引言:
上面我们看了IoService接口的定义及抽象实现，先来回顾一下：
抽象service关联一个IoHandler处理会话相关事件，关联一个执行器Executor，负责处理io事件的执行，一个会话配置IOsessionConfig，用于service创建会话时，配置会话，一个过滤链构建器IoFilterChainBuilder，用于构建会话的过滤链，会话数据结构工厂，用于创建会话的属性Map和写请求队列，还有service监听器和统计器。抽象service构造，首先检查会话配置和传输元数据，会话配置必须传输元数据的会话配置类型必须相同，即socket（TCP），会话配置为socketSessionConfig，报文通信（UDP），为DatagramSessionConfig；然后将会话创建监听器serviceActivationListener添加监听器管理器IoServiceListenerSupport；初始化会话配置，IO事件执行器executor和异常监视器。初始化会话就是将service会话数据结构工厂的会话属性添加到具体的会话中，将service会话数据结构工厂的写请求队列，设置到具体的会话中，如果是连接请求会话，则将连接结果添加会话属性中。
今天我们我们来看一下IoService的一个分支IoAcceptor：
/**
* Accepts incoming connection, communicates with clients, and fires events to
* {@link IoHandler}s.
接收连接请求，与客户端通信，触发IoHandler相关事件。
*
* Please refer to
* [url=../../../../../xref-examples/org/apache/mina/examples/echoserver/Main.html]EchoServer[/url]
* example.
*
* You should bind to the desired socket address to accept incoming
* connections, and then events for incoming connections will be sent to
* the specified default {@link IoHandler}.
*
你应该绑定socket地址，以接收连接请求，连接请求事件将会发送个默认的IoHandler。
* Threads accept incoming connections start automatically when
* {@link #bind()} is invoked, and stop when {@link #unbind()} is invoked.
*当IoAcceptor绑定地址时，相关线程将自动开始接收连接请求，当调用#unbind方法，将停止
线程接收连接请求
* @author [url=http://mina.apache.org]Apache MINA Project[/url]
*/
public interface IoAcceptor extends IoService {
/**
* Returns the local address which is bound currently. If more than one
* address are bound, only one of them will be returned, but it's not
* necessarily the firstly bound address.
* 返回当前绑定本地地址，当绑定多个地址时，返回其中一个，不需要非是第一个绑定的地址
* @return The bound LocalAddress
*/
SocketAddress getLocalAddress();
/**
* Returns a {@link Set} of the local addresses which are bound currently.
* 返回绑定的地址集
* @return The Set of bound LocalAddresses
*/
Set getLocalAddresses();
/**
* Returns the default local address to bind when no argument is specified
* in {@link #bind()} method. Please note that the default will not be
* used if any local address is specified. If more than one address are
* set, only one of them will be returned, but it's not necessarily the
* firstly specified address in {@link #setDefaultLocalAddresses(List)}.
* 当bind无参方法被调用时，返回一个默认的本地地址。
* @return The default bound LocalAddress
*/
SocketAddress getDefaultLocalAddress();
/**
* Returns a {@link List} of the default local addresses to bind when no
* argument is specified in {@link #bind()} method. Please note that the
* default will not be used if any local address is specified.
* 返回默认地址集
* @return The list of default bound LocalAddresses
*/
List getDefaultLocalAddresses();
/**
* Sets the default local address to bind when no argument is specified in
* {@link #bind()} method. Please note that the default will not be used
* if any local address is specified.
*设置默认socket地址
* @param localAddress The local addresses to bind the acceptor on
*/
void setDefaultLocalAddress(SocketAddress localAddress);
/**
* Sets the default local addresses to bind when no argument is specified
* in {@link #bind()} method. Please note that the default will not be
* used if any local address is specified.
设置默认地址集
* @param firstLocalAddress The first local address to bind the acceptor on
* @param otherLocalAddresses The other local addresses to bind the acceptor on
*/
void setDefaultLocalAddresses(SocketAddress firstLocalAddress, SocketAddress... otherLocalAddresses);
/**
* Sets the default local addresses to bind when no argument is specified
* in {@link #bind()} method. Please note that the default will not be
* used if any local address is specified.
*
* @param localAddresses The local addresses to bind the acceptor on
*/
void setDefaultLocalAddresses(Iterable localAddresses);
/**
* Sets the default local addresses to bind when no argument is specified
* in {@link #bind()} method. Please note that the default will not be
* used if any local address is specified.
