spring mvc 3.0 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：
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(value = "user") public class UserController extends MultiActionController { @RequestMapping(value = "/reg") public ModelAndView reg(@RequestParam("uname") 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; } }
jsp代码：
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> <%@ 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>