（一）使用ModelAndView类用来存储处理完后的结果数据，以及显示该数据的视图。从名字上看ModelAndView中的Model代表模型，View代表视图，这个名字就很好地解释了该类的作用。业务处理器调用模型层处理完用户请求后，把结果数据存储在该类的model属性中，把要返回的视图信息存储在该类的view属性中，然后让该ModelAndView返回该Spring MVC框架。框架通过调用配置文件中定义的视图解析器，对该对象进行解析，最后把结果数据显示在指定的页面上。

具体作用：

1、返回指定页面

ModelAndView构造方法可以指定返回的页面名称，

也可以通过setViewName()方法跳转到指定的页面 ,

2、返回所需数值

使用addObject()设置需要返回的值，addObject()有几个不同参数的方法，可以默认和指定返回对象的名字。

1、【其源码】：熟悉一个类的用法，最好从其源码入手。

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 >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(); 
}