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IND2UCE :: Webproject related contents like JSON, Autoconfiguration of Spring, etc.

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/*-
 * =================================LICENSE_START=================================
 * IND2UCE
 * %%
 * Copyright (C) 2016 Fraunhofer IESE (www.iese.fraunhofer.de)
 * %%
 * The Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V., Hansastrasse 27c, 80686 Munich, Germany (further: Fraunhofer) is holder of all proprietary rights on this computer program.
 * You can only use this computer program if you have closed a license agreement with Fraunhofer or you get the right to use the computer program from someone who is authorized to grant you that right.
 * Any use of the computer program without a valid license is prohibited and liable to prosecution.
 *
 * Copyright (C) 2018 Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V. acting on behalf of its Fraunhofer Institute for Experimental Software Engineering (IESE)
 *
 * All rights reserved.
 *
 * Contact: [email protected]
 * =================================LICENSE_END=================================
 */

package de.fraunhofer.iese.ind2uce.json;

import de.fraunhofer.iese.ind2uce.api.common.Ind2uceEntity;

import com.google.gson.Gson;
import com.google.gson.JsonIOException;
import com.google.gson.JsonParseException;
import com.google.gson.reflect.TypeToken;

import org.springframework.http.HttpHeaders;
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.GenericHttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;

import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.lang.reflect.Type;
import java.nio.charset.Charset;

// TODO: Auto-generated Javadoc
/**
 * Implementation of
 * {@link org.springframework.http.converter.HttpMessageConverter} that can read
 * and write JSON using the
 * Google Gson library's
 * {@link Gson} class.
 * 

 * This converter can be used to bind to typed beans or untyped {@code HashMap}
 * s. By default, it supports {@code application/json} and
 * {@code application/*+json}.
 * 

 * 

 * Tested against Gson 2.3; compatible with Gson 2.0 and higher.
 * 

 *
 * @author Roy Clarkson
 * @see #setSupportedMediaTypes
 * @since 4.1
 */
public class GsonConverter extends AbstractHttpMessageConverter implements GenericHttpMessageConverter {

  /**
   * The Constant DEFAULT_CHARSET.
   */
  public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");

  /**
   * The gson.
   */
  private final Gson gson = Ind2uceEntity.getGson();

  /**
   * Construct a new {@code GsonHttpMessageConverter}.
   */
  public GsonConverter() {
    super(new MediaType("application", "json", DEFAULT_CHARSET), new MediaType("application", "*+json", DEFAULT_CHARSET));
  }

  /*
   * (non-Javadoc)
   * @see
   * org.springframework.http.converter.AbstractHttpMessageConverter#canRead(
   * java.lang.Class, org.springframework.http.MediaType)
   */
  @Override
  public boolean canRead(Class clazz, MediaType mediaType) {
    return this.canRead(mediaType);
  }

  /*
   * (non-Javadoc)
   * @see
   * org.springframework.http.converter.GenericHttpMessageConverter#canRead(java
   * .lang.reflect.Type, java.lang.Class, org.springframework.http.MediaType)
   */
  @Override
  public boolean canRead(Type type, Class contextClass, MediaType mediaType) {
    return this.canRead(mediaType);
  }

  /*
   * (non-Javadoc)
   * @see
   * org.springframework.http.converter.AbstractHttpMessageConverter#canWrite(
   * java.lang.Class, org.springframework.http.MediaType)
   */
  @Override
  public boolean canWrite(Class clazz, MediaType mediaType) {
    return this.canWrite(mediaType);
  }

  /*
   * (non-Javadoc)
   * @see
   * org.springframework.http.converter.GenericHttpMessageConverter#canWrite(
   * java.lang.reflect.Type, java.lang.Class,
   * org.springframework.http.MediaType)
   */
  @Override
  public boolean canWrite(Type arg0, Class arg1, MediaType arg2) {
    return this.canWrite(arg2);
  }

