大家好，又见面了，我是你们的朋友全栈君。
在了解这三者之前，需要知道一点：SpringMVC在调用方法前会创建一个隐含的数据模型，作为模型数据的存储容器， 成为”隐含模型”。 也就是说在每一次的前后台请求的时候会随带这一个背包，不管你用没有，这个背包确实是存在的，用来盛放我们请求交互传递的值；关于这一点，spring里面有一个注解： @ModelAttribute ：被该注解修饰的方法，会在每一次请求时优先执行，用于接收前台jsp页面传入的参数 例子：
代码语言：javascript复制@Controller
public class User1Controller{
private static final Log logger = LogFactory.getLog(User1Controller.class);
// @ModelAttribute修饰的方法会先于login调用，该方法用于接收前台jsp页面传入的参数
@ModelAttribute
public void userModel(String loginname,String password,
Model model){
logger.info("userModel");
// 创建User对象存储jsp页面传入的参数
User2 user = new User2();
user.setLoginname(loginname);
user.setPassword(password);
// 将User对象添加到Model当中
model.addAttribute("user", user);
}
@RequestMapping(value="/login1")
public String login(Model model){
logger.info("login");
// 从Model当中取出之前存入的名为user的对象
User2 user = (User2) model.asMap().get("user");
System.out.println(user);
// 设置user对象的username属性
user.setUsername("测试");
return "result1";
}在前端向后台请求时，spring会自动创建Model与ModelMap实例，我们只需拿来使用即可；
无论是Mode还是ModelMap底层都是使用BindingAwareModelMap，所以两者基本没什么区别； 我们可以简单看一下两者区别：
①Model
Model是一个接口，它的实现类为ExtendedModelMap，继承ModelMap类
public class ExtendedModelMap extends ModelMap implements Model
②ModelMap
ModelMap继承LinkedHashMap，spring框架自动创建实例并作为controller的入参，用户无需自己创建
代码语言：javascript复制public class ModelMap extends LinkedHashMap
而是对于ModelAndView顾名思义，ModelAndView指模型和视图的集合，既包含模型 又包含视图；ModelAndView的实例是开发者自己手动创建的，这也是和ModelMap主要不同点之一；ModelAndView其实就是两个作用，一个是指定返回页面，另一个是在返回页面的同时添加属性； 它的源码：
代码语言：javascript复制public class ModelAndView {
/** View instance or view name String */
private Object view //该属性用来存储返回的视图信息
/** Model Map */
private ModelMap model;//<span style="color: rgb(0, 130, 0); font-family: Consolas, 'Courier New', Courier, mono, serif; line-height: 18px;">该属性用来存储处理后的结果数据</span>
/** * 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();
} a 它有很多构造方法，对应会有很多使用方法： 例子： （1）当你只有一个模型属性要返回时，可以在构造器中指定该属性来构造ModelAndView对象：
代码语言：javascript复制package com.apress.springrecipes.court.web;
...
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.AbstractController;
public class WelcomeController extends AbstractController{
public ModelAndView handleRequestInternal(HttpServletRequest request,
HttpServletResponse response)throws Exception{
Date today = new Date();
return new ModelAndView("welcome","today",today);
}
} （2）如果有不止一个属性要返回，可以先将它们传递到一个Map中再来构造ModelAndView对象。
代码语言：javascript复制package com.apress.springrecipes.court.web;
...
import org.springframework.web.servlet.ModelAndView;
import org. springframework.web.servlet.mvc.AbstractController;
public class ReservationQueryController extends AbstractController{
...
public ModelAndView handleRequestInternal(HttpServletRequest request,
HttpServletResponse response)throws Exception{
...
Map<String,Object> model = new HashMap<String,Object>();
if(courtName != null){
model.put("courtName",courtName);
model.put("reservations",reservationService.query(courtName));
}
return new ModelAndView("reservationQuery",model);
}
} 当然也可以使用spring提供的Model或者ModelMap,这是java.util.Map实现；
代码语言：javascript复制package com.apress.springrecipes.court.web;
...
import org.springframework.ui.ModelMap;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.AbstractController;
public class ReservationQueryController extends AbstractController{
...
public ModelAndView handleRequestInternal(HttpServletRequest request,
HttpServletResponse response)throws Exception{
...
