基于Java用户输入更新数据库

Question

我是一名新程序员，我被赋予创建一个Subject.java类的任务，在该类中，它将询问学生他们正在学习多少门科目，然后将科目信息存储到数据库中，但是问题是我当前的代码是数据库中只有一行被更新。我的代码如下，请帮助我。

                System.out.print("\nEnter number of subject: ");
                int sub = in.nextInt();
                int i=0;

                for (i=0; i<sub; i++)
                {
                    System.out.print("\nCode: ");
                    this.setCode(in.next());

                    System.out.print("\nName: ");
                    this.setName(in.next());

                    System.out.print("\nCredit: ");
                    this.setCredit(in.nextInt());

                // insert into database
                ResultSet rs = null;
                String sqlInsert = "INSERT INTO subject (code, name, credit) VALUES (?,?,?)";

                try (Connection conn = MySQLDB.getConnection(); 
                    PreparedStatement pstmt
                        = conn.prepareStatement(sqlInsert);)
                {  

                    // assign parameters for statement
                        pstmt.setString(1, this.getCode());
                        pstmt.setString(2, this.getName());
                        pstmt.setInt (3, this.getCredit());

                        pstmt.addBatch();


                    if (pstmt.executeUpdate() == 1) 
                    {
                        System.out.println("\nNew subject has been created succesfully!");
                    } 
                    else 
                    {
                        System.out.println("\nError");
                    }


                } 

                catch (SQLException ex) 
                {
                    System.out.println(ex.getMessage());
                } 

Answer 1

正如Nexevis所说，您需要将Connection代码放在for-loop之外，如下所示：

// insert into database
 ResultSet rs = null;
 String sqlInsert = "INSERT INTO subject (code, name, credit) VALUES (?,?,?)";

 System.out.print("\nEnter number of subject: ");
 int sub = in.nextInt();
 int i = 0;
 try {

     Connection conn = MySQLDB.getConnection();
     PreparedStatement pstmt
         = conn.prepareStatement(sqlInsert);

     for (i = 0; i < sub; i++) {
         System.out.print("\nCode: ");
         this.setCode( in.next());

         System.out.print("\nName: ");
         this.setName( in.next());

         System.out.print("\nCredit: ");
         this.setCredit( in.nextInt());

         // assign parameters for statement
         pstmt.setString(1, this.getCode());
         pstmt.setString(2, this.getName());
         pstmt.setInt(3, this.getCredit());
         pstmt.addBatch();
     }
     try {
         // execute it to insert the data
         pstmt.executeBatch();
     } catch (SQLException e) {
         System.out.println("Error message: " + e.getMessage());
         return; // Exit if there was an error
     }
         conn.close();
    } catch (SQLException ex) {
     System.out.println(ex.getMessage());
 }