the model

     * @param attributeValue object to add to the model (never <code>null</code>)

     * @see ModelMap#addAttribute(String, Object)

     * @see #getModelMap()

     */

    public ModelAndView addObject(String attributeName, Object attributeValue) {

       getModelMap().addAttribute(attributeName, attributeValue);

       return this;

    }

 

    /**

     * Add an attribute to the model using parameter name generation.

     * @param attributeValue the object to add to the model (never <code>null</code>)

     * @see ModelMap#addAttribute(Object)

     * @see #getModelMap()

     */

    public ModelAndView addObject(Object attributeValue) {

       getModelMap().addAttribute(attributeValue);

       return this;

    }

 

    /**

     * Add all attributes contained in the provided Map to the model.

     * @param modelMap a Map of attributeName -> attributeValue pairs

     * @see ModelMap#addAllAttributes(Map)

     * @see #getModelMap()

     */

    public ModelAndView addAllObjects(Map<String, ?> modelMap) {

       getModelMap().addAllAttributes(modelMap);

       return this;

    }

 

 

    /**

     * Clear the state of this ModelAndView object.

     * The object will be empty afterwards.

     * <p>Can be used to suppress rendering of a given ModelAndView object

     * in the <code>postHandle</code> method of a HandlerInterceptor.

     * @see #isEmpty()

     * @see HandlerInterceptor#postHandle

     */

    public void clear() {

       this.view = null;

       this.model = null;

       this.cleared = true;

    }

 

    /**

     * Return whether this ModelAndView object is empty,

     * i.e. whether it does not hold any view and does not contain a model.

     */

    public boolean isEmpty() {

       return (this.view == null && CollectionUtils.isEmpty(this.model));

    }

 

    /**

     * Return whether this ModelAndView object is empty as a result of a call to {@link #clear}

     * i.e. whether it does not hold any view and does not contain a model.

     * <p>Returns <code>false</code> if any additional state was added to the instance

     * <strong>after</strong> the call to {@link #clear}.

     * @see #clear()

     */

    public boolean wasCleared() {

       return (this.cleared && isEmpty());

    }

 

 

    /**

     * Return diagnostic information about this model and view.

     */

    @Override

    public String toString() {

       StringBuilder sb = new StringBuilder("ModelAndView: ");

       if (isReference()) {

           sb.append("reference to view with name ‘").append(this.view).append("‘");

       }

       else {

           sb.append("materialized View is [").append(this.view).append(‘]‘);

       }

       sb.append("; model is ").append(this.model);

       return sb.toString();

    }

}

 

测试代码如下：

package com.sxt.web;

 

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.servlet.ModelAndView;

import org.springframework.web.servlet.mvc.multiaction.MultiActionController;

 

import com.sxt.po.User;

 

@Controller

@RequestMapping("/user.do")

public class UserController extends MultiActionController  {

   

    @RequestMapping(params="method=reg")

    public ModelAndView reg(String uname){

       ModelAndView mv = new ModelAndView();

       mv.setViewName("index");

//     mv.setView(new RedirectView("index"));

      

       User u = new User();

       u.setUname("高淇");

       mv.addObject(u);   //查看源代码，得知，直接放入对象。属性名为”首字母小写的类名”。 一般建议手动增加属性名称。

       mv.addObject("a", "aaaa");

       return mv;

    }

 

}

<%@ page language="java"import="java.util.*" pageEncoding="gbk"%>

<%@ taglib prefix="c"uri="http://java.sun.com/jsp/jstl/core"%>

<!DOCTYPE HTMLPUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

  <head>

  </head>

  <body>

       <h1>${requestScope.a}</h1>

       <h1>${requestScope.user.uname}</h1>

  </body>

</html>

地址栏输入：http://localhost:8080/springmvc03/user.do?method=reg

结果为：

 

 

基于spring 3.0mvc 框架的文件上传实现

1. spring使用了apache-commons下得上传组件，因此，我们需要引入两个jar包：

1.      apache-commons-fileupload.jar

2.      apache-commons-io.jar

 

2.  在springmvc-servlet.xml配置文件中，增加CommonsMultipartResoler配置：

<!-- 处理文件上传 -->

<bean id="multipartResolver" 

    class="org.springframework.web.multipart.commons.CommonsMultipartResolver"> 

    <property name="defaultEncoding"value="gbk"/> <!-- 默认编码 (ISO-8859-1) --> 

    <property name="maxInMemorySize"value="10240"/> <!-- 最大内存大小 (10240)--> 

    <property name="uploadTempDir"value="/upload/"/> <!-- 上传后的目录名(WebUtils#TEMP_DIR_CONTEXT_ATTRIBUTE) --> 