*
* @param localAddresses The local addresses to bind the acceptor on
*/
void setDefaultLocalAddresses(List localAddresses);
/**
* Returns true if and only if all clients are closed when this
* acceptor unbinds from all the related local address (i.e. when the
* service is deactivated).
当且仅当所有客户端关闭，acceptor解绑所有相关本地地址
*
* @return true if the service sets the closeOnDeactivation flag
*/
boolean isCloseOnDeactivation();
/**
* Sets whether all client sessions are closed when this acceptor unbinds
* from all the related local addresses (i.e. when the service is
* deactivated). The default value is true.
* 无论所有客户端关闭是否，acceptor是否解绑所有相关本地地址，设置closeOnDeactivation
* @param closeOnDeactivation true if we should close on deactivation
*/
void setCloseOnDeactivation(boolean closeOnDeactivation);
/**
* Binds to the default local address(es) and start to accept incoming
* connections.
*绑定默认的socket本地地址，接收连接请求
* @throws IOException if failed to bind
*/
void bind() throws IOException;
/**
* Binds to the specified local address and start to accept incoming
* connections.
*绑定socket本地地址，接收连接请求
* @param localAddress The SocketAddress to bind to
*
* @throws IOException if failed to bind
*/
void bind(SocketAddress localAddress) throws IOException;
/**
* Binds to the specified local addresses and start to accept incoming
* connections. If no address is given, bind on the default local address.
* 绑定socket本地地址，接收连接请求，如果没给给定参数，绑定默认地址
* @param firstLocalAddress The first address to bind to
* @param addresses The SocketAddresses to bind to
*
* @throws IOException if failed to bind
*/
void bind(SocketAddress firstLocalAddress, SocketAddress... addresses) throws IOException;
/**
* Binds to the specified local addresses and start to accept incoming
* connections. If no address is given, bind on the default local address.
* 绑定socket本地地址，接收连接请求，如果没给给定参数，绑定默认地址
* @param addresses The SocketAddresses to bind to
*
* @throws IOException if failed to bind
*/
void bind(SocketAddress... addresses) throws IOException;
/**
* Binds to the specified local addresses and start to accept incoming
* connections.
*绑定socket本地地址，接收连接请求，如果没给给定参数，绑定默认地址
* @param localAddresses The local address we will be bound to
* @throws IOException if failed to bind
*/
void bind(Iterable localAddresses) throws IOException;
/**
* Unbinds from all local addresses that this service is bound to and stops
* to accept incoming connections. All managed connections will be closed
* if {@link #setCloseOnDeactivation(boolean) disconnectOnUnbind} property
* is true. This method returns silently if no local address is
* bound yet.
解绑service绑定的所有本地socket地址，停止接收，连接请求。如果CloseOnDeactivation参数为
解绑时，断开连接，则关闭service管理的所有会话。
*/
void unbind();
/**
* Unbinds from the specified local address and stop to accept incoming
* connections. All managed connections will be closed if
* {@link #setCloseOnDeactivation(boolean) disconnectOnUnbind} property is
* true. This method returns silently if the default local
* address is not bound yet.
* 解绑service绑定的所有本地socket地址，停止接收，连接请求。如果CloseOnDeactivation参数为
解绑时，断开连接，则关闭service管理的所有会话。
* @param localAddress The local address we will be unbound from
*/
void unbind(SocketAddress localAddress);
/**
* Unbinds from the specified local addresses and stop to accept incoming
* connections. All managed connections will be closed if
* {@link #setCloseOnDeactivation(boolean) disconnectOnUnbind} property is
* true. This method returns silently if the default local
* addresses are not bound yet.
* 解绑service绑定的所有本地socket地址，停止接收，连接请求。如果CloseOnDeactivation参数为
解绑时，断开连接，则关闭service管理的所有会话。
* @param firstLocalAddress The first local address to be unbound from
* @param otherLocalAddresses The other local address to be unbound from
*/
void unbind(SocketAddress firstLocalAddress, SocketAddress... otherLocalAddresses);
/**
* Unbinds from the specified local addresses and stop to accept incoming
* connections. All managed connections will be closed if
* {@link #setCloseOnDeactivation(boolean) disconnectOnUnbind} property is
* true. This method returns silently if the default local
* addresses are not bound yet.
