org.apache.commons.dbutils.handlers.BeanMapHandler Maven / Gradle / Ivy
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.commons.dbutils.handlers;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.apache.commons.dbutils.RowProcessor;
/**
*
* ResultSetHandler implementation that returns a Map of Beans.
* ResultSet rows are converted into Beans which are then stored in
* a Map under the given key.
*
*
* If you had a Person table with a primary key column called ID, you could
* retrieve rows from the table like this:
*
*
* ResultSetHandler<Map<Long, Person>> h = new BeanMapHandler<Long, Person>(Person.class, "id");
* Map<Long, Person> found = queryRunner.query("select id, name, age from person", h);
* Person jane = found.get(1L); // jane's id is 1
* String janesName = jane.getName();
* Integer janesAge = jane.getAge();
*
*
* Note that the "id" passed to BeanMapHandler can be in any case. The data type
* returned for id is dependent upon how your JDBC driver converts SQL column
* types from the Person table into Java types. The "name" and "age" columns are
* converted according to their property descriptors by DbUtils.
* </p>
*
* This class is thread safe.
* </p>
*
* @param
* the type of keys maintained by the returned map
* @param
* the type of the bean
* @see org.apache.commons.dbutils.ResultSetHandler
* @since DbUtils 1.5
*/
public class BeanMapHandler extends AbstractKeyedHandler {
/**
* The Class of beans produced by this handler.
*/
private final Class type;
/**
* The RowProcessor implementation to use when converting rows into Objects.
*/
private final RowProcessor convert;
/**
* The column index to retrieve key values from. Defaults to 1.
*/
private final int columnIndex;
/**
* The column name to retrieve key values from. Either columnName or
* columnIndex will be used but never both.
*/
private final String columnName;
/**
* Creates a new instance of BeanMapHandler. The value of the first column
* of each row will be a key in the Map.
*
* @param type
* The Class that objects returned from createRow()
* are created from.
*/
public BeanMapHandler(Class type) {
this(type, ArrayHandler.ROW_PROCESSOR, 1, null);
}
/**
* Creates a new instance of BeanMapHandler. The value of the first column
* of each row will be a key in the Map.
*
* @param type
* The Class that objects returned from createRow()
* are created from.
* @param convert
* The RowProcessor implementation to use when
* converting rows into Beans
*/
public BeanMapHandler(Class type, RowProcessor convert) {
this(type, convert, 1, null);
}
/**
* Creates a new instance of BeanMapHandler.
*
* @param type
* The Class that objects returned from createRow()
* are created from.
* @param columnIndex
* The values to use as keys in the Map are retrieved from the
* column at this index.
*/
public BeanMapHandler(Class type, int columnIndex) {
this(type, ArrayHandler.ROW_PROCESSOR, columnIndex, null);
}
/**
* Creates a new instance of BeanMapHandler.
*
* @param type
* The Class that objects returned from createRow()
* are created from.
* @param columnName
* The values to use as keys in the Map are retrieved from the
* column with this name.
*/
public BeanMapHandler(Class type, String columnName) {
this(type, ArrayHandler.ROW_PROCESSOR, 1, columnName);
}
/**
* Private Helper
*
* @param convert
* The RowProcessor implementation to use when
* converting rows into Beans
* @param columnIndex
* The values to use as keys in the Map are retrieved from the
* column at this index.
* @param columnName
* The values to use as keys in the Map are retrieved from the
* column with this name.
*/
private BeanMapHandler(Class type, RowProcessor convert,
int columnIndex, String columnName) {
super();
this.type = type;
this.convert = convert;
this.columnIndex = columnIndex;
this.columnName = columnName;
}
/**
* This factory method is called by handle() to retrieve the
* key value from the current ResultSet row.
* @param rs ResultSet to create a key from
*
* @return K from the configured key column name/index
*
* @throws SQLException if a database access error occurs
* @throws ClassCastException if the class datatype does not match the column type
*
* @see org.apache.commons.dbutils.handlers.AbstractKeyedHandler#createKey(ResultSet)
*/
// We assume that the user has picked the correct type to match the column
// so getObject will return the appropriate type and the cast will succeed.
@SuppressWarnings("unchecked")
@Override
protected K createKey(ResultSet rs) throws SQLException {
return (columnName == null) ?
(K) rs.getObject(columnIndex) :
(K) rs.getObject(columnName);
}
@Override
protected V createRow(ResultSet rs) throws SQLException {
return this.convert.toBean(rs, type);
}
}