book

Java Network Programming, Second Edition

by Elliotte Rusty Harold

August 2000

Intermediate to advanced

760 pages

21h

English

O'Reilly Media, Inc.

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About the Second Edition

What Can a Network Program Do?Retrieve Data and Display ItRepeatedly Retrieve DataSend DataFile storageMassively parallel computingSmart formsPeer-to-Peer InteractionGamesChatWhiteboardsServersSearching the WebElectronic CommerceApplications of the FutureUbiquitous computingInteractive televisionCollaboration
Networks
The Host-to-Network LayerThe Internet LayerThe Transport LayerThe Application Layer
IP Addresses and Domain NamesPorts
Internet Address ClassesFirewallsProxy Servers
IETF RFCsW3C Recommendations
URIsURNsURLsRelative URLs
Where Do Applets and Classes Come from?Security: Who Can an Applet Talk to and What Can It Say?
Output Streams
Marking and Resetting
Chaining Filters TogetherBuffered StreamsPrintStreamPrintStream is evil and network programmers shouldavoid it like the plaguePushbackInputStreamData StreamsCompressing StreamsDigest StreamsEncrypting Streams
WritersOutputStreamWriterReadersFilter Readers and WritersBuffered readers and writersLineNumberReaderPushbackReaderPrintWriter
Running ThreadsSubclassing ThreadImplementing the Runnable Interface
Race ConditionsPollingCallbacks
Synchronized BlocksSynchronized MethodsAlternatives to Synchronization
PrioritiesPreemptionBlockingYieldingSleepingJoining threadsWaiting on an objectPriority-based preemptionFinish
DNS, IP Addresses, and All That
Creating New InetAddress Objectspublic static InetAddress InetAddress.getByName(String hostName) throws UnknownHostExceptionpublic static InetAddress[ ] InetAddress.getAllByName (String hostName) throws UnknownHostExceptionpublic static InetAddress InetAddress.getLocalHost( ) throws UnknownHostExceptionSecurity issuesOther sources of InetAddress objectsGetter Methodspublic String getHostName( )public String getHostAddress( )public byte[ ] getAddress( )Object Methodspublic boolean equals(Object o)public int hashCode( )public String toString( )
HostLookupProcessing Web Server Log Files
The URL ClassCreating New URLsConstructing a URL from a stringConstructing a URL from its component partsConstructing relative URLsSpecifying a URLStreamHandlerOther sources of URL objectsSplitting a URL into Piecespublic String getProtocol( )public String getHost( )public int getPort( )public String getFile( )public String getPath( ) // Java 1.3public string getRef( )public string getQuery( ) // Java 1.3public string getUserInfo( ) // Java 1.3public string getAuthority( ) // Java 1.3Retrieving Data from a URLpublic final InputStream openStream( ) throws IOExceptionpublic URLConnection openConnection( ) throws IOExceptionpublic final Object getContent( ) throws IOExceptionpublic final Object getContent(Class[ ] classes) throws IOException // Java 1.3Utility Methodspublic boolean sameFile(URL other)public String toExternalForm( )The Object Methodspublic String toString( )public boolean equals(Object o)public int hashCode( )Methods for Protocol Handlerspublic static synchronized void setURLStreamHandlerFactory (URLStreamHandlerFactory factory)protected void set(String protocol, String host, int port, String file, String ref )
URLEncoderURLDecoder
The Authenticator ClassThe PasswordAuthentication ClassThe JPasswordField Class
HTML on Components
Constructing HTML User Interfaces on the FlyHandling HyperlinksReading HTML Directly
HTMLEditorKit.ParserHTMLEditorKit.ParserCallbackHTML.TagAttributes
Using java.applet.Applet to Download DataFiguring Out Where the Applet Came frompublic URL getDocumentBase( )public URL getCodeBase( )Downloading Imagespublic Image getImage(URL u)public Image getImage(URL path, String filename)Downloading Soundspublic void play(URL u)public void play(URL url, String filename)public AudioClip getAudioClip(URL u)public AudioClip getAudioClip(URL url, String filename)public static final AudioClip newAudioClip(URL url) // Java 1.2
The ImageObserver Constants
The ConstructorAdding Images to MediaTrackerspublic void addImage(Image image, int id)public void addImage(Image image, int id, int width, int height)Checking Whether Media Has Loadedpublic boolean checkID(int id)public boolean checkID(int id, boolean load)public boolean checkAll( )public boolean checkAll(boolean load)Waiting for Media to Loadpublic void waitForID(int id) throws InterruptedExceptionpublic boolean waitForID(int id, long milliseconds) throws InterruptedExceptionpublic boolean waitForAll( ) throws InterruptedExceptionpublic boolean waitForAll(long milliseconds) throws InterruptedExceptionError Checkingpublic boolean isErrorAny( )public Object[ ] getErrorsAny( )public boolean isErrorID(int id)public Object[ ] getErrorsID(int id)Checking the Status of Mediapublic int statusAll(boolean load)public int statusID(int id, boolean load)Removing Images from MediaTrackers
