Server

import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.HashMap;

//not yet threaded!!
public class Server {
	private static Connection connection;

	private static HashMap<Integer, Student> studentData;
	private static HashMap<Integer, Course> courseData;
	private static HashMap<Integer, Enrollment> enrollmentData; //maps of all the data from the server tables

	public static void main(String[] args) {
		try {

			connectToDB();
			studentData = mapStudentData();
			courseData = mapCourseData();
			enrollmentData = mapEnrollmentData(); //maps with asigned values

			ServerSocket server = new ServerSocket(5678);

			while(true) {
				Socket client = server.accept(); //looking for the client connection

				ObjectInputStream input = new ObjectInputStream(client.getInputStream());
				ObjectOutputStream output = new ObjectOutputStream(client.getOutputStream());
				Request request = (Request) input.readObject(); //recieving the request from the client

				String requestType = request.getRequestType();
				String studId = request.getStudetnId();
				String courseId = request.getCourseId();

				// for sending info back to the client
				if(requestType.equals("Student")) {
					ArrayList<Student> studentToClient = processStudentRequest(studId, courseId);
					output.writeObject(studentToClient.toArray(new Student[studentToClient.size()]));
				} else if(requestType.equals("Course")) {

				} else {

				}
			}

		} catch (Exception ex) {
			ex.printStackTrace();
		}
	}

	//for when the detected request type is student
	public static ArrayList<Student> processStudentRequest(String studId, String courseId) {
		ArrayList<Student> students = new ArrayList<Student>();
		if(courseId.length() == 0) { //if course is empty

			//just gets all students and adds them to the list
			for(Integer i : studentData.keySet()) {
				Student s = studentData.get(i);

				students.add(s);
			}
			return students;

			//course is filled (not yet handling improper inputs
		} else if(courseId.length() != 0) {
			ArrayList<Integer> ssn = new ArrayList<Integer>();

			//adds all ssns from enrolment that match the course id
			for(Integer i : enrollmentData.keySet()) {
				Enrollment e = enrollmentData.get(i);
				if(e.getCourseId().equals(courseId)) {
					ssn.add(e.getSsn());
				}
			}

			//looks the students for the found ssns
			for(Integer i : studentData.keySet()) {
				Student s = studentData.get(i);

				for(int j = 0; j < ssn.size(); j++) {
					if(ssn.get(j) == s.getSsn()) {
						students.add(s);
					}
				}
			}

			return students;
		} else {
			//might not be necesary now that im looking at it
			return null;
		}
	}

	public static void connectToDB() {
		try {
			Class.forName("com.mysql.jdbc.Driver");
			System.out.println("Driver Loaded");

			String host = "jdbc:mysql://18.191.16.207/ddherman";
			String uName = "ddherman";
			String uPass = "cs357";

			connection = DriverManager.getConnection(host, uName, uPass);
			System.out.println("Connection Succesful");

		} catch (Exception ex) {
			//System.out.println("Connection Failed");
			ex.printStackTrace();
		}
	}

	//next three methods just add all the data from each table
	//to a map.
	public static HashMap<Integer, Student> mapStudentData() {
		try {
			Statement st = connection.createStatement();
			ResultSet rs = st.executeQuery("SELECT * FROM Student");

			HashMap<Integer, Student> studentMap = new HashMap<Integer, Student>();
			Student studentData;

			while(rs.next()) {
				Integer ssn = rs.getInt("ssn");
				String firstName = rs.getString("firstName");
				String mi = rs.getString("mi");
				String lastName = rs.getString("lastName");
				String phone = rs.getString("phone");
				String birthDate = rs.getString("birthDate");
				String street = rs.getString("street");
				int zipCode = rs.getInt("zipCode");
				String deptId = rs.getString("deptId");

				studentData = new Student(ssn, firstName, mi, lastName, phone, birthDate,
						street, zipCode, deptId);

				studentMap.put(ssn, studentData);
			}

			return studentMap;

		} catch (SQLException ex) {
			ex.printStackTrace();
		}

		return null;
	}

	public static HashMap<Integer, Course> mapCourseData() {
		try {
			Statement st = connection.createStatement();
			ResultSet rs = st.executeQuery("SELECT * FROM Course");

			HashMap<Integer, Course> courseMap = new HashMap<Integer, Course>();
			Course courseData;

			while(rs.next()) {
				Integer courseId = rs.getInt("courseId");
				String subjectId = rs.getString("subjectId");
				int courseNumber = rs.getInt("courseNumber");
				String title = rs.getString("title");
				int numOfCredits = rs.getInt("numOfCredits");

				courseData = new Course(courseId, subjectId, courseNumber, title, numOfCredits);

				courseMap.put(courseId, courseData);
			}

			return courseMap;

		} catch (SQLException ex) {
			ex.printStackTrace();
		}

		return null;
	}

	public static HashMap<Integer, Enrollment> mapEnrollmentData() {
		try {
			Statement st = connection.createStatement();
			ResultSet rs = st.executeQuery("SELECT * FROM Enrollment");

			HashMap<Integer, Enrollment> enrollmentMap = new HashMap<Integer, Enrollment>();
			Enrollment enrollmentData;

			while(rs.next()) {
				Integer ssn = rs.getInt("ssn");
				String courseId = rs.getString("courseId");
				String dateRegistered = rs.getString("dateRegistered");
				String grade = rs.getString("grade");

				enrollmentData = new Enrollment(ssn, courseId, dateRegistered, grade);

				enrollmentMap.put(ssn, enrollmentData);
			}

			return enrollmentMap;

		} catch (SQLException ex) {
			ex.printStackTrace();
		}

		return null;
	}

}