* 解绑service绑定的所有本地socket地址，停止接收，连接请求。如果CloseOnDeactivation参数为
解绑时，断开连接，则关闭service管理的所有会话。
* @param localAddresses The local address we will be unbound from
*/
void unbind(Iterable localAddresses);
/**
* (Optional) Returns an {@link IoSession} that is bound to the specified
* localAddress and the specified remoteAddress which
* reuses the local address that is already bound by this service.
返回绑定本地地址和远端socket地址的会话，本地地址，service已绑定，并可以重用
*
* This operation is optional. Please throw {@link UnsupportedOperationException}
* if the transport type doesn't support this operation. This operation is
* usually implemented for connectionless transport types.
*操作时可选的，如果transport不支持此操作，则可抛出UnsupportedOperationException，
此操作一般报文通信会实现
* @param remoteAddress The remote address bound to the service
* @param localAddress The local address the session will be bound to
* @throws UnsupportedOperationException if this operation is not supported
* @throws IllegalStateException if this service is not running.
* @throws IllegalArgumentException if this service is not bound to the
* specified localAddress.
* @return The session bound to the the given localAddress and remote address
*/
IoSession newSession(SocketAddress remoteAddress, SocketAddress localAddress);
}
从IoAcceptor的接口定义可以看，IoAcceptor是将IoService添加了监听连接请求功能。
再来看抽象实现：
/**
* A base implementation of {@link IoAcceptor}.
*
* @author [url=http://mina.apache.org]Apache MINA Project[/url]
* @org.apache.xbean.XBean
*/
public abstract class AbstractIoAcceptor extends AbstractIoService implements IoAcceptor {
private final List defaultLocalAddresses = new ArrayList<>();//默认绑定的socket地址集
private final List unmodifiableDefaultLocalAddresses = Collections
.unmodifiableList(defaultLocalAddresses);//包装默认的地址集为不可修改集合
private final Set boundAddresses = new HashSet<>();//绑定地址集
private boolean disconnectOnUnbind = true;
/**
* The lock object which is acquired while bind or unbind operation is performed.
* Acquire this lock in your property setters which shouldn't be changed while
* the service is bound.
*/
protected final Object bindLock = new Object();
/**
* Constructor for {@link AbstractIoAcceptor}. You need to provide a default
* session configuration and an {@link Executor} for handling I/O events. If
* null {@link Executor} is provided, a default one will be created using
* {@link Executors#newCachedThreadPool()}.
* 根据会话配置和执行器构造抽象Io接收器
* @see AbstractIoService#AbstractIoService(IoSessionConfig, Executor)
*
* @param sessionConfig
* the default configuration for the managed {@link IoSession}
* @param executor
* the {@link Executor} used for handling execution of I/O
* events. Can be null.
*/
protected AbstractIoAcceptor(IoSessionConfig sessionConfig, Executor executor) {
super(sessionConfig, executor);
defaultLocalAddresses.add(null);
}
}
来看一下地址绑定操作：
/**
* {@inheritDoc}
*/
@Override
public final void bind() throws IOException {
bind(getDefaultLocalAddresses());
}
/**
* {@inheritDoc}
*/
@Override
public final void bind(SocketAddress localAddress) throws IOException {
if (localAddress == null) {
throw new IllegalArgumentException("localAddress");
}
List localAddresses = new ArrayList<>(1);
localAddresses.add(localAddress);
bind(localAddresses);
}
/**
* {@inheritDoc}
*/
@Override
public final void bind(SocketAddress... addresses) throws IOException {
if ((addresses == null) || (addresses.length == 0)) {
bind(getDefaultLocalAddresses());
return;
}
List localAddresses = new ArrayList<>(2);
for (SocketAddress address : addresses) {
localAddresses.add(address);
}
bind(localAddresses);
}
/**
* {@inheritDoc}
*/
@Override
public final void bind(SocketAddress firstLocalAddress, SocketAddress... addresses) throws IOException {
if (firstLocalAddress == null) {
bind(getDefaultLocalAddresses());
}
if ((addresses == null) || (addresses.length == 0)) {
