/*
* Copyright 2002-2012 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
*
* http://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.ByteArrayOutputStream;
import java.io.OutputStream;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.fasterxml.jackson.core.JsonEncoding;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.util.DefaultPrettyPrinter;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.validation.BindingResult;
import org.springframework.web.servlet.View;
import org.springframework.web.servlet.view.AbstractView;
/**
* Spring MVC {@link View} that renders JSON content by serializing the model for the current request
* using <a href="http://jackson.codehaus.org/">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}.
*
* @author Jeremy Grelle
* @author Arjen Poutsma
* @author Rossen Stoyanchev
* @since 3.1.2
* @see org.springframework.http.converter.json.MappingJackson2HttpMessageConverter
*/
public class MappingJackson2JsonView extends AbstractView {
/**
* Default content type. Overridable as bean property.
*/
public static final String DEFAULT_CONTENT_TYPE = "application/json";
private ObjectMapper objectMapper = new ObjectMapper();
private JsonEncoding encoding = JsonEncoding.UTF8;
private boolean prefixJson = false;
private Boolean prettyPrint;
private Set<String> modelKeys;
private boolean extractValueFromSingleKeyModel = false;
private boolean disableCaching = true;
private boolean updateContentLength = false;
/**
* Construct a new {@code JacksonJsonView}, setting the content type to {@code application/json}.
*/
public MappingJackson2JsonView() {
setContentType(DEFAULT_CONTENT_TYPE);
setExposePathVariables(false);
}
/**
* Sets the {@code ObjectMapper} for this view.
* If not set, a default {@link ObjectMapper#ObjectMapper() ObjectMapper} is used.
* <p>Setting a custom-configured {@code ObjectMapper} is one way to take further control
* of the JSON serialization process. For example, an extended {@code SerializerFactory}
* can be configured that provides custom serializers for specific types. The other option
* for refining the serialization process is to use Jackson's provided annotations on the
* types to be serialized, in which case a custom-configured ObjectMapper is unnecessary.
*/
public void setObjectMapper(ObjectMapper objectMapper) {
Assert.notNull(objectMapper, "'objectMapper' must not be null");
this.objectMapper = objectMapper;
configurePrettyPrint();
}
private void configurePrettyPrint() {
if (this.prettyPrint != null) {
this.objectMapper.configure(SerializationFeature.INDENT_OUTPUT, this.prettyPrint);
}
}
/**
* Set the {@code JsonEncoding} for this converter.
* By default, {@linkplain JsonEncoding#UTF8 UTF-8} is used.
*/
public void setEncoding(JsonEncoding encoding) {
Assert.notNull(encoding, "'encoding' must not be null");
this.encoding = encoding;
}
/**
* Indicates whether the JSON output by this view should be prefixed with <tt>"{} && "</tt>.
* Default is 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 does not affect the evaluation of JSON, but if JSON validation is performed
* on the string, the prefix would need to be ignored.
*/
public void setPrefixJson(boolean prefixJson) {
this.prefixJson = prefixJson;
}
/**
* Whether to use the {@link DefaultPrettyPrinter} when writing JSON.
* This is a shortcut for setting up an {@code ObjectMapper} as follows:
* <pre>
* ObjectMapper mapper = new ObjectMapper();
* mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
* converter.setObjectMapper(mapper);
* </pre>
* <p>The default value is {@code false}.
*/
public void setPrettyPrint(boolean prettyPrint) {
this.prettyPrint = prettyPrint;
configurePrettyPrint();
}
/**
* Set the attribute in the model that should be rendered by this view.
* When set, all other model attributes will be ignored.
*/
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(Set<String> modelKeys) {
this.modelKeys = modelKeys;
}
/**
* Return the attributes in the model that should be rendered by this view.
*/
public Set<String> getModelKeys() {
return this.modelKeys;
}
/**
* Set the attributes in the model that should be rendered by this view.
* When set, all other model attributes will be ignored.
* @deprecated use {@link #setModelKeys(Set)} instead
*/
@Deprecated
public void setRenderedAttributes(Set<String> renderedAttributes) {
this.modelKeys = renderedAttributes;
}
/**
* Return the attributes in the model that should be rendered by this view.
* @deprecated use {@link #getModelKeys()} instead
*/
@Deprecated
public Set<String> getRenderedAttributes() {
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 MappingJacksonHttpMessageConverter}
* with an {@code @ResponseBody} request-handling method.
* <p>Default is {@code false}.
*/
public void setExtractValueFromSingleKeyModel(boolean extractValueFromSingleKeyModel) {
this.extractValueFromSingleKeyModel = extractValueFromSingleKeyModel;
}
/**
* Disables caching of the generated JSON.
* <p>Default is {@code true}, which will prevent the client from caching the generated JSON.
*/
public void setDisableCaching(boolean disableCaching) {
this.disableCaching = disableCaching;
}
/**
* Whether to update the 'Content-Length' header of the response. When set to
* {@code true}, the response is buffered in order to determine the content
* length and set the 'Content-Length' header of the response.
* <p>The default setting is {@code false}.
*/
public void setUpdateContentLength(boolean updateContentLength) {
this.updateContentLength = updateContentLength;
}
@Override
protected void prepareResponse(HttpServletRequest request, HttpServletResponse response) {
setResponseContentType(request, response);
response.setCharacterEncoding(this.encoding.getJavaName());
if (this.disableCaching) {
response.addHeader("Pragma", "no-cache");
response.addHeader("Cache-Control", "no-cache, no-store, max-age=0");
response.addDateHeader("Expires", 1L);
}
}
@Override
protected void renderMergedOutputModel(Map<String, Object> model, HttpServletRequest request,
HttpServletResponse response) throws Exception {
OutputStream stream = this.updateContentLength ? createTemporaryOutputStream() : response.getOutputStream();
Object value = filterModel(model);
JsonGenerator generator = this.objectMapper.getJsonFactory().createJsonGenerator(stream, this.encoding);
// A workaround for JsonGenerators not applying serialization features
// https://github.com/FasterXML/jackson-databind/issues/12
if (this.objectMapper.isEnabled(SerializationFeature.INDENT_OUTPUT)) {
generator.useDefaultPrettyPrinter();
}
if (this.prefixJson) {
generator.writeRaw("{} && ");
}
this.objectMapper.writeValue(generator, value);
if (this.updateContentLength) {
writeToResponse(response, (ByteArrayOutputStream) stream);
}
}
/**
* Filters 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 #setRenderedAttributes renderedAttributes} property.
* @param model the model, as passed on to {@link #renderMergedOutputModel}
* @return the object to be rendered
*/
protected Object filterModel(Map<String, Object> model) {
Map<String, Object> result = new HashMap<String, Object>(model.size());
Set<String> renderedAttributes = (!CollectionUtils.isEmpty(this.modelKeys) ? this.modelKeys : model.keySet());
for (Map.Entry<String, Object> entry : model.entrySet()) {
if (!(entry.getValue() instanceof BindingResult) && renderedAttributes.contains(entry.getKey())) {
result.put(entry.getKey(), entry.getValue());
}
}
return (this.extractValueFromSingleKeyModel && result.size() == 1 ? result.values().iterator().next() : result);
}
}