急！java问题！我的查询语句为什么输不出值！

显示全部楼层 · 2010-9-13 11:04:04

package Demo;
import java.sql.*;
public class prepareUpdate {
public String execute()throws Exception{
String driverName = "com.microsoft.sqlserver.jdbc.SQLServerDriver";
String url = "jdbc:sqlserver://127.0.0.1:1433;DatabaseName=zap";

String userName = "sa";

String password = "123";

ResultSet rs = null;

Connection con=null;

PreparedStatement pstmt=null;

Book book = new Book();

intID = book.getID();

String SQL = "SELECT name,author,price from note where ID= ?";

try{

Class.forName(driverName).newInstance();

con=DriverManager.getConnection(url , userName,

password);

pstmt = con.prepareStatement(SQL) ;

PreparedStatement prestate=con.prepareStatement(SQL);

prestate.setInt(1,ID);

rs = prestate.executeQuery();

while(rs.next()){

book.setName(rs.getString(1));

book.setAuthor(rs.getString(2));

book.setPrice(rs.getString(3));

}

if(SQL != null)

{ return "success";

}

else{

return "fail"; }

}

catch(Exception e){

System.out.println(e.getMessage());

}
finally{

if (rs != null)

try {

rs.close();

} catch (Exception e) {}

if (pstmt != null)

try {

pstmt.close();

} catch (Exception e) {}

if (con != null)

try {

con.close();

} catch (Exception e) {}

}
return SQL;

}
}

千问 · 2010-9-13 11:04:04

Book book = new Book();intID = book.getID();看看上面这两句，Book这个类里面你在构造函数里就把ID那个属性赋值了吗？或者从其它方法赋值了吗？你应该在这两句下面再写句System.out.println("ID:"+ID);看看ID取到值了吗？其它的我没看，我经常用MYSQL，SQL忘的差不多了，你还要看看你是不是确实连接到数据库了。

千问 · 2010-9-13 11:04:04

pstmt = con.prepareStatement(SQL) ;
PreparedStatement prestate=con.prepareStatement(SQL);你这里为什么要写两次？还有你的 intID = book.getID();貌似没有值吧？只是构造了一个空的BOOK对象而已