org.oncoblocks.centromere.web.controller.ModelResourceAssembler.java Source code

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Here is the source code for org.oncoblocks.centromere.web.controller.ModelResourceAssembler.java

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/*
 * Copyright 2016 William Oemler, Blueprint Medicines
 *
 * 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.oncoblocks.centromere.web.controller;

import com.google.common.reflect.TypeToken;
import org.oncoblocks.centromere.core.model.ForeignKey;
import org.oncoblocks.centromere.core.model.Model;
import org.springframework.hateoas.EntityLinks;
import org.springframework.hateoas.Link;
import org.springframework.hateoas.mvc.ResourceAssemblerSupport;

import java.lang.reflect.Field;
import java.util.*;

/**
 * Extension of Spring HATEOAS's {@link ResourceAssemblerSupport}, which automatically builds self
 *   links, based upon the {@link Model} class's `getId()` method signature, and by inferring 
 *   related models by fields annotated with {@link ForeignKey}.
 * 
 * @author woemler
 */
public class ModelResourceAssembler<T extends Model<?>> extends ResourceAssemblerSupport<T, FilterableResource> {

    private final EntityLinks entityLinks;
    private final Class<?> modelController;
    private final Class<T> model;

    public ModelResourceAssembler(Class<?> controllerClass, Class<T> model, EntityLinks entityLinks) {
        super(controllerClass, FilterableResource.class);
        this.modelController = controllerClass;
        this.model = model;
        this.entityLinks = entityLinks;
    }

    public ModelResourceAssembler(Class<?> controllerClass, EntityLinks entityLinks) {
        super(controllerClass, FilterableResource.class);
        this.modelController = controllerClass;
        this.entityLinks = entityLinks;
        TypeToken<T> typeToken = new TypeToken<T>(getClass()) {
        };
        this.model = (Class<T>) typeToken.getRawType();
    }

    /**
     * Converts a {@link Model} object into a {@link FilterableResource}, adding the appropriate links.
     * 
      * @param t
     * @return
     */
    public FilterableResource toResource(T t) {
        FilterableResource<T> resource = new FilterableResource<>(t);
        resource.add(entityLinks.linkToSingleResource(model, t.getId()).withSelfRel());
        List<Link> links = addLinks(new ArrayList<>());
        links.addAll(this.addForeignKeyLinks(t));
        resource.add(links);
        return resource;
    }

    /**
     * Inspects the target {@link Model} class for {@link ForeignKey} annotations, and creates links
     *   based upon the inferred relationship and field names.
     * 
     * @param t
     * @return
     */
    private List<Link> addForeignKeyLinks(T t) {
        List<Link> links = new ArrayList<>();
        for (Field field : model.getDeclaredFields()) {
            ForeignKey fk = field.getAnnotation(ForeignKey.class);
            if (fk == null)
                continue;
            if (fk.model() == null)
                throw new RuntimeException(String.format(
                        "ForeignKey annotation for " + "class %s does not contain any class reference!",
                        model.getName()));
            Class<?> fkCLass = fk.model();
            String relName = fk.rel().equals("") ? field.getName() : fk.rel();
            String fieldName = fk.field().equals("") ? field.getName() : fk.field();
            if (!Model.class.isAssignableFrom(fkCLass))
                continue;
            Link link = null;
            try {
                field.setAccessible(true);
                if (fk.relationship().equals(ForeignKey.Relationship.MANY_TO_ONE)
                        && (!field.getType().isArray() && !Collection.class.isAssignableFrom(field.getType()))) {
                    link = entityLinks.linkToSingleResource(fkCLass, field.get(t)).withRel(relName);
                } else if (fk.relationship().equals(ForeignKey.Relationship.ONE_TO_MANY)
                        && (field.getType().isArray() || Collection.class.isAssignableFrom(field.getType()))) {
                    Map<String, Object> map = new HashMap<>();
                    map.put(fieldName, field.get(t));
                    link = entityLinks.linkToCollectionResource(fkCLass).expand(map).withRel(relName);
                } else if (fk.relationship().equals(ForeignKey.Relationship.MANY_TO_MANY)
                        && (field.getType().isArray() || Collection.class.isAssignableFrom(field.getType()))) {
                    Map<String, Object> map = new HashMap<>();
                    map.put(fieldName, field.get(t));
                    link = entityLinks.linkToCollectionResource(fkCLass).expand(map).withRel(relName);
                } else {
                    throw new RuntimeException(
                            String.format("Unable to determine correct link format for " + "field %s of class %s",
                                    field.getName(), model.getName()));
                }
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
            if (link != null)
                links.add(link);
        }
        return links;
    }

    private List<Link> addLinks(List<Link> links) {
        return links;
    }

    public EntityLinks getEntityLinks() {
        return entityLinks;
    }

    public Class<?> getModelController() {
        return modelController;
    }

    public Class<T> getModel() {
        return model;
    }
}