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";    }}

   
**********${requestScope.u.uname}
   
**********${sessionScope.u.uname}
  

   

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

 

@ModelAttribute

      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 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" %>           
${requestScope.a}
       
       

---

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] 

 

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 addObject.      * @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 addObject.      * @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 null, but the      * model Map may be null if there is no model data.      */      public ModelAndView(String viewName, Map
         
           model) {          this.view = viewName;          if (model != null) {              getModelMap().addAllAttributes(model);          }      }        /**      * Creates new ModelAndView given a View object and a model.      * 
          
           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
                * @param view View object to render      * @param model Map of model names (Strings) to model objects      * (Objects). Model entries may not be 
          null, but the      * model Map may be 
          null if there is no model data.      */      public ModelAndView(View view, Map
          
            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 
           null 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 
           null 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 
           ModelAndView 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. 
           true      * 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 
           null.      * Called by DispatcherServlet for evaluation of the model.      */      protected Map
           
             getModelInternal() {          return this.model;      }        /**      * Return the underlying 
            ModelMap instance (never 
            null).      */      public ModelMap getModelMap() {          if (this.model == null) {              this.model = new ModelMap();          }          return this.model;      }        /**      * Return the model map. Never returns 
            null.      * To be called by application code for modifying the model.      */      public Map
            
              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 
             null)      * @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 
             null)      * @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
             
               modelMap) {          getModelMap().addAllAttributes(modelMap);          return this;      }          /**      * Clear the state of this ModelAndView object.      * The object will be empty afterwards.      * 
              
Can be used to suppress rendering of a given ModelAndView object * in the postHandle 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. * 
              
Returns false if any additional state was added to the instance * after 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(); } }
             
            
           
          
         

 

[java] 

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" %>                         
${requestScope.a}
         
${requestScope.user.uname}
      

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