目錄
簡介
構造函數,2個open方法,方法validOps,bind,setOption,shutdownInput/Output
方法socket,isConnected,isConnectionPending,connect,finishConnect,getRemoteAddress
方法3個read,3個write,getLocalAddress
簡介
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;
/**
* 面向流的連接配接套接字的可選通道。
*
* <p> 套接字通道是通過調用該類的open方法之一來建立的。
* 為任意預先存在的套接字建立通道是不可能的。新建立的套接字通道已打開，但尚未連接配接。
* 嘗試在未連接配接的通道上調用I/O操作将導緻抛出NotYetConnectedException。
* 可以通過調用其connect方法來連接配接套接字通道;
* 一旦連接配接，套接字通道将保持連接配接，直到關閉。
* 套接字通道是否連接配接可以通過調用它的isConnected方法來确定。
*
* <p> 套接字通道支援非阻塞連接配接:
* 可以建立一個套接字通道，
* 建立遠端套接字連結的過程可以通過connect方法發起，稍後由finishConnect方法完成。
* 連接配接操作是否正在進行可以通過調用isConnectionPending方法來确定。
*
* <p> 套接字通道支援異步關閉，這類似于Channel類中指定的異步關閉操作。
* 如果一個線程關閉了套接字的輸入端，而另一個線程在套接字的通道上阻塞了讀操作，
* 那麼阻塞線程中的read操作将在不讀取任何位元組的情況下完成，并傳回-1。
* 如果套接字的輸出端被一個線程關閉，而另一個線程在套接字的通道上的寫操作中被阻塞，
* 那麼被阻塞的線程将收到一個AsynchronousCloseException。
*
* <p> 套接字選項使用setOption方法進行配置。套接字通道支援以下選項:
* <blockquote>
* <table border summary="Socket options">
* <tr>
* <th>Option Name</th>
* <th>Description</th>
* </tr>
* <tr>
* <td> {@link java.net.StandardSocketOptions#SO_SNDBUF SO_SNDBUF} </td>
* <td> 發送緩沖區的大小 </td>
* </tr>
* <tr>
* <td> {@link java.net.StandardSocketOptions#SO_RCVBUF SO_RCVBUF} </td>
* <td> 接收緩沖區的大小 </td>
* </tr>
* <tr>
* <td> {@link java.net.StandardSocketOptions#SO_KEEPALIVE SO_KEEPALIVE} </td>
* <td> 保持連接配接處于連接配接狀态 </td>
* </tr>
* <tr>
* <td> {@link java.net.StandardSocketOptions#SO_REUSEADDR SO_REUSEADDR} </td>
* <td> 重用位址 </td>
* </tr>
* <tr>
* <td> {@link java.net.StandardSocketOptions#SO_LINGER SO_LINGER} </td>
* <td> 在關閉時，如果資料存在(當配置為阻塞模式時) </td>
* </tr>
* <tr>
* <td> {@link java.net.StandardSocketOptions#TCP_NODELAY TCP_NODELAY} </td>
* <td> 禁用Nagle算法 </td>
* </tr>
* </table>
* </blockquote>
* 還可能支援其他(特定于實作的)選項。
*
* <p> 套接字通道對于多個并發線程來說是安全的。
* 它們支援并發讀寫，盡管在任何給定的時間内最多有一個線程在讀，最多有一個線程在寫。
* connect和finishConnect方法是互相同步的，當其中一個方法的調用正在進行時，嘗試發起讀寫操作将會阻塞，直到調用完成。</p>
*
* @author Mark Reinhold
* @author JSR-51 Expert Group
* @since 1.4
*/
public abstract class SocketChannel
extends AbstractSelectableChannel
implements ByteChannel, ScatteringByteChannel, GatheringByteChannel, NetworkChannel
構造函數,2個open方法,方法validOps,bind,setOption,shutdownInput/Output
/**
* 建立執行個體
*
* @param provider
* The provider that created this channel
*/
protected SocketChannel(SelectorProvider provider) {
super(provider);
}
/**
* 打開套接字通道。
*
* <p> 新通道是通過調用系統範圍預設java.nio.channels.spi的SelectorProvider對象的openSocketChannel方法建立的。</p>
*
* @return A new socket channel
*
* @throws IOException
* If an I/O error occurs
*/
public static SocketChannel open() throws IOException {
return SelectorProvider.provider().openSocketChannel();
}
/**
* 打開一個套接字通道并将其連接配接到一個遠端位址。
*
* <p> 這個友善的方法工作起來就像調用open()方法，在産生的套接字通道上調用connect方法，将其遠端傳遞，然後傳回該通道。 </p>
*
* @param remote
* The remote address to which the new channel is to be connected
*
* @return A new, and connected, socket channel
*
* @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 {
sc.connect(remote);
} catch (Throwable x) {
try {
sc.close();
} catch (Throwable suppressed) {
x.addSuppressed(suppressed);
}
throw x;
}
assert sc.isConnected();
return sc;
}
/**
* 傳回一個操作集，辨別此通道支援的操作。
*
* <p> 套接字通道支援連接配接、讀取和寫入，
* 是以該方法傳回(SelectionKey.OP_CONNECT | SelectionKey.OP_READ | SelectionKey.OP_WRITE)。</p>
*
* @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}
* @throws SecurityException
* If a security manager has been installed and its
* {@link SecurityManager#checkListen checkListen} method denies
* the operation
*
* @since 1.7
*/
@Override
public abstract SocketChannel bind(SocketAddress local)
throws IOException;
/**
* @throws UnsupportedOperationException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
* @throws ClosedChannelException {@inheritDoc}
* @throws IOException {@inheritDoc}
*
* @since 1.7
*/
@Override
public abstract <T> SocketChannel setOption(SocketOption<T> name, T value)
throws IOException;
/**
* 在不關閉通道的情況下關閉讀取連接配接。
*
* <p> 一旦停止讀取，則在通道上進一步讀取将傳回-1，即流結束訓示。
* 如果連接配接的輸入端已經關閉，則調用此方法沒有效果。
*
* @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;
/**
* 在不關閉通道的情況下關閉寫入連接配接。
*
* <p> 一旦因為寫入而關閉，那麼進一步嘗試寫入通道将抛出ClosedChannelException。
* 如果連接配接的輸出端已經關閉，那麼調用這個方法沒有效果。
*
* @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;
方法socket,isConnected,isConnectionPending,connect,finishConnect,getRemoteAddress
/**
* 檢索與此通道關聯的套接字。
*
* <p> 傳回的對象不會聲明沒有在java.net.Socket類中聲明的任何公共方法。 </p>
*
* @return A socket associated with this channel
*/
public abstract Socket socket();
/**
* 判斷此通道的網絡套接字是否已連接配接。
*
* @return <tt>true</tt> if, and only if, this channel's network socket
* is {@link #isOpen open} and connected
*/
public abstract boolean isConnected();
/**
* 說明該通道上是否有正在進行的連接配接操作。
*
* @return <tt>true</tt> if, and only if, a connection operation has been
* initiated on this channel but not yet completed by invoking the
* {@link #finishConnect finishConnect} method
*/
public abstract boolean isConnectionPending();
/**
* 連接配接此通道的套接字。
*
* <p> 如果此通道處于非阻塞模式，則此方法的調用将啟動非阻塞連接配接操作。
* 如果連接配接立即建立，就像本地連接配接一樣，那麼這個方法将傳回true。
* 否則，該方法将傳回false，并且連接配接操作必須在稍後通過調用finishConnect方法來完成。
*
* <p> 如果此通道處于阻塞模式，則此方法的調用将阻塞，直到建立連接配接或發生I/O錯誤。
*
* <p> 此方法執行與java.net.Socket類完全相同的安全檢查。
* 也就是說，如果已經安裝了安全管理器，那麼該方法将驗證其checkConnect方法是否允許連接配接到給定遠端端點的位址和端口号。
*
* <p> 這個方法可以在任何時候被調用。如果在此通道上的讀或寫操作被調用時，
* 該方法的調用正在進行中，那麼該操作将首先阻塞，直到該調用完成。
* 如果發起連接配接嘗試但失敗，也就是說，如果此方法的調用抛出一個檢查過的異常，則通道将被關閉。</p>
*
* @param remote
* The remote address to which this channel is to be connected
*
* @return <tt>true</tt> if a connection was established,
* <tt>false</tt> 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;
/**
* 完成連接配接socket通道的過程。
*
* <p> 通過将socket通道置于非阻塞模式，然後調用其connect方法，可以啟動非阻塞連接配接操作。
* 一旦建立了連接配接，或者嘗試失敗，套接字通道将變為可連接配接的，并且可能會調用此方法來完成連接配接序列。
* 如果connection操作失敗，則調用此方法将要抛出适當的java.io.IOException。
*
* <p> 如果此通道已經連接配接，則此方法不會阻塞，并将立即傳回true。
* 如果這個通道是非阻塞模式，那麼如果連接配接過程還沒有完成，這個方法将傳回false。
* 如果此通道處于blocking模式，則此方法将阻塞，
* 直到連接配接完成或失敗，并總是傳回true或抛出描述失敗的checked exception。
*
* <p> 這個方法可以在任何時候被調用。如果在此通道上的讀或寫操作被調用時，
* 該方法的調用正在進行中，那麼該操作将首先阻塞，直到該調用完成。
* 如果連接配接嘗試失敗，也就是說，如果這個方法的調用抛出一個檢查過的異常，那麼通道将被關閉。</p>
*
* @return <tt>true</tt> 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;
/**
* 傳回此通道套接字連接配接到的遠端位址。
*
* <p> 如果通道被綁定并連接配接到Internet Protocol 套接字位址，那麼該方法的傳回值類型為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;
方法3個read,3個write,getLocalAddress
// -- ByteChannel operations --
/**
* @throws NotYetConnectedException
* If this channel is not yet connected
*/
public abstract int read(ByteBuffer dst) throws IOException;
/**
* @throws NotYetConnectedException
* If this channel is not yet connected
*/
public abstract long read(ByteBuffer[] dsts, int offset, int length)
throws IOException;
/**
* @throws NotYetConnectedException
* If this channel is not yet connected
*/
public final long read(ByteBuffer[] dsts) throws IOException {
return read(dsts, 0, dsts.length);
}
/**
* @throws NotYetConnectedException
* If this channel is not yet connected
*/
public abstract int write(ByteBuffer src) throws IOException;
/**
* @throws NotYetConnectedException
* If this channel is not yet connected
*/
public abstract long write(ByteBuffer[] srcs, int offset, int length)
throws IOException;
/**
* @throws NotYetConnectedException
* If this channel is not yet connected
*/
public final long write(ByteBuffer[] srcs) throws IOException {
return write(srcs, 0, srcs.length);
}
/**
* {@inheritDoc}
* <p>
* 如果設定了安全管理器，則使用本地位址和-1作為參數調用其checkConnect方法，以檢視是否允許該操作。
* 如果不允許該操作，則傳回一個表示環回位址和通道套接字的本地端口的SocketAddress。
*
* @return The {@code SocketAddress} that the socket is bound to, or the
* {@code SocketAddress} representing the loopback address if
* denied by the security manager, or {@code null} if the
* channel's socket is not bound
*
* @throws ClosedChannelException {@inheritDoc}
* @throws IOException {@inheritDoc}
*/
@Override
public abstract SocketAddress getLocalAddress() throws IOException;