Apache Commons DbUtils

Commons DbUtils包含一组的JDBC辅助类，用来简化JDBC操作。

 

下面用一些简单的例子来演示几个主要类的用法：

 

BasicRowProcessor可以用来处理查询结果集（ResultSet），它可以将ResultSet的一行装换为数组、javabean或Map（键值分别是字段名称和字段值），也可以将整个ResultSet装换为一组javabean。

 

下面一个例子演示BasicRowProcessor的用法：

 

package com.test.dbutils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Arrays;
import java.util.List;
import java.util.Map;

import org.apache.commons.dbutils.BasicRowProcessor;
import org.apache.commons.dbutils.DbUtils;
import org.apache.commons.dbutils.QueryRunner;

import com.test.bean.Person;
import com.test.utils.DatabaseUtils;

/**
 * {@link org.apache.commons.dbutils.BasicRowProcessor}
 */
public class TestBasicRowProcessor {
	private static BasicRowProcessor processor = new BasicRowProcessor();

	public static void main(String[] args) throws Exception {
		DatabaseUtils.prepare();
		prepareData();

		Connection connection = DatabaseUtils.getConnection();
		String sql = "select * from person";
		ResultSet resultSet = connection.createStatement().executeQuery(sql);

		/**
		 * {@link org.apache.commons.dbutils.BasicRowProcessor#toArray(ResultSet)}
		 */
		System.out.println("toArray()");
		testToArray(resultSet);
		System.out.println();

		/**
		 * {@link org.apache.commons.dbutils.BasicRowProcessor#toBean(ResultSet, Class)}
		 */
		resultSet.beforeFirst();
		System.out.println("toBean()");
		testToBean(resultSet);
		System.out.println();

		/**
		 * {@link org.apache.commons.dbutils.BasicRowProcessor#toBeanList(ResultSet, Class)}
		 */
		resultSet.beforeFirst();
		System.out.println("toBeanList()");
		testToBeanList(resultSet);
		System.out.println();

		/**
		 * {@link org.apache.commons.dbutils.BasicRowProcessor#toMap(ResultSet)}
		 */
		resultSet.beforeFirst();
		System.out.println("toMap()");
		testToMap(resultSet);
		System.out.println();

		DbUtils.close(connection);
	}

	/**
	 * @throws Exception
	 */
	private static void prepareData() throws SQLException {
		Connection connection = DatabaseUtils.getConnection();
		connection.setAutoCommit(false);

		String sql = "insert into person(id, name, age) values(?, ?, ?)";
		Object[][] params = new Object[][] { { "id1", "name1", 20 },
				{ "id2", "name2", 25 }, { "id3", "name3", 30 } };
		try {
			QueryRunner runner = new QueryRunner();
			runner.batch(connection, sql, params);
			DbUtils.commitAndClose(connection);
		} catch (SQLException e) {
			DbUtils.rollbackAndClose(connection);
			throw e;
		}
	}

	/**
	 * {@link org.apache.commons.dbutils.BasicRowProcessor#toArray(ResultSet)}
	 * 
	 * @throws Exception
	 */
	private static void testToArray(ResultSet resultSet) throws SQLException {
		while (resultSet.next()) {
			System.out.println(Arrays.toString(processor.toArray(resultSet)));
		}
	}

	/**
	 * {@link org.apache.commons.dbutils.BasicRowProcessor#toBean(ResultSet, Class)}
	 * 
	 * @throws Exception
	 */
	private static void testToBean(ResultSet resultSet) throws SQLException {
		while (resultSet.next()) {
			System.out.println(processor.toBean(resultSet, Person.class));
		}
	}

	/**
	 * {@link org.apache.commons.dbutils.BasicRowProcessor#toBeanList(ResultSet, Class)}
	 * 
	 * @throws Exception
	 */
	private static void testToBeanList(ResultSet resultSet) throws SQLException {
		List<Person> list = processor.toBeanList(resultSet, Person.class);
		System.out.println(Arrays.toString(list.toArray()));
	}

	/**
	 * {@link org.apache.commons.dbutils.BasicRowProcessor#toMap(ResultSet)}
	 * 
	 * @throws Exception
	 */
	private static void testToMap(ResultSet resultSet) throws SQLException {
		while (resultSet.next()) {
			Map<String, Object> map = processor.toMap(resultSet);
			System.out.println(map.toString());
		}
	}
}

 

另一个重要的类是QueryRunner，这个类提供了一组JDBC操作辅助方法。使用QueryRunner，我们在执行sql命令时就不需要显示地创建和关闭Connection、Statement、ResultSet等对象，只需要提供sql命令、参数（和ResultSetHandler的实现类来处理查询时返回的结果集）给相应的方法，用起来非常方便。

 

在org.apache.commons.dbutils.handlers包中有多个ResultSetHandler的实现类，用来对查询返回的ResultSet进行处理。

 

下面用一个例子演示QueryRunner的和一些ResultSetHandler实现类的用法：

 

package com.test.dbutils;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.Arrays;
import java.util.List;
import java.util.Map;

import org.apache.commons.dbutils.DbUtils;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.ResultSetHandler;
import org.apache.commons.dbutils.handlers.ArrayHandler;
import org.apache.commons.dbutils.handlers.ArrayListHandler;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ColumnListHandler;
import org.apache.commons.dbutils.handlers.KeyedHandler;
import org.apache.commons.dbutils.handlers.MapHandler;
import org.apache.commons.dbutils.handlers.MapListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

import com.test.bean.Person;
import com.test.utils.DatabaseUtils;

