AbstractInterruptibleChannel接口定义: http://donald-draper.iteye.com/blog/2369238
SelectableChannel接口定义: http://donald-draper.iteye.com/blog/2369317
SelectionKey定义: http://donald-draper.iteye.com/blog/2369499
SelectorProvider定义: http://donald-draper.iteye.com/blog/2369615
AbstractSelectableChannel定义: http://donald-draper.iteye.com/blog/2369742
NetworkChannel接口定义: http://donald-draper.iteye.com/blog/2369773
ServerSocketChannel定义: http://donald-draper.iteye.com/blog/2369836
ServerSocketChannelImpl解析: http://donald-draper.iteye.com/blog/2370912
Selector定义: http://donald-draper.iteye.com/blog/2370015
AbstractSelector定义: http://donald-draper.iteye.com/blog/2370138
SelectorImpl分析 : http://donald-draper.iteye.com/blog/2370519
WindowsSelectorImpl解析一(FdMap,PollArrayWrapper):
http://donald-draper.iteye.com/blog/2370811
WindowsSelectorImpl解析二(选择操作,通道注册,通道反注册,选择器关闭等):
http://donald-draper.iteye.com/blog/2370862
ByteChannel,分散聚集通道接口的定义(SocketChannel):
http://donald-draper.iteye.com/blog/2371065
前面一篇文章我们看了一个socket通道继承的接口 ByteChannel, ByteChannel主要是继承了
可读(ReadableByteChannel)可写(WritableByteChannel)通道接口和分散(ScatteringByteChannel)聚集(ScatteringByteChannel)通道接口;可读通道接口,可以从通道读取字节序列写到缓存区;可写通道接口,可以从缓存区读取字节序列写到通道;分散通道可以从通道读取字节序列,写到一组缓存区中,聚集通道可以从一组缓存区读取字节序列,写到通道。今天我们就来看下SocketChannel接口的定义。
package java.nio.channels; import java.io.IOException; import java.net.Socket; import java.net.SocketOption; import java.net.SocketAddress; import java.nio.ByteBuffer; import java.nio.channels.spi.AbstractSelectableChannel; import java.nio.channels.spi.SelectorProvider; /** * A selectable channel for stream-oriented connecting sockets. *SocketChannel是一个面向流的连接socket可选通道。 * A socket channel is created by invoking one of the {@link #open open} * methods of this class. It is not possible to create a channel for an arbitrary, * pre-existing socket. A newly-created socket channel is open but not yet * connected. An attempt to invoke an I/O operation upon an unconnected * channel will cause a {@link NotYetConnectedException} to be thrown. A * socket channel can be connected by invoking its {@link #connect connect} * method; once connected, a socket channel remains connected until it is * closed. Whether or not a socket channel is connected may be determined by * invoking its {@link #isConnected isConnected} method. *socket通道调用#open方法创建一个socket通道。如果socket已经存在,则不可能强制创建一个通道。 一个新创建的socket通道处于打开状态,但还没有连接。在一个没有连接的通道,调用IO操作,将会引起 一个NotYetConnectedException抛出。socket通道可以调用#connect方法连接一个socket地址; 一旦建立连接,在连接关闭之前,通道都是可连接的。我们可以通道#isConnected方法,判断一个socket通道 是否建立连接。 * A socket * channel may be created and the process of establishing the link to the * remote socket may be initiated via the {@link #connect connect} method for * later completion by the {@link #finishConnect finishConnect} method. * Whether or not a connection operation is in progress may be determined by * invoking the {@link #isConnectionPending isConnectionPending} method. *socket通道支持非阻塞模式连接;一个socket通道已经建立的情况下,调用#connect方法 初始化建立远端socket过程,之后通过#finishConnect完成连接。一个连接操作是否正在进行, 可以通过#isConnectionPending方法判断。 *Socket channels support asynchronous shutdown, which is similar * to the asynchronous close operation specified in the {@link Channel} class. * If the input side of a socket is shut down by one thread while another * thread is blocked in a read operation on the socket's channel, then the read * operation in the blocked thread will complete without reading any bytes and * will return -1. If the output side of a socket is shut down by one * thread while another thread is blocked in a write operation on the socket's * channel, then the blocked thread will receive an {@link * AsynchronousCloseException}. *socket通道支持异步关闭,这个与Channel的关闭操作相似。如果其他线程阻塞在通道的读操作上, 一个线程关闭了socket的输入流,阻塞的读操作线程将会返回-1,即没有读取任何字节。 如果其他线程阻塞在通道的写操作上, 一个线程关闭了socket的输出流, 阻塞的写操作线程将会将会接受到一个AsynchronousCloseException。 *
