Question

我似乎无法做到这一点：

import com.mysql.jdbc.Connection;
import java.sql.DriverManager;

public class connect {
    public static Connection sqlconnect;
    public static Connection OpenDB()
    {
        String database = "jdbc:mysql://localhost:3306/library";
        String user = "root";
        String password = "";

        if (sqlconnect == null){
            try{
                DriverManager.registerDriver(new com.mysql.jdbc.Driver());
                sqlconnect = (Connection) DriverManager.getConnection(database, user, password);
                System.out.print("Connection Passed");
            }
            catch (Exception e){
                System.out.print("Connection Failed!");
            }
        }
        return sqlconnect;
}

}

我尝试了很多我在网上看到的代码而且没有一个代码可以正常工作，每次使用此代码时都没有出现任何错误，但是如果我发现错误，它就不会打印或显示给我我在数据库中连接。我将它用作按钮中的对象。

我用这个来调用对象：

private void btnSubmitActionPerformed(java.awt.event.ActionEvent evt) {                                          
    // TODO add your handling code here:
    connect c = new connect();
}

Answer 1

import java.sql.*;

public class FirstExample {

   static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";  
   static final String DB_URL = "jdbc:mysql://localhost/databasename";


   static final String USER = "root";
   static final String PASS = "password";

   public static void main(String[] args) {
   Connection conn = null;
   Statement stmt = null;
   try{

       Class.forName("com.mysql.jdbc.Driver");  


      System.out.println("Connecting to database...");
      conn = DriverManager.getConnection(DB_URL,USER,PASS);


      System.out.println("Creating statement...");
      stmt = conn.createStatement();
      String sql;
      sql = "select * from tablename";
      ResultSet rs = stmt.executeQuery(sql);


      while(rs.next()){


         String first = rs.getString(1);
         String last = rs.getString(2);



         System.out.print(", First: " + first);
         System.out.println(", Last: " + last);
      }

      rs.close();
      stmt.close();
      conn.close();
   }catch(SQLException se){

      se.printStackTrace();
   }catch(Exception e){

      e.printStackTrace();
   }finally{

      try{
         if(stmt!=null)
            stmt.close();
      }catch(SQLException se2){
      }
      try{
         if(conn!=null)
            conn.close();
      }catch(SQLException se){
         se.printStackTrace();
      }
   }

}
}

复制上面的代码并添加mysql-connector-java-5.0.8-bin jar文件。并运行它eclipse。但请确保数据库名称和用户名，密码详细信息有效。

我的SQL连接代码有问题

1 个答案: