ModelAndView怎么在SpringMVC中使用?針對這個問題,這篇文章詳細介紹了相對應的分析和解答,希望可以幫助更多想解決這個問題的小伙伴找到更簡單易行的方法。
公司主營業(yè)務:網站建設、網站制作、移動網站開發(fā)等業(yè)務。幫助企業(yè)客戶真正實現(xiàn)互聯(lián)網宣傳,提高企業(yè)的競爭能力。創(chuàng)新互聯(lián)公司是一支青春激揚、勤奮敬業(yè)、活力青春激揚、勤奮敬業(yè)、活力澎湃、和諧高效的團隊。公司秉承以“開放、自由、嚴謹、自律”為核心的企業(yè)文化,感謝他們對我們的高要求,感謝他們從不同領域給我們帶來的挑戰(zhàn),讓我們激情的團隊有機會用頭腦與智慧不斷的給客戶帶來驚喜。創(chuàng)新互聯(lián)公司推出武穴免費做網站回饋大家。
(一)使用ModelAndView類用來存儲處理完后的結果數(shù)據,以及顯示該數(shù)據的視圖。從名字上看ModelAndView中的Model代表模型,View代表視圖,這個名字就很好地解釋了該類的作用。業(yè)務處理器調用模型層處理完用戶請求后,把結果數(shù)據存儲在該類的model屬性中,把要返回的視圖信息存儲在該類的view屬性中,然后讓該ModelAndView返回該Spring MVC框架??蚣芡ㄟ^調用配置文件中定義的視圖解析器,對該對象進行解析,最后把結果數(shù)據顯示在指定的頁面上。
具體作用:
1、返回指定頁面
ModelAndView構造方法可以指定返回的頁面名稱,
也可以通過setViewName()方法跳轉到指定的頁面 ,
2、返回所需數(shù)值
使用addObject()設置需要返回的值,addObject()有幾個不同參數(shù)的方法,可以默認和指定返回對象的名字。
1、【其源碼】:熟悉一個類的用法,最好從其源碼入手。
public class ModelAndView { /** View instance or view name String */ private Object view //該屬性用來存儲返回的視圖信息 /** Model Map */ private ModelMap model;//該屬性用來存儲處理后的結果數(shù)據 /** * 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 withaddObject
. * @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 withaddObject
. * @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 benull
, but the * model Map may benull
if there is no model data. */ public ModelAndView(String viewName, Mapmodel) { 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 benull
, but the * model Map may benull
if there is no model data. */ public ModelAndView(View view, Mapmodel) { 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, ornull
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 thisModelAndView
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 returnnull
. * Called by DispatcherServlet for evaluation of the model. */ protected MapgetModelInternal() { return this.model; } /** * Return the underlying ModelMap
instance (nevernull
). */ public ModelMap getModelMap() { if (this.model == null) { this.model = new ModelMap(); } return this.model; } /** * Return the model map. Never returnsnull
. * To be called by application code for modifying the model. */ public MapgetModel() { 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 (nevernull
) * @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(MapmodelMap) { 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(); }
在源碼中有7個構造函數(shù),如何用?是一個重點。
構造ModelAndView對象當控制器處理完請求時,通常會將包含視圖名稱或視圖對象以及一些模型屬性的ModelAndView對象返回到DispatcherServlet。
因此,經常需要在控制器中構造ModelAndView對象。
ModelAndView類提供了幾個重載的構造器和一些方便的方法,讓你可以根據自己的喜好來構造ModelAndView對象。這些構造器和方法以類似的方式支持視圖名稱和視圖對象。
