org.eclipse.packagedrone.storage.apm.AbstractSimpleGsonStorageModelProvider.java Source code

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Here is the source code for org.eclipse.packagedrone.storage.apm.AbstractSimpleGsonStorageModelProvider.java

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/*******************************************************************************
 * Copyright (c) 2016 IBH SYSTEMS GmbH and others.
 * 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:
 *     IBH SYSTEMS GmbH - initial API and implementation
 *******************************************************************************/
package org.eclipse.packagedrone.storage.apm;

import java.io.Reader;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.NoSuchFileException;
import java.nio.file.Path;
import java.time.Instant;

import org.eclipse.packagedrone.storage.apm.util.ReplaceOnCloseWriter;
import org.eclipse.packagedrone.utils.gson.InstantTypeAdapter;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

/**
 * An abstract base for creating storage model providers which are based on a
 * simple JSON model
 *
 * @param <V>
 *            the view model
 * @param <W>
 *            the write model
 * @param <G>
 *            the GSON persistence model
 */
public abstract class AbstractSimpleGsonStorageModelProvider<V, W, G>
        extends AbstractSimpleStorageModelProvider<V, W> {
    protected final Class<G> gsonModelClass;

    public AbstractSimpleGsonStorageModelProvider(final Class<W> writeClazz, final Class<G> gsonModelClass) {
        super(writeClazz);
        this.gsonModelClass = gsonModelClass;
    }

    @Override
    protected void persistWriteModel(final StorageContext context, final W writeModel) throws Exception {
        try (ReplaceOnCloseWriter writer = new ReplaceOnCloseWriter(makePath(context), StandardCharsets.UTF_8)) {
            createGson().toJson(toGsonModel(writeModel), writer);
            writer.commit();
        }
    }

    protected abstract G toGsonModel(final W writeModel);

    protected abstract W fromGsonModel(final G gsonModel);

    protected Gson createGson() {
        final GsonBuilder gb = new GsonBuilder();

        gb.setPrettyPrinting();
        gb.registerTypeAdapter(Instant.class, InstantTypeAdapter.DEFAULT_INSTANCE);

        return gb.create();
    }

    @Override
    protected W loadWriteModel(final StorageContext context) throws Exception {
        try (Reader reader = Files.newBufferedReader(makePath(context))) {
            return fromGsonModel(createGson().fromJson(reader, this.gsonModelClass));
        } catch (final NoSuchFileException e) {
            return createNewModel();
        }
    }

    protected abstract W createNewModel();

    protected abstract Path makePath(final StorageContext context);
}