Socket options are configured using the {@link #setOption(SocketOption,Object) * setOption} method. Socket channels support the following options: *
** Additional (implementation specific) options may also be supported. * **
*Socket的选项配置通过setOption(SocketOption,Object)方法,Socket channels 支持一下选项配置。 * *Option Name *Description *发送缓存区大小 * *{@link java.net.StandardSocketOptions#SO_SNDBUF SO_SNDBUF} *The size of the socket send buffer *接受缓存区大小 * *{@link java.net.StandardSocketOptions#SO_RCVBUF SO_RCVBUF} *The size of the socket receive buffer *是否保活,心跳 * *{@link java.net.StandardSocketOptions#SO_KEEPALIVE SO_KEEPALIVE} *Keep connection alive *地址是否可以重用 * *{@link java.net.StandardSocketOptions#SO_REUSEADDR SO_REUSEADDR} *Re-use address *在通道阻塞模式下,再通道关闭时,如果socket输出流还有数据没发送,则延时等待 数据发送。 * *{@link java.net.StandardSocketOptions#SO_LINGER SO_LINGER} *Linger on close if data is present (when configured in blocking mode * only) *TCP延时,Disable the Nagle algorithm.具体可以在StandardSocketOptions中查看 * *{@link java.net.StandardSocketOptions#TCP_NODELAY TCP_NODELAY} *Disable the Nagle algorithm *Socket channels are safe for use by multiple concurrent threads. They * support concurrent reading and writing, though at most one thread may be * reading and at most one thread may be writing at any given time. The {@link * #connect connect} and {@link #finishConnect finishConnect} methods are * mutually synchronized against each other, and an attempt to initiate a read * or write operation while an invocation of one of these methods is in * progress will block until that invocation is complete. *多线程可以安全地并发访问时socket通道。尽管至多只有一个线程进行读写操作,socket通道 支持并发的读写。#connect和#finishConnect是手动synchronized,在#connect和#finishConnect方法 调用的过程中,尝试读写操作,将会阻塞至#connect和#finishConnect方法结束。 * @author Mark Reinhold * @author JSR-51 Expert Group * @since 1.4 */ public abstract class SocketChannel extends AbstractSelectableChannel implements ByteChannel, ScatteringByteChannel, GatheringByteChannel, NetworkChannel { /** * Initializes a new instance of this class. */ protected SocketChannel(SelectorProvider provider) { super(provider); } /** * Opens a socket channel. *打开一个通道 * The new channel is created by invoking the {@link * java.nio.channels.spi.SelectorProvider#openSocketChannel * openSocketChannel} method of the system-wide default {@link * java.nio.channels.spi.SelectorProvider} object. *一个通道通过默认的SelectorProvider的openSocketChannel创建 * @return A new socket channel * * @throws IOException * If an I/O error occurs */ public static SocketChannel open() throws IOException { return SelectorProvider.provider().openSocketChannel(); } /** * Opens a socket channel and connects it to a remote address. *打开一个通道,并连接一个远程地址 * This convenience method works as if by invoking the {@link #open()} * method, invoking the {@link #connect(SocketAddress) connect} method upon * the resulting socket channel, passing it remote, and then * returning that channel. *此方法与open方法基本相同,只是在创建SocketChannel后,调用connect(SocketAddress) 连接远程地址 * @param remote * The remote address to which the new channel is to be connected * * @throws AsynchronousCloseException * If another thread closes this channel * while the connect operation is in progress * * @throws ClosedByInterruptException * If another thread interrupts the current thread * while the connect operation is in progress, thereby * closing the channel and setting the current thread's * interrupt status * * @throws UnresolvedAddressException * If the given remote address is not fully resolved * * @throws UnsupportedAddressTypeException * If the type of the given remote address is not supported * * @throws SecurityException * If a security manager has been installed * and it does not permit access to the given remote endpoint * * @throws IOException * If some other I/O error occurs */ public static SocketChannel open(SocketAddress remote) throws IOException { SocketChannel sc = open(); try { //连接远程地址 sc.connect(remote); } catch (Throwable x) { try { sc.close(); } catch (Throwable suppressed) { //当一个异常被抛出的时候,可能有其他异常因为该异常而被抑制住, //从而无法正常抛出。