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/* * 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.view.json; import java.io.IOException; import java.util.Collections; import java.util.HashMap; import java.util.Map; import java.util.Set; import com.fasterxml.jackson.annotation.JsonView; import com.fasterxml.jackson.core.JsonGenerator; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.ser.FilterProvider; import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder; import org.springframework.lang.Nullable; import org.springframework.util.CollectionUtils; import org.springframework.validation.BindingResult; import org.springframework.web.servlet.View; /** * Spring MVC {@link View} that renders JSON content by serializing the model for the current request * using <a href="https://github.com/FasterXML/jackson">Jackson 2's</a> {@link ObjectMapper}. * * <p>By default, the entire contents of the model map (with the exception of framework-specific classes) * will be encoded as JSON. If the model contains only one key, you can have it extracted encoded as JSON * alone via {@link #setExtractValueFromSingleKeyModel}. * * <p>The default constructor uses the default configuration provided by {@link Jackson2ObjectMapperBuilder}. * * <p>Compatible with Jackson 2.6 and higher, as of Spring 4.3. * * @author Jeremy Grelle * @author Arjen Poutsma * @author Rossen Stoyanchev * @author Juergen Hoeller * @author Sebastien Deleuze * @since 3.1.2 */ public class MappingJackson2JsonView extends AbstractJackson2View { /** * Default content type: "application/json". * Overridable through {@link #setContentType}. */ public static final String DEFAULT_CONTENT_TYPE = "application/json"; @Nullable private String jsonPrefix; @Nullable private Set<String> modelKeys; private boolean extractValueFromSingleKeyModel = false; /** * Construct a new {@code MappingJackson2JsonView} using default configuration * provided by {@link Jackson2ObjectMapperBuilder} and setting the content type * to {@code application/json}. */ public MappingJackson2JsonView() { super(Jackson2ObjectMapperBuilder.json().build(), DEFAULT_CONTENT_TYPE); } /** * Construct a new {@code MappingJackson2JsonView} using the provided * {@link ObjectMapper} and setting the content type to {@code application/json}. * @since 4.2.1 */ public MappingJackson2JsonView(ObjectMapper objectMapper) { super(objectMapper, DEFAULT_CONTENT_TYPE); } /** * Specify a custom prefix to use for this view's JSON output. * Default is none. * @see #setPrefixJson */ public void setJsonPrefix(String jsonPrefix) { this.jsonPrefix = jsonPrefix; } /** * Indicates whether the JSON output by this view should be prefixed with <tt>")]}', "</tt>. * Default is {@code false}. * <p>Prefixing the JSON string in this manner is used to help prevent JSON Hijacking. * The prefix renders the string syntactically invalid as a script so that it cannot be hijacked. * This prefix should be stripped before parsing the string as JSON. * @see #setJsonPrefix */ public void setPrefixJson(boolean prefixJson) { this.jsonPrefix = (prefixJson ? ")]}', " : null); } /** * {@inheritDoc} */ @Override public void setModelKey(String modelKey) { this.modelKeys = Collections.singleton(modelKey); } /** * Set the attributes in the model that should be rendered by this view. * When set, all other model attributes will be ignored. */ public void setModelKeys(@Nullable Set<String> modelKeys) { this.modelKeys = modelKeys; } /** * Return the attributes in the model that should be rendered by this view. */ @Nullable public final Set<String> getModelKeys() { return this.modelKeys; } /** * Set whether to serialize models containing a single attribute as a map or * whether to extract the single value from the model and serialize it directly. * <p>The effect of setting this flag is similar to using * {@code MappingJackson2HttpMessageConverter} with an {@code @ResponseBody} * request-handling method. * <p>Default is {@code false}. */ public void setExtractValueFromSingleKeyModel(boolean extractValueFromSingleKeyModel) { this.extractValueFromSingleKeyModel = extractValueFromSingleKeyModel; } /** * Filter out undesired attributes from the given model. * The return value can be either another {@link Map} or a single value object. * <p>The default implementation removes {@link BindingResult} instances and entries * not included in the {@link #setModelKeys modelKeys} property. * @param model the model, as passed on to {@link #renderMergedOutputModel} * @return the value to be rendered */ @Override protected Object filterModel(Map<String, Object> model) { Map<String, Object> result = new HashMap<>(model.size()); Set<String> modelKeys = (!CollectionUtils.isEmpty(this.modelKeys) ? this.modelKeys : model.keySet()); model.forEach((clazz, value) -> { if (!(value instanceof BindingResult) && modelKeys.contains(clazz) && !clazz.equals(JsonView.class.getName()) && !clazz.equals(FilterProvider.class.getName())) { result.put(clazz, value); } }); return (this.extractValueFromSingleKeyModel && result.size() == 1 ? result.values().iterator().next() : result); } @Override protected void writePrefix(JsonGenerator generator, Object object) throws IOException { if (this.jsonPrefix != null) { generator.writeRaw(this.jsonPrefix); } } }