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 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 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:
- 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 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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