-2
我有一个实现动作监听器的注册对话框。如果用户输入一个名称并且它已经存在,我想在控制台上打印一条消息。如果用户名不存在,MySQL应该将其添加到数据库中。不幸的是这个代码将无法正常工作:检查用户名是否存在于MySQL Java中
private void regButtonActionPerformed(java.awt.event.ActionEvent evt) {
if(!userBox.getText().equals(""))
{
try
{
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/genx", "root", "Warlock1989");
Statement stmt = con.createStatement();
String query = "SELECT name FROM accounts";
ResultSet rs = stmt.executeQuery(query);
while(rs.next())
{
String uname = rs.getString("name");
if(!uname.equals(userBox.getText()))
{
PreparedStatement pstmt = con.prepareStatement("INSERT INTO accounts(name) VALUES(?)");
pstmt.setString(1, userBox.getText());
pstmt.executeUpdate();
System.out.println("Username " + userBox.getText() + " has been registered.");
}
else
{
System.out.println("Username " + userBox.getText() + " already exists.");
}
}
}
catch(Exception ex)
{
ex.printStackTrace();
}
}
“不起作用”是什么意思? – Tunaki
打印堆栈跟踪 – Shriram
没有堆栈跟踪。完全没有任何反应。它不会调用if,else或catch。 –