Spring框架中的设计模式（四）

public class AdapterTest {
 
  public static void main(String[] args) {
    HoleMaker maker = new HoleMakerImpl();
    maker.makeHole(1);
    maker.makeHole(2);
    maker.makeHole(30);
    maker.makeHole(40);
  }
}
 
interface HoleMaker {
  public void makeHole(int diameter);
}
 
interface DrillBit {
  public void makeSmallHole();
  public void makeBigHole();
}
 
// Two adaptee objects
class BigDrillBit implements DrillBit {
         
  @Override
  public void makeSmallHole() {
    // do nothing
  }
 
  @Override
  public void makeBigHole() {
    System.out.println("Big hole is made byt WallBigHoleMaker");
  }
}
 
class SmallDrillBit implements DrillBit {
         
  @Override
  public void makeSmallHole() {
    System.out.println("Small hole is made byt WallSmallHoleMaker");
  }
 
  @Override
  public void makeBigHole() {
    // do nothing
  }
}
 
// Adapter class
class Drill implements HoleMaker {
 
  private DrillBit drillBit;
 
  public Drill(int diameter) {
    drillBit = getMakerByDiameter(diameter);
  }
 
  @Override
  public void makeHole(int diameter) {
    if (isSmallDiameter(diameter)) {
            drillBit.makeSmallHole();
    } else {
            drillBit.makeBigHole();
    }
  }
 
  private DrillBit getMakerByDiameter(int diameter) {
    if (isSmallDiameter(diameter)) {
            return new SmallDrillBit();
    }
    return new BigDrillBit();
  }
 
  private boolean isSmallDiameter(int diameter) {
    return diameter < 10;
  }
}
 
// Client class
class HoleMakerImpl implements HoleMaker {
         
  @Override
  public void makeHole(int diameter) {
    HoleMaker maker = new Drill(diameter);
    maker.makeHole(diameter);
  }
}

public JBossLoadTimeWeaver(ClassLoader classLoader) {
  private final JBossClassLoaderAdapter adapter;
 
  Assert.notNull(classLoader, "ClassLoader must not be null");
  if (classLoader.getClass().getName().startsWith("org.jboss.modules")) {
    // JBoss AS 7 or WildFly 8
    this.adapter = new JBossModulesAdapter(classLoader);
  }
  else {
    // JBoss AS 6
    this.adapter = new JBossMCAdapter(classLoader);
  }
}

@Override
public void addTransformer(ClassFileTransformer transformer) {
  this.adapter.addTransformer(transformer);
}
 
@Override
public ClassLoader getInstrumentableClassLoader() {
  return this.adapter.getInstrumentableClassLoader();
}

public class DecoratorSample {
 
  @Test
  public void test() {
    Coffee sugarMilkCoffee=new MilkDecorator(new SugarDecorator(new BlackCoffee()));
    assertEquals(sugarMilkCoffee.getPrice(), 6d, 0d);
  }
}
 
// decorated
abstract class Coffee{
  protected int candied=0;
  protected double price=2d;
  public abstract int makeMoreCandied();
  public double getPrice(){
    return this.price;
  }
  public void setPrice(double price){
    this.price+=price;
  }
}
class BlackCoffee extends Coffee{
  @Override
  public int makeMoreCandied(){
    return 0;
  }
  @Override
  public double getPrice(){
    return this.price;
  }
}
 
// abstract decorator
abstract class CoffeeDecorator extends Coffee{
  protected Coffee coffee;
  public CoffeeDecorator(Coffee coffee){
    this.coffee=coffee;
  }
  @Override
  public double getPrice(){
    return this.coffee.getPrice();
  }
  @Override
  public int makeMoreCandied(){
    return this.coffee.makeMoreCandied();
  }
}
 