bind(getDefaultLocalAddresses());
return;
}
List localAddresses = new ArrayList<>(2);
localAddresses.add(firstLocalAddress);
for (SocketAddress address : addresses) {
localAddresses.add(address);
}
bind(localAddresses);
}
以上的绑定方法，实际由bind(Iterable localAddresses)完成。
/**
* {@inheritDoc}
*/
@Override
public final void bind(Iterable localAddresses) throws IOException {
if (isDisposing()) {
throw new IllegalStateException("The Accpetor disposed is being disposed.");
}
if (localAddresses == null) {
throw new IllegalArgumentException("localAddresses");
}
List localAddressesCopy = new ArrayList<>();
for (SocketAddress a : localAddresses) {
checkAddressType(a);//检查地址类
localAddressesCopy.add(a);
}
if (localAddressesCopy.isEmpty()) {
throw new IllegalArgumentException("localAddresses is empty.");
}
boolean activate = false;
//同步绑定锁和地址绑定集合
synchronized (bindLock) {
synchronized (boundAddresses) {
if (boundAddresses.isEmpty()) {
activate = true;
}
}
if (getHandler() == null) {
throw new IllegalStateException("handler is not set.");
}
try {
//完成实际绑定
Set addresses = bindInternal(localAddressesCopy);
synchronized (boundAddresses) {
//将绑定地址添加到绑定集合boundAddresses
boundAddresses.addAll(addresses);
}
} catch (IOException | RuntimeException e) {
throw e;
} catch (Exception e) {
throw new RuntimeIoException("Failed to bind to: " + getLocalAddresses(), e);
}
}
if (activate) {
//通知Service监听器，Service已激活
getListeners().fireServiceActivated();
}
}
绑定方法有以下几点要看
1. checkAddressType(a);//检查地址类
private void checkAddressType(SocketAddress a) {
//检查绑定的socket地址与传输元数据的地址类型是否相同
if (a != null && !getTransportMetadata().getAddressType().isAssignableFrom(a.getClass())) {
throw new IllegalArgumentException("localAddress type: " + a.getClass().getSimpleName() + " (expected: "
+ getTransportMetadata().getAddressType().getSimpleName() + ")");
}
}
2. //完成实际绑定 Setaddresses = bindInternal(localAddressesCopy);
/**
* Starts the acceptor, and register the given addresses
* 待子类扩展，启动监听器，注册地址
* @param localAddresses The address to bind to
* @return the {@link Set} of the local addresses which is bound actually
* @throws Exception If the bind failed
*/
protected abstract Set bindInternal(List localAddresses) throws Exception;
从上面可以看出，绑定地址首先要检查绑定的socket地址与传输元数据的地址类型是否相同，相同则通过bindInternal完成实际的绑定，然后通知Service监听器，Service已激活fireServiceActivated。
再来看地址解绑：
/**
* {@inheritDoc}
*/
@Override
public final void unbind() {
unbind(getLocalAddresses());
}
/**
* {@inheritDoc}
*/
@Override
public final void unbind(SocketAddress localAddress) {
if (localAddress == null) {
throw new IllegalArgumentException("localAddress");
}
List localAddresses = new ArrayList<>(1);
localAddresses.add(localAddress);
unbind(localAddresses);
}
/**
* {@inheritDoc}
*/
@Override
public final void unbind(SocketAddress firstLocalAddress, SocketAddress... otherLocalAddresses) {
if (firstLocalAddress == null) {
throw new IllegalArgumentException("firstLocalAddress");
}
if (otherLocalAddresses == null) {
throw new IllegalArgumentException("otherLocalAddresses");
}
List localAddresses = new ArrayList<>();
localAddresses.add(firstLocalAddress);
Collections.addAll(localAddresses, otherLocalAddresses);
unbind(localAddresses);
}
上面所有的解绑方法实际通过unbind(Iterable localAddresses)方法完成：
/**
* {@inheritDoc}
*/
@Override
public final void unbind(Iterable localAddresses) {
if (localAddresses == null) {
throw new IllegalArgumentException("localAddresses");
}
boolean deactivate = false;
//同步绑定锁和绑定地址集合
synchronized (bindLock) {
synchronized (boundAddresses) {
if (boundAddresses.isEmpty()) {
return;
}
List localAddressesCopy = new ArrayList<>();
int specifiedAddressCount = 0;
for (SocketAddress a : localAddresses) {
specifiedAddressCount++;
if ((a != null) && boundAddresses.contains(a)) {
localAddressesCopy.add(a);
}
}
if (specifiedAddressCount == 0) {
