org.springframework.web.servlet.mvc.method.annotation.support.AbstractMessageConverterMethodArgumentResolver.java Source code

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/*
 * Copyright 2002-2011 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.web.servlet.mvc.method.annotation.support;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.core.MethodParameter;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.server.ServletServerHttpRequest;
import org.springframework.util.Assert;
import org.springframework.web.HttpMediaTypeNotSupportedException;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;

/**
 * A base class for resolving method argument values by reading from the body of a request 
 * with {@link HttpMessageConverter}s.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public abstract class AbstractMessageConverterMethodArgumentResolver implements HandlerMethodArgumentResolver {

    protected final Log logger = LogFactory.getLog(getClass());

    protected final List<HttpMessageConverter<?>> messageConverters;

    protected final List<MediaType> allSupportedMediaTypes;

    public AbstractMessageConverterMethodArgumentResolver(List<HttpMessageConverter<?>> messageConverters) {
        Assert.notEmpty(messageConverters, "'messageConverters' must not be empty");
        this.messageConverters = messageConverters;
        this.allSupportedMediaTypes = getAllSupportedMediaTypes(messageConverters);
    }

    /**
     * Returns the media types supported by all provided message converters preserving their ordering and 
     * further sorting by specificity via {@link MediaType#sortBySpecificity(List)}. 
     */
    private static List<MediaType> getAllSupportedMediaTypes(List<HttpMessageConverter<?>> messageConverters) {
        Set<MediaType> allSupportedMediaTypes = new LinkedHashSet<MediaType>();
        for (HttpMessageConverter<?> messageConverter : messageConverters) {
            allSupportedMediaTypes.addAll(messageConverter.getSupportedMediaTypes());
        }
        List<MediaType> result = new ArrayList<MediaType>(allSupportedMediaTypes);
        MediaType.sortBySpecificity(result);
        return Collections.unmodifiableList(result);
    }

    /**
     * Creates the method argument value of the expected parameter type by reading from the given request.
     * 
     * @param <T> the expected type of the argument value to be created 
     * @param webRequest the current request
     * @param methodParam the method argument
     * @param paramType the type of the argument value to be created
     * @return the created method argument value
     * @throws IOException if the reading from the request fails
     * @throws HttpMediaTypeNotSupportedException if no suitable message converter is found
     */
    protected <T> Object readWithMessageConverters(NativeWebRequest webRequest, MethodParameter methodParam,
            Class<T> paramType) throws IOException, HttpMediaTypeNotSupportedException {

        HttpInputMessage inputMessage = createInputMessage(webRequest);
        return readWithMessageConverters(inputMessage, methodParam, paramType);
    }

    /**
     * Creates the method argument value of the expected parameter type by reading from the given HttpInputMessage. 
     * 
     * @param <T> the expected type of the argument value to be created 
     * @param inputMessage the HTTP input message representing the current request
     * @param methodParam the method argument
     * @param paramType the type of the argument value to be created
     * @return the created method argument value
     * @throws IOException if the reading from the request fails
     * @throws HttpMediaTypeNotSupportedException if no suitable message converter is found
     */
    @SuppressWarnings("unchecked")
    protected <T> Object readWithMessageConverters(HttpInputMessage inputMessage, MethodParameter methodParam,
            Class<T> paramType) throws IOException, HttpMediaTypeNotSupportedException {

        MediaType contentType = inputMessage.getHeaders().getContentType();
        if (contentType == null) {
            contentType = MediaType.APPLICATION_OCTET_STREAM;
        }

        for (HttpMessageConverter<?> messageConverter : this.messageConverters) {
            if (messageConverter.canRead(paramType, contentType)) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Reading [" + paramType.getName() + "] as \"" + contentType + "\" using ["
                            + messageConverter + "]");
                }
                return ((HttpMessageConverter<T>) messageConverter).read(paramType, inputMessage);
            }
        }

        throw new HttpMediaTypeNotSupportedException(contentType, allSupportedMediaTypes);
    }

    /**
     * Creates a new {@link HttpInputMessage} from the given {@link NativeWebRequest}.
     *
     * @param webRequest the web request to create an input message from
     * @return the input message
     */
    protected ServletServerHttpRequest createInputMessage(NativeWebRequest webRequest) {
        HttpServletRequest servletRequest = webRequest.getNativeRequest(HttpServletRequest.class);
        return new ServletServerHttpRequest(servletRequest);
    }

}