DBUtils方法详解02

上篇文章介绍了前五种DBUtils的方法，这篇文章为大家介绍剩下的五种，剩下的这五种是平时比较常用的

6、MapListHandler 每一行都是一个map，把map放入list里表示多行***

public static void test6() throws SQLException{QueryRunner qr = new QueryRunner(C3P0Utils.getDateSource());String sql = "select * from teacher";List<Map<String, Object>> list = qr.query(sql, new MapListHandler());for(int i = 0;i<list.size();i++){for(Map.Entry<String , Object> m:list.get(i).entrySet()){System.out.print(m.getKey()+" "+ m.getValue());}System.out.println();System.out.println("--------------------------------");}}

7、ScalarHandler取单行单列*** 

它的构造方法的参数默认是1，意思是取第一行的第1列，你可以改为其他列，但都是第一行的。*****当查询的内容如果是count，那么实际的返回是Long

public static void test7() throws SQLException{QueryRunner qr = new QueryRunner(C3P0Utils.getDateSource());String sql = "select count(*) from student where ssex=?";Object obj = qr.query(sql, new ScalarHandler(),"男");System.out.println(obj);}

8、BeanHandler*****返回一个实体对象，必须要创建了实体类

public static void test8() throws SQLException{QueryRunner qr = new QueryRunner(C3P0Utils.getDateSource());String sql = "select * from User where username=?";User user = qr.query(sql,new BeanHandler<User>(User.class),"zhangsan");System.out.println(user);}

9、BeanListHandler*****看名字就能知道，这是取出多个实体对象最后返回的是一个List集合

public static void test9() throws SQLException{QueryRunner qr = new QueryRunner(C3P0Utils.getDateSource());String sql = "select * from user";List<User> list = qr.query(sql, new BeanListHandler<User>(User.class));for(int i =0;i<list.size();i++){System.out.println(list.get(i));}}

10、最简单，也是最常用的增删改方法，insert、update、delete

public static void testInsert() throws SQLException{QueryRunner qr = new QueryRunner(C3P0Utils.getDateSource());String sql = "insert into user(username,password) values(?,?)";int i = qr.update(sql,"wangwu","123321");if(i>0){System.out.println("插入成功");}}public static void testUpdate() throws SQLException{QueryRunner qr = new QueryRunner(C3P0Utils.getDateSource());String sql = "update user set password=? where username=?";int i = qr.update(sql,"111111","wangwu");if(i>0){System.out.println("修改成功");}}public static void testDelete() throws SQLException{QueryRunner qr = new QueryRunner(C3P0Utils.getDateSource());String sql = "delete from user where username=?";int i = qr.update(sql,"wangwu");if(i>0){System.out.println("删除成功");}}

这五种是平时比较常用的方法，大家需要加强记忆。