一、結構介紹

高層結構圖：

wrappers包：

handlers包（部分）:

二、功能介紹

commons.dbutils是一個對JDBC操作進行封裝的類集，其有如下幾個優點：

（1）沒有可能的資源泄漏，避免了繁鎖的JDBC代碼

（2）代碼更整潔

（3）從ResultSet自動生成JavaBeans屬性

（4）無其他依賴包

三、基本使用

基本用到的類有：QueryRunner、ResultSetHandler及其子類等

QueryRunner -- 執行查詢的類，可以執行SELECT、INSERT、UPDATE、DELETE等語句，QueryRunner用ResultSetHandler的子類來處理ResultSet並返回結果；而包提供的ResultSetHandler子類使用RowProcessor的子類來處理ResultSet中的每一行；RowProcessor的默認實現為BasicRowProcessor；BeanProcessor不是RowProcessor，可以看作一個工具類

ResultHandler及其子類 -- 實現了Object handle(ResultSet rs) throws SQLException方法

AbstractListHandler -- 返回多行List的抽象類

ArrayHandler --  返回一行的Object[]

ArrayListHandler -- 返回List，每行是Object[]

BeanHandler -- 返回第一個Bean對象

BeanListHandler -- 返回List，每行是Bean

ColumnListHandler -- 返回一列的List

KeyedHandler -- 返回Map，具體見代碼

MapHandler -- 返回單個Map

MapListHandler -- 返回List，每行是Map

ScalarHandler -- 返回列的頭一個值

代碼：

//建表語句DROP TABLE IF EXISTS `test`.`user`;CREATE TABLE `test`.`user` ( `name` varchar(10) DEFAULT NULL, `password` varchar(10) DEFAULT NULL) ENGINE=MyISAM DEFAULT CHARSET=latin1;表中數據'user1', 'pwd1''user2', 'pwd2'//User類public class User { private String name; private String pwd; public User(){ } public void setName(String val) { this.name = val; } public void setPassword(String val) { this.pwd = val; } public String getName() { return name; } public String getPassword() { return pwd; }}

package dbutiltest;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;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.MapListHandler;public class TestDbUtils { static { try { Class.forName("org.gjt.mm.mysql.Driver"); } catch (ClassNotFoundException e) { e.printStackTrace(); System.exit(1); } } public Connection getConnection() { Connection conn = null; try { conn = DriverManager.getConnection( "jdbc:mysql://localhost:3306/test", "root", "pwd"); } catch (SQLException e) { e.printStackTrace(); } return conn; } public static void main(String[] args) { TestDbUtils u = new TestDbUtils(); u.testArrayHandler(); u.testArrayListHandler(); u.testBeanListHandler(); u.testMapListHandler(); u.testColumnListHandler(); u.testNonQuery(); } public void testArrayHandler() { System.out.println("----testArrayHandler----"); String sql = "select * from user"; ResultSetHandler handler = new ArrayHandler(); QueryRunner query = new QueryRunner(); Connection conn = null; try { conn = getConnection(); Object[] arr = (Object[])query.query(conn, sql, handler); for (int i = 0; i < arr.length; i++) { System.out.println(arr[i].toString()); } } catch (SQLException e) { e.printStackTrace(); } finally { try { DbUtils.close(conn); } catch (SQLException e) { // ignore } } } public void testArrayListHandler() { System.out.println("----testArrayListHandler----"); String sql = "select * from user"; ResultSetHandler handler = new ArrayListHandler(); QueryRunner query = new QueryRunner(); Connection conn = null; try { conn = getConnection(); List list = (List)query.query(conn, sql, handler); for (int i = 0; i < list.size(); i++) { Object[] arr = (Object[])list.get(i); for (int j = 0; j < arr.length; j++) { System.out.print(arr[j] + " "); } System.out.println(); } } catch (SQLException e) { e.printStackTrace(); } finally { try { DbUtils.close(conn); } catch (SQLException e) { // ignore } } } public void testBeanListHandler() { System.out.println("----testBeanListHandler----"); String sql = "select * from user where name=?"; Object[] params = new Object[]{"user1"}; ResultSetHandler handler = new BeanListHandler(User.class); QueryRunner query = new QueryRunner(); Connection conn = null; try { conn = getConnection(); List list = (List)query.query(conn, sql, params, handler); for (int i = 0; i < list.size(); i++) { User user = (User)list.get(i); System.out.println(user.getName() + " " + user.getPassword()); } } catch (SQLException e) { e.printStackTrace(); } finally { try { DbUtils.close(conn); } catch (SQLException e) { // ignore } } } public void testMapListHandler() { System.out.println("----testMapListHandler----"); String sql = "select * from user where name=?"; Object[] params = new Object[]{"user1"}; ResultSetHandler handler = new MapListHandler(); QueryRunner query = new QueryRunner(); Connection conn = null; try { conn = getConnection(); List list = (List)query.query(conn, sql, params, handler); for (int i = 0; i < list.size(); i++) { Map user = (Map)list.get(i); System.out.println(user.get("name") + " " + user.get("password")); } } catch (SQLException e) { e.printStackTrace(); } finally { try { DbUtils.close(conn); } catch (SQLException e) { // ignore } } } public void testColumnListHandler() { System.out.println("----testColumnListHandler----"); String sql = "select * from user"; ResultSetHandler handler = new ColumnListHandler("name"); QueryRunner query = new QueryRunner(); Connection conn = null; try { conn = getConnection(); List list = (List)query.query(conn, sql, handler); for (int i = 0; i < list.size(); i++) { System.out.println(list.get(i)); } } catch (SQLException e) { e.printStackTrace(); } finally { try { DbUtils.close(conn); } catch (SQLException e) { // ignore } } } public void testKeyedHandler() { System.out.println("----testKeyedHandler----"); String sql = "select * from user"; ResultSetHandler handler = new KeyedHandler("name"); QueryRunner query = new QueryRunner(); Connection conn = null; try { conn = getConnection(); Map map = (Map)query.query(conn, sql, handler); Map user = (Map)map.get("user2"); System.out.println(user.get("password")); } catch (SQLException e) { e.printStackTrace(); } finally { try { DbUtils.close(conn); } catch (SQLException e) { // ignore } } } public void testNonQuery() { System.out.println("----testNonQuery----"); String sql = "insert into `user` values('user_test','pwd_test')"; QueryRunner query = new QueryRunner(); Connection conn = null; try { conn = getConnection(); query.update(conn, sql); } catch (SQLException e) { e.printStackTrace(); } finally { try { DbUtils.close(conn); } catch (SQLException e) { // ignore } } }}

關於wrappers包:

在新建QueryRunner時，覆蓋父類的方法wrap

QueryRunner query = new QueryRunner() { protected ResultSet wrap(ResultSet rs) { return StringTrimmedResultSet.wrap(rs); } };

四、擴展

1.RowProcessor接口

2.ResultSetHandler接口