// concrete decorators
class MilkDecorator extends CoffeeDecorator{
  public MilkDecorator(Coffee coffee){
    super(coffee);
  }
  @Override
  public double getPrice(){
    return super.getPrice()+1d;
  }
  @Override
  public int makeMoreCandied(){
    return super.makeMoreCandied()+1;
  }
}
class SugarDecorator extends CoffeeDecorator{
  public SugarDecorator(Coffee coffee){
    super(coffee);
  }
  @Override
  public double getPrice(){
    return super.getPrice()+3d;
  }
  @Override
  public int makeMoreCandied(){
    return super.makeMoreCandied()+1;
  }
}

private final Cache targetCache;
/**
 * Create a new TransactionAwareCache for the given target Cache.
 * @param targetCache the target Cache to decorate
 */
public TransactionAwareCacheDecorator(Cache targetCache) {
  Assert.notNull(targetCache, "Target Cache must not be null");
  this.targetCache = targetCache;
}

@Override
public void put(final Object key, final Object value) {
  if (TransactionSynchronizationManager.isSynchronizationActive()) {
    TransactionSynchronizationManager.registerSynchronization(
      new TransactionSynchronizationAdapter() {
        @Override
        public void afterCommit() {
          targetCache.put(key, value);
        }
    });
  }
  else {
    this.targetCache.put(key, value);
  }
}
 
@Override
public void evict(final Object key) {
  if (TransactionSynchronizationManager.isSynchronizationActive()) {
          TransactionSynchronizationManager.registerSynchronization(
            new TransactionSynchronizationAdapter() {
              @Override
              public void afterCommit() {
                targetCache.evict(key);
              }
          });
  }
  else {
    this.targetCache.evict(key);
  }
}

/**
 * Event published as early as conceivably possible as soon as a {@link SpringApplication}
 * has been started - before the {@link Environment} or {@link ApplicationContext} is
 * available, but after the {@link ApplicationListener}s have been registered. The source
 * of the event is the {@link SpringApplication} itself, but beware of using its internal
 * state too much at this early stage since it might be modified later in the lifecycle.
 *
 * @author Dave Syer
 */
@SuppressWarnings("serial")
public class ApplicationStartedEvent extends SpringApplicationEvent {

	/**
	 * Create a new {@link ApplicationStartedEvent} instance.
	 * @param application the current application
	 * @param args the arguments the application is running with
	 */
	public ApplicationStartedEvent(SpringApplication application, String[] args) {
		super(application, args);
	}

}

/**
 * Listener for the {@link SpringApplication} {@code run} method.
 * {@link SpringApplicationRunListener}s are loaded via the {@link SpringFactoriesLoader}
 * and should declare a public constructor that accepts a {@link SpringApplication}
 * instance and a {@code String[]} of arguments. A new
 * {@link SpringApplicationRunListener} instance will be created for each run.
 *
 * @author Phillip Webb
 * @author Dave Syer
 */
public interface SpringApplicationRunListener {

	/**
	 * Called immediately when the run method has first started. Can be used for very
	 * early initialization.
	 */
	void started();

	/**
	 * Called once the environment has been prepared, but before the
	 * {@link ApplicationContext} has been created.
	 * @param environment the environment
	 */
	void environmentPrepared(ConfigurableEnvironment environment);

	/**
	 * Called once the {@link ApplicationContext} has been created and prepared, but
	 * before sources have been loaded.
	 * @param context the application context
	 */
	void contextPrepared(ConfigurableApplicationContext context);

	/**
	 * Called once the application context has been loaded but before it has been
	 * refreshed.
	 * @param context the application context
	 */
	void contextLoaded(ConfigurableApplicationContext context);

	/**
	 * Called immediately before the run method finishes.
	 * @param context the application context or null if a failure occurred before the
	 * context was created
	 * @param exception any run exception or null if run completed successfully.
	 */
	void finished(ConfigurableApplicationContext context, Throwable exception);

}

/**
 * {@link SpringApplicationRunListener} to publish {@link SpringApplicationEvent}s.
 * <p>
 * Uses an internal {@link ApplicationEventMulticaster} for the events that are fired
 * before the context is actually refreshed.
 *
 * @author Phillip Webb
 * @author Stephane Nicoll
 */
public class EventPublishingRunListener implements SpringApplicationRunListener, Ordered {

	private final SpringApplication application;

	private final String[] args;

	private final ApplicationEventMulticaster initialMulticaster;

	public EventPublishingRunListener(SpringApplication application, String[] args) {
		this.application = application;
		this.args = args;
		this.initialMulticaster = new SimpleApplicationEventMulticaster();
		for (ApplicationListener<?> listener : application.getListeners()) {
			this.initialMulticaster.addApplicationListener(listener);
		}
	}

