EntityDescriptor.java

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package com.sun.jersey.server.linking.impl;

import com.sun.jersey.server.linking.Link;
import com.sun.jersey.server.linking.Links;
import com.sun.jersey.server.linking.Ref;
import java.lang.reflect.Field;
import java.net.URI;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Describes an entity in terms of its fields, bean properties and {@link Ref}
 * annotated fields.
 * @author mh124079
 */
public class EntityDescriptor {

    // Maintains an internal static cache to optimize processing

    private static Map<Class<?>, EntityDescriptor> descriptors
        = new HashMap<Class<?>, EntityDescriptor>();

    public static synchronized EntityDescriptor getInstance(Class<?> entityClass) {
        if (descriptors.containsKey(entityClass)) {
            return descriptors.get(entityClass);
        } else {
            EntityDescriptor descriptor = new EntityDescriptor(entityClass);
            descriptors.put(entityClass, descriptor);
            return descriptor;
        }
    }

    // instance

    private Map<String, FieldDescriptor> nonLinkFields;
    private Map<String, RefFieldDescriptor> linkFields;
    private List<LinkDescriptor> linkHeaders;

    /**
     * Construct an new descriptor by inspecting the supplied class.
     * @param entityClass
     */
    private EntityDescriptor(Class<?> entityClass) {
        // create a list of link headers
        this.linkHeaders = new ArrayList<LinkDescriptor>();
        findLinkHeaders(entityClass);
        this.linkHeaders = Collections.unmodifiableList(linkHeaders);

        // create a list of field names
        this.nonLinkFields = new HashMap<String, FieldDescriptor>();
        this.linkFields = new HashMap<String, RefFieldDescriptor>();
        findFields(entityClass);
        this.nonLinkFields = Collections.unmodifiableMap(this.nonLinkFields);
        this.linkFields = Collections.unmodifiableMap(this.linkFields);
    }

    public Collection<RefFieldDescriptor> getLinkFields() {
        return linkFields.values();
    }

    public Collection<FieldDescriptor> getNonLinkFields() {
        return nonLinkFields.values();
    }

    public List<LinkDescriptor> getLinkHeaders() {
        return linkHeaders;
    }

    /**
     * Find and cache the fields of the supplied class and its superclasses and
     * interfaces.
     * @param entityClass the class
     */
    private void findFields(Class<?> entityClass) {
        for (Field f: entityClass.getDeclaredFields()) {
            Ref a = f.getAnnotation(Ref.class);
            if (a != null) {
                Class<?> t = f.getType();
                if (t.equals(String.class) || t.equals(URI.class)) {
                    if (!linkFields.containsKey(f.getName())) {
                        linkFields.put(f.getName(), new RefFieldDescriptor(f, a, t));
                    }
                } else {
                    // TODO unsupported type
                }
            } else {
                nonLinkFields.put(f.getName(), new FieldDescriptor(f));
            }
        }

        // look for nonLinkFields in superclasses
        Class<?> sc = entityClass.getSuperclass();
        if (sc != null && sc != Object.class) {
            findFields(sc);
        }

        // look for nonLinkFields in interfaces
        for (Class<?> ic : entityClass.getInterfaces()) {
            findFields(ic);
        }
    }

    private void findLinkHeaders(Class<?> entityClass) {
        Link linkHeaderAnnotation = entityClass.getAnnotation(Link.class);
        if (linkHeaderAnnotation != null) {
            linkHeaders.add(new LinkDescriptor(linkHeaderAnnotation));
        }
        Links linkHeadersAnnotation = entityClass.getAnnotation(Links.class);
        if (linkHeadersAnnotation != null) {
            for (Link linkHeader: linkHeadersAnnotation.value()) {
                linkHeaders.add(new LinkDescriptor(linkHeader));
            }
        }

        // look in superclasses
        Class<?> sc = entityClass.getSuperclass();
        if (sc != null && sc != Object.class) {
            findLinkHeaders(sc);
        }

        // look in interfaces
        for (Class<?> ic : entityClass.getInterfaces()) {
            findLinkHeaders(ic);
        }
    }
}