org.gbif.registry2.utils.JsonBackedData.java Source code

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Here is the source code for org.gbif.registry2.utils.JsonBackedData.java

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/*
 * Copyright 2013 Global Biodiversity Information Facility (GBIF)
 *
 * 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.gbif.registry2.utils;

import java.io.IOException;

import com.google.common.base.Charsets;
import com.google.common.base.Throwables;
import com.google.common.io.Resources;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.type.TypeReference;

/**
 * Base class providing basic Jackson based factories for new object instances.
 */
abstract class JsonBackedData<T> {

    private static final ObjectMapper MAPPER = new ObjectMapper();
    private final TypeReference<T> type;
    private final String json; // for reuse to save file IO

    // only for instantiation by subclasses, type references are required to keep typing at runtime
    protected JsonBackedData(String file, TypeReference<T> type) {
        json = getJson(file);
        this.type = type;
    }

    protected T newTypedInstance() {
        try {
            return MAPPER.readValue(json, type);
        } catch (Exception e) {
            throw Throwables.propagate(e);
        }
    }

    // utility method to read the file, and throw RTE if there is a problem
    private String getJson(String file) {
        try {
            return Resources.toString(Resources.getResource(file), Charsets.UTF_8);
        } catch (IOException e) {
            throw Throwables.propagate(e);
        }
    }

}