org.springframework.web.method.annotation.ModelFactory(Source code)

001/*
002 * Copyright 2002-2019 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.web.method.annotation;
018
019import java.lang.reflect.Method;
020import java.util.ArrayList;
021import java.util.Collection;
022import java.util.HashSet;
023import java.util.List;
024import java.util.Map;
025import java.util.Set;
026
027import org.springframework.beans.BeanUtils;
028import org.springframework.core.Conventions;
029import org.springframework.core.GenericTypeResolver;
030import org.springframework.core.MethodParameter;
031import org.springframework.lang.Nullable;
032import org.springframework.ui.Model;
033import org.springframework.ui.ModelMap;
034import org.springframework.util.Assert;
035import org.springframework.util.StringUtils;
036import org.springframework.validation.BindingResult;
037import org.springframework.web.HttpSessionRequiredException;
038import org.springframework.web.bind.WebDataBinder;
039import org.springframework.web.bind.annotation.ModelAttribute;
040import org.springframework.web.bind.support.WebDataBinderFactory;
041import org.springframework.web.context.request.NativeWebRequest;
042import org.springframework.web.method.HandlerMethod;
043import org.springframework.web.method.support.InvocableHandlerMethod;
044import org.springframework.web.method.support.ModelAndViewContainer;
045
046/**
047 * Assist with initialization of the {@link Model} before controller method
048 * invocation and with updates to it after the invocation.
049 *
050 * <p>On initialization the model is populated with attributes temporarily stored
051 * in the session and through the invocation of {@code @ModelAttribute} methods.
052 *
053 * <p>On update model attributes are synchronized with the session and also
054 * {@link BindingResult} attributes are added if missing.
055 *
056 * @author Rossen Stoyanchev
057 * @since 3.1
058 */
059public final class ModelFactory {
060
061        private final List<ModelMethod> modelMethods = new ArrayList<>();
062
063        private final WebDataBinderFactory dataBinderFactory;
064
065        private final SessionAttributesHandler sessionAttributesHandler;
066
067
068        /**
069         * Create a new instance with the given {@code @ModelAttribute} methods.
070         * @param handlerMethods the {@code @ModelAttribute} methods to invoke
071         * @param binderFactory for preparation of {@link BindingResult} attributes
072         * @param attributeHandler for access to session attributes
073         */
074        public ModelFactory(@Nullable List<InvocableHandlerMethod> handlerMethods,
075                        WebDataBinderFactory binderFactory, SessionAttributesHandler attributeHandler) {
076
077                if (handlerMethods != null) {
078                        for (InvocableHandlerMethod handlerMethod : handlerMethods) {
079                                this.modelMethods.add(new ModelMethod(handlerMethod));
080                        }
081                }
082                this.dataBinderFactory = binderFactory;
083                this.sessionAttributesHandler = attributeHandler;
084        }
085
086
087        /**
088         * Populate the model in the following order:
089         * <ol>
090         * <li>Retrieve "known" session attributes listed as {@code @SessionAttributes}.
091         * <li>Invoke {@code @ModelAttribute} methods
092         * <li>Find {@code @ModelAttribute} method arguments also listed as
093         * {@code @SessionAttributes} and ensure they're present in the model raising
094         * an exception if necessary.
095         * </ol>
096         * @param request the current request
097         * @param container a container with the model to be initialized
098         * @param handlerMethod the method for which the model is initialized
099         * @throws Exception may arise from {@code @ModelAttribute} methods
100         */
101        public void initModel(NativeWebRequest request, ModelAndViewContainer container, HandlerMethod handlerMethod)
102                        throws Exception {
103
104                Map<String, ?> sessionAttributes = this.sessionAttributesHandler.retrieveAttributes(request);
105                container.mergeAttributes(sessionAttributes);
106                invokeModelAttributeMethods(request, container);
107
108                for (String name : findSessionAttributeArguments(handlerMethod)) {
109                        if (!container.containsAttribute(name)) {
110                                Object value = this.sessionAttributesHandler.retrieveAttribute(request, name);
111                                if (value == null) {
112                                        throw new HttpSessionRequiredException("Expected session attribute '" + name + "'", name);
113                                }
114                                container.addAttribute(name, value);
115                        }
116                }
117        }
118
119        /**
120         * Invoke model attribute methods to populate the model.
