CODEWITHSUNDEEP
javaresultset
user813056
user813056

Reputation: 21

How to get the first element in ResultSet

How to get the first element in ResultSet in the following code:

    public List getUserTest(String username, String password) {

    List userList = new ArrayList();


    Connection connection = null;
    String rstring = null;
    Statement stmt = null;///*******
    ResultSet resultSet = null;
    try {

        connection = dataSource.getConnection();
        stmt = connection.createStatement();///*******
        resultSet = stmt.executeQuery("SELECT * FROM users WHERE (username)='" + username + "'"
                + "AND (password)='" + password + "'");///*******

        while (resultSet.next()) {
            UsersTest user = new UsersTest();
            user.setId(resultSet.getString("id"));
            user.setUsername(resultSet.getString("username"));
            user.setPassword(resultSet.getString("password"));
            userList.add(user);
        }


    } catch (SQLException e) {
        System.err.println(e);
    } finally {
        try {

            if (resultSet != null) {
                resultSet.close();
            }

            if (stmt != null) {
                stmt.close();
            }

            if (connection != null) {
                connection.close();
            }
        } catch (SQLException e) {
        }
    }
    return  userList;
}

Upvotes: 2

Views: 44784

Answers (5)

glarkou
glarkou

Reputation: 7101

Do:

resultSet.first()

Check the API here: https://docs.oracle.com/javase/7/docs/api/java/sql/ResultSet.html

PS:

In my opinion is better to replace:

while (resultSet.next()) {
        UsersTest user = new UsersTest();
        user.setId(resultSet.getString("id"));
        user.setUsername(resultSet.getString("username"));
        user.setPassword(resultSet.getString("password"));
        userList.add(user);
    }

With: (RETURNS OBJECT)

if (!rs.next())
  //No user found.
else {
  UsersTest user = new UsersTest();
  resultSet.first();
  user.setId(resultSet.getString("id"));
  user.setUsername(resultSet.getString("username"));
  user.setPassword(resultSet.getString("password"));
}

return user;

Return list: (RETURNS LIST)

List userList = new ArrayList();

if (!rs.next())
  //No user found.     
else {
  UsersTest user = new UsersTest();
  resultSet.first();
  user.setId(resultSet.getString("id"));
  user.setUsername(resultSet.getString("username"));
  user.setPassword(resultSet.getString("password"));
  userList.add(user) //it will only add one element
}

return userList;

To call your method do:

UsersTest u = new UserTest();
List l = getUserTest(username, password)

if(l.size > 0)
  u = l.get(0);
else
  System.out.println("Cannot find user");

I suggest that because I do not think that you will have 2 results(List is unnecessary). You expect to have 0 or 1 result!

Upvotes: 5

Big Zed
Big Zed

Reputation: 447

use if(resultSet.first)... instead of while(resultSet.next)... but if you want to get all results and then choose the first from all this is a way to do so :

List<UsersTest> users = new ArrayList<UsersTest>();
while(resultSet.next){
   UsersTest user = new UsersTest();
   /*
      * All your Setters but you should create a constructor with fields
   */
   users.add(user);
}

and to get the first result UsersTest firstUser = users.get(0);

Upvotes: 0

duffymo
duffymo

Reputation: 308743

Like this: 

List users = List getUserTest(username, password);
User user = ((users.size() > 0 ? users.get(0) : null);

The truth is that your database ought to enforce the idea that a username/password combination ought to be enough to identify a unique individual. A query should either return a unique individual or null. Your code as written will behave this way if your database has this constraint.

If it doesn't, you need to think about your schema design.

Upvotes: 0

DoubleMalt
DoubleMalt

Reputation: 1283

A ResultSet is not a Java collection so there is no real first element. You have access to the columns of the first returned row in the first iteration of the 

<!-- language: lang-java -->
while(resultSet.next())
{
 ...
}

loop.

Upvotes: 0

Ryan Stewart
Ryan Stewart

Reputation: 128779

The first element of the ResultSet is the one that you're working with the first time you execute the while (resultSet.next()) loop, and therefore its contents are used to build the first element of userList.

Upvotes: 5

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