JDK中有关23个经典设计模式的示例
2013-07-06 13:59
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Creational patterns
Abstract factory (recognizeable by creational methods returning an abstract/interface type)
java.util.Calendar#getInstance()
java.util.Arrays#asList()
java.util.ResourceBundle#getBundle()
java.net.URL#openConnection()
java.sql.DriverManager#getConnection()
java.sql.Connection#createStatement()
java.sql.Statement#executeQuery()
java.text.NumberFormat#getInstance()
java.lang.management.ManagementFactory(all
getXXX()methods)
java.nio.charset.Charset#forName()
javax.xml.parsers.DocumentBuilderFactory#newInstance()
javax.xml.transform.TransformerFactory#newInstance()
javax.xml.xpath.XPathFactory#newInstance()
Builder (recognizeable by creational methods returning the instance itself)
java.lang.StringBuilder#append()(unsynchronized)
java.lang.StringBuffer#append()(synchronized)
java.nio.ByteBuffer#put()(also on
CharBuffer,
ShortBuffer,
IntBuffer,
LongBuffer,
FloatBufferand
DoubleBuffer)
javax.swing.GroupLayout.Group#addComponent()
All implementations of
java.lang.Appendable
Factory method (recognizeable by creational methods returning a concrete type)
java.lang.Object#toString()(overrideable in all subclasses)
java.lang.Class#newInstance()
java.lang.Integer#valueOf(String)(also on
Boolean,
Byte,
Character,
Short,
Long,
Floatand
Double)
java.lang.Class#forName()
java.lang.reflect.Array#newInstance()
java.lang.reflect.Constructor#newInstance()
Prototype (recognizeable by creational methods returning a different instance of itself with the same properties)
java.lang.Object#clone()(the class has to implement
java.lang.Cloneable)
Singleton (recognizeable by creational methods returning the same instance (usually of itself) everytime)
java.lang.Runtime#getRuntime()
java.awt.Desktop#getDesktop()
Structural patterns
Adapter (recognizeable by creational methods taking an instance of different abstract/interface type and returning an implementation of own/another abstract/interface type which decorates/overrides the given instance)
java.io.InputStreamReader(InputStream)(returns a
Reader)
java.io.OutputStreamWriter(OutputStream)(returns a
Writer)
javax.xml.bind.annotation.adapters.XmlAdapter#marshal()and
#unmarshal()
Bridge (recognizeable by creational methods taking an instance of different abstract/interface type and returning an implementation of own abstract/interface type which delegates/uses the given instance)
None comes to mind yet. A fictive example would benew LinkedHashMap(LinkedHashSet<K>, List<V>)which returns an unmodifiable linked map which doesn't clone the items, but uses them. The
java.util.Collections#newSetFromMap()and
singletonXXX()methods however comes close.
Composite (recognizeable by behavioral methods taking an instance of same abstract/interface type)
java.util.Map#putAll(Map)
java.util.List#addAll(Collection)
java.util.Set#addAll(Collection)
java.nio.ByteBuffer#put(ByteBuffer)(also on
CharBuffer,
ShortBuffer,
IntBuffer,
LongBuffer,
FloatBufferand
DoubleBuffer)
java.awt.Container#add(Component)(practically all over Swing thus)
Decorator (recognizeable by creational methods taking an instance of same abstract/interface type)
All subclasses ofjava.io.InputStream,
OutputStream,
Readerand
Writerhave a constructor taking an instance of same type.
Almost all implementations of
java.util.List,
Setand
Maphave a constructor taking an instance of same type.
java.util.Collections, the
checkedXXX(),
synchronizedXXX()and
unmodifiableXXX()methods.
javax.servlet.http.HttpServletRequestWrapperand
HttpServletResponseWrapper
Facade (recognizeable by behavioral methods which internally uses instances of different independent abstract/interface types)
javax.faces.webapp.FacesServlet, it internally uses among others the abstract/interface types
ServletContext,
LifeCycle,
ViewHandler,
NavigationHandlerand many more without that the enduser has to worry about it (which are however overrideable by injection).