121         * Attributes are added only if not already present in the model.
122         */
123        private void invokeModelAttributeMethods(NativeWebRequest request, ModelAndViewContainer container)
124                        throws Exception {
125
126                while (!this.modelMethods.isEmpty()) {
127                        InvocableHandlerMethod modelMethod = getNextModelMethod(container).getHandlerMethod();
128                        ModelAttribute ann = modelMethod.getMethodAnnotation(ModelAttribute.class);
129                        Assert.state(ann != null, "No ModelAttribute annotation");
130                        if (container.containsAttribute(ann.name())) {
131                                if (!ann.binding()) {
132                                        container.setBindingDisabled(ann.name());
133                                }
134                                continue;
135                        }
136
137                        Object returnValue = modelMethod.invokeForRequest(request, container);
138                        if (!modelMethod.isVoid()){
139                                String returnValueName = getNameForReturnValue(returnValue, modelMethod.getReturnType());
140                                if (!ann.binding()) {
141                                        container.setBindingDisabled(returnValueName);
142                                }
143                                if (!container.containsAttribute(returnValueName)) {
144                                        container.addAttribute(returnValueName, returnValue);
145                                }
146                        }
147                }
148        }
149
150        private ModelMethod getNextModelMethod(ModelAndViewContainer container) {
151                for (ModelMethod modelMethod : this.modelMethods) {
152                        if (modelMethod.checkDependencies(container)) {
153                                this.modelMethods.remove(modelMethod);
154                                return modelMethod;
155                        }
156                }
157                ModelMethod modelMethod = this.modelMethods.get(0);
158                this.modelMethods.remove(modelMethod);
159                return modelMethod;
160        }
161
162        /**
163         * Find {@code @ModelAttribute} arguments also listed as {@code @SessionAttributes}.
164         */
165        private List<String> findSessionAttributeArguments(HandlerMethod handlerMethod) {
166                List<String> result = new ArrayList<>();
167                for (MethodParameter parameter : handlerMethod.getMethodParameters()) {
168                        if (parameter.hasParameterAnnotation(ModelAttribute.class)) {
169                                String name = getNameForParameter(parameter);
170                                Class<?> paramType = parameter.getParameterType();
171                                if (this.sessionAttributesHandler.isHandlerSessionAttribute(name, paramType)) {
172                                        result.add(name);
173                                }
174                        }
175                }
176                return result;
177        }
178
179        /**
180         * Promote model attributes listed as {@code @SessionAttributes} to the session.
181         * Add {@link BindingResult} attributes where necessary.
182         * @param request the current request
183         * @param container contains the model to update
184         * @throws Exception if creating BindingResult attributes fails
185         */
186        public void updateModel(NativeWebRequest request, ModelAndViewContainer container) throws Exception {
187                ModelMap defaultModel = container.getDefaultModel();
188                if (container.getSessionStatus().isComplete()){
189                        this.sessionAttributesHandler.cleanupAttributes(request);
190                }
191                else {
192                        this.sessionAttributesHandler.storeAttributes(request, defaultModel);
193                }
194                if (!container.isRequestHandled() && container.getModel() == defaultModel) {
195                        updateBindingResult(request, defaultModel);
196                }
197        }
198
199        /**
200         * Add {@link BindingResult} attributes to the model for attributes that require it.
