SpringMVC3.0深入及对注解的详细讲解

核心原理

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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:

 

 

        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

     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"%>

 

 

       

${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] view plaincopy

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] 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")  

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  

     

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