org.xflatdb.xflat.ShardsetConfig.java Source code

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Here is the source code for org.xflatdb.xflat.ShardsetConfig.java

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/* 
*   Copyright 2013 Gordon Burgett and individual contributors
*
*   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.xflatdb.xflat;

import org.xflatdb.xflat.query.IntervalProvider;
import org.jdom2.xpath.XPathExpression;
import org.jdom2.xpath.XPathFactory;
import org.xflatdb.xflat.query.XPathQuery;
import org.xflatdb.xflat.util.XPathExpressionEqualityMatcher;

/**
 * Represents the configuration for a sharded table.  A sharded table is one which
 * splits its data up among several files.
 * @author Gordon
 */
public class ShardsetConfig<T> {

    private ShardsetConfig() {

    }

    private ShardsetConfig(ShardsetConfig other) {
        this.shardPropertyClass = other.shardPropertyClass;
        this.shardPropertySelector = other.shardPropertySelector;
        this.intervalProvider = other.intervalProvider;

    }

    private Class<T> shardPropertyClass;

    /**
     * Gets the class to which the string value of the property selected by the
     * shard property selector must be convertible.  The converted value is fed
     * to the Interval Provider to determine the correct shard for a data row.
     */
    public Class<T> getShardPropertyClass() {
        return shardPropertyClass;
    }

    private XPathExpression<?> shardPropertySelector;

    /**
     * Gets the XPath expression that selects a property of a row which determines
     * the shard where the row will be placed.
     */
    public XPathExpression<?> getShardPropertySelector() {
        return shardPropertySelector;
    }

    private IntervalProvider<T> intervalProvider;

    /**
     * Gets the interval provider used to choose which shard a row will be placed in.
     */
    public IntervalProvider<T> getIntervalProvider() {
        return intervalProvider;
    }

    private boolean isId = false;

    /**
     * Gets a flag indicating whether the shard property selector is the {@link org.xflatdb.xflat.query.XPathQuery#Id} expression.
     */
    public boolean isShardedById() {
        return this.isId;
    }

    /**
     * Creates a ShardsetConfig describing a table sharded by ID.  The shard selector
     * will use the {@link XPathQuery#Id} expression.
     * @param <U> The generic type of the ID property; all objects in the table must have the same property.
     * @param idClass The class of the property selected by the xpath expression.
     * @param idIntervalProvider A IntervalProvider that determines the static ranges for the
     * property, each range will have its own file.
     * @return A new shardset config.
     */
    public static <U> ShardsetConfig<U> byId(Class<U> idClass, IntervalProvider<U> idIntervalProvider) {
        if (idClass == null) {
            throw new IllegalArgumentException("idClass cannot be null");
        }
        if (idIntervalProvider == null) {
            throw new IllegalArgumentException("idIntervalProvider cannot be null");
        }

        ShardsetConfig<U> ret = new ShardsetConfig<>();
        ret.shardPropertySelector = XPathQuery.Id;
        ret.shardPropertyClass = idClass;
        ret.intervalProvider = idIntervalProvider;
        ret.isId = true;

        return ret;
    }

    /**
     * Creates a ShardsetConfig with the minimum configuration necessary for static-range sharding.
     * The remainder can be left default or set as desired.
     * @param <U> The generic type of the ID property; all objects in the table must have the same property.
     * @param xpathProperty An XPath expression selecting a property of the data to shard on.
     * @param propertyClass The class of the property selected by the xpath expression.
     * @param intervalProvider A IntervalProvider that determines the static ranges for the
     * property, each range will have its own file.
     * @return A new shardset config.
     */
    public static <U> ShardsetConfig<U> by(String xpathProperty, Class<U> propertyClass,
            IntervalProvider<U> intervalProvider) {
        return by(XPathFactory.instance().compile(xpathProperty), propertyClass, intervalProvider);
    }

    /**
     * Creates a ShardsetConfig with the minimum configuration necessary for static-range sharding.
     * The remainder can be left default or set as desired.
     * @param <U> The generic type of the ID property; all objects in the table must have the same property.
     * @param xpathProperty An XPath expression selecting a property of the data to shard on.
     * @param propertyClass The class of the property selected by the xpath expression.
     * @param intervalProvider An {@link IntervalProvider} that determines the static ranges for the
     * property, each range will have its own file.
     * @return A new shardset config.
     */
    public static <U> ShardsetConfig<U> by(XPathExpression<?> xpathProperty, Class<U> propertyClass,
            IntervalProvider<U> intervalProvider) {
        if (xpathProperty == null) {
            throw new IllegalArgumentException("xpathProperty cannot be null");
        }
        if (propertyClass == null) {
            throw new IllegalArgumentException("propertyClass cannot be null");
        }
        if (intervalProvider == null) {
            throw new IllegalArgumentException("intervalProvider cannot be null");
        }

        ShardsetConfig<U> ret = new ShardsetConfig<>();
        ret.shardPropertySelector = xpathProperty;
        ret.shardPropertyClass = propertyClass;
        ret.intervalProvider = intervalProvider;

        if (XPathExpressionEqualityMatcher.equals(xpathProperty, XPathQuery.Id)) {
            ret.isId = true;
        }

        return ret;
    }
}