这时可以通过Java 7中为Throwable类增加的addSuppressed方法把这些被抑制的方法记录下来。 //被抑制的异常会出现在抛出的异常的堆栈信息中, //也可以通过getSuppressed方法来获取这些异常。这样做的好处是不会丢失任何异常,方便开发人员进行调试。 x.addSuppressed(suppressed); } throw x; } //断言是否连接 assert sc.isConnected(); return sc; } /** * Returns an operation set identifying this channel's supported * operations. *返回通道支持的操作事件集,通道支持读写连接操作事件 * Socket channels support connecting, reading, and writing, so this * method returns ({@link SelectionKey#OP_CONNECT} * | {@link SelectionKey#OP_READ} | {@link * SelectionKey#OP_WRITE}). * * @return The valid-operation set */ public final int validOps() { return (SelectionKey.OP_READ | SelectionKey.OP_WRITE | SelectionKey.OP_CONNECT); } // -- Socket-specific operations -- /** * @throws ConnectionPendingException * If a non-blocking connect operation is already in progress on * this channel * @throws AlreadyBoundException {@inheritDoc} * @throws UnsupportedAddressTypeException {@inheritDoc} * @throws ClosedChannelException {@inheritDoc} * @throws IOException {@inheritDoc} *地址绑定 * @since 1.7 */ @Override public abstract SocketChannel bind(SocketAddress local) throws IOException; /** * @throws UnsupportedOperationException {@inheritDoc} * @throws IllegalArgumentException {@inheritDoc} * @throws ClosedChannelException {@inheritDoc} * @throws IOException {@inheritDoc} *数字socket通道选项配置 * @since 1.7 */ @Override public abstract
SocketChannel setOption(SocketOption name, T value) throws IOException; /** * Shutdown the connection for reading without closing the channel. *在没有关闭通道的情况下,关闭读操作连接,即不能从通道读取数据,写到缓冲区。 * Once shutdown for reading then further reads on the channel will * return {@code -1}, the end-of-stream indication. If the input side of the * connection is already shutdown then invoking this method has no effect. *读连接关闭,进一步的读操作将会返回-1,表示读到流的末端。如果连接的输入流已经 关闭,调用此方法无效。 * @return The channel * * @throws NotYetConnectedException * If this channel is not yet connected * @throws ClosedChannelException * If this channel is closed * @throws IOException * If some other I/O error occurs * * @since 1.7 */ public abstract SocketChannel shutdownInput() throws IOException; /** * Shutdown the connection for writing without closing the channel. *在没有关闭通道的情况下,关闭到通道的写操作连接 * Once shutdown for writing then further attempts to write to the * channel will throw {@link ClosedChannelException}. If the output side of * the connection is already shutdown then invoking this method has no * effect. *在写连接关闭时,进一步尝试从缓冲区读数据,写到通道,将会抛出ClosedChannelException。 如果连接的输出流关闭,则调用此方法无效。 * @return The channel * * @throws NotYetConnectedException * If this channel is not yet connected * @throws ClosedChannelException * If this channel is closed * @throws IOException * If some other I/O error occurs * * @since 1.7 */ public abstract SocketChannel shutdownOutput() throws IOException; /** * Retrieves a socket associated with this channel. *获取与通道关联的socket *
The returned object will not declare any public methods that are not * declared in the {@link java.net.Socket} class. *返回的socket不会声明任何在socket中没有声明的public方法 * @return A socket associated with this channel */ public abstract Socket socket(); /** * Tells whether or not this channel's network socket is connected. *判断通道的网络socket是否连接 * @return true if, and only if, this channel's network socket * is {@link #isOpen open} and connected 当且仅当通道的网络socket打开,或者连接,则返回true */ public abstract boolean isConnected(); /** * Tells whether or not a connection operation is in progress on this * channel. *判断一个通道是不是正在进行连接操作。 * @return true if, and only if, a connection operation has been * initiated on this channel but not yet completed by invoking the * {@link #finishConnect finishConnect} method 当且仅当一个连接操作正在进行,还没有完成,调用#finishConnect方法,完成连接。 */ public abstract boolean isConnectionPending(); /** * Connects this channel's socket. *连接通道的socket * If this channel is in non-blocking mode then an invocation of this * method initiates a non-blocking connection operation. If the connection * is established immediately, as can happen with a local connection, then * this method returns true. Otherwise this method returns * false and the connection operation must later be completed by * invoking the {@link #finishConnect finishConnect} method. *如果通道是非阻塞模式,调用此方法将会初始化一个非阻塞的连接操作。如果连接立即 建立,则伴随着一个本地的连接,方法将会返回true。如果连接操作通过调用#finishConnect 方法完成,则方法返回false。 *
If this channel is in blocking mode then an invocation of this * method will block until the connection is established or an I/O error * occurs. *如果通道是阻塞模式的,方法将会阻塞到连接建立或者一个IO操作异常。 *
This method performs exactly the same security checks as the {@link * java.net.Socket} class. That is, if a security manager has been * installed then this method verifies that its {@link * java.lang.SecurityManager#checkConnect checkConnect} method permits * connecting to the address and port number of the given remote endpoint. *此方法将进行与java.net.Socket相同的安全检查。如果如果安全管理器配置,这个方法将会 通过java.lang.SecurityManager#checkConnect检查是否允许连接到远程终端的地址和port。 *
This method may be invoked at any time. If a read or write * operation upon this channel is invoked while an invocation of this * method is in progress then that operation will first block until this * invocation is complete. If a connection attempt is initiated but fails, * that is, if an invocation of this method throws a checked exception, * then the channel will be closed. *此方法可以在任何时候调用。如果当前线程调用读写操作时,有其他线程正在进程 读写操作,则当前线程阻塞到其他线程完成读写操作后,方可读写通道。如果连接已经初始化, 单连接失败调用此方法将会抛出一个检查异常,然后关闭通道。 * @param remote * The remote address to which this channel is to be connected * * @return true if a connection was established, * false if this channel is in non-blocking mode * and the connection operation is in progress * * @throws AlreadyConnectedException * If this channel is already connected * * @throws ConnectionPendingException * If a non-blocking connection operation is already in progress * on this channel * * @throws ClosedChannelException * If this channel is closed * * @throws AsynchronousCloseException * If another thread closes this channel * while the connect operation is in progress * * @throws ClosedByInterruptException * If another thread interrupts the current thread * while the connect operation is in progress, thereby * closing the channel and setting the current thread's * interrupt status * * @throws UnresolvedAddressException * If the given remote address is not fully resolved * * @throws UnsupportedAddressTypeException * If the type of the given remote address is not supported * * @throws SecurityException * If a security manager has been installed * and it does not permit access to the given remote endpoint * * @throws IOException * If some other I/O error occurs */ public abstract boolean connect(SocketAddress remote) throws IOException; /** * Finishes the process of connecting a socket channel. *完成到socket通道的连接任务。 * A non-blocking connection operation is initiated by placing a socket * channel in non-blocking mode and then invoking its {@link #connect * connect} method. Once the connection is established, or the attempt has * failed, the socket channel will become connectable and this method may * be invoked to complete the connection sequence. If the connection * operation failed then invoking this method will cause an appropriate * {@link java.io.IOException} to be thrown. *在设置socket通道非阻塞模式时,一个非阻塞的连接操作初始化,然后调用#connect方法建立 到通道连接。如果连接已经建立或尝试连接失败,在finishConnect方法调用完成连接工作后, socket通道将会变得connectable。如果一个连接操作失败,调用此方将会抛出IO异常。 *
