org.springframework.data.rest.webmvc.alps.AlpsJsonHttpMessageConverter.java Source code

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Here is the source code for org.springframework.data.rest.webmvc.alps.AlpsJsonHttpMessageConverter.java

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/*
 * Copyright 2014-2019 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
 *
 *      https://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.data.rest.webmvc.alps;

import java.lang.reflect.Type;
import java.util.Arrays;
import java.util.Collections;

import org.springframework.core.MethodParameter;
import org.springframework.core.convert.converter.Converter;
import org.springframework.data.rest.webmvc.RootResourceInformation;
import org.springframework.hateoas.MediaTypes;
import org.springframework.hateoas.mediatype.alps.Alps;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.util.Assert;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;

import com.fasterxml.jackson.annotation.JsonInclude.Include;
import com.fasterxml.jackson.databind.ObjectMapper;

/**
 * {@link HttpMessageConverter} to render {@link Alps} and {@link RootResourceInformation} instances as
 * {@code application/alps+json}.
 *
 * @author Oliver Gierke
 * @author Greg Turnquist
 */
public class AlpsJsonHttpMessageConverter extends MappingJackson2HttpMessageConverter
        implements ResponseBodyAdvice<Object> {

    private final RootResourceInformationToAlpsDescriptorConverter converter;

    /**
     * Creates a new {@link AlpsJsonHttpMessageConverter} for the given {@link Converter}.
     *
     * @param converter must not be {@literal null}.
     */
    public AlpsJsonHttpMessageConverter(RootResourceInformationToAlpsDescriptorConverter converter) {

        Assert.notNull(converter, "Converter must not be null!");

        this.converter = converter;

        ObjectMapper mapper = getObjectMapper();
        mapper.setSerializationInclusion(Include.NON_EMPTY);

        setPrettyPrint(true);
        setSupportedMediaTypes(Arrays.asList(MediaTypes.ALPS_JSON, MediaType.APPLICATION_JSON, MediaType.ALL));
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.http.converter.json.MappingJackson2HttpMessageConverter#canWrite(java.lang.Class, org.springframework.http.MediaType)
     */
    @Override
    public boolean canWrite(Class<?> clazz, MediaType mediaType) {
        return (clazz.isAssignableFrom(Alps.class) || clazz.isAssignableFrom(RootResourceInformation.class))
                && super.canWrite(clazz, mediaType);
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.http.converter.AbstractGenericHttpMessageConverter#canWrite(java.lang.reflect.Type, java.lang.Class, org.springframework.http.MediaType)
     */
    @Override
    public boolean canWrite(Type type, Class<?> clazz, MediaType mediaType) {
        return canWrite(clazz, mediaType);
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.http.converter.json.MappingJackson2HttpMessageConverter#canRead(java.lang.reflect.Type, java.lang.Class, org.springframework.http.MediaType)
     */
    @Override
    public boolean canRead(Type type, Class<?> contextClass, MediaType mediaType) {
        return false;
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice#beforeBodyWrite(java.lang.Object, org.springframework.core.MethodParameter, org.springframework.http.MediaType, java.lang.Class, org.springframework.http.server.ServerHttpRequest, org.springframework.http.server.ServerHttpResponse)
     */
    @Override
    public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,
            Class<? extends HttpMessageConverter<?>> selectedConverterType, ServerHttpRequest request,
            ServerHttpResponse response) {

        return body instanceof RootResourceInformation
                ? Collections.singletonMap("alps", converter.convert((RootResourceInformation) body))
                : body;
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice#supports(org.springframework.core.MethodParameter, java.lang.Class)
     */
    @Override
    public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {
        return converterType.equals(AlpsJsonHttpMessageConverter.class);
    }
}