DBUtils使用详解

DBUtils三大核心功能1.QueryRunner类2.ResultSetHandler接口3.DBUtils类 DBUtils: DBUtilsjar包.（首先导入jar包）

DBUtils三大核心功能

1.QueryRunner类

QueryRunner有三个方法： 1.query（）：用于执行查询语句 2.update（）：用于执行增删改语句 3.batch（）：用于执行批处理

构造函数有无参new QueryRunner（）和有参new QueryRunner（DataSource ds），如果使用了有参的构造方法就不需要再传入connection

1.insert语句：

public static void insert(){ QueryRunner qr = new QueryRunner(); String sql = "insert into student values(112,'张三',19)"; Connection conn = null; try { conn = JDBCUtils.getConnection(); int count = qr.update(conn,sql); System.out.println(count); DbUtils.closeQuietly(conn); } catch (SQLException e) { e.printStackTrace(); } }

2.delete语句

public static void delete(){ QueryRunner qr = new QueryRunner(); String sql = "delete from student where sno = 112"; Connection conn = null; try { conn = JDBCUtils.getConnection(); int count = qr.update(conn,sql); System.out.println(count); DbUtils.closeQuietly(conn); } catch (SQLException e) { e.printStackTrace(); } }

3.update语句：

public static void update(){ QueryRunner qr = new QueryRunner(); String sql = "update student set sage= sage+10 where sno = 110"; Connection conn = null; try { conn = JDBCUtils.getConnection(); int count = qr.update(conn,sql); System.out.println(count); DbUtils.closeQuietly(conn); } catch (SQLException e) { e.printStackTrace(); } }

2.ResultSetHandler接口

1.ArrayHandler：将查询结果的第一行数据，保存到Object数组中

public static void arrayHandler(){ QueryRunner qr = new QueryRunner(); String sql = "select * from student"; try { Connection conn = JDBCUtils.getConnection(); Object[] query = qr.query(conn, sql, new ArrayHandler()); for(Object obj : query) System.out.print(obj); DbUtils.closeQuietly(conn); } catch (SQLException e) { e.printStackTrace(); } }

2.arrayListHandler： 将查询的结果，每一行先封装到Object数组中，然后将数据存入List集合

public static void arrayListHandler(){ QueryRunner qr = new QueryRunner(); String sql = "select * from student"; try { Connection conn = JDBCUtils.getConnection(); List<Object[]> query = qr.query(conn, sql, new ArrayListHandler()); for(Object[] objs : query){ for (Object obj : objs){ System.out.print(obj+" "); } System.out.println(); DbUtils.closeQuietly(conn); } } catch (SQLException e) { e.printStackTrace(); } }

3.BeanHandler： 将查询结果的第一行数据，封装到student对象

public static void BeanHandler(){ QueryRunner qr = new QueryRunner(); String sql = "select * from student"; try { Connection conn = JDBCUtils.getConnection(); Student query = qr.query(conn, sql, new BeanHandler<Student>(Student.class)); System.out.println(query); DbUtils.closeQuietly(conn); } catch (SQLException e) { e.printStackTrace(); } }

4.BeanLIstHandler： 将查询结果的每一行封装到student对象，然后再存入List集合

public static void BeanListHandler(){ QueryRunner qr = new QueryRunner(); String sql = "select * from student"; try { Connection conn = JDBCUtils.getConnection(); List<Student> query = qr.query(conn, sql, new BeanListHandler<Student>(Student.class)); for (Student student : query){ System.out.println(student+" "); } DbUtils.closeQuietly(conn); } catch (SQLException e) { e.printStackTrace(); } }

5.ColumnListHandler：将查询结果的指定列的数据封装到List集合中

public static void ColumnListHandler(){ QueryRunner qr = new QueryRunner(); String sql = "select * from student"; try { Connection conn = JDBCUtils.getConnection(); List<Object> sno = qr.query(conn, sql, new ColumnListHandler<>("sno")); for (Object obj : sno) System.out.println(obj); DbUtils.closeQuietly(conn); } catch (SQLException e) { e.printStackTrace(); } }

6.ScalarHanlder：将结果集第一行的某一列放到某个对象中

public static void ScalarHandler(){ QueryRunner qr = new QueryRunner(); String sql = "select count(*) from student"; try { Connection conn = JDBCUtils.getConnection(); long query = qr.query(conn, sql, new ScalarHandler<Long>()); System.out.println(query); DbUtils.closeQuietly(conn); } catch (SQLException e) { e.printStackTrace(); } }

7.MapHandler：将结果集中的第一行数据封装到一个Map

public static void MapHandler(){ QueryRunner qr = new QueryRunner(); String sql = "select * from student where sno = ?"; try { Connection conn = JDBCUtils.getConnection(); Map<String, Object> query = qr.query(conn, sql, new MapHandler(), 110); System.out.println(query); DbUtils.closeQuietly(conn); } catch (SQLException e) { e.printStackTrace(); } }

8.MapListHandler：将结果集中的每一行数据都封装到一个Map里，然后再存放到List

public static void MapListHandler() { QueryRunner qr = new QueryRunner(); String sql = "select * from student where sno = ?"; try { Connection conn = JDBCUtils.getConnection(); List<Map<String, Object>> query = qr.query(conn, sql, new MapListHandler(),110); for (Map<String, Object> map : query) { System.out.println(map); } DbUtils.closeQuietly(conn); } catch (SQLException e) { e.printStackTrace(); } } KeyedHandler:将结果集中的每一行数据都封装到一个Map里(List)，再把这些map再存到一个map public static void KeyedHandler(){ QueryRunner queryRunner = new QueryRunner(); String sql = "select * from student"; Map<String,Map<String,Object>>map = null; try { Connection conn = JDBCUtils.getConnection(); map = queryRunner.query(conn,sql,new KeyedHandler<String>("sname")); for(Map.Entry<String,Map<String,Object>> entry : map.entrySet()){ System.out.println(entry.getKey()); System.out.println(entry.getValue()); } DbUtils.closeQuietly(conn); } catch (SQLException e) { e.printStackTrace(); } }

3.DBUtils类

它提供关于关闭资源以及事务rollback,commit操作。里面的方法都是静态的。

DbUtils.closeQuietly(conn);//用来关闭安静地连接