ForEach loop to iterate through ArrayList got from external Class

Question

I've got two classes: Subject and Subjects. Subject stores data containing data found in a database (id, name and abbreviation). Subjects makes a database connection and returns an ArrayList containing Subjects.

Subject.java:

public class Subject {

   public int id;
   public String subjectName;
   public String subjectAbbr;

 //and some getters and setters

}

Subjects.java:

public class Subjects {

    public ArrayList getAllFromSubject() throws SQLException {

        Database DB = new Database();

        String query = "SELECT * FROM `subject`;";
        //DB.exequteQuery returns a ResultSet with the data from the query.
        ResultSet result = DB.executeQuery(query);

        ArrayList<Subject> output = new ArrayList();

        while (result.next()) {

            Subject subject = new Subject();

            subject.setId(result.getInt("id"));
            subject.setSubjectName(result.getString("subjectname"));
            subject.setSubjectAbbr(result.getString("subjectabbr"));

            output.add(subject);

        }

        DB.closeExistingConnection();

        return output;

    }

}

I've got signup.jsp, containing a dropdown select menu and I want the user be able to choose from the abbrevations found in the database. So I can call Subjects.getAllFromSubject() and I get an ArrayList containing a number of Subjects. I'd like to display all those Subjects abbrevations in a <select>-menu. This can be done by a forEach loop, but I'm am not sure how to do that and how to get the abbrevation from a Subject.

Any help would be greatly appreciated!

Unrelated: you want to read about not using raw types with generics. For example, a much better return type for your method would look like : public List<Subject> getAllFromSubject() or something alike. Really, that are important basics; and unless you understand such things, you better stay away from talking to databases or other advanced topics. — GhostCat
– GhostCat, Commented Dec 23, 2016 at 12:20
+ChristosLoupasdakis my jsp is nothing more than a file with HTML and some Javascript — J van Amerongen
– J van Amerongen, Commented Dec 23, 2016 at 12:24

Mário Moura da Silva · Accepted Answer · 2016-12-24 02:29:34Z

1

I hope this help:

index.jsp

<%@page language="java" contentType="text/html" pageEncoding="UTF-8"%>
<%@page import="jvanamerongen.example.Subjects"%>
<%@page import="jvanamerongen.example.Subject"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    </head>
    <body>
        <% Subjects list = new Subjects(); %>
        <select>
            <% for(Subject s : list.getAllFromSubject()) { %>
                <option value="<% out.print(s.getId()); %>"><% out.print(s.getSubjectAbbr()); %></option>
            <%}%>
        </select>
    </body>
</html>

edited Dec 24, 2016 at 2:29

answered Dec 23, 2016 at 12:40

Mário Moura da Silva

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8 Comments

J van Amerongen Over a year ago

I will try this in a minute, but now you're accessing subject.id directly, is it possible to just use a getter?

J van Amerongen Over a year ago

Thank you for your effort, but unfortunately your code doesn't seem to work. I added the line <%@page import="business.*"%> to include both classes, but without success

Mário Moura da Silva Over a year ago

<%@page import="business.Subjects"%> <% Subjects obj = new Subjects(); %>

J van Amerongen Over a year ago

I'm sorry to tell you that this doesn't solve the problem either. My IDE does say that obj is not used.

Mário Moura da Silva Over a year ago

What is your IDE?

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