Demonstration of set functionality in beans : Java Beans « Language Basics « Java
Demonstration of set functionality in beans
/*
* file: BeanCollections.java
* package: oreilly.hcj.collections
*
* This software is granted under the terms of the Common Public License,
* CPL, which may be found at the following URL:
* http://www-124.ibm.com/developerworks/oss/CPLv1.0.htm
*
* Copyright(c) 2003-2005 by the authors indicated in the @author tags.
* All Rights are Reserved by the various authors.
*
########## DO NOT EDIT ABOVE THIS LINE ########## */
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import java.beans.PropertyVetoException;
import java.beans.VetoableChangeListener;
import java.beans.VetoableChangeSupport;
import java.io.Serializable;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
/*
* file: Purchase.java package: oreilly.hcj.collections
*
* This software is granted under the terms of the Common Public License, CPL,
* which may be found at the following URL:
* http://www-124.ibm.com/developerworks/oss/CPLv1.0.htm
*
* Copyright(c) 2003-2005 by the authors indicated in the @author tags. All
* Rights are Reserved by the various authors.
*
* ########## DO NOT EDIT ABOVE THIS LINE ##########
*/
/**
* A demo purchase bean.
*
* @author <a href=mailto:kraythe@arcor.de>Robert Simmons jr. (kraythe)</a>
* @version $Revision: 1.3 $
*/
class Purchase {
/** Holder for the property itemName. */
private String itemName;
/** Holder for the property price. */
private float price;
/**
* Creates a new Purchase object.
*/
public Purchase() {
}
/**
* Creates a new Purchase object.
*
* @param itemName
* The name of the item purchased.
* @param price
* The price of the item purchased.
*/
public Purchase(final String itemName, final float price) {
setItemName(itemName);
setPrice(price);
}
/**
* Setter for the property itemName.
*
* @param itemName
* The new name.
*/
public void setItemName(String itemName) {
this.itemName = itemName;
}
/**
* Getter for the property itemName.
*
* @return The current name.
*/
public String getItemName() {
return this.itemName;
}
/**
* Setter for the property price.
*
* @param price
* The new price.
*/
public void setPrice(float price) {
this.price = price;
}
/**
* Getter for the property price.
*
* @return The current price.
*/
public float getPrice() {
return this.price;
}
}
/* ########## End of File ########## */
/**
* Demonstration of set functionality in beans.
*
* @author <a href=mailto:kraythe@arcor.de>Robert Simmons jr. (kraythe)</a>
* @version $Revision: 1.3 $
*/
class Customer extends Object implements Serializable {
/** Use serialVersionUID for interoperability. */
private static final long serialVersionUID = 7282170508738698519L;
/** Provides support for property change events. */
private PropertyChangeSupport propertyChangeSupport = new PropertyChangeSupport(this);
/** Holds value of property purchases. */
private Set purchases;
/** Holds value of property purchases2. */
private Set purchases2;
/** Holds value of property purchases3. */
private Set purchases3 = new HashSet();
/** Name of the customer. */
private String name;
/** Utility field used by constrained properties. */
private VetoableChangeSupport vetoableChangeSupport = new VetoableChangeSupport(this);
/**
* Creates new Customer
*/
public Customer() {
}
/**
* Setter for the property name.
*
* @param name
* The new value for the property name.
*
* @throws PropertyVetoException
* If the change is vetoed.
*/
public void setName(final String name) throws PropertyVetoException {
final String oldName = this.name;
vetoableChangeSupport.fireVetoableChange("name", oldName, this.name);
this.name = name;
propertyChangeSupport.firePropertyChange("name", oldName, this.name);
}
/**
* Getter for the property name.
*
* @return The current value of the property name.
*/
public String getName() {
return this.name;
}
/**
* Setter for property purchases. Note that this doesn't protect the sets as
* they are given out to the PropertyChangeListener and PropertyVetoListener
* objects.
*
* @param purchases
* New value of property purchases.
*
* @throws PropertyVetoException
* If the change is vetoed.
*/
public void setPurchases(Set purchases) throws PropertyVetoException {
Set oldPurchases = this.purchases;
vetoableChangeSupport.fireVetoableChange("purchases", oldPurchases, this.purchases);
this.purchases = purchases;
propertyChangeSupport.firePropertyChange("purchases", oldPurchases, this.purchases);
}
/**
* Getter for property purchases.Note that this doesn't protect the sets as
* they are given out to the callers of this method.
