package com.stormpath.blog.spring.http.converter.json;
import org.codehaus.jackson.JsonEncoding;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.JsonGenerator;
import org.codehaus.jackson.JsonParseException;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.type.TypeFactory;
import org.codehaus.jackson.type.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;
/**
* Replaces Spring's {@link org.springframework.http.converter.json.MappingJacksonHttpMessageConverter}, which is
* difficult to configure for pretty-printing. This implementation enables pretty-printing easily via a setter/getter.
* <p/>
* See <a href="http://stackoverflow.com/questions/6541757/when-using-spring-mvc-for-rest-how-do-you-enable-jackson-to-pretty-print-render">
* When using Spring MVC for REST, how do you enable Jackson to pretty-print rendered JSON?</a> and the latest
* <a href="https://gist.github.com/2423129">Spring Framework incarnation supporting pretty printing</a>
* (not yet released at the time of writing).
*
* @author Les Hazlewood
*/
public class DefaultJacksonHttpMessageConverter extends AbstractHttpMessageConverter<Object> {
public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");
private ObjectMapper objectMapper = new ObjectMapper();
private boolean prefixJson = false;
private boolean prettyPrint = false;
/**
* Construct a new {@code DefaultJacksonHttpMessageConverter}.
*/
public DefaultJacksonHttpMessageConverter() {
super(new MediaType("application", "json", DEFAULT_CHARSET));
}
@Override
public boolean canRead(Class<?> clazz, MediaType mediaType) {
JavaType javaType = getJavaType(clazz);
return objectMapper.canDeserialize(javaType) && canRead(mediaType);
}
@Override
public boolean canWrite(Class<?> clazz, MediaType mediaType) {
return objectMapper.canSerialize(clazz) && canWrite(mediaType);
}
/**
* Returns the Jackson {@link JavaType} for the specific class.
* <p/>
* <p>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.type(clazz);
}
@Override
protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage)
throws IOException, HttpMessageNotReadableException {
JavaType javaType = getJavaType(clazz);
try {
return objectMapper.readValue(inputMessage.getBody(), javaType);
} catch (JsonParseException ex) {
throw new HttpMessageNotReadableException("Could not read JSON: " + ex.getMessage(), ex);
}
}
@Override
protected boolean supports(Class<?> clazz) {
// should not be called, since we override canRead/Write instead
throw new UnsupportedOperationException();
}
@Override
protected void writeInternal(Object o, HttpOutputMessage outputMessage)
throws IOException, HttpMessageNotWritableException {
JsonEncoding encoding = getEncoding(outputMessage.getHeaders().getContentType());
JsonGenerator jsonGenerator =
getObjectMapper().getJsonFactory().createJsonGenerator(outputMessage.getBody(), encoding);
try {
if (prefixJson) {
jsonGenerator.writeRaw("{} && ");
}
if (isPrettyPrint()) {
jsonGenerator.useDefaultPrettyPrinter();
}
getObjectMapper().writeValue(jsonGenerator, o);
} catch (JsonGenerationException ex) {
throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex);
}
}
private JsonEncoding getEncoding(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;
}
public ObjectMapper getObjectMapper() {
return objectMapper;
}
/**
* 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 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.
*
* @param objectMapper -
*/
public void setObjectMapper(ObjectMapper objectMapper) {
Assert.notNull(objectMapper, "'objectMapper' must not be null");
this.objectMapper = objectMapper;
}
public boolean isPrettyPrint() {
return prettyPrint;
}
public void setPrettyPrint(boolean prettyPrint) {
this.prettyPrint = prettyPrint;
}
/**
* Indicates 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.
*
* @param prefixJson -
*/
public void setPrefixJson(boolean prefixJson) {
this.prefixJson = prefixJson;
}
}