Java tutorial
/* * Copyright (c) 2012 Lei Hu. All rights reserved. * Lei Hu PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package org.ccntgrid.extend.spring.http.converter.json; import com.fasterxml.jackson.core.JsonEncoding; import com.fasterxml.jackson.core.JsonGenerator; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.type.TypeFactory; import com.fasterxml.jackson.databind.JavaType; import org.springframework.http.HttpInputMessage; import org.springframework.http.HttpOutputMessage; import org.springframework.http.MediaType; import org.springframework.http.converter.AbstractHttpMessageConverter; import org.springframework.http.converter.HttpMessageNotReadableException; import org.springframework.http.converter.HttpMessageNotWritableException; import org.springframework.util.Assert; import java.io.IOException; import java.nio.charset.Charset; /** * Modify Spring Jackson converter to support jackson 2.0 * * @author L <qiyuan4f@gmail.com> * @version 1.0 * @date 2012-06 * @see org.springframework.http.converter.json.MappingJacksonHttpMessageConverter */ public class MappingJackson2HttpMessageConverter extends AbstractHttpMessageConverter<Object> { public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8"); private ObjectMapper objectMapper = new ObjectMapper(); private boolean prefixJson = false; /** * Construct a new {@code BindingJacksonHttpMessageConverter}. */ public MappingJackson2HttpMessageConverter() { super(new MediaType("application", "json", DEFAULT_CHARSET)); } /** * Set 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 org.codehaus.jackson.map.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; } /** * Return the underlying {@code ObjectMapper} for this view. */ public ObjectMapper getObjectMapper() { return this.objectMapper; } /** * Indicate whether the JSON output by this view should be prefixed with "{} &&". 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; } @Override public boolean canRead(Class<?> clazz, MediaType mediaType) { JavaType javaType = getJavaType(clazz); return (this.objectMapper.canDeserialize(javaType) && canRead(mediaType)); } @Override public boolean canWrite(Class<?> clazz, MediaType mediaType) { return (this.objectMapper.canSerialize(clazz) && canWrite(mediaType)); } @Override protected boolean supports(Class<?> clazz) { // should not be called, since we override canRead/Write instead throw new UnsupportedOperationException(); } @Override protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException { JavaType javaType = getJavaType(clazz); try { return this.objectMapper.readValue(inputMessage.getBody(), javaType); } catch (JsonProcessingException ex) { throw new HttpMessageNotReadableException("Could not read JSON: " + ex.getMessage(), ex); } } @Override protected void writeInternal(Object object, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException { JsonEncoding encoding = getJsonEncoding(outputMessage.getHeaders().getContentType()); JsonGenerator jsonGenerator = this.objectMapper.getJsonFactory() .createJsonGenerator(outputMessage.getBody(), encoding); try { if (this.prefixJson) { jsonGenerator.writeRaw("{} && "); } this.objectMapper.writeValue(jsonGenerator, object); } catch (JsonProcessingException ex) { throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex); } } /** * Return the Jackson {@link JavaType} for the specified class. * <p>The default implementation returns {@link org.codehaus.jackson.map.type.TypeFactory#type(java.lang.reflect.Type)}, * but this can be overridden in subclasses, to allow for custom generic collection handling. * For instance: * <pre class="code"> * protected JavaType getJavaType(Class<?> clazz) { * if (List.class.isAssignableFrom(clazz)) { * return TypeFactory.collectionType(ArrayList.class, MyBean.class); * } else { * return super.getJavaType(clazz); * } * } * </pre> * * @param clazz the class to return the java type for * * @return the java type */ protected JavaType getJavaType(Class<?> clazz) { return TypeFactory.defaultInstance().constructType(clazz); } /** * Determine the JSON encoding to use for the given content type. * * @param contentType the media type as requested by the caller * * @return the JSON encoding to use (never <code>null</code>) */ protected JsonEncoding getJsonEncoding(MediaType contentType) { if (contentType != null && contentType.getCharSet() != null) { Charset charset = contentType.getCharSet(); for (JsonEncoding encoding : JsonEncoding.values()) { if (charset.name().equals(encoding.getJavaName())) { return encoding; } } } return JsonEncoding.UTF8; } }