commons.dbutils1.2介绍及使用

一、结构介绍

高层结构图：

wrappers包：

handlers包（部分）:

二、功能介绍

commons.dbutils是一个对JDBC操作进行封装的类集，其有如下几个优点：

（1）没有可能的资源泄漏，避免了繁锁的JDBC代码

（2）代码更整洁

（3）从ResultSet自动生成JavaBeans属性

（4）无其他依赖包

三、基本使用

基本用到的类有：QueryRunner、ResultSetHandler及其子类等

QueryRunner -- 执行查询的类，可以执行SELECT、INSERT、UPDATE、DELETE等语句，QueryRunner用ResultSetHandler的子类来处理ResultSet并返回结果；而包提供的ResultSetHandler子类使用RowProcessor的子类来处理ResultSet中的每一行；RowProcessor的默认实现为BasicRowProcessor；BeanProcessor不是RowProcessor，可以看作一个工具类

ResultHandler及其子类 -- 实现了Object handle(ResultSet rs) throws SQLException方法

AbstractListHandler -- 返回多行List的抽象类

ArrayHandler -- 返回一行的Object[]

ArrayListHandler -- 返回List，每行是Object[]

BeanHandler -- 返回第一个Bean对象

BeanListHandler -- 返回List，每行是Bean

ColumnListHandler -- 返回一列的List

KeyedHandler -- 返回Map，具体见代码

MapHandler -- 返回单个Map

MapListHandler -- 返回List，每行是Map

ScalarHandler -- 返回列的头一个值

代码：

//建表语句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;表中数据'user1', 'pwd1''user2', 'pwd2'//User类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 } } }}

关于wrappers包:

在新建QueryRunner时，覆盖父类的方法wrap

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

四、扩展

1.RowProcessor接口

2.ResultSetHandler接口

一、结构介绍

二、功能介绍

三、基本使用

四、扩展

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