com.expedia.seiso.web.jackson.hal.HalResourceAssembler.java Source code

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Here is the source code for com.expedia.seiso.web.jackson.hal.HalResourceAssembler.java

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/* 
 * Copyright 2013-2015 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 com.expedia.seiso.web.jackson.hal;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;

import lombok.NonNull;
import lombok.val;

import org.springframework.stereotype.Component;

import com.expedia.seiso.web.hateoas.Link;
import com.expedia.seiso.web.hateoas.PagedResources;
import com.expedia.seiso.web.hateoas.Resource;
import com.expedia.seiso.web.hateoas.Resources;

/**
 * Maps base resources to a HAL-specific representation to support HAL serialization.
 * 
 * @author Willie Wheeler
 */
@Component
public class HalResourceAssembler {

    public HalResource toHalResources(@NonNull Resources resources) {
        val halResources = new HalResource();
        halResources.setLinks(toHalLinks(resources.getLinks(), true));
        halResources.setEmbedded(toHalEmbeddedItems(resources.getItems()));
        return halResources;
    }

    public HalResource toHalPagedResources(@NonNull PagedResources pagedResources) {
        val halPagedResources = new HalResource();
        halPagedResources.setLinks(toHalLinks(pagedResources.getLinks(), true));
        halPagedResources.setEmbedded(toHalEmbeddedItems(pagedResources.getItems()));

        // State (page metadata)
        val state = new TreeMap<String, Object>();
        state.put("metadata", pagedResources.getMetadata());
        halPagedResources.setState(state);

        return halPagedResources;
    }

    public HalResource toHalResource(@NonNull Resource resource, boolean topLevel) {
        val halResource = new HalResource();
        halResource.setLinks(toHalLinks(resource.getLinks(), topLevel));

        // State
        val state = new TreeMap<String, Object>();
        val props = resource.getProperties();
        for (val prop : props.entrySet()) {
            val propName = prop.getKey();
            val propValue = prop.getValue();

            // Suppress database ID, as we don't want clients knowing/using it. We want them to use URIs.
            if (!"id".equals(propName)) {
                state.put(propName, propValue);
            }
        }

        // Embedded
        val embedded = new TreeMap<String, Object>();
        val assocs = resource.getAssociations();
        for (val assoc : assocs.entrySet()) {
            val assocName = assoc.getKey();
            val assocValue = assoc.getValue();
            if (assocValue == null) {
                embedded.put(assocName, null);
            } else if (assocValue instanceof Resource) {
                embedded.put(assocName, toHalResource((Resource) assocValue, false));
            } else if (assocValue instanceof List) {
                val halResourceKids = new ArrayList<HalResource>();
                val resourceKids = (List<Resource>) assocValue;
                for (val resourceKid : resourceKids) {
                    halResourceKids.add(toHalResource(resourceKid, false));
                }
                embedded.put(assocName, halResourceKids);
            } else {
                // Failing fast here. Considered simply logging a warning, but
                // 1) it would generate too many repetitive warnings in the logs and
                // 2) it would easily go unnoticed by clients
                throw new IllegalArgumentException("Unsupported association type: " + assocValue.getClass());
            }
        }

        halResource.setEmbedded(embedded.isEmpty() ? null : embedded);
        halResource.setState(state);

        return halResource;
    }

    private Map<String, Object> toHalLinks(List<Link> links, boolean includeCuries) {

        // Don't show _links unless there are actually links.
        if (links == null || links.isEmpty()) {
            return null;
        }

        val halLinks = new LinkedHashMap<String, Object>();

        // FIXME If the link relation can have multiple links, then we need to generate an array here. Note that this
        // depends on the nature of the relation itself, not the actual number of links in any given case. So for
        // example if a manager has a single direct report, we would still generate an array of direct report links
        // since in principle the manager could have many.
        for (val link : links) {
            val halLink = new LinkedHashMap<String, Object>();
            halLink.put("href", link.getHref());

            val title = link.getTitle();
            if (title != null) {
                halLink.put("title", title);
            }

            val templated = link.getTemplated();
            if (templated != null) {
                halLink.put("templated", templated);
            }

            halLinks.put(link.getRel(), halLink);
        }

        if (includeCuries) {
            halLinks.put("curies", Curie.SEISO_CURIES);
        }

        return halLinks;
    }

    private Map<String, Object> toHalEmbeddedItems(List<Resource> resourceList) {
        val embedded = new TreeMap<String, Object>();
        val halResourceList = new ArrayList<HalResource>();
        for (val resource : resourceList) {
            halResourceList.add(toHalResource(resource, false));
        }
        embedded.put("items", halResourceList);
        return embedded;
    }
}