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Spring MVC 3.0 深入及对注解的详细讲解

2013-01-04 11:33 579 查看

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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