ModelMap model = new ModelMap();
if(courtName != null){
model.addAttribute("courtName",courtName);
model.addAttribute("reservations",reservationService.query(courtName));
}
return new ModelAndView("reservationQuery",model);
}
} 在页面上可以通过el变量方式${key}或者bboss的一系列数据展示标签获取并展示modelmap中的数据；上面主要讲了ModelAndView的使用，其实Model与ModelMap使用方法都是一致；
下面我通过一个下例子展示一下： 在spring项目中，在配置文件中配置好 视图解析器：
代码语言：javascript复制<!-- 视图解析器 -->
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<!-- 前缀 -->
<property name="prefix" value="/WEB-INF/jsp/"/>
<!-- 后缀 -->
<property name="suffix" value=".jsp"/>
</bean>在后台写：
代码语言：javascript复制 @RequestMapping("/test1")
public ModelAndView test1(ModelMap mm ,HttpServletRequest request){
ModelAndView mv = new ModelAndView("mytest");
mv.addObject("key1","123");
mm.addAttribute("key1","1234");
return mv;
}//前端为 123 123
@RequestMapping("/test2")
public String test2(ModelMap mm ,HttpServletRequest request){
mm.addAttribute("key1", "1234");
return "mytest";
}//前端为 1234 1234
@RequestMapping("/test3")
public String test3(Model mm ,HttpServletRequest request){
mm.addAttribute("key1", "12345");
return "mytest";
}
@RequestMapping("/test4")
public String test4(Model mm ,HttpServletRequest request){
mm.addAttribute("key1", "12345");
request.setAttribute("key1", "123456");
return "mytest";
}//前端为 12345 12345
@RequestMapping("/test5")
public String test5(Model mm ,ModelMap mmp,HttpServletRequest request){
request.setAttribute("key1", "123456");
mm.addAttribute("key1", "12345");
mmp.addAttribute("key1", "1234567");
return "mytest";
}//前端为 1234567 1234567对应前端：
代码语言：javascript复制<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<% String test = String.valueOf(request.getAttribute("key1")); %>
</head>
<body>
<%=test %>
${key1 }
</body>
</html>从上面测试可以看到Model，ModelMap与ModelAndView的具体使用；同时可以看出Model与ModelMap的值是能够替换的；并且两者赋值后作用比request.setAttribute()要大；这点在使用时需要注意；具体为啥，估计是最终解析时还是放在request上，最终还是替换了；我们知道
代码语言：javascript复制 request.setAttribute("key1", "123456");
request.setAttribute("key1", "123457");这样的代码最终得到的是“123457”；具体原因这里不看了，先学会熟练使用；
终上所述，我们知道了Model与ModelMap其实都是实现了hashMap,并且用法都是一样的；两者都是spring在请求时自动生成，拿来用便可；ModelAndView就是在两者的基础上可以指定返回页面； 赋值能力 ModelAndView > Model/ModelMap>request ;
附加： 转发与重定向： a 原始servlet：
代码语言：javascript复制转发时可以将页面的资源传给另一个页面，使用相对路径!
重定向只是单纯的进行页面跳转。使用绝对路径
if(username.equals("123")&&password.equals("123")){
request.getRequestDispatcher("/success.html").forward(request, response);
}else{
//在sendRedict中url前必须加上当前web程序的路径名.....
response.sendRedirect(request.getContextPath() "/fail.html");
} springMVC中，默认转发，重定向的话使用如下：
代码语言：javascript复制@RequestMapping("filesUpload")
public String filesUpload(@RequestParam("files") MultipartFile[] files) {
//判断file数组不能为空并且长度大于0
if(files!=null&&files.length>0){
//循环获取file数组中得文件
for(int i = 0;i<files.length;i ){
MultipartFile file = files[i];
//保存文件
saveFile(file);
}
}
// 重定向
return "redirect:/list.html";
}发布者：全栈程序员栈长，转载请注明出处：https://javaforall.cn/148457.html原文链接：https://javaforall.cn
