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/*
 * Copyright 2002-2012 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.springframework.http.converter;

import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;

import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.util.FileCopyUtils;

/**
 * Implementation of {@link HttpMessageConverter} that can read and write strings.
 * 
 * 
 * By default, this converter supports all media types (*/*), and writes with a
 * {@code Content-Type} of {@code text/plain}. This can be overridden by setting the
 * {@link #setSupportedMediaTypes(java.util.List) supportedMediaTypes} property.
 * 
 * @author Arjen Poutsma
 * @author Roy Clarkson
 * @since 1.0
 */
public class StringHttpMessageConverter extends AbstractHttpMessageConverter {

	private final Charset defaultCharset;

	private final List availableCharsets;

	private boolean writeAcceptCharset = true;

	/**
	 * Create a new StringHttpMessageConverter instance with a default {@link Charset} of ISO-8859-1,
	 * and default list of available {@link Charset}'s from {@link Charset#availableCharsets()}.
	 */
	public StringHttpMessageConverter() {
		this(Charset.forName("ISO-8859-1"));
	}

	/**
	 * Create a new StringHttpMessageConverter instance with a default {@link Charset},
	 * and default list of available {@link Charset}'s from {@link Charset#availableCharsets()}.
	 * @param defaultCharset the Charset to use 
	 */
	public StringHttpMessageConverter(Charset defaultCharset) {
		this(defaultCharset, new ArrayList(Charset.availableCharsets().values()));
	}

	/**
	 * Create a new StringHttpMessageConverter instance with a default {@link Charset},
	 * and list of available {@link Charset}'s.
	 * @param defaultCharset the Charset to use 
	 * @param availableCharsets the list of available Charsets
	 */
	public StringHttpMessageConverter(Charset defaultCharset, List availableCharsets) {
		super(new MediaType("text", "plain", defaultCharset), MediaType.ALL);
		this.defaultCharset = defaultCharset;
		this.availableCharsets = availableCharsets;
	}

	/**
	 * The default {@link Charset} is ISO-8859-1. Can be overridden in subclasses,
	 * or through the use of the alternate constructor.
	 * @return default Charset
	 */
	public Charset getDefaultCharset() {
		return this.defaultCharset;
	}

	/**
	 * Indicates whether the {@code Accept-Charset} should be written to any outgoing request.
	 * 

	 * Default is {@code true}.
	 */
	public void setWriteAcceptCharset(boolean writeAcceptCharset) {
		this.writeAcceptCharset = writeAcceptCharset;
	}

	@Override
	public boolean supports(Class clazz) {
		return String.class.equals(clazz);
	}

	@Override
	protected String readInternal(Class clazz, HttpInputMessage inputMessage) throws IOException {
		Charset charset = getContentTypeCharset(inputMessage.getHeaders().getContentType());
		return FileCopyUtils.copyToString(new InputStreamReader(inputMessage.getBody(), charset));
	}

	@Override
	protected Long getContentLength(String s, MediaType contentType) {
		Charset charset = getContentTypeCharset(contentType);
		try {
			return (long) s.getBytes(charset.displayName()).length;
		} catch (UnsupportedEncodingException ex) {
			// should not occur
			throw new InternalError(ex.getMessage());
		}
	}

	@Override
	protected void writeInternal(String s, HttpOutputMessage outputMessage) throws IOException {
		if (writeAcceptCharset) {
			outputMessage.getHeaders().setAcceptCharset(getAcceptedCharsets());
		}
		Charset charset = getContentTypeCharset(outputMessage.getHeaders().getContentType());
		FileCopyUtils.copy(s, new OutputStreamWriter(outputMessage.getBody(), charset));
	}

	/**
	 * Return the list of supported {@link Charset}.
	 * 
	 * 
	 * By default, returns {@link Charset#availableCharsets()}. Can be overridden in subclasses,
	 * or through the use of the alternate constructor.
	 * 
	 * @return the list of accepted charsets
	 */
	protected List getAcceptedCharsets() {
		return this.availableCharsets;
	}

	private Charset getContentTypeCharset(MediaType contentType) {
		if (contentType != null && contentType.getCharSet() != null) {
			return contentType.getCharSet();
		} else {
			return getDefaultCharset();
		}
	}

}