If this channel is already connected then this method will not block * and will immediately return true. If this channel is in * non-blocking mode then this method will return false if the * connection process is not yet complete. If this channel is in blocking * mode then this method will block until the connection either completes * or fails, and will always either return true or throw a checked * exception describing the failure. *如果通道已经连接,则此方法不会阻塞,将会立即返回true。如果通道是非阻塞模式,在连接还没有 建立时,此方法将会返回false。如果通道是阻塞模式,调用finishConnect将会阻塞到连接操作完成 或者失败,返回true或者抛出一个不检查的异常描述失败。 *
This method may be invoked at any time. If a read or write * operation upon this channel is invoked while an invocation of this * method is in progress then that operation will first block until this * invocation is complete. If a connection attempt fails, that is, if an * invocation of this method throws a checked exception, then the channel * will be closed. *此方法可以在任何时候调用。如果当前线程调用读写操作时,有其他线程正在进程 读写操作,则当前线程阻塞到其他线程完成读写操作后,方可读写通道。如果连接已经初始化, 单连接失败调用此方法将会抛出一个检查异常,然后关闭通道。 * @return true if, and only if, this channel's socket is now * connected * * @throws NoConnectionPendingException * If this channel is not connected and a connection operation * has not been initiated * * @throws ClosedChannelException * If this channel is closed * * @throws AsynchronousCloseException * If another thread closes this channel * while the connect operation is in progress * * @throws ClosedByInterruptException * If another thread interrupts the current thread * while the connect operation is in progress, thereby * closing the channel and setting the current thread's * interrupt status * * @throws IOException * If some other I/O error occurs */ public abstract boolean finishConnect() throws IOException; /** * Returns the remote address to which this channel's socket is connected. *返回通道socket连接的远端地址。 *
Where the channel is bound and connected to an Internet Protocol * socket address then the return value from this method is of type {@link * java.net.InetSocketAddress}. *在通道绑定地址并连接到一个网络协议的socket地址,此方法返回的值为类型为java.net.InetSocketAddress * @return The remote address; {@code null} if the channel's socket is not * connected * * @throws ClosedChannelException * If the channel is closed * @throws IOException * If an I/O error occurs * * @since 1.7 */ public abstract SocketAddress getRemoteAddress() throws IOException; // -- ByteChannel operations -- /** 从通道读取字节序列,写到缓存区 * @throws NotYetConnectedException * If this channel is not yet connected */ public abstract int read(ByteBuffer dst) throws IOException; /** 从通道读取字节序列,写到一组缓存区 * @throws NotYetConnectedException * If this channel is not yet connected */ public abstract long read(ByteBuffer[] dsts, int offset, int length) throws IOException; /** 与read(ByteBuffer[] dsts, int offset, int length)含义相同 * @throws NotYetConnectedException * If this channel is not yet connected */ public final long read(ByteBuffer[] dsts) throws IOException { return read(dsts, 0, dsts.length); } /** 从缓冲区读取字节序列,写到通道 * @throws NotYetConnectedException * If this channel is not yet connected */ public abstract int write(ByteBuffer src) throws IOException; /** 从一组缓冲区读取字节序列,写到通道 * @throws NotYetConnectedException * If this channel is not yet connected */ public abstract long write(ByteBuffer[] srcs, int offset, int length) throws IOException; /** 与方法write(ByteBuffer[] srcs, int offset, int length)无异 * @throws NotYetConnectedException * If this channel is not yet connected */ public final long write(ByteBuffer[] srcs) throws IOException { return write(srcs, 0, srcs.length); } }
附:
![SocketChannel接口定义_第1张图片](http1://img.it610.com/image/info5/c92b647ecd164f80b1c9a7310e5539ff.png)