/*
* Copyright 2008-2010 biaoping.yin
*
* 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.frameworkset.web.servlet.view.json;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.codehaus.jackson.JsonEncoding;
import org.codehaus.jackson.JsonGenerator;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.SerializerFactory;
import org.frameworkset.spi.support.validate.BindingResult;
import org.frameworkset.util.Assert;
import org.frameworkset.util.CollectionUtils;
import org.frameworkset.web.servlet.view.AbstractView;
import org.frameworkset.web.servlet.view.View;
/**
* Bboss-MVC {@link View} that renders JSON content by serializing the model for the current request using <a
* href="http://jackson.codehaus.org/">Jackson'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. For cases where the contents of the map need to be filtered, users may specify a specific set of
* model attributes to encode via the {@link #setRenderedAttributes(Set) renderedAttributes} property.
*
* @author Jeremy Grelle
* @author Arjen Poutsma
* @see converter.json.MappingJacksonHttpMessageConverter
* @since 3.0
*/
public class MappingJacksonJsonView 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 Set<String> renderedAttributes;
private boolean disableCaching = true;
/**
* Construct a new {@code JacksonJsonView}, setting the content type to {@code application/json}.
*/
public MappingJacksonJsonView() {
setContentType(DEFAULT_CONTENT_TYPE);
}
/**
* 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 {@link 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;
}
/**
* Sets 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 "{@code {} &&}". 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;
}
/**
* Returns the attributes in the model that should be rendered by this view.
*/
public Set<String> getRenderedAttributes() {
return renderedAttributes;
}
/**
* Sets the attributes in the model that should be rendered by this view. When set, all other model attributes will be
* ignored.
*/
public void setRenderedAttributes(Set<String> renderedAttributes) {
this.renderedAttributes = renderedAttributes;
}
/**
* 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;
}
@Override
protected void prepareResponse(HttpServletRequest request, HttpServletResponse response) {
response.setContentType(getContentType());
response.setCharacterEncoding(encoding.getJavaName());
if (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 {
Object value = filterModel(model);
JsonGenerator generator =
objectMapper.getJsonFactory().createJsonGenerator(response.getOutputStream(), encoding);
if (prefixJson) {
generator.writeRaw("{} && ");
}
objectMapper.writeValue(generator, value);
}
/**
* Filters out undesired attributes from the given model. The return value can be either another {@link Map}, or a
* single value object.
*
* <p>Default implementation removes {@link BindingResult} instances and entries not included in the {@link
* #setRenderedAttributes(Set) 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.renderedAttributes) ? this.renderedAttributes : 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 result;
}
}