Socket Basics
The Constructorspublic Socket(String host, int port) throws UnknownHostException, IOExceptionpublic Socket(InetAddress host, int port) throws IOExceptionpublic Socket(String host, int port, InetAddress interface, int localPort) throws IOExceptionpublic Socket(InetAddress host, int port, InetAddress interface, int localPort) throws IOExceptionprotected Socket( )protected Socket(SocketImpl impl)Getting Information About a Socketpublic InetAddress getInetAddress( )public int getPort( )public int getLocalPort( )public InetAddress getLocalAddress( )public InputStream getInputStream( ) throws IOExceptionpublic OutputStream getOutputStream( ) throws IOExceptionClosing the Socketpublic synchronized void close( ) throws IOExceptionHalf-closed sockets // Java 1.3The Object Methodspublic String toString( )Setting Socket OptionsTCP_NODELAYSO_LINGERSO_TIMEOUTSO_RCVBUFSO_SNDBUFSO_KEEPALIVE
FingerWhois
The ServerSocket ClassThe Constructorspublic ServerSocket(int port) throws IOException, BindExceptionpublic ServerSocket(int port, int queueLength) throws IOException, BindExceptionpublic ServerSocket(int port, int queueLength, InetAddress bindAddress) throws BindException, IOExceptionAccepting and Closing Connectionspublic Socket accept( ) throws IOExceptionpublic void close( ) throws IOExceptionThe get Methodspublic InetAddress getInetAddress( )public int getLocalPort( )Socket Optionspublic void setSoTimeout(int timeout) throws SocketExceptionpublic int getSoTimeout( ) throws IOExceptionThe Object Methodspublic String toString( )Implementationpublic static synchronized void setSocketFactory (SocketImpl Factory fac) throws IOExceptionProtected final void implAccept(Socket s) throws IOException
Client TesterHTTP ServersA single-file serverA redirectorA full-fledged HTTP server
Secure Communications
Choosing the Cipher SuitesEvent HandlersSession ManagementClient Mode
Choosing the Cipher SuitesSession ManagementClient Mode
The UDP Protocol
The ConstructorsConstructors for receiving datagramsConstructors for sending datagramsThe get Methodspublic InetAddress getAddress( )public int getPort( )public byte[ ] getData( )public int getLength( )public int getOffset( ) // Java 1.2The set Methodspublic void setData(byte[ ] data)public void setData(byte[ ] data, int offset, int length) // Java 1.2public void setAddress(InetAddress remote)public void setPort(int port)public void setLength(int length)
The Constructorspublic DatagramSocket( ) throws SocketExceptionpublic DatagramSocket(int port) throws SocketExceptionpublic DatagramSocket(int port, InetAddress address) throws SocketExceptionSending and Receiving Datagramspublic void send(DatagramPacket dp) throws IOExceptionpublic void receive(DatagramPacket dp) throws IOExceptionpublic void close( )public int getLocalPort( )Managing Connectionspublic void connect(InetAddress host, int port) // Java 1.2public void disconnect( ) // Java 1.2public int getPort( ) // Java 1.2public InetAddress getInetAddress( ) // Java 1.2Socket OptionsSO_TIMEOUTSO_RCVBUFSO_SNDBUF
Simple UDP ClientsUDPServerA UDP Echo Client
What Is a Multicast Socket?Multicast Addresses and GroupsClients and ServersRouters and Routing
The Constructorspublic MulticastSocket( ) throws SocketExceptionpublic MulticastSocket(int port) throws SocketExceptionCommunicating with a Multicast Grouppublic void joinGroup(InetAddress address) throws IOExceptionpublic void leaveGroup(InetAddress address) throws IOExceptionpublic void send(DatagramPacket packet, byte ttl) throws IOExceptionpublic void setInterface(InetAddress address) throws SocketExceptionpublic InetAddress getInterface( ) throws SocketExceptionpublic void setTimeToLive(int ttl) throws IOException // Java 1.2public int getTimeToLive( ) throws IOException // Java 1.2
Opening URLConnections
Retrieving Specific MIME Header Fieldspublic String getContentType( )public int getContentLength( )public String getContentEncoding( )public long getDate( )public long getExpiration( )public long getLastModified( )Retrieving Arbitrary MIME Header Fieldspublic String getHeaderField(String name)public String getHeaderFieldKey(int n)public String getHeaderField(int n)public long getHeaderFieldDate(String name, long default)public int getHeaderFieldInt(String name, int default)
protected URL urlconnectedallowUserInteractiondefaultAllowUserInteractiondoInputdoOutputifModifiedSinceuseCachesdefaultUseCaches
