org.molgenis.util.GsonHttpMessageConverter.java Source code

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Here is the source code for org.molgenis.util.GsonHttpMessageConverter.java

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/*
 * Copyright 2002-2013 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.molgenis.util;

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;

import org.apache.commons.io.IOUtils;
import org.apache.log4j.Logger;
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.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonIOException;
import com.google.gson.JsonParseException;
import com.google.gson.JsonSyntaxException;

/**
 * Converts objects to json string and vica versa If logging is set to debug it will print the incoming and outgoing
 * json strings
 * 
 * @author Roy Clarkson
 * @since 1.0
 */
public class GsonHttpMessageConverter extends AbstractHttpMessageConverter<Object> {
    private static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");
    private static final Logger LOG = Logger.getLogger(GsonHttpMessageConverter.class);
    private final Gson gson;
    private Type type = null;
    private boolean prefixJson = false;

    /**
     * Construct a new {@code GsonHttpMessageConverter} with a default {@link Gson#Gson() Gson}.
     */
    public GsonHttpMessageConverter() {
        this(false);
    }

    /**
     * Construct a new {@code GsonHttpMessageConverter} with a default {@link Gson#Gson() Gson}.
     */
    public GsonHttpMessageConverter(boolean prettyPrinting) {
        super(new MediaType("application", "json", DEFAULT_CHARSET));

        GsonBuilder builder = new GsonBuilder().setDateFormat(MolgenisDateFormat.DATEFORMAT_DATETIME)
                .disableHtmlEscaping();
        if (prettyPrinting) {
            builder = builder.setPrettyPrinting();
        }

        gson = builder.create();
    }

    /**
     * Construct a new {@code GsonHttpMessageConverter}.
     * 
     * @param gson
     *            a customized {@link Gson#Gson() Gson}
     */
    public GsonHttpMessageConverter(Gson gson) {
        super(new MediaType("application", "json", DEFAULT_CHARSET));
        this.gson = gson;
    }

    public void setType(Type type) {
        this.type = type;
    }

    public Type getType() {
        return type;
    }

    public Gson getGson() {
        return gson;
    }

    /**
     * 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.
     */
    public void setPrefixJson(boolean prefixJson) {
        this.prefixJson = prefixJson;
    }

    @Override
    public boolean canRead(Class<?> clazz, MediaType mediaType) {
        return canRead(mediaType);
    }

    @Override
    public boolean canWrite(Class<?> clazz, MediaType mediaType) {
        return 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 {
        Reader json = new InputStreamReader(inputMessage.getBody(), getCharset(inputMessage.getHeaders()));
        try {
            Type typeOfT = getType();
            if (LOG.isTraceEnabled()) {
                String jsonStr = IOUtils.toString(json);
                LOG.trace("Json request:\n" + jsonStr);

                if (typeOfT != null) {
                    return this.gson.fromJson(jsonStr, typeOfT);
                }

                return this.gson.fromJson(jsonStr, clazz);
            } else {
                if (typeOfT != null) {
                    return this.gson.fromJson(json, typeOfT);
                }

                return this.gson.fromJson(json, clazz);
            }
        } catch (JsonSyntaxException ex) {
            throw new HttpMessageNotReadableException("Could not read JSON: " + ex.getMessage(), ex);
        } catch (JsonIOException ex) {
            throw new HttpMessageNotReadableException("Could not read JSON: " + ex.getMessage(), ex);
        } catch (JsonParseException ex) {
            throw new HttpMessageNotReadableException("Could not read JSON: " + ex.getMessage(), ex);
        } finally {
            IOUtils.closeQuietly(json);
        }
    }

    @Override
    protected void writeInternal(Object o, HttpOutputMessage outputMessage)
            throws IOException, HttpMessageNotWritableException {

        OutputStreamWriter writer = new OutputStreamWriter(outputMessage.getBody(),
                getCharset(outputMessage.getHeaders()));

        try {
            Type typeOfSrc = getType();

            if (LOG.isTraceEnabled()) {
                StringBuilder sb = new StringBuilder();
                if (this.prefixJson) {
                    sb.append("{} && ");
                }

                if (typeOfSrc != null) {
                    sb.append(gson.toJson(o, typeOfSrc));
                } else {
                    sb.append(gson.toJson(o));
                }

                LOG.debug("Json response:\n" + sb.toString());
                writer.write(sb.toString());
            } else {
                if (this.prefixJson) {
                    writer.append("{} && ");
                }

                if (typeOfSrc != null) {
                    this.gson.toJson(o, typeOfSrc, writer);
                } else {
                    this.gson.toJson(o, writer);
                }
            }
        } catch (JsonIOException ex) {
            throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex);
        } finally {
            IOUtils.closeQuietly(writer);
        }

    }

    // helpers

    private Charset getCharset(HttpHeaders headers) {
        if (headers != null && headers.getContentType() != null && headers.getContentType().getCharSet() != null) {
            return headers.getContentType().getCharSet();
        }
        return DEFAULT_CHARSET;
    }

}