org.sonar.server.util.cache.DiskCache.java Source code

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Here is the source code for org.sonar.server.util.cache.DiskCache.java

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/*
 * SonarQube
 * Copyright (C) 2009-2017 SonarSource SA
 * mailto:info AT sonarsource DOT com
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */
package org.sonar.server.util.cache;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.io.Serializable;
import org.apache.commons.io.FileUtils;
import org.apache.commons.io.IOUtils;
import org.sonar.api.utils.System2;
import org.sonar.core.util.CloseableIterator;
import org.sonar.server.util.ObjectInputStreamIterator;

/**
 * Serialize and deserialize objects on disk. No search capabilities, only traversal (full scan).
 */
public class DiskCache<O extends Serializable> {

    private final File file;
    private final System2 system2;

    public DiskCache(File file, System2 system2) {
        this.system2 = system2;
        this.file = file;
        OutputStream output = null;
        boolean threw = true;
        try {
            // writes the serialization stream header required when calling "traverse()"
            // on empty stream. Moreover it allows to call multiple times "newAppender()"
            output = new ObjectOutputStream(new FileOutputStream(file));
            output.flush();
            threw = false;
        } catch (IOException e) {
            throw new IllegalStateException("Fail to write into file: " + file, e);
        } finally {
            if (threw) {
                // do not hide initial exception
                IOUtils.closeQuietly(output);
            } else {
                // raise an exception if can't close
                system2.close(output);
            }
        }
    }

    public DiskAppender newAppender() {
        return new DiskAppender();
    }

    public CloseableIterator<O> traverse() {
        try {
            return new ObjectInputStreamIterator<>(FileUtils.openInputStream(file));
        } catch (IOException e) {
            throw new IllegalStateException("Fail to traverse file: " + file, e);
        }
    }

    public class DiskAppender implements AutoCloseable {
        private final ObjectOutputStream output;

        private DiskAppender() {
            try {
                this.output = new ObjectOutputStream(new FileOutputStream(file, true)) {
                    @Override
                    protected void writeStreamHeader() throws IOException {
                        // do not write stream headers as it's already done in constructor of DiskCache
                    }
                };
            } catch (IOException e) {
                throw new IllegalStateException("Fail to open file " + file, e);
            }
        }

        public DiskAppender append(O object) {
            try {
                output.writeObject(object);
                output.reset();
                return this;
            } catch (IOException e) {
                throw new IllegalStateException("Fail to write into file " + file, e);
            }
        }

        @Override
        public void close() {
            system2.close(output);
        }
    }
}