Getting Contentpublic Object getContent( ) throws IOExceptionpublic Object getContent(Class[ ] classes) throws IOException // Java 1.3ContentHandlerFactory
The Request MethodHEADOPTIONSDELETEPUTTRACEDisconnecting from the ServerHandling Server ResponsesError conditionsRedirectsProxies
What Is a Protocol Handler?
The ConstructorMethods for Parsing URLsProtected void parseURL(URL u, String spec, int start, int limit)Protected String toExternalForm(URL u)Protected void setURL(URL u, String protocol, String host, int port, String file, String ref )Protected int getDefaultPort( ) // Java 1.3Protected InetAddress getHostAddress(URL u) // Java 1.3Protected boolean hostsEqual(URL u1, URL u2) // Java 1.3Protected boolean sameFile(URL u1, URL u2) // Java 1.3Protected boolean equals(URL u1, URL u2) // Java 1.3Protected int hashCode(URL u) // Java 1.3A Method for ConnectingProtected abstract URLConnection openConnection(URL u) throws IOException
A daytime Protocol HandlerA chargen Protocol Handler
What Is a Content Handler?
A Content Handler for Tab-Separated ValuesUsing Content HandlersChoosing Return Types
The createContentHandler( ) MethodInstalling Content Handler Factories
What Is Remote Method Invocation?SecurityObject SerializationUnder the Hood
The Server SideThe Client SideCompiling the StubsStarting the ServerRunning the Client
An Applet Client for a Remote ObjectAn Application Client for a Remote Object
The Remote InterfaceThe Naming Classpublic static String[ ] list(String url) throws RemoteException, MalformedURLExceptionpublic static Remote lookup(String url) throws RemoteException, NotBoundException, AccessException, MalformedURLExceptionpublic static void bind(String url, Remote object) throws RemoteException, AlreadyBoundException, MalformedURLException, AccessExceptionpublic static void unbind(String url) throws RemoteException, NotBoundException, AlreadyBoundException, MalformedURLException, AccessException // Java 1.2public static void rebind(String url, Remote object) throws RemoteException, AccessException, MalformedURLExceptionThe RMISecurityManager Classpublic RMISecurityManager( )public Object getSecurityContext( )Checking operationsRemote Exceptions
The Registry InterfaceThe LocateRegistry Class
The RemoteObject ClassThe RemoteServer ClassConstructorsGetting information about the clientLoggingThe UnicastRemoteObject ClassExceptions
What Is the JavaMail API?
Sending Email from an ApplicationSending Email from an Applet
The Address ClassThe InternetAddress ClassThe NewsAddress Class
The ConstructorsParsing Methods
Creating MessagesReplying to messagesGetting messages from foldersBasic Header InfoThe From addressThe Reply-to addressThe recipient addressesThe subject of the messageThe date of the messageSaving changesFlagsFoldersSearching
AttributesHeadersContentReading the contents of the partWriting the contents of the part
Opening FoldersBasic Folder InfoManaging FoldersManaging Messages in FoldersSubscriptionsListing the Contents of a FolderChecking for MailGetting Messages from FoldersSearching FoldersFlagsEvent HandlingUtility Methods

Content preview from Java Network Programming, Second Edition

Chapter 15. The URLConnection Class

URLConnection is an abstract class that represents an active connection to a resource specified by a URL. The URLConnection class has two different but related purposes. First, it provides more control over the interaction with a server than the URL class. With a URLConnection, you can inspect the MIME headers sent by an HTTP server and respond accordingly. You can adjust the MIME header fields used in the client request. You can use a URLConnection to download binary files. Finally, a URLConnection lets you send data back to a web server with POST or PUT and use other HTTP request methods. We will explore all of these techniques in this chapter.

Second, the URLConnection class is part of Java’s protocol handler mechanism, which also includes the URLStreamHandler class. The idea behind protocol handlers is simple: they separate the details of processing a protocol from processing particular data types, providing user interfaces, and doing the other work that a monolithic web browser performs. The base java.net.URLConnection class is abstract; to implement a specific protocol, you write a subclass. These subclasses can be loaded at runtime by your own applications or by the HotJava browser; in the future, it may be possible for Java applications to download protocol handlers over the Net as needed, making them automatically extensible. For example, if your browser runs across a URL with a strange prefix, such as compress:, rather than throwing ...