oracle 连接数据库并查询，返回List<Map<String, Object>> 数据

package JDBC;

import java.sql.Clob;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Timestamp;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class OracleJdbcTest {
    //数据库连接对象
    private static Connection conn = null;

    private static String driver = "oracle.jdbc.OracleDriver";//"oracle.jdbc.driver.OracleDriver"; //驱动

    private static String url = "jdbc:oracle:thin:@127.0.0.1:1521:orcl"; //连接字符串

    private static String username = "******"; //用户名

    private static String password = "******"; //密码

    // 获得连接对象
    private static synchronized Connection getConn(){
        if(conn == null){
            try {
                Class.forName(driver);
                conn = DriverManager.getConnection(url, username, password);
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return conn;
    }

    //执行查询语句
    public void query(String sql, boolean isSelect) throws SQLException{
        PreparedStatement pstmt;

        try {
            pstmt = getConn().prepareStatement(sql);
            //建立一个结果集，用来保存查询出来的结果
            ResultSet rs = pstmt.executeQuery();
            while (rs.next()) {
                String name = rs.getString("bm_mc");
                System.out.println(name);
            }
            rs.close();
            pstmt.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    } 

    private static String clob2String(Clob clob) throws Exception {
        return (clob != null ? clob.getSubString(1, (int) clob.length()) : null);
    }

    private static List<Map<String, Object>> ResultSetToList(ResultSet rs) throws Exception {
        ResultSetMetaData md = rs.getMetaData();  // 得到结果集的结构信息，比如字段数、字段名等
        // .getMetaData().getTableName(1) 就可以返回表名
        int columnCount = md.getColumnCount();  // 得到结果集的列数
        // System.out.println(columnCount);
        List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
        Map<String, Object> rowData;
        while (rs.next()) { //记录指针向下移动一个位置，如果其指向一条有效记录，则返回真；否则返回假。只有使记录指针不断移动，才能不断取出数据库中的数据

            rowData = new HashMap<String, Object>(columnCount);
            for (int i = 1; i <= columnCount; i++) {
                Object v = rs.getObject(i); // 将任何数据类型返回为 Java Object
                if (v != null && (v.getClass() == Date.class || v.getClass() == java.sql.Date.class)) { // 反射
                    Timestamp ts = rs.getTimestamp(i);  // 返回时间和日期     java.sql.Timestamp
                    //rs.getDate()只是返回日期部分     java.sql.Date
                    //rs.getTime()只是返回时间部分     java.sql.Time
                    v = new java.util.Date(ts.getTime());
                    // v = ts;
                } else if (v != null && v.getClass() == Clob.class) {
                    v = clob2String((Clob) v); // oracle11g 遇到取出来的字段是clob类型，clob用来存储大量文本数据
                }
                 //System.out.println("ResultSetToList:"+md.getColumnLabel(i));
                // rowData.put(camelName(md.getColumnLabel(i)), v==null?"":v);
                rowData.put(md.getColumnLabel(i).toLowerCase(), v == null ? "" : v);
                //getColumnName(int column)：获取指定列的名称
                //getColumnLabel(int column)：获取用于打印输出和显示的指定列的建议标题。
                // toUpperCase 的意思是将所有的英文字符转换为大写字母
                // toLowerCase的意思是将所有的英文字符转换为小写字母
            }
            list.add(rowData);
        }
        return list;
    }

  //执行查询语句
    public List<Map<String, Object>> queryList(String sql, boolean isSelect) throws Exception{
        PreparedStatement pstmt = getConn().prepareStatement(sql);;
        List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
        //建立一个结果集，用来保存查询出来的结果
        ResultSet rs = pstmt.executeQuery();
        list = ResultSetToList(rs);
        rs.close();
        pstmt.close();
        return list;
    } 

    public void query(String sql) throws SQLException{
        PreparedStatement pstmt;
        pstmt = getConn().prepareStatement(sql);
        pstmt.execute();
        pstmt.close();
    }

    //关闭连接
    public void close(){
        try {
            getConn().close();

        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

}

...

package JDBC;

import java.sql.SQLException;
import java.util.List;
import java.util.Map;

public class ConnOracle {
    public static void main(String[] args) throws Exception {
        OracleJdbcTest test = new OracleJdbcTest();
        try {
            test.query("drop table student");
        } catch (SQLException e) {}

        //test.query("create table student(id int, name nchar(20))");

        //test.query("insert into student values(1,'zhangsan')");

        //test.query("insert into student values(2,'lisi')");

        //test.query("select r.id from T_ry r", true);

        String sql = "select r.* from T_RY r where r.data_flag <> 'D' ";
        List<Map<String, Object>> list = test.queryList(sql, true);
        System.out.println(list);
        test.close();
    }
}