java - Jsp/MySQL- 将 SELECT 查询的输出存储到字符串中？

Question

这是我的选择查询

("SELECT firstName FROM user WHERE username = username;")

我如何将它存储到一个字符串变量中，以便我可以在我的 jsp 页面上输出它？

编辑:我运行的代码

string firstname;

try{  


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

Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/contacts","root","root"); 


Statement stmt=con.createStatement();  

ResultSet rs=stmt.executeQuery("SELECT firstName FROM user WHERE username = username;");



while(rs.next())  {
fname=new String(rs.getString(1));
System.out.println("First Name:"+firstname);  
con.close();  
   }
}
catch(Exception e){ 
  System.out.println(e);
 }  

Answer 1

查询错误，类似于SELECT firstName FROM user。您需要将 userName 设置为参数。

PreparedStatement stmt=con.prepareStatement("SELECT firstName FROM user WHERE username = ?;");  
stmt.setString(1, userName);

ResultSet rs=stmt.executeQuery();

if(rs.next())  {
    fname=new String(rs.getString(1));
    System.out.println("First Name:"+firstname);  
}