com.linuxbox.util.dbmigration.AbstractColletionMigrator.java Source code

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Here is the source code for com.linuxbox.util.dbmigration.AbstractColletionMigrator.java

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/*******************************************************************************
 * Copyright 2013 The Linux Box Corporation.
 *
 * This file is part of Enkive CE (Community Edition).
 *
 * Enkive CE is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version.
 *
 * Enkive CE 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public
 * License along with Enkive CE. If not, see
 * <http://www.gnu.org/licenses/>.
 *******************************************************************************/
package com.linuxbox.util.dbmigration;

import java.util.Collection;
import java.util.Map;

import com.mongodb.BasicDBObject;
import com.mongodb.DBCollection;

/**
 * Abstract base class for migrating a MongoDB collection  It provides 2 main
 * services, before calling the implementation: removing and renaming fields.
 * First, a list of dead fields is removed from every document in the collection.
 * Next, a map of <old-name, new-name> pairs is run, where each old-name is
 * renamed to it's new-name.  Finally, the child class's implementation is
 * called to do complex work.
 * @author dang
 *
 */
public abstract class AbstractColletionMigrator {
    protected DBCollection collection;
    protected Collection<String> deadFields;
    protected Map<String, String> renamedFields;

    public AbstractColletionMigrator(DBCollection collection) {
        this.collection = collection;
    }

    public void setDeadFields(Collection<String> deadFields) {
        this.deadFields = deadFields;
    }

    public Collection<String> getDeadFields() {
        return this.deadFields;
    }

    /**
     * Set the map of fields to rename.  For each entry, the field represented by
     * key() is renamed to value().
     * @param renamedFields
     */
    public void setRenamedFields(Map<String, String> renamedFields) {
        this.renamedFields = renamedFields;
    }

    public Map<String, String> getRenamedFields() {
        return this.renamedFields;
    }

    public void migrateCollection() throws DbMigrationException {
        migrateFields();
        migrateCollectionImpl();
    }

    /**
     * Class specific migration code
     * @throws DbMigrationException
     */
    public abstract void migrateCollectionImpl() throws DbMigrationException;

    private void migrateFields() throws DbMigrationException {
        // Remove all dead fields
        if (deadFields != null) {
            for (String deadField : deadFields) {
                collection.update(new BasicDBObject(), new BasicDBObject("$unset", new BasicDBObject(deadField, 1)),
                        false, true);
            }
        }

        // Rename changed fields
        if (renamedFields != null) {
            BasicDBObject rename = new BasicDBObject();
            for (Map.Entry<String, String> entry : renamedFields.entrySet()) {
                rename.append(entry.getKey(), entry.getValue());
            }
            collection.update(new BasicDBObject(), new BasicDBObject("$rename", rename), true, true);
        }
    }
}