zoukankan      html  css  js  c++  java
  • java_jdbc_利用结果集元数据将查询结果封装为map_MetaData

    package cn.itcast.batch;
    
    import java.sql.Connection;
    import java.sql.ParameterMetaData;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    
    import cn.itcast.JdbcUtils;
    
    public class ResultSetMetaData {
    
    	public static void main(String[] args) throws SQLException {
    		// TODO Auto-generated method stub
    		List<Map<String, Object>> list = read2("select username,password from t_user where id <5 ");
    		System.out.println(list);
    	}
    
    	// 一行数据
    	public static Map<String, Object> read(String sql) throws SQLException {
    		Connection conn = null;
    		PreparedStatement ps = null;
    		ResultSet rs = null;
    		try {
    			conn = JdbcUtils.getConnection();
    			ps = conn.prepareStatement(sql);
    			rs = ps.executeQuery();
    
    			java.sql.ResultSetMetaData rsmd = rs.getMetaData();
    
    			int count = rsmd.getColumnCount();
    			String[] colNames = new String[count];
    
    			for (int i = 1; i <= count; i++) {
    				// System.out.println(rsmd.getColumnClassName(i) + " "
    				// + rsmd.getColumnName(i) + " " + rsmd.getColumnLabel(i));
    				colNames[i - 1] = rsmd.getColumnName(i);
    
    			}
    			Map<String, Object> data = null;
    			if (rs.next()) {
    				data = new HashMap<String, Object>();
    				for (int i = 0; i < colNames.length; i++) {
    					data.put(colNames[i], rs.getObject(colNames[i]));
    				}
    			}
    			return data;
    		} finally {
    			JdbcUtils.free(rs, ps, conn);
    		}
    	}
    
    	// 多行行数据
    	public static List<Map<String, Object>> read2(String sql)
    			throws SQLException {
    		Connection conn = null;
    		PreparedStatement ps = null;
    		ResultSet rs = null;
    		try {
    			conn = JdbcUtils.getConnection();
    			ps = conn.prepareStatement(sql);
    			rs = ps.executeQuery();
    
    			java.sql.ResultSetMetaData rsmd = rs.getMetaData();
    
    			int count = rsmd.getColumnCount();
    			String[] colNames = new String[count];
    
    			for (int i = 1; i <= count; i++) {
    				// System.out.println(rsmd.getColumnClassName(i) + " "
    				// + rsmd.getColumnName(i) + " " + rsmd.getColumnLabel(i));
    				colNames[i - 1] = rsmd.getColumnName(i);
    
    			}
    			List<Map<String, Object>> datas = new ArrayList<Map<String, Object>>();
    			while (rs.next()) {
    				Map<String, Object> data = new HashMap<String, Object>();
    				for (int i = 0; i < colNames.length; i++) {
    					data.put(colNames[i], rs.getObject(colNames[i]));
    				}
    				datas.add(data);
    			}
    			return datas;
    		} finally {
    			JdbcUtils.free(rs, ps, conn);
    		}
    	}
    }
    


  • 相关阅读:
    div在父集高度未知的情况下垂直居中的方法
    固比固布局 圣杯布局 css实现传统手机app布局
    img标签的onerror事件
    vue中的swiper element ui
    前后端分离跨域 关于前后端分离开发环境下的跨域访问问题(angular proxy=>nginx )
    自己开发的网页在跳转至微信公众号文章后,点击微信的返回,无法返回原网页
    关于audio元素在实际项目中遇到的问题总结
    移动端HTML5<video>视频播放优化实践
    数据类型转换
    穿越宇宙的邀请函——镜像图片技巧
  • 原文地址:https://www.cnblogs.com/MarchThree/p/3720420.html
Copyright © 2011-2022 走看看