    <property name="maxUploadSize"value="-1"/> <!-- 最大文件大小，-1为无限止(-1) --> 

</bean>

 

3.  建立upload.jsp页面，内容如下：

        

<%@ page language="java"import="java.util.*" pageEncoding="gbk"%>

<!DOCTYPE HTMLPUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

    <head>

       <title>测试springmvc中上传的实现</title>

    </head>

    <body>

<form action="upload.do"  method="post"enctype="multipart/form-data">

           <input type="text" name="name"/>

           <input type="file" name="file"/>

           <input type="submit" />

       </form>

    </body>

</html>

 

4. 建立控制器，代码如下：

        

package com.sxt.web;

 

import java.io.File;

import java.util.Date;

 

import javax.servlet.ServletContext;

 

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestMethod;

import org.springframework.web.bind.annotation.RequestParam;

import org.springframework.web.context.ServletContextAware;

import org.springframework.web.multipart.commons.CommonsMultipartFile;

 

@Controller

public class FileUploadController implements ServletContextAware {

 

         private ServletContext servletContext;

        

         @Override

         public void setServletContext(ServletContext context) {

                   this.servletContext  = context;

         }

        

         @RequestMapping(value="http://www.mamicode.com/upload.do", method = RequestMethod.POST)

         public String handleUploadData(String name,@RequestParam("file")[微软用户2] CommonsMultipartFile file){

                   if (!file.isEmpty()) {

                               String path = this.servletContext.getRealPath("/tmp/");  //获取本地存储路径

                               System.out.println(path);

                               String fileName = file.getOriginalFilename();

                               String fileType = fileName.substring(fileName.lastIndexOf("."));

                               System.out.println(fileType);

                               File file2 = new File(path,new Date().getTime() + fileType); //新建一个文件

                               try {

                                         file.getFileItem().write(file2); //将上传的文件写入新建的文件中

                               } catch (Exception e) {

                                         e.printStackTrace();

                               }

                               return "redirect:upload_ok.jsp";

                            }else{

                                     return "redirect:upload_error.jsp";

                            }

         }

}

 

5. 建立upload_ok.jsp页面

<%@ page language="java"import="java.util.*" pageEncoding="gbk"%>

<!DOCTYPE HTMLPUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

  <head>

  </head>

  <body>

       <h1>上传成功！</h1>

  </body>

</html>

 

6. 建立upload_error.jsp页面

  <%@ page language="java"import="java.util.*" pageEncoding="gbk"%>

<!DOCTYPE HTMLPUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

  <head>

  </head>

  <body>

       <h1>上传失败！</h1>

  </body>

</html>

 

1.      发布项目，运行测试：http://localhost:8080/springmvc03/upload.jsp

   进入项目发布后的目录，发现文件上传成功：

 

处理ajax请求

spring使用了jackson类库，帮助我们在java对象和json、xml数据之间的互相转换。他可以将控制器返回的对象直接转换成json数据，供客户端使用。客户端也可以传送json数据到服务器进行直接转换。使用步骤如下：

 

1.  项目中需要引入如下两个jar包：

                  jackson-core-asl-1.7.2jar

                   jackson-mapper-asl-1.7.2jar

2.  spring配置文件中修改：

             <mvc:annotation-driven />  <!-- 支持spring3.0新的mvc注解 -->

    <!-- 启动Spring MVC的注解功能，完成请求和注解POJO的映射 -->

      <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"> 

        <property name="cacheSeconds"value="0" /> 

        <property name="messageConverters"> 

            <list> 

                <bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"></bean> 

            </list> 

        </property>

    </bean>  

 

3.      客户端代码a.jsp如下：

<%@ page language="java"import="java.util.*" pageEncoding="gbk"%>

<%

String path = request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

%>

 

<!DOCTYPE HTML PUBLIC"-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

  <head>

    <base href="<%=basePath%>">

   

    <title>My JSP ‘index.jsp‘ starting page</title>

    <meta http-equiv="pragma"content="no-cache">

    <meta http-equiv="cache-control"content="no-cache">

    <meta http-equiv="expires"content="0">   

    <meta http-equiv="keywords"content="keyword1,keyword2,keyword3">

    <meta http-equiv="description"content="This is my page">

    <script>

       function createAjaxObj(){

           var req;

           if(window.XMLHttpRequest){

              req = new XMLHttpRequest();

           }else{

              req = new ActiveXObject("Msxml2.XMLHTTP");  //ie

           }

           return req;