通過ModelAndView構造方法可以指定返回的頁面名稱,也可以通過setViewName()方法跳轉到指定的頁面 , 使用addObject()設置需要返回的值,addObject()有幾個不同參數(shù)的方法,可以默認和指定返回對象的名字。
(1)當你只有一個模型屬性要返回時,可以在構造器中指定該屬性來構造ModelAndView對象:
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)如果有不止一個屬性要返回,可以先將它們傳遞到一個Map中再來構造ModelAndView對象。
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{ ... Mapmodel = 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,這是java.util.Map實現(xiàn),可以根據模型屬性的具體類型自動生成模型屬性的名稱。
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); } }
這里,我又想多說一句:ModelMap對象主要用于傳遞控制方法處理數(shù)據到結果頁面,
也就是說我們把結果頁面上需要的數(shù)據放到ModelMap對象中即可,他的作用類似于request對象的setAttribute方法的作用,用來在一個請求過程中傳遞處理的數(shù)據。
通過以下方法向頁面?zhèn)鬟f參數(shù):
addAttribute(String key,Object value); //modelMap的方法
在頁面上可以通過el變量方式${key}或者bboss的一系列數(shù)據展示標簽獲取并展示modelmap中的數(shù)據。
modelmap本身不能設置頁面跳轉的url地址別名或者物理跳轉地址,那么我們可以通過控制器方法的返回值來設置跳轉url地址別名或者物理跳轉地址。 比如:
public String xxxxmethod(String someparam,ModelMap model) { //省略方法處理邏輯若干 //將數(shù)據放置到ModelMap對象model中,第二個參數(shù)可以是任何java類型 model.addAttribute("key",someparam); ...... //返回跳轉地址 return "path:handleok"; }
在這些構造函數(shù)中最簡單的ModelAndView是持有View的名稱返回,之后View名稱被view resolver,也就是實作org.springframework.web.servlet.View接口的實例解析,
例如: InternalResourceView或JstlView等等:ModelAndView(String viewName);
如果您要返回Model對象,則可以使用Map來收集這些Model對象,然后設定給ModelAndView,使用下面這個版本:
ModelAndView:ModelAndView(String viewName, Map model),Map對象中設定好key與value值,之后可以在視圖中取出
如果您只是要返回一個Model對象,則可以使用下面這個 ModelAndView版本:
ModelAndView(String viewName, String modelName, Object modelObject),其中modelName,您可以在視圖中取出Model并顯示
ModelAndView類別提供實作View接口的對象來作View的參數(shù):
ModelAndView(View view) ModelAndView(View view, Map model) ModelAndView(View view, String modelName, Object modelObject)
2【方法使用】:給ModelAndView實例設置view的方法有兩個:setViewName(String viewName) 和 setView(View view)。
前者是使用viewName,后者是使用預先構造好的View對象。其中前者比較常用。事實上View是一個接口,而不是一個可以構造的具體類,我們只能通過其他途徑來獲取View的實例。對于viewName,它既可以是jsp的名字,也可以是tiles定義的名字,取決于使用的ViewNameResolver如何理解這個view name。如何獲取View的實例以后再研究。
而對應如何給ModelAndView實例設置model則比較復雜。有三個方法可以使用:
addObject(Object modelObject); addObject(String modelName, Object modelObject); addAllObjects(Map modelMap);
3【作用簡介】:
ModelAndView對象有兩個作用:
作用一: 設置轉向地址,如下所示(這也是ModelAndView和ModelMap的主要區(qū)別)
ModelAndView view = new ModelAndView("path:ok");
作用二 :用于傳遞控制方法處理結果數(shù)據到結果頁面,也就是說我們把需要在結果頁面上需要的數(shù)據放到ModelAndView對象中即可,
他的作用類似于request對象的setAttribute方法的作用,用來在一個請求過程中傳遞處理的數(shù)據。通過以下方法向頁面?zhèn)鬟f參數(shù):
addObject(String key,Object value);
關于ModelAndView怎么在SpringMVC中使用問題的解答就分享到這里了,希望以上內容可以對大家有一定的幫助,如果你還有很多疑惑沒有解開,可以關注創(chuàng)新互聯(lián)行業(yè)資訊頻道了解更多相關知識。