三大核心类
QueryRunner中提供对sql语句操作的API.
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
QueryRunner
数据库新增：
//1定义QueryRunner 核心类
QueryRunner query = new QueryRunner();
//2、执行QueryRunner update方法执行sql语句
Connection conn = JdbcUtil.con();
String sql = "insert into stu(no,name,subject,score) values(?,?,?,?)";
Object[] param = {1,"tom1","C#",99};
try {
int i = query.update(conn, sql, param);
int j = query.update(JdbcUtil.con(), "insert into stu(no,name,subject,score) values(?,?,?,?)", 2,"tom2","C#",100);
System.out.println("结果为"+i+" "+j);
} catch (SQLException e) {
e.printStackTrace();
}finally {
//3、释放资源
try {
DbUtils.close(conn);
} catch (SQLException e) {
e.printStackTrace();
}
}数据库更新：
//1定义QueryRunner 核心类
QueryRunner query = new QueryRunner();
//2、执行QueryRunner update方法执行sql语句
try {
int i = query.update(JdbcUtil.con(),"update stu set name=? where no=?","mao",1);
System.out.println("影响的行数："+i);
} catch (SQLException e) {
e.printStackTrace();
}数据库删除：
//1定义QueryRunner 核心类
QueryRunner query = new QueryRunner();
//2、执行QueryRunner update方法执行sql语句
try {
int i = query.update(JdbcUtil.con(),"delete from stu where no=?",1);
System.out.println("结果为："+i);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} ResultSetHandler(八大类)
一、ArrayHandler()//查询返回值为数据Object[]
QueryRunner query = new QueryRunner();
try {
//获取第一行数据存入数组中
Object[] obj = query.query(JdbcUtil.con(),"select * from stu",new ArrayHandler());
System.out.println(obj[0]);
} catch (SQLException e) {
e.printStackTrace();
} 二、 ArrayListHandler()//获取每一行存入数组中，在将数据存入List集合中
QueryRunner query = new QueryRunner();
try {
//获取每一行存入数组中，在将数据存入List集合中
List<Object[]> obj = query.query(JdbcUtil.con(),"select * from stu",new ArrayListHandler());
for(Object[] objects : obj){
for(int i=0;i< objects.length;i++){
System.out.println(objects[i]);
}
}
} catch (SQLException e) {
e.printStackTrace();
} 三、BeanHandler()//将数据库表中一条数据封装到指定的javaBean中
//1、定义核心类
QueryRunner query = new QueryRunner();
//2、执行查询语句
try {
Stu stu = query.query(JdbcUtil.con(), "select * from stu", new BeanHandler<Stu>(Stu.class));
System.out.println(stu.getNo()+" "+stu.getName());
} catch (SQLException e) {
e.printStackTrace();
} 四、BeanListHandler()//得到数据库中每条数据并封装到javaBean集合中
//1、定义核心类
QueryRunner query = new QueryRunner();
//2、执行查询语句
try {
List<Stu> list = query.query(JdbcUtil.con(), "select * from stu", new BeanListHandler<Stu>(Stu.class));
for(Stu s : list){
System.out.println(s.getNo()+"====="+s.getName());
}
} catch (SQLException e) {
e.printStackTrace();
}五、ColumnListHandler()//将结果集中指定的数据封装到List集合中
//1、定义核心类
QueryRunner query = new QueryRunner();
//2、执行查询语句
try {
List<Object> list = query.query(JdbcUtil.con(), "select * from stu", new ColumnListHandler<Object>("name"));
for(Object obj : list){
System.out.println(obj);
}
} catch (SQLException e) {
e.printStackTrace();
}六、ScalarHandler()//用于处理单数据，用于执行select count(*) from stu的操作
//1、定义核心类
QueryRunner query = new QueryRunner();
//2、执行查询语句
try {
Object obj = query.query(JdbcUtil.con(), "select count(*) from stu", new ScalarHandler<Object>());
System.out.println(obj);
} catch (SQLException e) {
e.printStackTrace();
} 七、MapHandler()//以字段名为键，以内容为值，只取第一行。
//1、定义核心类
QueryRunner query = new QueryRunner();
//2、执行查询语句
try {
Map<String,Object> map = query.query(JdbcUtil.con(), "select * from stu", new MapHandler());
for(String key : map.keySet()){
System.out.println("键"+key+"值"+map.get(key));
}
} catch (SQLException e) {
e.printStackTrace();
}八、MapListHandler()//将数据库中每一条数据存入Map集合中
//1、定义核心类
QueryRunner query = new QueryRunner();
//2、执行查询语句
List<Map<String, Object>> list;
try {
list = query.query(JdbcUtil.con(), "select * from stu",new MapListHandler());
for(Map<String,Object> map :list){
for(String key : map.keySet()){
System.out.println("键"+key+"值"+map.get(key));
}
}
} catch (SQLException e) {
e.printStackTrace();
}