不知道資料庫中表的列型別的前提下,使用JDBC正確的取出資料（取出Result結果集中的欄位（不同型別））
概要： 使用jdbc 如果在不知道表結構的情況下，如何讀出表資訊？
使用ResultSetMetaData;
然後使用getColumnType 獲取column 型別
使用getColumnName 獲取column名字
根據型別，使用ResultSet 的getInt("column1")....獲取每個欄位的值
本文使用 Vector 做為容器，把拿到的查詢結果，臨時放在容器內。
1. 資料庫準備
a. create database study;
b. create table
CREATE TABLE `test` ( `id` int(11) NOT NULLDEFAULT '0', `name` varchar(10) DEFAULT NULL,
`birthday` datetime DEFAULT NULL, `score` double DEFAULT NULL, `info` text,
PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8
mysql> desc test;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | 0 | |
| name | varchar(10) | YES | | NULL | |
| birthday | datetime | YES | | NULL | |
| score | double | YES | | NULL | |
| info | text | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
c. 插入幾條資料
mysql> insert into test values(20131026,'Marry','1983-10-18 21:11:13',65.5,'she
is so nice');
2. 下載mysql jdbc connector
3.建立相應的類
import java.sql.Connection; import java.sql.DatabaseMetaData; import java.sql.DriverManager; import java.util.Scanner; public class DBConnection { publicstatic Connection getDBConnection() throws Exception { try{ Connection con = null; Scanner input=new Scanner(System.in); System.out.println("please enter the IP"); String ip=input.next(); if(ip.matches("\\d{1,3}.\\d{1,3}.\\d{1,3}.\\d{1,3}")) { System.out.println("Your IP is:\n"+ip); } else { ip="127.0.0.1"; System.out.println("Invaild IP address use default:\n"+ip); } System.out.println("please enter the ODBC port"); int port=input.nextInt(); if(1000<port && port < 50000) { System.out.println("your port is :\n"+port); } else { port=3306; System.out.println("Invaild port use defalt port:\n"+port); } System.out.println("please enter the UserName"); String user=input.next(); System.out.println("please enter the Password"); String password =input.next(); String url="jdbc:mysql://"+ip+":"+port+"/"+"study"; // String url="jdbc:mysql://localhost:3306/study"; System.out.println(url); String driver ="com.mysql.jdbc.Driver"; Class.forName(driver); con = DriverManager.getConnection(url,"root", "3edc4rfv"); DatabaseMetaData dma = con.getMetaData();//get the database info System.out.println("Connected to:" + dma.getURL()); System.out.println("Driver " + dma.getDriverName()); return con; } catch (Exception e) { System.out.println("[Error] Connection refused: connect"); e.printStackTrace(); return null; } } }
import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.SQLException; import java.sql.Statement; import java.sql.Types; import java.util.Vector; public class mysql { static void runquery() throws SQLException { Connection con=null ; long start=System.currentTimeMillis(); //count runtime ResultSetMetaData resultMetaData; try{ con = DBConnection.getDBConnection(); if(con==null){ System.out.println("can't open DBConnection"); } con.setAutoCommit(false); System.out.println("enter the sql you want excute\n eg select * from test;");
Statement stmt = con.createStatement();
String sql=new Scanner(System.in).nextLine(); ResultSet rs =stmt.executeQuery(sql); resultMetaData=rs.getMetaData(); int cols = resultMetaData.getColumnCount(); //get the count of all the coulums ,this will be 5 Vector currentRow = new Vector(); while(rs.next()) { for (int j = 1; j < cols; j++) { switch (resultMetaData.getColumnType(j)) //translate the column of table type to java type then write to vector { case Types.VARCHAR: currentRow.addElement(rs.getString(resultMetaData.getColumnName(j))); break; case Types.INTEGER: currentRow.addElement(new Integer(rs.getInt(resultMetaData.getColumnName(j)))); break; case Types.TIMESTAMP: currentRow.addElement(rs.getDate(resultMetaData.getColumnName(j))); break; case Types.DOUBLE: currentRow.addElement(rs.getDouble(resultMetaData.getColumnName(j))); break; case Types.FLOAT: currentRow.addElement(rs.getFloat(resultMetaData.getColumnName(j))); break; case Types.CLOB: currentRow.addElement(rs.getBlob(resultMetaData.getColumnName(j))); break; default: currentRow.add("error"); } } System.out.println(currentRow); currentRow.clear(); } } catch (Exception e) { e.printStackTrace(); } con.close(); long end=System.currentTimeMillis(); System.out.println(end-start); } public static void main(String[] args) throws SQLException { // TODO Auto-generated method stub System.out.println("enter the query SQL you want run\nex. select * from test ") ; runquery(); }
執行結果：
ex. select * from test
please enter the IP
localhost
Invaild IP address use default:
127.0.0.1
please enter the ODBC port
3306
your port is :
3306
please enter the UserName
root
please enter the Password
3edc4rfv
jdbc:mysql://127.0.0.1:3306/study
Connected to:jdbc:mysql://127.0.0.1:3306/study
Driver MySQL Connector Java
enter the sql you want excute
eg select * from test;
select * from test;
[20131024, Jason, 1980-05-07, 60.5]
[20131025, Young, 1988-01-09, 56.8]
[20131026, Marry, 1983-10-18, 65.5]
31977
enter the instert SQL you want run