com.strategicgains.hyperexpress.serialization.jackson.HalResourceSerializer.java Source code

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Here is the source code for com.strategicgains.hyperexpress.serialization.jackson.HalResourceSerializer.java

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/*
Copyright 2014, Strategic Gains, Inc.
    
   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 com.strategicgains.hyperexpress.serialization.jackson;

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.strategicgains.hyperexpress.domain.Link;
import com.strategicgains.hyperexpress.domain.Namespace;
import com.strategicgains.hyperexpress.domain.Resource;
import com.strategicgains.hyperexpress.domain.hal.HalLink;
import com.strategicgains.hyperexpress.domain.hal.HalResource;

/**
 * @author toddf
 * @since May 2, 2014
 */
public class HalResourceSerializer extends JsonSerializer<HalResource> {

    private static final String CURIES = "curies";
    private static final String EMBEDDED = "_embedded";
    private static final String LINKS = "_links";

    public HalResourceSerializer() {
        super();
    }

    @Override
    public void serialize(HalResource resource, JsonGenerator jgen, SerializerProvider provider)
            throws IOException, JsonProcessingException {
        jgen.writeStartObject();
        renderJson(resource, jgen, false);
        jgen.writeEndObject();
    }

    private void renderJson(HalResource resource, JsonGenerator jgen, boolean isEmbedded)
            throws JsonGenerationException, IOException {
        writeLinks(resource, isEmbedded, jgen);
        writeEmbedded(resource, jgen);
        writeProperties(resource.getProperties(), jgen);
    }

    private void writeLinks(HalResource resource, boolean isEmbedded, JsonGenerator jgen)
            throws JsonGenerationException, IOException {
        List<Link> links = resource.getLinks();
        List<Namespace> namespaces = resource.getNamespaces();
        if (links.isEmpty() && (isEmbedded || namespaces.isEmpty()))
            return;

        jgen.writeObjectFieldStart(LINKS);
        writeCuries(namespaces, isEmbedded, jgen);

        Map<String, List<HalLink>> linksByRel = indexLinksByRel(resource.getLinks());

        for (Entry<String, List<HalLink>> entry : linksByRel.entrySet()) {
            if (entry.getValue().size() == 1 && !resource.isMultipleLinks(entry.getKey())) // Write single link
            {
                HalLink link = entry.getValue().iterator().next();

                if (null == link.getTemplated()) {
                    link.setTemplated(link.hasTemplate() ? true : null);
                }

                jgen.writeObjectField(entry.getKey(), link);
            } else // Write link array
            {
                jgen.writeArrayFieldStart(entry.getKey());

                for (HalLink link : entry.getValue()) {
                    if (null == link.getTemplated()) {
                        link.setTemplated(link.hasTemplate() ? true : null);
                    }

                    jgen.writeObject(link);
                }

                jgen.writeEndArray();
            }

        }

        jgen.writeEndObject();
    }

    private Map<String, List<HalLink>> indexLinksByRel(List<Link> links) {
        Map<String, List<HalLink>> linksByRel = new HashMap<String, List<HalLink>>();

        for (Link link : links) {
            List<HalLink> linksForRel = linksByRel.get(link.getRel());

            if (linksForRel == null) {
                linksForRel = new ArrayList<HalLink>();
                linksByRel.put(link.getRel(), linksForRel);
            }

            linksForRel.add(new HalLink(link));
        }

        return linksByRel;
    }

    private void writeCuries(List<Namespace> namespaces, boolean isEmbedded, JsonGenerator jgen)
            throws IOException, JsonGenerationException, JsonProcessingException {
        if (isEmbedded || namespaces.isEmpty())
            return;

        if (namespaces.size() == 1) // Write single namespace
        {
            jgen.writeObjectField(CURIES, namespaces.iterator().next());
        } else // Write namespace array
        {
            jgen.writeArrayFieldStart(CURIES);

            for (Namespace ns : namespaces) {
                jgen.writeObject(ns);
            }

            jgen.writeEndArray();
        }
    }

    private void writeEmbedded(Resource resource, JsonGenerator jgen) throws JsonGenerationException, IOException {
        Map<String, List<Resource>> embedded = resource.getResources();

        if (embedded.isEmpty())
            return;

        jgen.writeObjectFieldStart(EMBEDDED);

        for (Entry<String, List<Resource>> entry : embedded.entrySet()) {
            if (entry.getValue().size() == 1 && !resource.isMultipleResources(entry.getKey())) {
                jgen.writeObjectFieldStart(entry.getKey());
                renderJson((HalResource) entry.getValue().iterator().next(), jgen, true);
                jgen.writeEndObject();
            } else {
                jgen.writeArrayFieldStart(entry.getKey());

                for (Resource r : entry.getValue()) {
                    jgen.writeStartObject();
                    renderJson((HalResource) r, jgen, true);
                    jgen.writeEndObject();
                }

                jgen.writeEndArray();
            }
        }

        jgen.writeEndObject();
    }

    private void writeProperties(Map<String, Object> properties, JsonGenerator jgen)
            throws JsonProcessingException, IOException {
        if (properties.isEmpty())
            return;

        for (Entry<String, Object> entry : properties.entrySet()) {
            jgen.writeObjectField(entry.getKey(), entry.getValue());
        }
    }
}