/**
 * {@link org.apache.commons.dbutils.QueryRunner}
 */
public class TestQueryRunner {
	private static QueryRunner runner = new QueryRunner();

	public static void main(String[] args) throws Exception {
		DatabaseUtils.prepare();
		testBatch();
		testUpdate();
		testQuery();
	}

	/**
	 * {@link org.apache.commons.dbutils.QueryRunner#batch(Connection, String, Object[][])}
	 * 
	 * @throws Exception
	 */
	private static void testBatch() throws SQLException {
		Connection connection = DatabaseUtils.getConnection();
		connection.setAutoCommit(false);

		String sql = "insert into person(id, name, age) values(?, ?, ?)";
		Object[][] params = new Object[][] { { "id1", "name1", 20 },
				{ "id2", "name2", 25 } };

		try {
			runner.batch(connection, sql, params);
			DbUtils.commitAndClose(connection);
		} catch (SQLException e) {
			DbUtils.rollbackAndClose(connection);
			throw e;
		}
	}

	/**
	 * {@link org.apache.commons.dbutils.QueryRunner#update(Connection, String, Object...)}
	 * 
	 * @throws Exception
	 */
	private static void testUpdate() throws SQLException {
		Connection connection = DatabaseUtils.getConnection();
		connection.setAutoCommit(false);

		String sql = "update person set name = ?, age = ? where id = ?";
		Object[] params = new Object[] { "name3", 30, "id2" };

		try {
			runner.update(connection, sql, params);
			DbUtils.commitAndClose(connection);
		} catch (SQLException e) {
			DbUtils.rollbackAndClose(connection);
			throw e;
		}
	}

	/**
	 * {@link org.apache.commons.dbutils.QueryRunner#query(Connection, String, ResultSetHandler)}
	 * 
	 * @throws Exception
	 */
	private static void testQuery() throws SQLException {
		Connection connection = DatabaseUtils.getConnection();
		String sql = "select * from person";

		/**
		 * {@link org.apache.commons.dbutils.handlers.ArrayHandler }
		 */
		Object[] array = runner.query(connection, sql, new ArrayHandler());
		print(ArrayHandler.class, Arrays.toString(array));

		/**
		 * {@link org.apache.commons.dbutils.handlers.ArrayListHandler }
		 */
		List<Object[]> arrayList = runner.query(connection, sql,
				new ArrayListHandler());
		print(ArrayListHandler.class, toString(arrayList));

		/**
		 * {@link org.apache.commons.dbutils.handlers.BeanHandler }
		 */
		Person person = runner.query(connection, sql, new BeanHandler<Person>(
				Person.class));
		print(BeanHandler.class, person.toString());

		/**
		 * {@link org.apache.commons.dbutils.handlers.BeanListHandler }
		 */
		List<Person> personList = runner.query(connection, sql,
				new BeanListHandler<Person>(Person.class));
		print(BeanListHandler.class, Arrays.toString(personList.toArray()));

		/**
		 * {@link org.apache.commons.dbutils.handlers.ColumnListHandler }
		 */
		List<Object> list = runner.query(connection, sql,
				new ColumnListHandler("name"));
		print(ColumnListHandler.class, Arrays.toString(list.toArray()));

		/**
		 * {@link org.apache.commons.dbutils.handlers.KeyedHandler }
		 */
		Map<Object, Map<String, Object>> keyedMap = runner.query(connection,
				sql, new KeyedHandler());
		print(KeyedHandler.class, keyedMap.toString());

		/**
		 * {@link org.apache.commons.dbutils.handlers.MapHandler }
		 */
		Map<String, Object> map = runner.query(connection, sql,
				new MapHandler());
		print(MapHandler.class, map.toString());

		/**
		 * {@link org.apache.commons.dbutils.handlers.MapListHandler }
		 */
		List<Map<String, Object>> mapList = runner.query(connection, sql,
				new MapListHandler());
		print(MapListHandler.class, Arrays.toString(mapList.toArray()));

		/**
		 * {@link org.apache.commons.dbutils.handlers.ScalarHandler }
		 */
		Object object = runner
				.query(connection, sql, new ScalarHandler("name"));
		print(ScalarHandler.class, object.toString());

		DbUtils.close(connection);
	}

	public static void print(Class<?> clazz, String str) {
		System.out.println(clazz.getName());
		System.out.println(str);
		System.out.println();
	}

	private static String toString(List<Object[]> arrayList) {
		String[] rows = new String[arrayList.size()];
		for (int i = 0; i != arrayList.size(); ++i) {
			rows[i] = Arrays.toString(arrayList.get(i));
		}
		return Arrays.toString(rows);
	}
}

 

还有两个很有用的类：QueryLoader和DbUtils。QueryLoader用来将properties文件中的sql加载到内存中（保存到一个Map中），然后可以通过键值获得对应的sql；DbUtils中提供了一组静态方法，用于完成关闭Connection、提交或回滚事务、打印异常等工作。