at.tugraz.kmi.medokyservice.json.GsonHandler.java Source code

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Here is the source code for at.tugraz.kmi.medokyservice.json.GsonHandler.java

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/*
 * 
 * MEDoKyService:
 * A web service component for learner modelling and learning recommendations.
 * Copyright (C) 2015 KTI, TUGraz, Contact: simone.kopeinik@tugraz.at
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; 
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  
 * See the GNU Affero General Public License for more details.  
 * For more information about the GNU Affero General Public License see <http://www.gnu.org/licenses/>.
 * 
 */
package at.tugraz.kmi.medokyservice.json;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import java.nio.charset.Charset;

import javax.ws.rs.Consumes;
import javax.ws.rs.Produces;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.MessageBodyReader;
import javax.ws.rs.ext.MessageBodyWriter;
import javax.ws.rs.ext.Provider;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

/*
 * adapted from: http://eclipsesource.com/blogs/2012/11/02/integrating-gson-into-a-jax-rs-based-application/
 * */
@Provider
@Produces(MediaType.APPLICATION_JSON)
@Consumes(MediaType.APPLICATION_JSON)
public final class GsonHandler implements MessageBodyWriter<Object>, MessageBodyReader<Object> {

    private Gson gson;

    private Gson gson() {
        if (gson == null)
            gson = new GsonBuilder().setExclusionStrategies(new AnnotationExclusionStrategy()).create();
        return gson;
    }

    @Override
    public boolean isReadable(Class<?> type, Type genericType, java.lang.annotation.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) throws IOException {
        InputStreamReader in = new InputStreamReader(entityStream, Charset.forName("UTF-8"));
        if (type.equals(genericType))
            genericType = type;
        try {
            Object result = gson().fromJson(in, genericType);
            return result;
        } catch (Throwable t) {
            t.printStackTrace();
            throw new IOException(t.getMessage());
        } finally {
            in.close();
        }
    }

    @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, Charset.forName("UTF-8"));
        if (type.equals(genericType))
            genericType = type;
        try {
            gson().toJson(object, genericType, writer);
        } catch (Throwable t) {
            t.printStackTrace();
            new IOException(t.getMessage());
        } finally {
            writer.close();
        }
    }
}