Spring MVC 3.0 深入及对注解的详细讲解

来源：互联网发布：信息泄露知乎编辑：程序博客网时间：2024/05/29 03:21

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、    Control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

@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。
publicclass 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"})
publicclass 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,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。

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")
publicclass 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")
publicclass 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")
publicclass UserControllerextends 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 HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head></head>
<body>
       <h1>${requestScope.a}</h1>
       <c:out value="${requestScope.a}"></c:out>
</body>
</html>
将属性u的值赋给形参uname

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：
[java] view plaincopy
publicclass 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()}.
     */
   privateboolean 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.
     */
   publicvoid 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.viewinstanceof String ? (String)this.view :null);
    }

   /**
     * Set a View object for this ModelAndView. Will override any
     * pre-existing view name or View.
     */
   publicvoid 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.viewinstanceof 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.
     */
   publicboolean 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.
     */
   publicboolean isReference() {
       return (this.viewinstanceof String);
    }

   /**
     * Return the model map. May return <code>null</code>.
     * Called by DispatcherServlet for evaluation of the model.
     */
   protected Map<String, Object> getModelInternal() {
       returnthis.model;
    }

   /**
     * Return the underlying <code>ModelMap</code> instance (never <code>null</code>).
     */
   public ModelMap getModelMap() {
       if (this.model == null) {
           this.model =new ModelMap();
        }
       returnthis.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);
       returnthis;
    }

   /**
     * 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);
       returnthis;
    }

   /**
     * 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);
       returnthis;
    }

   /**
     * 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
     */
   publicvoid 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.
     */
   publicboolean 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()
     */
   publicboolean 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();
    }
}

[java] view plaincopy
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")
publicclass UserControllerextends 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 HTML PUBLIC"-//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：

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Spring MVC 3.0 深入及对注解的详细讲解

核心原理

spring3.0中相关jar包的含义

@Controller控制器定义

@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

@RequestParam

@SessionAttributes

@ModelAttribute

Controller类中方法参数的处理

Controller类中方法返回值的处理

请求转发和重定向

获得request对象、session对象

ModelMap

ModelAndView模型视图类

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