我正在使用登录表单。此代码用于检查数据库中的登录详细信息。我可以在提供正确的用户名和密码时登录,但会显示异常。我的代码如下:
public void signin() throws ClassNotFoundException, SQLException
{
try {
Class.forName("com.mysql.jdbc.Driver");
connect2 = DriverManager
.getConnection("jdbc:mysql://localhost:3306/mysql?"
+ "user=root&password=virus");
statement2 = connect2.createStatement();
preparedStatement2 = connect2
.prepareStatement("select username,password from "+t11.getText()+";");
resultSet2 = preparedStatement2.executeQuery();
writeResultSet(resultSet2);
preparedStatement2.executeUpdate();
}
catch (ClassNotFoundException | SQLException e) {
throw e;
} finally {
close1();
}
}
private void writeResultSet(ResultSet resultSet) throws SQLException {
while (resultSet.next()) {
String username = resultSet.getString("username");
String password = resultSet.getString("password");
String usr = (String)t11.getText();
String pwd = (String)pw11.getText();
if( t11.getText().equals(username) && pwd.equals(password))
{
((Stage)b1.getScene().getWindow()).setScene(new Scene(new UserPage()));
}
else
{
//...THIS IS WHERE I WANT TO DISPLAY THE ALERT BOX
}
}
}
private void close1() {
try {
if (resultSet2 != null) {
resultSet2.close();
}
if (statement != null) {
statement.close();
}
if (connect != null) {
connect.close();
}
} catch (SQLException e) {
}
}
例外是:
java.sql.SQLException: Can not issue executeUpdate() for SELECTs
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1074)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:988)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:974)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:919)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2416)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2375)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2359)
at login.Login.signin(Login.java:159)
at login.Login$1.handle(Login.java:118)
at login.Login$1.handle(Login.java:113)
为什么要显示此异常?我该如何纠正?
答案 0 :(得分:4)
问题是您没有正确使用JDBC。为什么要使用select查询调用executeUpdate
?您可能想尝试executeQuery
。使用JDBC进行简单SQL选择查询的Here is an example。
另外,请注意不要编写易受SQL注入影响的代码。