*
* @return Value of property purchases.
*/
public Set getPurchases() {
return this.purchases;
}
/**
* Setter for property purchases2.This method fully protects the incomming set
* so that the vetoable change listener, and the propertyChangeListener cant
* change it.
*
* @param purchases2
* New value of property purchases2.
*
* @throws PropertyVetoException
* If the change is vetoed.
*/
public void setPurchases2(final Set purchases2) throws PropertyVetoException {
final Set newPurchases2;
if (purchases2 != null) {
newPurchases2 = Collections.unmodifiableSet(purchases2);
} else {
newPurchases2 = null;
}
final Set oldpurchases2 = this.getPurchases2();
vetoableChangeSupport.fireVetoableChange("purchases2", oldpurchases2, newPurchases2);
this.purchases2 = new HashSet(purchases2);
propertyChangeSupport.firePropertyChange("purchases2", oldpurchases2, getPurchases2());
}
/**
* Getter for property purchases2. Note that you will have to check for null
* in the return value.
*
* @return Value of property purchases2.
*/
public Set getPurchases2() {
if (this.purchases2 == null) {
return null;
}
return Collections.unmodifiableSet(this.purchases2);
}
/**
* Setter for property purchases3. This method fully protects the incomming
* set so that the vetoable change listener, and the propertyChangeListener
* cant change it. In addition, since the property can never be null, you dont
* have to worry about checking for null.
*
* @param purchases3
* New value of property purchases3.
*
* @throws PropertyVetoException
* If the change is vetoed.
* @throws NullPointerException
* If null is passed for purchases3.
*/
public void setPurchases3(final Set purchases3) throws PropertyVetoException {
if (purchases3 == null) {
throw new NullPointerException();
}
final Set oldPurchases3 = this.getPurchases3();
final Set newPurchases3 = Collections.unmodifiableSet(purchases3);
vetoableChangeSupport.fireVetoableChange("purchases3", oldPurchases3, newPurchases3);
this.purchases3 = new HashSet(purchases3);
propertyChangeSupport.firePropertyChange("purchases3", oldPurchases3, getPurchases3());
}
/**
* Getter for property purchases3.Returns the value of the property. Since the
* property can never be null, the user has the ability to use the return
* value without checking for null.
*
* @return Value of property purchases3; Note that this will never be null.
*/
public Set getPurchases3() {
return Collections.unmodifiableSet(this.purchases3);
}
/**
* @see java.beans.PropertyChangeListener
*/
public void addPropertyChangeListener(final PropertyChangeListener l) {
propertyChangeSupport.addPropertyChangeListener(l);
}
/**
* @see java.beans.VetoableChangeListener
*/
public void addVetoableChangeListener(final VetoableChangeListener l) {
vetoableChangeSupport.addVetoableChangeListener(l);
}
/**
* @see java.beans.PropertyChangeListener
*/
public void removePropertyChangeListener(final PropertyChangeListener l) {
propertyChangeSupport.removePropertyChangeListener(l);
}
/**
* @see java.beans.VetoableChangeListener
*/
public void removeVetoableChangeListener(final VetoableChangeListener l) {
vetoableChangeSupport.removeVetoableChangeListener(l);
}
}
/* ########## End of File ########## */
/**
* Demonstrate the collections issues with beans.
*
* @author <a href=mailto:kraythe@arcor.de>Robert Simmons jr. (kraythe)</a>
* @version $Revision: 1.3 $
*/
public class BeanCollections {
/** A demo customer set. */
private static final Set CUSTOMERS;
static {
CUSTOMERS = new HashSet();
try {
Customer customer = null;
HashSet purchs = null;
// -- Joe
customer = new Customer();
customer.setName("Joe");
purchs = new HashSet();
purchs.add(new Purchase("Cat Food", 22.34f));
purchs.add(new Purchase("Cat Treats", 5.45f));
purchs.add(new Purchase("Cat Toy", 12.95f));
customer.setPurchases(purchs);
customer.setPurchases2(purchs);
customer.setPurchases3(purchs);
CUSTOMERS.add(customer);
// -- Jon
customer = new Customer();
customer.setName("Jon");
purchs = new HashSet();
purchs.add(new Purchase("Dog Food", 35.95f));
purchs.add(new Purchase("Dog Toy", 9.24f));
customer.setPurchases(purchs);
customer.setPurchases2(purchs);
customer.setPurchases3(purchs);
CUSTOMERS.add(customer);
// -- Jane
customer = new Customer();
customer.setName("Jane");
purchs = new HashSet();
customer.setPurchases(purchs);
customer.setPurchases2(purchs);
customer.setPurchases3(purchs);
CUSTOMERS.add(customer);
} catch (final Exception ex) {
ex.printStackTrace();
}
}
/**
* Main Method.