201         */
202        private void updateBindingResult(NativeWebRequest request, ModelMap model) throws Exception {
203                List<String> keyNames = new ArrayList<>(model.keySet());
204                for (String name : keyNames) {
205                        Object value = model.get(name);
206                        if (value != null && isBindingCandidate(name, value)) {
207                                String bindingResultKey = BindingResult.MODEL_KEY_PREFIX + name;
208                                if (!model.containsAttribute(bindingResultKey)) {
209                                        WebDataBinder dataBinder = this.dataBinderFactory.createBinder(request, value, name);
210                                        model.put(bindingResultKey, dataBinder.getBindingResult());
211                                }
212                        }
213                }
214        }
215
216        /**
217         * Whether the given attribute requires a {@link BindingResult} in the model.
218         */
219        private boolean isBindingCandidate(String attributeName, Object value) {
220                if (attributeName.startsWith(BindingResult.MODEL_KEY_PREFIX)) {
221                        return false;
222                }
223
224                if (this.sessionAttributesHandler.isHandlerSessionAttribute(attributeName, value.getClass())) {
225                        return true;
226                }
227
228                return (!value.getClass().isArray() && !(value instanceof Collection) &&
229                                !(value instanceof Map) && !BeanUtils.isSimpleValueType(value.getClass()));
230        }
231
232
233        /**
234         * Derive the model attribute name for the given method parameter based on
235         * a {@code @ModelAttribute} parameter annotation (if present) or falling
236         * back on parameter type based conventions.
237         * @param parameter a descriptor for the method parameter
238         * @return the derived name
239         * @see Conventions#getVariableNameForParameter(MethodParameter)
240         */
241        public static String getNameForParameter(MethodParameter parameter) {
242                ModelAttribute ann = parameter.getParameterAnnotation(ModelAttribute.class);
243                String name = (ann != null ? ann.value() : null);
244                return (StringUtils.hasText(name) ? name : Conventions.getVariableNameForParameter(parameter));
245        }
246
247        /**
248         * Derive the model attribute name for the given return value. Results will be
249         * based on:
250         * <ol>
251         * <li>the method {@code ModelAttribute} annotation value
252         * <li>the declared return type if it is more specific than {@code Object}
253         * <li>the actual return value type
254         * </ol>
255         * @param returnValue the value returned from a method invocation
256         * @param returnType a descriptor for the return type of the method
257         * @return the derived name (never {@code null} or empty String)
258         */
259        public static String getNameForReturnValue(@Nullable Object returnValue, MethodParameter returnType) {
260                ModelAttribute ann = returnType.getMethodAnnotation(ModelAttribute.class);
261                if (ann != null && StringUtils.hasText(ann.value())) {
262                        return ann.value();
263                }
264                else {
265                        Method method = returnType.getMethod();
266                        Assert.state(method != null, "No handler method");
267                        Class<?> containingClass = returnType.getContainingClass();
268                        Class<?> resolvedType = GenericTypeResolver.resolveReturnType(method, containingClass);
269                        return Conventions.getVariableNameForReturnType(method, resolvedType, returnValue);
270                }
271        }
272
273
274        private static class ModelMethod {
275
276                private final InvocableHandlerMethod handlerMethod;
277
278                private final Set<String> dependencies = new HashSet<>();
279
280                public ModelMethod(InvocableHandlerMethod handlerMethod) {
281                        this.handlerMethod = handlerMethod;
282                        for (MethodParameter parameter : handlerMethod.getMethodParameters()) {
283                                if (parameter.hasParameterAnnotation(ModelAttribute.class)) {
284                                        this.dependencies.add(getNameForParameter(parameter));
285                                }
286                        }
287                }
288
289                public InvocableHandlerMethod getHandlerMethod() {
290                        return this.handlerMethod;
291                }
292
293                public boolean checkDependencies(ModelAndViewContainer mavContainer) {
294                        for (String name : this.dependencies) {
295                                if (!mavContainer.containsAttribute(name)) {
296                                        return false;
297                                }
298                        }
299                        return true;
300                }
301
302                @Override
303                public String toString() {
304                        return this.handlerMethod.getMethod().toGenericString();
305                }
306        }
307
308}