Flyweight (recognizeable by creational methods returning a cached instance, a bit the "multiton" idea)
java.lang.Integer#valueOf(int)(also on
Boolean,
Byte,
Character,
Short,
Long,
Floatand
Double)
Proxy (recognizeable by creational methods which returns an implementation of given abstract/interface type which in turn delegates/uses a different implementation of given abstract/interface type)
java.lang.reflect.Proxy
java.rmi.*, the whole API actually.
The Wikipedia example is IMHO a bit poor, lazy loading has actually completely nothing to do with the proxy pattern at all.
Behavioral patterns
Chain of responsibility (recognizeable by behavioral methods which (indirectly) invokes the same method inanother implementation of same abstract/interface type in a queue)
java.util.logging.Logger#log()
javax.servlet.Filter#doFilter()
Command (recognizeable by behavioral methods in an abstract/interface type which invokes a method in an implementation of a different abstract/interface type which has been encapsulated by the command implementation during its creation)
All implementations ofjava.lang.Runnable
All implementations of
javax.swing.Action
Interpreter (recognizeable by behavioral methods returning a structurally different instance/type of the given instance/type; note that parsing/formatting is not part of the pattern, determining the pattern and how to apply it is)
java.util.Pattern
java.text.Normalizer
All subclasses of
java.text.Format
All subclasses of
javax.el.ELResolver
Iterator (recognizeable by behavioral methods sequentially returning instances of a different type from a queue)
All implementations ofjava.util.Iterator(thus among others also
java.util.Scanner!).
All implementations of
java.util.Enumeration
Mediator (recognizeable by behavioral methods taking an instance of different abstract/interface type (usually using the command pattern) which delegates/uses the given instance)
java.util.Timer(all
scheduleXXX()methods)
java.util.concurrent.Executor#execute()
java.util.concurrent.ExecutorService(the
invokeXXX()and
submit()methods)
java.util.concurrent.ScheduledExecutorService(all
scheduleXXX()methods)
java.lang.reflect.Method#invoke()
Memento (recognizeable by behavioral methods which internally changes the state of the whole instance)
java.util.Date(the setter methods do that,
Dateis internally represented by a
longvalue)
All implementations of
java.io.Serializable
All implementations of
javax.faces.component.StateHolder
Observer (or Publish/Subscribe) (recognizeable by behavioral methods which invokes a method on an instance of another abstract/interface type, depending on own state)
java.util.Observer/
java.util.Observable(rarely used in real world though)
All implementations of
java.util.EventListener(practically all over Swing thus)
javax.servlet.http.HttpSessionBindingListener
javax.servlet.http.HttpSessionAttributeListener
javax.faces.event.PhaseListener
State (recognizeable by behavioral methods which changes its behaviour depending on the instance's state which can be controlled externally)
All implementations ofjava.util.Iterator
javax.faces.lifecycle.LifeCycle#execute()(controlled by
FacesServlet, the behaviour is dependent on current phase (state) of JSF lifecycle)
Strategy (recognizeable by behavioral methods in an abstract/interface type which invokes a method in an implementation of a different abstract/interface type which has been passed-in as method argument into the strategy implementation)
java.util.Comparator#compare(), executed by among others
Collections#sort().
javax.servlet.http.HttpServlet, the
service()and all
doXXX()methods take
HttpServletRequestand
HttpServletResponseand the implementor has to process them (and not to get hold of them as instance variables!).
javax.servlet.Filter#doFilter()
Template method (recognizeable by behavioral methods which already have a "default" behaviour definied by an abstract type)
All non-abstract methods ofjava.io.InputStream,
java.io.OutputStream,
java.io.Readerand
java.io.Writer.
All non-abstract methods of
java.util.AbstractList,
java.util.AbstractSetand
java.util.AbstractMap.
javax.servlet.http.HttpServlet, all the
doXXX()methods by default sends a HTTP 405 "Method Not Allowed" error to the response. You're free to implement none or any of them.
Visitor (recognizeable by two different abstract/interface types which has methods definied which takes each the otherabstract/interface type; the one actually calls the method of the other and the other executes the desired strategy on it)
javax.lang.model.element.AnnotationValueand
AnnotationValueVisitor
javax.lang.model.element.Elementand
ElementVisitor
javax.lang.model.type.TypeMirrorand
TypeVisitor
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