*
* @param args
* command line arguments.
*/
public static void main(String[] args) {
try {
Iterator iter = CUSTOMERS.iterator();
Customer customer = null;
while (iter.hasNext()) {
customer = (Customer) iter.next();
someFunction(customer);
makeCustomerReport(customer);
}
} catch (final ClassCastException ex) {
System.out.println("--- See? I told you. ---");
ex.printStackTrace(System.out);
System.out.flush();
}
System.out.println();
System.out.println("--------------------------------------");
System.out.println();
// -- Write out the two types of report to show that they
// do the same thing. Note that the order might be slightly
// different due to the nature of Set iterators.
makeGroupReport(CUSTOMERS);
System.out.println();
System.out.println("--------------------------------------");
System.out.println();
makeGroupReportBetter(CUSTOMERS);
}
/**
* Make a purchases report for a customer.
*
* @param customer
* The customer for which to make a report.
*
* @throws NullPointerException
* If customers is null.
*/
public static void makeCustomerReport(final Customer customer) {
if (customer == null) {
throw new NullPointerException();
}
Set purchases = customer.getPurchases();
if (purchases != null) {
Iterator iter = purchases.iterator();
Purchase purch = null;
System.out.println("Purchases for " + customer.getName());
while (iter.hasNext()) {
purch = (Purchase) iter.next();
System.out.println(purch.getItemName() + "\t" + purch.getPrice());
}
}
}
/**
* Prepare a report of purchases for the given customers. Example with
* potential null in Set peoperties.
*
* @param customers
* The customers for which to prepare a report.
*
* @throws NullPointerException
* If customers is null.
*/
public static void makeGroupReport(final Set customers) {
if (customers == null) {
throw new NullPointerException();
}
Iterator purchaseIter = null;
Iterator customerIter = null;
Set purchases = null;
Customer customer = null;
Purchase purch = null;
customerIter = customers.iterator();
while (customerIter.hasNext()) {
customer = (Customer) customerIter.next();
System.out.println("Purchases for " + customer.getName());
purchases = customer.getPurchases3();
if (purchases != null) {
purchaseIter = purchases.iterator();
while (purchaseIter.hasNext()) {
purch = (Purchase) purchaseIter.next();
System.out.println(purch.getItemName() + "\t" + purch.getPrice());
}
}
System.out.print("Total Purchases = ");
if (purchases != null) {
System.out.println(purchases.size());
} else {
System.out.println(0);
}
System.out.println();
}
}
/**
* Prepare a report of purchases for the given customers. Example with
* potential no nulls in Set peoperties.
*
* @param customers
* The customers for which to prepare a report.
*
* @throws NullPointerException
* If customers is null.
*/
public static void makeGroupReportBetter(final Set customers) {
if (customers == null) {
throw new NullPointerException();
}
Iterator purchaseIter = null;
Iterator customerIter = null;
Set purchases = null;
Customer customer = null;
Purchase purch = null;
customerIter = customers.iterator();
while (customerIter.hasNext()) {
customer = (Customer) customerIter.next();
System.out.println("Purchases for " + customer.getName());
purchases = customer.getPurchases3();
purchaseIter = customer.getPurchases3().iterator();
while (purchaseIter.hasNext()) {
purch = (Purchase) purchaseIter.next();
System.out.println(purch.getItemName() + "\t" + purch.getPrice());
}
System.out.println("Total Purchases = " + purchases.size());
System.out.println();
}
}
/**
* Manipulate a customer.
*
* @param customer
* The customer to manipulate.
*
* @throws NullPointerException
* If customer is null.
*/
public static void someFunction(final Customer customer) {
if (customer == null) {
throw new NullPointerException();
}
Set purchs = customer.getPurchases();
Set names = new HashSet(); // going to use to store customer names.
names.add(new String("Jason"));
purchs.add(new String("Fred")); // typo, he meant names, not purchs.
}
}
/* ########## End of File ########## */
