如何使用oracle数据库中的值验证我的密码，以及java中return 0和return 1有什么区别

Question

I am not so good in Java. I am doing an an application and I want to validate the value entered as password in a text box with the value stored in the database for the password. If both the values do not match, I want to show an error message. I am creating a web service of this Java code that I will be using. What is the difference between return 0 , return 1 , return (value) ?? How can I do this? Can someone give me a sample code example? I have created the connection in a separate class and created an object for it called- dbsource.

package com.daoImpl;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import com.dto.LoginBean;

 public class ApplicationStatusDAO {

DBSource dbsouce = new DBSource();

public List<LoginBean> userLogin()
  {
    List<LoginBean> listloginBean=new ArrayList<LoginBean>();
    LoginBean loginbean=null;
    Statement stmt= null;
    try {

        String query = "select * from user_self";

        try {
            stmt = dbsouce.getConnection().createStatement();
            ResultSet rs = stmt.executeQuery(query);
            while(rs.next()) {
                loginbean=new LoginBean();
                 System.out.println("results: " + rs.getString("uname")+" "+        rs.getString("s_gender")+" "+ rs.getString("s_lname"));

                 loginbean.setUname(rs.getString("uname"));
                 loginbean.setPass(rs.getString("pass"));
                 loginbean.setGender(rs.getString("s_gender"));
                 loginbean.setLname(rs.getString("s_lname"));
                 listloginBean.add(loginbean);
            }

            System.out.println("size of list"+ listloginBean.size());
        } catch (SQLException e ) {
            System.out.println("result set Error: " + e);
        }


    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    return listloginBean;
    }

The second class used:

import java.util.List;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import com.daoImpl.ApplicationStatusDAO;
import com.dto.LoginBean;



@Path("/selfservice")
public class ServiceDispatcher {
@GET
@Produces("application/json")
@Path("login/")
public LoginBean loginAuth(@QueryParam("uname") String uname,@QueryParam("pass")    String pass) 
{
    LoginBean loginBean=new LoginBean();
    System.out.println("loginAuth- user name=" + uname + " password=" + pass);
    ApplicationStatusDAO applicationStatusDAO=new ApplicationStatusDAO();

    List<LoginBean> bean =applicationStatusDAO.userLogin();


    for(LoginBean aa:bean)
    {
    if(uname.equals(aa.getUname())&& pass.equals(aa.getPass()))
          {
        System.out.println("ssssssssssssssssssssssss");

        loginBean.setGender(aa.getGender());
        loginBean.setUname(aa.getUname());
        loginBean.setLname(aa.getLname());
        return loginBean;
           }

    else
    {
        System.out.println("ffffffffffffffffffffffffff");
        //LoginBean loginBean1=new LoginBean();
        //loginBean1.setFname("user name not ok");
        //return loginBean1; 
    }

    }



    return loginBean;
   }

Answer 1

1. What a method returns really depends on what it does. Unlike in C, you have a primitive boolean type, so if you want to return success/failure of a method, you should return true / false , respectively. However, you may also want to have a void method that throws some Exception instead of returning a value instead.

2. Get the value of the password from the database and compare it to the input string with the equals() method.

Answer 2

Get the password from user and store it in String object.

String pass = "yourpassword"; // or get it from System using Scanner
String username = "username";

Now make a function where you will Fetch the data from table

   public int present(){

   // make query for Oracle data base
       String yourQry = "select * from yourtable where password = '"+pass+"' and username='"+username+"'" . 
    //Use this query when you are fetching data from user.
    Resultset rs;// fetch your data in resultset
         if(rs.next()){
               // if data got fetched 
               return 1;// In other languages(C,C++) 0 and 1 are treated as true or false
               // 1 means true
          }
         else{
                  return 0; // 0 means false (No datafound) 
         }

        }

Now call this function from main()

int a = present();

if (a==0){
  System.out.print("data not found")
}
else{
    System.out.print("data found")
}