Spring MVC 3.0 深入及对注解的详细讲解

来源：互联网发布：2015年国内旅游数据编辑：程序博客网时间：2024/05/16 14:32

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"%>

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

<html>

<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：

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. */@Overridepublic 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 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：