	@Override
	public int getOrder() {
		return 0;
	}

	@Override
	public void started() {
		this.initialMulticaster
				.multicastEvent(new ApplicationStartedEvent(this.application, this.args));
	}

	@Override
	public void environmentPrepared(ConfigurableEnvironment environment) {
		this.initialMulticaster.multicastEvent(new ApplicationEnvironmentPreparedEvent(
				this.application, this.args, environment));
	}

	@Override
	public void contextPrepared(ConfigurableApplicationContext context) {

	}

	@Override
	public void contextLoaded(ConfigurableApplicationContext context) {
		for (ApplicationListener<?> listener : this.application.getListeners()) {
			if (listener instanceof ApplicationContextAware) {
				((ApplicationContextAware) listener).setApplicationContext(context);
			}
			context.addApplicationListener(listener);
		}
		this.initialMulticaster.multicastEvent(
				new ApplicationPreparedEvent(this.application, this.args, context));
	}

	@Override
	public void finished(ConfigurableApplicationContext context, Throwable exception) {
		// Listeners have been registered to the application context so we should
		// use it at this point
		context.publishEvent(getFinishedEvent(context, exception));
	}

	private SpringApplicationEvent getFinishedEvent(
			ConfigurableApplicationContext context, Throwable exception) {
		if (exception != null) {
			return new ApplicationFailedEvent(this.application, this.args, context,
					exception);
		}
		return new ApplicationReadyEvent(this.application, this.args, context);
	}

}

public class SingletonTest {
 
  @Test
  public void test() {
    President president1 = (President) SingletonsHolder.PRESIDENT.getHoldedObject();
    President president2 = (President) SingletonsHolder.PRESIDENT.getHoldedObject();
    assertTrue("Both references of President should point to the same object", president1 == president2);
    System.out.println("president1 = "+president1+" and president2 = "+president2);
    // sample output
    // president1 = com.waitingforcode.test.President@17414c8 and president2 = com.waitingforcode.test.President@17414c8
 
  }
 
}
 
enum SingletonsHolder {
   
  PRESIDENT(new President());
   
  private Object holdedObject;
   
  private SingletonsHolder(Object o) {
          this.holdedObject = o;
  }
   
  public Object getHoldedObject() {
          return this.holdedObject;
  }
         
}
 
class President {
}

/**
 * Expose the singleton instance or create a new prototype instance.
 * @see #createInstance()
 * @see #getEarlySingletonInterfaces()
 */
@Override
public final T getObject() throws Exception {
  if (isSingleton()) {
    return (this.initialized ? this.singletonInstance : getEarlySingletonInstance());
  }
  else {
    return createInstance();
  }
}

public class SingletonSpringTest {
 
  @Test
  public void test() {
    // retreive two different contexts
    ApplicationContext firstContext = new FileSystemXmlApplicationContext("applicationContext-test.xml");
    ApplicationContext secondContext = new FileSystemXmlApplicationContext("applicationContext-test.xml");
     
    // prove that both contexts are loaded by the same class loader
    assertTrue("Class loaders for both contexts should be the same", 
      firstContext.getClassLoader() == secondContext.getClassLoader());
    // compare the objects from different contexts
    ShoppingCart firstShoppingCart = (ShoppingCart) firstContext.getBean("shoppingCart");
    ShoppingCart secondShoppingCart = (ShoppingCart) secondContext.getBean("shoppingCart");
    assertFalse("ShoppingCart instances got from different application context shouldn't be the same", 
      firstShoppingCart == secondShoppingCart);
     
    // compare the objects from the same context
    ShoppingCart firstShoppingCartBis = (ShoppingCart) firstContext.getBean("shoppingCart");
    assertTrue("ShoppingCart instances got from the same application context should be the same", 
      firstShoppingCart == firstShoppingCartBis);
  }
}