The database is checked by PreparedStatement

1 Inserting data

public boolean ChaRu3 (user user) {
Boolean flag=true;
        Connection Conn=null;
        PreparedStatement Ps=null;    Creating PreparedStatement Objects
        String sql= "INSERT into User (NAME,PWD) VALUES (?,?)";  The SQL statement no longer uses the concatenation method to write the SQL statement in the form of a placeholder question mark.
        Conn=dbconnutil.getconn ();
try {
            Ps=conn.preparestatement (SQL);
            Ps.setstring (1, User.getname ()); Sets the value for the placeholder, which starts at 1, the first argument is the position of the placeholder, and the second parameter is the value of the placeholder.
            
int i=ps.executeupdate ();
if (i==0) {
                Flag=false;
            }
        catch (SQLException e) {
TODO auto-generated Catch block
            E.printstacktrace ();
        }finally{
            Dbconnutil.closeall (NULL, PS, conn);
        }
return flag;

    }

2 Modifying data

public boolean XiuGai3 (user user) {
Boolean flag=true;
        Connection Conn=null;
        PreparedStatement Ps=null;
        String sql= "Update user set pwd=?" where name=? ";
        Conn=dbconnutil.getconn ();
try {
            Ps=conn.preparestatement (SQL);
            Ps.setstring (1, user.getpwd ());
            Ps.setstring (2, User.getname ());
int i= ps.executeupdate ();
if (i==0) {
                Flag=false;
            }

        catch (SQLException e) {
TODO auto-generated Catch block
            E.printstacktrace ();
        }finally{
            Dbconnutil.closeall (NULL, PS, conn);
        }
return flag;
    }

3 Deleting data

public boolean SHANCHU3 (int id) {
Boolean flag=true;
        Connection Conn=null;
        PreparedStatement Ps=null;
        String sql= "Delete from user where id=?";
        Conn=dbconnutil.getconn ();
try {
            Ps=conn.preparestatement (SQL);
            Ps.setint (1, id);
int i=ps.executeupdate ();
if (i==0) {
                Flag=false;
            }
        catch (SQLException e) {
TODO auto-generated Catch block
            E.printstacktrace ();
        }finally{
            Dbconnutil.closeall (NULL, PS, conn);
        }

return flag;
    }

4 Viewing data

public list<user> ChaKan3 () {
 list<user> list= new Arraylist<user > (); 
 Connection Conn=null; 
 PreparedStatement Ps=null; 
 ResultSet Rs=null; 
 String sql= "SELECT * from user"; 
 Conn=dbconnutil.getconn ();             
 try {
 ps=conn.preparestatement (SQL); 
 Rs=ps.executequery ();                
 while (Rs.next ()) {
 User user= new User (); 
 User.setname (rs.getstring ("name")); 
 List.add (user); 
} 
 catch (SQLException e) {
//TODO auto-generated catch block 
 E.printstack Trace ();        
}finally{
 Dbconnutil.closeall (RS, PS, conn); 
     } 
 
 return list; 
 }