JavaWeb之DButils整理

一、DBUtils介绍  apache

什么是dbutils，它的作用

DBUtils是java编程中的数据库操作实用工具，小巧简单实用。

用前导包！！！DBUtils包！！！

二、DBUtils的三个核心对象

> QueryRunner类

>ResultSetHandler接口

> DBUtils类

QueryRunner类

QueryRunner中提供对sql语句操作的API.

它主要有三个方法

query() 用于执行select

update() 用于执行insert update delete

batch() 批处理

ResultSetHandler接口

用于定义select操作后，怎样封装结果集.

DbUtils类

它就是一个工具类,定义了关闭资源与事务处理的方法

三、QueryRunner对象

1.1 构造函数：

> new QueryRunner(); 它的事务可以手动控制。

也就是说此对象调用的方法（如：query、update、batrch）参数中要有Connection对象。

> new QueryRunner(DataSource ds); 它的事务是自动控制的。一个sql一个事务。
              此对象调用的方法（如：query、update、batrch）参数中无需Connection对象。

1.2 使用案例

private void doQueryAll() {

//ArrayHandler

//       QueryRunner queryRunner = new QueryRunner(UtilC3P0.getDataSource());

//        try {

//           Object[] objects = queryRunner.query("select * from user", newArrayHandler());

//            for(Object object : objects) {

//               System.out.println("object = " + object);

//

//            }

//        } catch(SQLException e) {

//           e.printStackTrace();

//        }

//--------------------------------------------------------------------------------------------------------

//ArrayListHandler

//       QueryRunner queryRunner = new QueryRunner(UtilC3P0.getDataSource());

//        try {

//           List<Object[]> list = queryRunner.query("select * fromuser", new ArrayListHandler());

//            for(Object[] objects : list) {

//               for (Object object : objects) {

//                   System.out.print(object+"\t");

//                }

//               System.out.println();

//

//            }

//        } catch (SQLException e) {

//           e.printStackTrace();

//        }

//--------------------------------------------------------------------------------------------------------

//ColumnListHandler

//       QueryRunner queryRunner = new QueryRunner(UtilC3P0.getDataSource());

//

//        try {

//           List<Object> list = queryRunner.query("select * fromuser", new ColumnListHandler(1));

//            for(Object o : list) {

//               System.out.println(o);

//

//            }

//        } catch(SQLException e) {

//           e.printStackTrace();

//        }

//--------------------------------------------------------------------------------------------------------

//KeyedHandler

//大map的key，是一行数据的一个标识，这个标识取当前行数据的某一列值

//小map就是当前行的数据  ，以键值对形式封装

//       QueryRunner queryRunner = new QueryRunner(UtilC3P0.getDataSource());

//        try {

//           Map<Object, Map<String, Object>> map =queryRunner.query("select * from user", new KeyedHandler(1));

//           Set<Object> objects = map.keySet();

//            for(Object object : objects) {

//               System.out.println("key "+object);

//               Map<String, Object> stringObjectMap = map.get(object);

//               System.out.println("value: "+stringObjectMap);

//            }

//

//        } catch(SQLException e) {

//           e.printStackTrace();

//        }

//--------------------------------------------------------------------------------------------------------

//常用1-----ScalarHandler查询某行某列数据

//       QueryRunner queryRunner = new QueryRunner(UtilC3P0.getDataSource());

//        try {

//           Object o = queryRunner.query("select money from user", newScalarHandler(1));

//           System.out.println(o);

//        } catch(SQLException e) {

//           e.printStackTrace();

//        }

//--------------------------------------------------------------------------------------------------------

//常用2-----BeanHandler  查询一行数据(一个对象)

//       QueryRunner queryRunner = new QueryRunner(UtilC3P0.getDataSource());

//        try {

//            Useruser = queryRunner.query("select * from user whereusername='dahuang1'", new BeanHandler<User>(User.class));

//            System.out.println(user);

//        } catch(SQLException e) {

//           e.printStackTrace();

//        }

//--------------------------------------------------------------------------------------------------------

//常用3-----BeanListHandler  查询多行数据(一个对象集合)

QueryRunnerqueryRunner = new QueryRunner(UtilC3P0.getDataSource());

try {

List<User> users = queryRunner.query("select * from userwhere money>?", new BeanListHandler<User>(User.class),50);

System.out.println(users);

} catch(SQLException e) {

e.printStackTrace();

}

}

//更新操作

private voiddoUpdate() {

QueryRunnerqueryRunner = new QueryRunner(UtilC3P0.getDataSource());

try {

queryRunner.update("update user set money=? where username=?", 99999, "dahuang1");

} catch(SQLException e) {

e.printStackTrace();

}

}

//删除操作

private voiddoDelete1() {

QueryRunnerqueryRunner = new QueryRunner(UtilC3P0.getDataSource());

try {

queryRunner.update("delete from user where username=?","hehedada");

