com.victorjabur.springbatch.partitioner.ColumnRangePartitioner.java Source code

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Here is the source code for com.victorjabur.springbatch.partitioner.ColumnRangePartitioner.java

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/*
 * Copyright 2009-2014 the original author or authors.
 *
 * 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 com.victorjabur.springbatch.partitioner;

import java.util.HashMap;
import java.util.Map;

import javax.sql.DataSource;

import org.springframework.batch.core.partition.support.Partitioner;
import org.springframework.batch.item.ExecutionContext;
import org.springframework.jdbc.core.JdbcOperations;
import org.springframework.jdbc.core.JdbcTemplate;

/**
 * Simple minded partitioner for a range of values of a column in a database
 * table. Works best if the values are uniformly distributed (e.g.
 * auto-generated primary key values).
 *
 * @author Dave Syer
 *
 */
public class ColumnRangePartitioner implements Partitioner {

    private JdbcOperations jdbcTemplate;

    private String table;

    private String column;

    /**
     * The name of the SQL table the data are in.
     *
     * @param table the name of the table
     */
    public void setTable(String table) {
        this.table = table;
    }

    /**
     * The name of the column to partition.
     *
     * @param column the column name.
     */
    public void setColumn(String column) {
        this.column = column;
    }

    /**
     * The data source for connecting to the database.
     *
     * @param dataSource a {@link DataSource}
     */
    public void setDataSource(DataSource dataSource) {
        jdbcTemplate = new JdbcTemplate(dataSource);
    }

    /**
     * Partition a database table assuming that the data in the column specified
     * are uniformly distributed. The execution context values will have keys
     * <code>minValue</code> and <code>maxValue</code> specifying the range of
     * values to consider in each partition.
     *
     * @see Partitioner#partition(int)
     */
    @Override
    public Map<String, ExecutionContext> partition(int gridSize) {
        int min = jdbcTemplate.queryForObject("SELECT MIN(" + column + ") from " + table, Integer.class);
        int max = jdbcTemplate.queryForObject("SELECT MAX(" + column + ") from " + table, Integer.class);
        int targetSize = (max - min) / gridSize + 1;

        Map<String, ExecutionContext> result = new HashMap<String, ExecutionContext>();
        int number = 0;
        int start = min;
        int end = start + targetSize - 1;

        while (start <= max) {
            ExecutionContext value = new ExecutionContext();
            result.put("partition" + number, value);

            if (end >= max) {
                end = max;
            }
            value.putInt("minValue", start);
            value.putInt("maxValue", end);
            start += targetSize;
            end += targetSize;
            number++;
        }

        return result;
    }
}