spring-batch ColumnRangePartitioner 源码
spring-batch ColumnRangePartitioner 代码
文件路径：/spring-batch-samples/src/main/java/org/springframework/batch/sample/common/ColumnRangePartitioner.java
/*
* 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
*
* https://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.springframework.batch.sample.common;
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<>();
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;
}
}
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