不知道数据库中表的列类型的前提下,使用JDBC正确的取出数据

概要： 使用jdbc 如果在不知道表结构的情况下，如何读出表信息？

使用ResultSetMetaData;

然后使用getColumnType 获取column 类型

使用getColumnName 获取column名字

根据类型，使用ResultSet 的getInt("column1")....获取每个字段的值

本文使用 Vector 做为容器，把拿到的查询结果，临时放在容器内。

1.   数据库准备

a. create database study;

　　b. create table

CREATE TABLE `test` (   `id` int(11) NOT NULL DEFAULT '',   `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. 插入几条数据

mysql> insert into test values(20131026,'Marry','1983-10-18 21:11:13',65.5,'she
is so nice');

2. 下载mysql jdbc connector

http://dev.mysql.com/downloads/connector/j/

3.创建相应的类

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.util.Scanner;
public class DBConnection {

    public static 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();
}

运行结果：

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