QueryRunner类结果处理的八种方法

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:fleur_de_lis: 在连接数据库的时候(MySQL)时，会遇到的问题：QueryRunner类结果处理的八种方法

QueryRunner类结果集处理的八种方法

调用QueryRunner的方法是：

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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

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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

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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

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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。

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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

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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

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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

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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[]

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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);
    	}
    }
}