       }

      

       function sendAjaxReq(){

           var req = createAjaxObj();

           req.open("get","myajax.do?method=test2&uname=张三");

           req.setRequestHeader("accept","application/json");

           req.onreadystatechange  = function(){

              eval("var result="+req.responseText);

              document.getElementById("div1").innerHTML=result[0].uname;

           }

           req.send(null);

       }

    </script>

  </head>

 

  <body>

    <a href="javascript:void(0);"onclick="sendAjaxReq();">测试</a>

    <div id="div1"></div>

  </body>

</html>

 

 

4.      服务器端代码如下：

        

package com.sxt.web;

 

import java.io.UnsupportedEncodingException;

import java.util.ArrayList;

import java.util.List;

 

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestBody;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestMethod;

import org.springframework.web.bind.annotation.ResponseBody;

 

import com.sxt.po.User;

 

@Controller

@RequestMapping("myajax.do")

public class MyAjaxController {

        

         @RequestMapping(params="method=test1",method=RequestMethod.GET)

         public @ResponseBody List<User> test1(String uname) throws Exception{

                   String uname2 = new String(uname.getBytes("iso8859-1"),"gbk");

                   System.out.println(uname2);

                   System.out.println("MyAjaxController.test1()");

                   List<User> list = new ArrayList<User>();

                   list.add(new User("高淇","123"));

                   list.add(new User("马士兵","456"));

                  

                   return list;

         }

        

}

 

 

5.      测试。

a)        启动服务器。输入：http://localhost:8080/springmvc03/a.jsp

 

 

 

 

 

 

Spring中的拦截器

定义spring拦截器两种基本方式

1.      实现接口：org.springframework.web.servlet.HandlerInterceptor。

接口中有如下方法需要重写：

注意：参数中的Object handler是下一个拦截器。

a)        public boolean preHandle
(HttpServletRequest request,HttpServletResponse response,
Object handler) throws Exception

该方法在action执行前执行，可以实现对数据的预处理，比如：编码、安全控制等。

如果方法返回true，则继续执行action。

b)        public void postHandle
(HttpServletRequest request,HttpServletResponse response,
Object handler,   ModelAndViewmodelAndView) throws Exception

该方法在action执行后，生成视图前执行。在这里，我们有机会修改视图层数据。

c)        public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler,Exception ex)   throws Exception

最后执行，通常用于释放资源，处理异常。我们可以根据ex是否为空，来进行相关的异常处理。因为我们在平时处理异常时，都是从底层向上抛出异常，最后到了spring框架从而到了这个方法中。

2.      继承适配器：
org.springframework.web.servlet.handler.HandlerInterceptorAdapter

这个适配器实现了HandlerInterceptor接口。提供了这个接口中所有方法的空实现。

 

如下我们写出两个拦截器的示例代码，仅供大家参考：

package com.sxt.interceptor;

 

import javax.interceptor.Interceptors;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

 

import org.springframework.web.servlet.HandlerInterceptor;

import org.springframework.web.servlet.ModelAndView;

 

 

public class MyInterceptor implements HandlerInterceptor {

 

    @Override

    public void afterCompletion(HttpServletRequest request,    HttpServletResponse response, Object handler, Exception ex)    throws Exception {

       System.out.println("最后执行！！！一般用于释放资源！！");

      

    }

 

    @Override

    public void postHandle(HttpServletRequest request,HttpServletResponse response, Object handler,    ModelAndView modelAndView) throws Exception {

       System.out.println("Action执行之后，生成视图之前执行！！");

    }

 

    @Override

    public boolean preHandle(HttpServletRequest request,HttpServletResponse response, Object handler) throws Exception {

       System.out.println("action之前执行！！！");

       return true;  //继续执行action

    }

 

}

 

package com.sxt.interceptor;

 

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

 

import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

 

 

public class MyInterceptor2 extends HandlerInterceptorAdapter {

 

    @Override

    public boolean preHandle(HttpServletRequest request,HttpServletResponse response, Object handler) throws Exception {

       System.out.println("MyInterceptor2.preHandle()");

       return true;  //继续执行action

    }

 

}

 

 

 

3.      XML中如何配置。如下为示例代码：

    <mvc:interceptors>

       <bean class="com.sxt.interceptor.MyInterceptor"></bean> <!-- 拦截所有springmvc的url！ -->

       <mvc:interceptor>

           <mvc:mapping path="/user.do"/>

           <!--<mvc:mapping path="/test/*" />-->

           <bean class="com.sxt.interceptor.MyInterceptor2"></bean>

       </mvc:interceptor>

    </mvc:interceptors>

 




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