} catch(SQLException e) {

e.printStackTrace();

}

}

//插入操作

private voiddoInsert() {

//       QueryRunner queryRunner=new QueryRunner(UtilC3P0.getDataSource());

//        try {

//           queryRunner.update("insert into user values(?,?,?,?)","hehedada","123456","nan",123.45);

//        } catch(SQLException e) {

//           e.printStackTrace();

//        }

QueryRunnerqueryRunner = new QueryRunner();

Connectionconnection = UtilC3P0.openConn();

try {

queryRunner.update(connection, "insert into uservalues(?,?,?,?)", "hehedada22", "123456","nan", 123.45);

} catch(SQLException e) {

e.printStackTrace();

} finally {

try {

connection.close();

} catch(SQLException e) {

e.printStackTrace();

}

}

}

1.3 批处理操作---batch

QueryRunner queryRunner=newQueryRunner(UtilC3P0.getDataSource());

Object[][] objects=new Object[100][];

for (int i = 0; i < objects.length;i++) {

objects[i]=new Object[]{"大黄"+i,"123456"+i};

}

try {

queryRunner.batch("INSERT  INTO user(username,userpwd) VALUES(?,?)",objects);

} catch (SQLException e) {

e.printStackTrace();

}

四、ResultSetHandler接口

ResultSetHandler下的所有结果处理器

1.      ArrayHandler:适合取1条记录。把该条记录的每列值封装到一个数组中Object[]

QueryRunnerqr = new QueryRunner(C3P0Util.getDataSource());

Object[]arr  = qr.query("select * fromusers", new ArrayHandler());

for(Object o : arr) {

System.out.println(o);

}

2.ArrayListHandler:适合取多条记录。把每条记录的每列值封装到一个数组中Object[]，把数组封装到一个List中

QueryRunnerqr = new QueryRunner(C3P0Util.getDataSource());

List<Object[]>query = qr.query("select * from users", new ArrayListHandler());

for(Object[] os : query) {

for(Object o : os) {

System.out.println(o);

}

System.out.println("--------------");

}

3.ColumnListHandler:取某一列的数据。封装到List中。

QueryRunnerqr = new QueryRunner(C3P0Util.getDataSource());

List<Object>list = qr.query("select username,password from users", newColumnListHandler(1));

for(Object o : list) {

System.out.println(o);

}

4.KeyedHandler:取多条记录，每一条记录封装到一个Map中，再把这个Map封装到另外一个Map中，key为指定的字段值。

QueryRunnerqr = new QueryRunner(C3P0Util.getDataSource());

//大Map的key是表中的某列数据，小Map中的key是表的列名，所以大Map的key是Object类型，小Map的key是String类型

Map<Object,Map<String,Object>>map = qr.query("select * from users", new KeyedHandler(1));

for(Map.Entry<Object, Map<String,Object>> m : map.entrySet()) {

System.out.println(m.getKey());//大Map中key值就是id列的值

for(Map.Entry<String, Object> mm : m.getValue().entrySet()) {

System.out.println(mm.getKey()+"\t"+mm.getValue());//取出小Map中的列名和列值

}

System.out.println("---------------------");

}

5.MapHandler:适合取1条记录。把当前记录的列名和列值放到一个Map中

QueryRunner qr = newQueryRunner(C3P0Util.getDataSource());

Map<String,Object>map = qr.query("select * from users where id=?", newMapHandler(),20);

for(Map.Entry<String, Object> m : map.entrySet()) {

System.out.println(m.getKey()+"\t"+m.getValue());

}

6.MapListHandler:适合取多条记录。把每条记录封装到一个Map中，再把Map封装到List中

QueryRunner qr = newQueryRunner(C3P0Util.getDataSource());

List<Map<String,Object>>list = qr.query("select * from users", new MapListHandler());

for(Map<String, Object> map : list) {

for(Map.Entry<String, Object> m : map.entrySet()) {

System.out.println(m.getKey()+"\t"+m.getValue());

}

System.out.println("---------------");

}

7.ScalarHandler:适合取单行单列数据（常用）

QueryRunner qr = newQueryRunner(C3P0Util.getDataSource());

Objecto = qr.query("select count(*) from users", new ScalarHandler(1));

System.out.println(o.getClass().getName());

8.BeanHandler 返回我们所需要的实体（常用）

QueryRunnerqr = new QueryRunner(C3P0Util.getDataSource());

Useruser = qr.query("select * from users where id=?", newBeanHandler<User>(User.class),1);

System.out.println(user);

9.BeanListHandler 返回一组实体（常用）

QueryRunnerqr = new QueryRunner(C3P0Util.getDataSource());

List<User>list = qr.query("select * from users where id=?", newBeanListHandler<User>(User.class),1);

System.out.println(list.size());