Java tutorial
/* * Copyright 2002-2018 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * https://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.springframework.web.servlet; import java.util.Map; import org.springframework.http.HttpStatus; import org.springframework.lang.Nullable; import org.springframework.ui.ModelMap; import org.springframework.util.CollectionUtils; /** * Holder for both Model and View in the web MVC framework. * Note that these are entirely distinct. This class merely holds * both to make it possible for a controller to return both model * and view in a single return value. * * <p>Represents a model and view returned by a handler, to be resolved * by a DispatcherServlet. The view can take the form of a String * view name which will need to be resolved by a ViewResolver object; * alternatively a View object can be specified directly. The model * is a Map, allowing the use of multiple objects keyed by name. * * @author Rod Johnson * @author Juergen Hoeller * @author Rob Harrop * @author Rossen Stoyanchev * @see DispatcherServlet * @see ViewResolver * @see HandlerAdapter#handle * @see org.springframework.web.servlet.mvc.Controller#handleRequest */ public class ModelAndView { /** View instance or view name String. */ @Nullable private Object view; /** Model Map. */ @Nullable private ModelMap model; /** Optional HTTP status for the response. */ @Nullable private HttpStatus status; /** 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}. * @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}. * @param view the View object to render * @see #addObject */ public ModelAndView(View view) { this.view = view; } /** * Create a 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 a Map of model names (Strings) to model objects * (Objects). Model entries may not be {@code null}, but the * model Map may be {@code null} if there is no model data. */ public ModelAndView(String viewName, @Nullable Map<String, ?> model) { this.view = viewName; if (model != null) { getModelMap().addAllAttributes(model); } } /** * Create a new ModelAndView given a View object and a model. * <em>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</em> * @param view the View object to render * @param model a Map of model names (Strings) to model objects * (Objects). Model entries may not be {@code null}, but the * model Map may be {@code null} if there is no model data. */ public ModelAndView(View view, @Nullable Map<String, ?> model) { this.view = view; if (model != null) { getModelMap().addAllAttributes(model); } } /** * Create a new ModelAndView given a view name and HTTP status. * @param viewName name of the View to render, to be resolved * by the DispatcherServlet's ViewResolver * @param status an HTTP status code to use for the response * (to be set just prior to View rendering) * @since 4.3.8 */ public ModelAndView(String viewName, HttpStatus status) { this.view = viewName; this.status = status; } /** * Create a new ModelAndView given a view name, model, and HTTP status. * @param viewName name of the View to render, to be resolved * by the DispatcherServlet's ViewResolver * @param model a Map of model names (Strings) to model objects * (Objects). Model entries may not be {@code null}, but the * model Map may be {@code null} if there is no model data. * @param status an HTTP status code to use for the response * (to be set just prior to View rendering) * @since 4.3 */ public ModelAndView(@Nullable String viewName, @Nullable Map<String, ?> model, @Nullable HttpStatus status) { this.view = viewName; if (model != null) { getModelMap().addAllAttributes(model); } this.status = status; } /** * 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 the 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(@Nullable String viewName) { this.view = viewName; } /** * Return the view name to be resolved by the DispatcherServlet * via a ViewResolver, or {@code null} if we are using a View object. */ @Nullable 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(@Nullable View view) { this.view = view; } /** * Return the View object, or {@code null} if we are using a view name * to be resolved by the DispatcherServlet via a ViewResolver. */ @Nullable public View getView() { return (this.view instanceof View ? (View) this.view : null); } /** * Indicate whether or not this {@code 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. {@code 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 {@code null}. * Called by DispatcherServlet for evaluation of the model. */ @Nullable protected Map<String, Object> getModelInternal() { return this.model; } /** * Return the underlying {@code ModelMap} instance (never {@code null}). */ public ModelMap getModelMap() { if (this.model == null) { this.model = new ModelMap(); } return this.model; } /** * Return the model map. Never returns {@code null}. * To be called by application code for modifying the model. */ public Map<String, Object> getModel() { return getModelMap(); } /** * Set the HTTP status to use for the response. * <p>The response status is set just prior to View rendering. * @since 4.3 */ public void setStatus(@Nullable HttpStatus status) { this.status = status; } /** * Return the configured HTTP status for the response, if any. * @since 4.3 */ @Nullable public HttpStatus getStatus() { return this.status; } /** * Add an attribute to the model. * @param attributeName name of the object to add to the model (never {@code null}) * @param attributeValue object to add to the model (can be {@code null}) * @see ModelMap#addAttribute(String, Object) * @see #getModelMap() */ public ModelAndView addObject(String attributeName, @Nullable 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}) * @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(@Nullable 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} 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} 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() { return "ModelAndView [view=" + formatView() + "; model=" + this.model + "]"; } private String formatView() { return isReference() ? "\"" + this.view + "\"" : "[" + this.view + "]"; } }