Deserializers.java

package org.photon;

import com.fasterxml.jackson.annotation.ObjectIdGenerator;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.BeanDescription;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.deser.impl.PropertyBasedObjectIdGenerator;
import com.fasterxml.jackson.databind.deser.impl.ReadableObjectId;
import com.fasterxml.jackson.databind.introspect.AnnotatedMember;
import com.fasterxml.jackson.databind.introspect.AnnotatedMethod;
import com.fasterxml.jackson.databind.introspect.BeanPropertyDefinition;
import com.fasterxml.jackson.databind.type.CollectionType;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.LazyLoader;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public final class Deserializers {

    public static class ManyToOne extends JsonDeserializer<Object> {

        private final AnnotatedMember member;

        public ManyToOne(AnnotatedMember member) {
            this.member = member;
        }

        @Override
        public Object deserialize(JsonParser jp, DeserializationContext ctx) throws IOException {
            JavaType jt;

            if (member instanceof AnnotatedMethod) {
                jt = ctx.constructType(((AnnotatedMethod) member).getGenericParameterType(0));
            } else {
                jt = ctx.constructType(member.getGenericType());
            }

            BeanDescription bd = ctx.getConfig().getClassIntrospector()
                    .forDeserializationWithBuilder(ctx.getConfig(), jt, ctx.getConfig());
            String property = bd.getObjectIdInfo().getPropertyName();

            AnnotatedMember member = null;

            for (BeanPropertyDefinition bpd : bd.findProperties()) {
                if (bpd.getName().equals(property)) {
                    member = bpd.getAccessor();
                    break;
                }
            }

            if (member == null) throw new IllegalStateException(String.format("unknown property `%s' on `%s'", property, bd.getType()));

            Object id = jp.readValueAs(member.getRawType());

            final ReadableObjectId roi = ctx.findObjectId(id, new FakeObjectIdGenerator(bd.getBeanClass(), member));

            if (roi.item != null) {
                return roi.item;
            } else {
                return Enhancer.create(this.member.getRawType(), new LazyLoader() {
                    @Override
                    public Object loadObject() throws Exception {
                        return roi.item;
                    }
                });
            }
        }
    }

    public static class OneToMany extends JsonDeserializer<List<Object>> {

        private final AnnotatedMember member;

        public OneToMany(AnnotatedMember member) {
            this.member = member;
        }

        @Override
        public List<Object> deserialize(JsonParser jp, DeserializationContext ctx) throws IOException {
            JavaType jt;

            if (member instanceof AnnotatedMethod) {
                jt = ctx.constructType(((AnnotatedMethod) member).getGenericParameterType(0));
            } else {
                jt = ctx.constructType(member.getGenericType());
            }

            BeanDescription bd = ctx.getConfig().getClassIntrospector()
                    .forDeserializationWithBuilder(ctx.getConfig(), jt.getContentType(), ctx.getConfig());
            String property = bd.getObjectIdInfo().getPropertyName();

            AnnotatedMember member = null;

            for (BeanPropertyDefinition bpd : bd.findProperties()) {
                if (bpd.getName().equals(property)) {
                    member = bpd.getAccessor();
                    break;
                }
            }

            if (member == null) throw new IllegalStateException(String.format("unknown property `%s' on `%s'", property, bd.getType()));

            List<Object> res = new ArrayList<>();

            JsonDeserializer<Object> des = ctx.findRootValueDeserializer(CollectionType.construct(
                    List.class, ctx.constructType(member.getRawType())));

            for (Object id : (Iterable) des.deserialize(jp, ctx)) {
                final ReadableObjectId roi = ctx.findObjectId(id,
                        new FakeObjectIdGenerator(bd.getBeanClass(), member));

                if (roi.item != null) {
                    res.add(roi.item);
                } else {
                    res.add(Enhancer.create(bd.getBeanClass(), new LazyLoader() {
                        @Override
                        public Object loadObject() throws Exception {
                            return roi.item;
                        }
                    }));
                }
            }

            return res;
        }
    }

    public static class FakeObjectIdGenerator extends ObjectIdGenerator<Object> {
        private final Class<?> scope;
        private final AnnotatedMember member;

        public FakeObjectIdGenerator(Class<?> scope, AnnotatedMember member) {
            this.scope = scope;
            this.member = member;
        }

        @Override
        public Class<?> getScope() {
            return scope;
        }

        @Override
        public boolean canUseFor(ObjectIdGenerator<?> gen) {
            return gen.getScope() == this.getScope();
        }

        @Override
        public ObjectIdGenerator<Object> forScope(Class<?> scope) {
            return new FakeObjectIdGenerator(scope, member);
        }

        @Override
        public ObjectIdGenerator<Object> newForSerialization(Object context) {
            return this;
        }

        @Override
        public IdKey key(Object key) {
            return new IdKey(PropertyBasedObjectIdGenerator.class, scope, key);
        }

        @Override
        public Object generateId(Object forPojo) {
            return member.getValue(forPojo);
        }
    }
}