  /*
   * (non-Javadoc)
   * @see
   * org.springframework.http.converter.GenericHttpMessageConverter#write(java.
   * lang.Object, java.lang.reflect.Type, org.springframework.http.MediaType,
   * org.springframework.http.HttpOutputMessage)
   */
  @Override
  public void write(Object o, Type type, MediaType contentType, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException {
    write(o, contentType, outputMessage);
  }

  /*
   * (non-Javadoc)
   * @see
   * org.springframework.http.converter.AbstractHttpMessageConverter#supports(
   * java.lang.Class)
   */
  @Override
  protected boolean supports(Class clazz) {
    // should not be called, since we override canRead/Write instead
    throw new UnsupportedOperationException();
  }

  /**
   * Read internal.
   *
   * @param arg0 the arg 0
   * @param arg1 the arg 1
   * @return the object
   * @throws IOException Signals that an I/O exception has occurred.
   * @throws HttpMessageNotReadableException the http message not readable
   *           exception
   */
  @Override
  protected Object readInternal(Class arg0, HttpInputMessage arg1) throws IOException, HttpMessageNotReadableException {
    final TypeToken token = this.getTypeToken(arg0);
    return this.readTypeToken(token, arg1);

  }

  /*
   * (non-Javadoc)
   * @see
   * org.springframework.http.converter.GenericHttpMessageConverter#read(java.
   * lang.reflect.Type, java.lang.Class,
   * org.springframework.http.HttpInputMessage)
   */
  @Override
  public Object read(Type type, Class contextClass, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {
    final TypeToken token = this.getTypeToken(type);
    return this.readTypeToken(token, inputMessage);
  }

  /**
   * Return the Gson {@link TypeToken} for the specified type.
   * 

   * The default implementation returns {@code TypeToken.get(type)}, but this
   * can be overridden in subclasses to allow for custom generic collection
   * handling. For instance:
   *
   * 
   * protected TypeToken<?> getTypeToken(Type type) {
   *   if (type instanceof Class && List.class.isAssignableFrom((Class<?>)type)) {
   *     return new TypeToken<ArrayList<MyBean>>() {
   *     };
   *   } else {
   *     return super.getTypeToken(type);
   *   }
   * }
   * 

   *
   * @param type the type for which to return the TypeToken
   * @return the type token
   */
  protected TypeToken getTypeToken(Type type) {
    return TypeToken.get(type);
  }

  /**
   * Read type token.
   *
   * @param token the token
   * @param inputMessage the input message
   * @return the object
   * @throws IOException Signals that an I/O exception has occurred.
   */
  private Object readTypeToken(TypeToken token, HttpInputMessage inputMessage) throws IOException {
    final Reader json = new InputStreamReader(inputMessage.getBody(), this.getCharset(inputMessage.getHeaders()));
    try {
      return this.gson.fromJson(json, token.getType());
    } catch (final JsonParseException ex) {
      throw new HttpMessageNotReadableException("Could not read JSON: " + ex.getMessage(), ex);
    }
  }

  /**
   * Gets the charset.
   *
   * @param headers the headers
   * @return the charset
   */
  private Charset getCharset(HttpHeaders headers) {
    if (headers == null || headers.getContentType() == null || headers.getContentType().getCharset() == null) {
      return DEFAULT_CHARSET;
    }
    return headers.getContentType().getCharset();
  }

  /*
   * (non-Javadoc)
   * @see org.springframework.http.converter.AbstractHttpMessageConverter#
   * writeInternal(java.lang.Object, org.springframework.http.HttpOutputMessage)
   */
  @Override
  public void writeInternal(Object o, HttpOutputMessage outputMessage) throws IOException {
    final Charset charset = this.getCharset(outputMessage.getHeaders());
    final OutputStreamWriter writer = new OutputStreamWriter(outputMessage.getBody(), charset);
    try {
      final String json = this.gson.toJson(o);
      writer.write(json);
      writer.close();
    } catch (final JsonIOException ex) {
      throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex);
    }
  }

}
    

    

    

            

    

            



    
    






    
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