QueryRunner类结果处理的八种方法

    科技2022-07-20  100

    在连接数据库的时候(MySQL)时,会遇到的问题。

    调用QueryRunner的方法是:

    query(Connection con,String Sql,ResultSetHandler r,Object.params)

    MapListHandler

    将结果集每一行存储到Map集合中,键:列名;值:数据

    public static void mapListHandler()throws SQLException{ QueryRunner qr = new QueryRunner(); String sql = "select * from db"; Lsit<Map<String,Object>> list = qr.query(con,sql,new MapListHandler()); for(Map<String,Object> map:list){ System.out.print(key+'..'+map.get(key)); } System.out.prinln(); }

    MapHandler

    将结果集的第一行数据,封存到Map集合中

    public static void mapHandler()throws SQLException{ QueryRunner qr = new QueryRunner(); String sql = "select * from db"; Map map = qr.query(con,sql,new MapHandler()); for(String key:map.keySet()){ System.out.print(key+'..'+map.get(key)); } System.out.prinln(); }

    ScalarHandler

    查询后,只有一个结果

    Public static void scalarHandler() throws SQLException(){ QueryRunner qr = new QueryRunner(); String sql = "select * from db"; long count = qr.query(con,sql,new ScalarHandler()); System.out.prinln(count); }

    ColumnListHandler

    结果集,指定列的数据存储到List集合中,

    List每个列数据类型不同。

    public static void columnListHandler()throws SQLException(){ QueryRunner qr = new QueryRunner(); String sql = "select * from db"; List<Object> list = qr.query(con,sql,new ColumnListHandler<Object>("name")); for(Object obj:list){ System.out.println(obj); } System.out.prinln(obj); }

    BeanListHandler

    结果集每一行数据,封装JavaBean对象

    多个JavaBean对象,存储到List集合

    public static void columnListHandler()throws SQLException(){ QueryRunner qr = new QueryRunner(); String sql = "select * from db"; List list = qr.query(con,sql,new BeanListHandler<Sort>(Sort.class)); for(Sort s:list){ System.out.println(s); } }

    BeanHandler

    将结果集的第一行数据,封装成JavaBean对象

    public static void beanHandler()throws SQLException{ QueryRunner qr = new QueryRunner(); String sql = "SELECT * FROM sort "; Sort s = qr.query(con, sql, new BeanHandler<Sort>(Sort.class)); System.out.println(s); }

    ArrayListHandler

    将结果集的每一行,封装到对象数组中

    public static void arrayListHandler()throws SQLException{ QueryRunner qr = new QueryRunner(); String sql = "SELECT * FROM sort"; List<Object[]> result= qr.query(con, sql, new ArrayListHandler()); for( Object[] objs : result){ for(Object obj : objs){ System.out.print(obj+" "); } System.out.println(); } }

    ArrayHandler

    将结果集的第一行存储到对象数组中 Object[]

    public static void arrayHandler()throws SQLException{ QueryRunner qr = new QueryRunner(); String sql = "SELECT * FROM sort"; Object[] result = qr.query(con, sql, new ArrayHandler()); for(Object obj : result){ System.out.print(obj); } } }

    精益求精

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