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SpringMVC中ModelAndView怎么用

小编给大家分享一下SpringMVC中ModelAndView怎么用,相信大部分人都还不怎么了解,因此分享这篇文章给大家参考一下,希望大家阅读完这篇文章后大有收获,下面让我们一起去了解一下吧!

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(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;//该属性用来存储处理后的结果数据  /**  * 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 addObject.  * @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 addObject.  * @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 null, but the  * model Map may be null if there is no model data.  */ public ModelAndView(String viewName, Map model) {   this.view = viewName;   if (model != null) {     getModelMap().addAllAttributes(model);   } }  /**  * Creates new ModelAndView given a View object and a model.  * 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  * @param view View object to render  * @param model Map of model names (Strings) to model objects  * (Objects). Model entries may not be null, but the  * model Map may be null if there is no model data.  */ public ModelAndView(View view, Map 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 null 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 null 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 ModelAndView 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. true  * 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 null.  * Called by DispatcherServlet for evaluation of the model.  */ protected Map getModelInternal() {   return this.model; }  /**  * Return the underlying ModelMap instance (never null).  */ public ModelMap getModelMap() {   if (this.model == null) {     this.model = new ModelMap();   }   return this.model; }  /**  * Return the model map. Never returns null.  * To be called by application code for modifying the model.  */ public Map 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 null)  * @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 null)  * @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 modelMap) {   getModelMap().addAllAttributes(modelMap);   return this; }   /**  * Clear the state of this ModelAndView object.  * The object will be empty afterwards.  *

Can be used to suppress rendering of a given ModelAndView object  * in the postHandle 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.  *

Returns false if any additional state was added to the instance  * after 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(); }

在源码中有7个构造函数,如何用?是一个重点。

构造ModelAndView对象当控制器处理完请求时,通常会将包含视图名称或视图对象以及一些模型属性的ModelAndView对象返回到DispatcherServlet。

因此,经常需要在控制器中构造ModelAndView对象。

ModelAndView类提供了几个重载的构造器和一些方便的方法,让你可以根据自己的喜好来构造ModelAndView对象。这些构造器和方法以类似的方式支持视图名称和视图对象。

通过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 , 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)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:

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。

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 model = new HashMap();     if(courtName != null){       model.put("courtName",courtName);       model.put("reservations",reservationService.query(courtName));     }     return new ModelAndView("reservationQuery",model);   } }

Spring也提供了ModelMap,这是java.util.Map实现,可以根据模型属性的具体类型自动生成模型属性的名称。

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);   } }

这里,我又想多说一句:ModelMap对象主要用于传递控制方法处理数据到结果页面,

也就是说我们把结果页面上需要的数据放到ModelMap对象中即可,他的作用类似于request对象的setAttribute方法的作用,用来在一个请求过程中传递处理的数据。

通过以下方法向页面传递参数:

addAttribute(String key,Object value); //modelMap的方法

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。

modelmap本身不能设置页面跳转的url地址别名或者物理跳转地址,那么我们可以通过控制器方法的返回值来设置跳转url地址别名或者物理跳转地址。 比如:

public String xxxxmethod(String someparam,ModelMap model) {    //省略方法处理逻辑若干    //将数据放置到ModelMap对象model中,第二个参数可以是任何java类型    model.addAttribute("key",someparam);    ......    //返回跳转地址    return "path:handleok"; }

在这些构造函数中最简单的ModelAndView是持有View的名称返回,之后View名称被view resolver,也就是实作org.springframework.web.servlet.View接口的实例解析,

例如: InternalResourceView或JstlView等等:ModelAndView(String viewName);

如果您要返回Model对象,则可以使用Map来收集这些Model对象,然后设定给ModelAndView,使用下面这个版本:

ModelAndView:ModelAndView(String viewName, Map model),Map对象中设定好key与value值,之后可以在视图中取出如果您只是要返回一个Model对象,则可以使用下面这个 ModelAndView版本:

ModelAndView(String viewName, String modelName, Object modelObject),其中modelName,您可以在视图中取出Model并显示

ModelAndView类别提供实作View接口的对象来作View的参数:

ModelAndView(View view)ModelAndView(View view, Map model)ModelAndView(View view, String modelName, Object modelObject)

2【方法使用】:给ModelAndView实例设置view的方法有两个:setViewName(String viewName) 和 setView(View view)。

前者是使用viewName,后者是使用预先构造好的View对象。其中前者比较常用。事实上View是一个接口,而不是一个可以构造的具体类,我们只能通过其他途径来获取View的实例。对于viewName,它既可以是jsp的名字,也可以是tiles定义的名字,取决于使用的ViewNameResolver如何理解这个view name。如何获取View的实例以后再研究。

而对应如何给ModelAndView实例设置model则比较复杂。有三个方法可以使用:

addObject(Object modelObject);addObject(String modelName, Object modelObject);addAllObjects(Map modelMap);

3【作用简介】:

ModelAndView对象有两个作用:

作用一: 设置转向地址,如下所示(这也是ModelAndView和ModelMap的主要区别)

ModelAndView view = new ModelAndView("path:ok");

作用二 :用于传递控制方法处理结果数据到结果页面,也就是说我们把需要在结果页面上需要的数据放到ModelAndView对象中即可,

他的作用类似于request对象的setAttribute方法的作用,用来在一个请求过程中传递处理的数据。通过以下方法向页面传递参数:

addObject(String key,Object value);

以上是“SpringMVC中ModelAndView怎么用”这篇文章的所有内容,感谢各位的阅读!相信大家都有了一定的了解,希望分享的内容对大家有所帮助,如果还想学习更多知识,欢迎关注创新互联行业资讯频道!


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