DtoFactory.java

/*******************************************************************************
 * Copyright (c) 2012-2017 Codenvy, S.A.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *   Codenvy, S.A. - initial API and implementation
 *******************************************************************************/
package org.eclipse.che.ide.dto;

import com.google.gwt.json.client.JSONArray;
import com.google.gwt.json.client.JSONParser;
import com.google.inject.Singleton;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Provides implementations of all registered DTO interfaces.
 *
 * @author Artem Zatsarynnyi
 */
@Singleton
public class DtoFactory {
    private final Map<Class<?>, DtoProvider<?>> dtoInterface2Providers = new HashMap<>();

    /**
     * Creates new instance of class which implements specified DTO interface.
     *
     * @param dtoInterface
     *         DTO interface
     * @return new instance of DTO implementation
     * @throws IllegalArgumentException
     *         if can't provide any implementation for specified interface
     */
    public <T> T createDto(Class<T> dtoInterface) {
        return getDtoProvider(dtoInterface).newInstance();
    }

    /**
     * Creates new instance of class which implements specified DTO interface, parses specified JSON string and uses
     * parsed data for initializing fields of DTO object.
     *
     * @param json
     *         JSON data
     * @param dtoInterface
     *         DTO interface
     * @return new instance of DTO implementation
     * @throws IllegalArgumentException
     *         if can't provide any implementation for specified interface
     */
    public <T> T createDtoFromJson(String json, Class<T> dtoInterface) {
        return getDtoProvider(dtoInterface).fromJson(json);
    }

    /**
     * Parses the JSON data from the specified sting into list of objects of the specified type.
     *
     * @param json
     *         JSON data
     * @param dtoInterface
     *         DTO interface
     * @return list of DTO
     * @throws IllegalArgumentException
     *         if can't provide any implementation for specified interface
     */
    public <T> List<T> createListDtoFromJson(String json, Class<T> dtoInterface) {
        final DtoProvider<T> dtoProvider = getDtoProvider(dtoInterface);
        final JSONArray jsonArray = JSONParser.parseStrict(json).isArray();
        final List<T> result = new ArrayList<>();
        for (int i = 0; i < jsonArray.size(); i++) {
            String payload = jsonArray.get(i).isObject().toString();
            result.add(dtoProvider.fromJson(payload));
        }
        return result;
    }

    /** Serializes dto to JSON format. */
    public <T> String toJson(T dto) {
        if (dto instanceof JsonSerializable) {
            return ((JsonSerializable)dto).toJson();
        }
        throw new IllegalArgumentException("JsonSerializable instance required. ");
    }
    
    /** Serializes array of DTO objects to JSON format. */
    public <T> String toJson(List<T> array) {
        StringBuilder sb = new StringBuilder("[");
        for (int i = 0; i < array.size(); i++){
            T dto = array.get(i);
            if (dto instanceof JsonSerializable) {
                if (i > 0){
                    sb.append(", ");
                }
                sb.append(((JsonSerializable)dto).toJson());
            } else {
                throw new IllegalArgumentException("JsonSerializable instance required. ");
            }
        }
        sb.append("]");
        return sb.toString();
    }

    /**
     * Registers DtoProvider for DTO interface.
     *
     * @param dtoInterface
     *         DTO interface
     * @param provider
     *         provider for DTO interface
     * @see DtoProvider
     */
    public void registerProvider(Class<?> dtoInterface, DtoProvider<?> provider) {
        dtoInterface2Providers.put(dtoInterface, provider);
    }

    private <T> DtoProvider<T> getDtoProvider(Class<T> dtoInterface) {
        DtoProvider<?> dtoProvider = dtoInterface2Providers.get(dtoInterface);
        if (dtoProvider == null) {
            throw new IllegalArgumentException("Unknown DTO type " + dtoInterface);
        }
        return (DtoProvider<T>)dtoProvider;
    }
}