import java.io.*; public class Customer implements Serializable { public Customer(int theAge, int theSex, String[] theHobbies) { age = theAge; sex = theSex; hobbies = theHobbies; } public int getAge() { return age; } public int getSex() { return sex; } public boolean hasHobby(String aHobby) { if (aHobby == "") return true; for (int i = 0; i < hobbies.length; i++) if (hobbies[i].equals(aHobby)) return true; return false; }

public void reset() { age = 0; sex = 0; hobbies = null; } public String toString() { String result = "Age: " + age + ", Sex: "; if (sex == Product.MALE) result += "Male"; else if (sex == Product.FEMALE) result += "Female"; else result += "Male or Female"; result += ", Hobbies:"; for (int i = 0; i < hobbies.length; i++) result += " " + hobbies[i]; return result; } private int age; private int sex; private String[] hobbies; }

import java.rmi.*; public interface Product extends Remote { String getDescription() throws RemoteException; static final int MALE = 1; static final int FEMALE = 2; static final int BOTH = MALE + FEMALE; }

import java.rmi.*; import java.rmi.server.*; public class ProductImpl extends UnicastRemoteObject implements Product { public ProductImpl(String n, int s, int age1, int age2, String h) throws RemoteException { name = n; ageLow = age1; ageHigh = age2; sex = s; hobby = h; } public boolean match(Customer c) // local method { if (c.getAge() ageHigh) return false; if (!c.hasHobby(hobby)) return false; if ((sex & c.getSex()) == 0) return false; return true; }

public String getDescription() throws RemoteException { return "I am a " + name + ". Buy me!"; } private String name; private int ageLow; private int ageHigh; private int sex; private String hobby; }

import java.awt.*; import java.awt.event.*; import java.io.*; import java.rmi.*; import java.rmi.server.*; import java.util.*; import javax.swing.*; public class WarehouseClient { public static void main(String[] args) { JFrame frame = new WarehouseClientFrame(); frame.show(); }

class WarehouseClientFrame extends JFrame implements ActionListener { public WarehouseClientFrame() { initUI(); System.setSecurityManager(new RMISecurityManager()); try { Properties props = new Properties(); String fileName = "WarehouseClient.properties"; FileInputStream in = new FileInputStream(fileName); props.load(in); String url = props.getProperty("warehouse.url"); if (url == null) url = "rmi://localhost/central_warehouse"; centralWarehouse = (Warehouse)Naming.lookup(url); } catch(Exception e) { System.out.println("Error: Can't connect to warehouse. " + e); }

private void callWarehouse(Customer c) { try { Vector recommendations = centralWarehouse.find(c); result.setText(c + "\n"); for (int i = 0; i < recommendations.size(); i++) { Product p = (Product)recommendations.get(i); String t = p.getDescription() + "\n"; result.append(t); } catch(Exception e) { result.setText("Error: " + e); }

public void actionPerformed(ActionEvent evt) { Object[] hobbyObjects = hobbies.getSelectedValues(); String[] hobbyStrings = new String[hobbyObjects.length]; System.arraycopy(hobbyObjects, 0, hobbyStrings, 0, hobbyObjects.length); Customer c = new Customer(Integer.parseInt(age.getText()), (male.isSelected() ? Product.MALE : 0) + (female.isSelected() ? Product.FEMALE : 0), hobbyStrings); callWarehouse(c); } private void initUI() { setTitle("WarehouseClient"); setSize(300, 300); addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent e) { System.exit(0); } } ); getContentPane().setLayout(new GridBagLayout());

GridBagConstraints gbc = new GridBagConstraints(); gbc.fill = GridBagConstraints.HORIZONTAL; gbc.weightx = 100; gbc.weighty = 0; add(new JLabel("Age:"), gbc, 0, 0, 1, 1); age = new JTextField(4); age.setText("20"); add(age, gbc, 1, 0, 1, 1); male = new JCheckBox("Male", true); female = new JCheckBox("Female", true); add(male, gbc, 0, 1, 1, 1); add(female, gbc, 1, 1, 1, 1); gbc.weighty = 100; add(new JLabel("Hobbies"), gbc, 0, 2, 1, 1); String[] choices = { "Gardening", "Beauty", "Computers", "Household", "Sports" }; gbc.fill = GridBagConstraints.BOTH; hobbies = new JList(choices); add(new JScrollPane(hobbies), gbc, 1, 2, 1, 1);

gbc.weighty = 0; gbc.fill = GridBagConstraints.NONE; JButton submitButton = new JButton("Submit"); add(submitButton, gbc, 0, 3, 2, 1); submitButton.addActionListener(this); gbc.weighty = 100; gbc.fill = GridBagConstraints.BOTH; result = new JTextArea(4, 40); result.setEditable(false); add(result, gbc, 0, 4, 2, 1); } private void add(Component c, GridBagConstraints gbc, int x, int y, int w, int h) { gbc.gridx = x; gbc.gridy = y; gbc.gridwidth = w; gbc.gridheight = h; getContentPane().add(c, gbc); }

private Warehouse centralWarehouse; private JTextField age; private JCheckBox male; private JCheckBox female; private JList hobbies; private JTextArea result; }

RMI Callbacks Server Calls Back the Client True Peer-to-Peer Interaction Client itself must be exportable remote object Registered with a remote server

Example Quote Client/Server Server maintains a list of quotes Client makes additions to list of quotes Callback used to allow server to asynchronously update clients with list of quotes

Steps Specify Remote Server Interface Specify Remote Client Interface Develop Remote-server object Develop Client Compile Run