Jersey Gson#
Jersey does not provide any inbuilt support for Gson, as it provide for MOXy and JSONP etc.
Gson can be used with Jersey as JSON serializer/deserializer by implementing interfaces javax.ws.rs.ext.MessageBodyWriter
and javax.ws.rs.ext.MessageBodyReader
, and register to configuration either using @Provider
annotation OR using ResourceConfig.register()
method.
Create Gson Provider#
public class GsonMessageBodyHandler
implements MessageBodyWriter<Object>, MessageBodyReader<Object> {
private static final String UTF_8 = "UTF-8";
private Gson gson;
// Customize the gson behavior here
private Gson getGson() {
if (gson == null) {
final GsonBuilder gsonBuilder = new GsonBuilder();
gson = gsonBuilder.disableHtmlEscaping()
.setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE)
.setPrettyPrinting().serializeNulls().create();
}
return gson;
}
@Override
public boolean isReadable(Class<?> type, Type genericType,
Annotation[] annotations, MediaType mediaType) {
return true;
}
@Override
public Object readFrom(Class<Object> type, Type genericType,
Annotation[] annotations, MediaType mediaType,
MultivaluedMap<String, String> httpHeaders,
InputStream entityStream) {
InputStreamReader streamReader = null;
try {
streamReader = new InputStreamReader(entityStream, UTF_8);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
try {
Type jsonType;
if (type.equals(genericType)) {
jsonType = type;
} else {
jsonType = genericType;
}
return getGson().fromJson(streamReader, jsonType);
} finally {
try {
streamReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
@Override
public boolean isWriteable(Class<?> type, Type genericType,
Annotation[] annotations, MediaType mediaType) {
return true;
}
@Override
public long getSize(Object object, Class<?> type, Type genericType,
Annotation[] annotations, MediaType mediaType) {
return -1;
}
@Override
public void writeTo(Object object, Class<?> type, Type genericType,
Annotation[] annotations, MediaType mediaType,
MultivaluedMap<String, Object> httpHeaders,
OutputStream entityStream)
throws IOException, WebApplicationException {
OutputStreamWriter writer = new OutputStreamWriter(entityStream, UTF_8);
try {
Type jsonType;
if (type.equals(genericType)) {
jsonType = type;
} else {
jsonType = genericType;
}
getGson().toJson(object, jsonType, writer);
} finally {
writer.close();
}
}
}
Register Gson Provider#
public class JerseyApplication extends ResourceConfig {
public JerseyApplication() {
packages("t5750.rest.jersey.resources", "t5750.rest.jersey.service");
register(GsonMessageBodyHandler.class);
register(AuthenticationFilter.class);
}
}
Extending Gson Functionality#
You can extend/customize Gson behavior anytime inside GsonMessageBodyHandler.getGson()
method.
private Gson getGson() {
if (gson == null) {
final GsonBuilder gsonBuilder = new GsonBuilder();
gson = gsonBuilder.disableHtmlEscaping()
.setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE)
.setPrettyPrinting()
.serializeNulls()
.create();
}
return gson;
}