Solved MySQL check if entry is set

Im trying to check if a entry is set, so for example in a row with: 'user, password, birth' I check if in column 'user' f.e. 'mxrlin' is

For that im using that code in my Main Class:

Code (Java):

if(!mySQL.isSet(tableName, "houseNumber", houseNumberStr)){
            System.out.println(house.getHouseNumber() + " not set yet");
            inserts.add(new BetterMySQL.KeyValue("houseNumber", houseNumberStr));
            mySQL.insertEntry(tableName, inserts);
        }else {
            System.out.println(house.getHouseNumber() + " set -> updating");
            mySQL.update(tableName, inserts, "houseNumber", houseNumberStr);
        }

And the mySQL.isSet() method looks like this:

Code (Java):

public boolean isSet(String tableName, String key, String value){
    Check.checkNotEmpty(tableName);
    Check.checkNotEmpty(key);
    Check.checkNotEmpty(value);
    ResultSet resultSet = MySQL.getResultSetPrepareStatement(connection, "SELECT * FROM " + tableName + " WHERE ?=?", Arrays.asList(key, value));
    try {
        if(resultSet.next()){
            return resultSet.getObject(value) != null;
        }
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        try {
            resultSet.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    return false;
}

But with this code it always debugs me "house.getHouseNumber() + " not set yet", so the Class doesnt find the entry that is set

 

Nope. I have it like this now:

Code (Java):

public boolean isSet(String tableName, String key, String value){
        Check.checkNotEmpty(tableName);
        Check.checkNotEmpty(key);
        Check.checkNotEmpty(value);
        ResultSet resultSet = MySQL.getResultSetPrepareStatement(connection, "SELECT * FROM " + tableName + " WHERE '?'='?'", Arrays.asList(key, value));
        try {
            return resultSet != null && resultSet.next(); // if there is found anything that isnt null -> true - else false
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return false;
    }

But still returning false everytime.

 

As soon as I do WHERE ?='?' instead of WHERE ?=? the Error "java.sql.SQLException: Parameter index out of range (2 > number of parameters, which is 1)." appears

 

Yeah, but the Problem is there, and thats why im using prepared statements, is SQL injection. If im using just result sets an hacker as it easy to hack the databank.

EDIT: I dont know the error, but I just used getObject() == null instead of isSet() and it was working. Still no sense for me, but i got it working