我的Eclipse中的Java代码似乎可以运行，但是MySQL为什么不将其插入表中？ 我们可以使用两个try catch吗？

Question

I am not getting where I am wrong. Java code is running smoothly but MySQL database doesn't displays the values inserted through query. Can we use multiple try catch as I have used?Here is the main part of my code:

**Part of my main code:: 
        JButton btnSubmit = new JButton("Submit");
        btnSubmit.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {

                 int regno;
                 String bname,aname;
                 double cost;
                try{
                    regno = Integer.parseInt(textField_regno.getText());
                    bname = textField_bookname.getText();
                    aname = textField_authorname.getText();
                    cost  = Double.parseDouble(textField_cost.getText());

                    Class.forName("com.mysql.jdbc.Driver");
                    try{
                    Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:1521/book","username","passwrd");

                    PreparedStatement stmt  = conn.prepareStatement("INSERT INTO book('reg_no','b_name','a_name','cost')Values(?,?,?,?)");
                    stmt.setString(1, "regno");
                    stmt.setString(2, "bname");
                    stmt.setString(3, "aname");
                    stmt.setString(4, "cost");


                    JOptionPane.showMessageDialog(null,"Successfully added to the database");

                        }

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

                }
                catch(Exception e1){
                    JOptionPane.showMessageDialog(null,"Check your Values" +e1);
                }

            }
        });**

Answer 1

You are missing call to executeUpdate()

Add below line in your code -

stmt.executeUpdate()

After

stmt.setString(4, "cost");

Answer 2

 stmt.setString(1, "regno"); stmt.setString(2, "bname"); stmt.setString(3, "aname"); stmt.setString(4, "cost"); 

Here everything is being passed as a String (regardless of variable's value). So try this:

stmt.setString(1, regno);
stmt.setString(2, bname);
stmt.setString(3, aname);
stmt.setString(4, cost);

Also, you haven't used stmnt.executeUpdate() . Add that after this.

And you don't need multiple try/catch . One does all the work. Just make sure you code it properly.

Answer 3

Kunal,

All looks fine except That you have not executed your prepared statement.

stmt.executeUpdate();

You can take help from here .

Do close your connection in finally.