throw new IllegalArgumentException("localAddresses is empty.");
}
if (!localAddressesCopy.isEmpty()) {
try {
unbind0(localAddressesCopy);
} catch (RuntimeException e) {
throw e;
} catch (Exception e) {
throw new RuntimeIoException("Failed to unbind from: " + getLocalAddresses(), e);
}
//清空绑定地址集合
boundAddresses.removeAll(localAddressesCopy);
if (boundAddresses.isEmpty()) {
deactivate = true;
}
}
}
}
if (deactivate) {
//触发Service监听器无效事件
getListeners().fireServiceDeactivated();
}
}
/** * Implement this method to perform the actual unbind operation. * 待子类实现，具体解绑 * @param localAddresses The address to unbind from * @throws Exception If the unbind failed */ protected abstract void unbind0(List localAddresses) throws Exception;
从解绑地址方法来看，主要是委托unbind0方法完成实际解绑工作，清空绑定地址集合boundAddresses，触发Service监听器无效事件fireServiceDeactivated。
再来看其他方法，下面这些方法就不讲了，都是set和get操作看看就行：
/**
* {@inheritDoc}
*/
@Override
public SocketAddress getLocalAddress() {
Set localAddresses = getLocalAddresses();
if (localAddresses.isEmpty()) {
return null;
}
return localAddresses.iterator().next();
}
/**
* {@inheritDoc}
*/
@Override
public final Set getLocalAddresses() {
Set localAddresses = new HashSet<>();
synchronized (boundAddresses) {
localAddresses.addAll(boundAddresses);
}
return localAddresses;
}
/**
* {@inheritDoc}
*/
@Override
public SocketAddress getDefaultLocalAddress() {
if (defaultLocalAddresses.isEmpty()) {
return null;
}
return defaultLocalAddresses.iterator().next();
}
/**
* {@inheritDoc}
*/
@Override
public final void setDefaultLocalAddress(SocketAddress localAddress) {
setDefaultLocalAddresses(localAddress);
}
/**
* {@inheritDoc}
*/
@Override
public final List getDefaultLocalAddresses() {
return unmodifiableDefaultLocalAddresses;
}
/**
* {@inheritDoc}
* @org.apache.xbean.Property nestedType="java.net.SocketAddress"
*/
@Override
public final void setDefaultLocalAddresses(List localAddresses) {
if (localAddresses == null) {
throw new IllegalArgumentException("localAddresses");
}
setDefaultLocalAddresses((Iterable) localAddresses);
}
/**
* {@inheritDoc}
*/
@Override
public final void setDefaultLocalAddresses(Iterable localAddresses) {
if (localAddresses == null) {
throw new IllegalArgumentException("localAddresses");
}
synchronized (bindLock) {
synchronized (boundAddresses) {
if (!boundAddresses.isEmpty()) {
throw new IllegalStateException("localAddress can't be set while the acceptor is bound.");
}
Collection newLocalAddresses = new ArrayList<>();
for (SocketAddress a : localAddresses) {
checkAddressType(a);
newLocalAddresses.add(a);
}
if (newLocalAddresses.isEmpty()) {
throw new IllegalArgumentException("empty localAddresses");
}
this.defaultLocalAddresses.clear();
this.defaultLocalAddresses.addAll(newLocalAddresses);
}
}
}
/**
* {@inheritDoc}
* @org.apache.xbean.Property nestedType="java.net.SocketAddress"
*/
@Override
public final void setDefaultLocalAddresses(SocketAddress firstLocalAddress, SocketAddress... otherLocalAddresses) {
if (otherLocalAddresses == null) {
otherLocalAddresses = new SocketAddress[0];
}
Collection newLocalAddresses = new ArrayList<>(otherLocalAddresses.length + 1);
newLocalAddresses.add(firstLocalAddress);
for (SocketAddress a : otherLocalAddresses) {
newLocalAddresses.add(a);
}
setDefaultLocalAddresses(newLocalAddresses);
}
/**
* {@inheritDoc}
*/
@Override
public final boolean isCloseOnDeactivation() {
return disconnectOnUnbind;
}
/**
* {@inheritDoc}
*/
@Override
public final void setCloseOnDeactivation(boolean disconnectClientsOnUnbind) {
this.disconnectOnUnbind = disconnectClientsOnUnbind;
}
/**
* A {@Link IoFuture}
监听操作结果
*/
public static class AcceptorOperationFuture extends ServiceOperationFuture {
private final List localAddresses;
/**
* Creates a new AcceptorOperationFuture instance
*
* @param localAddresses The list of local addresses to listen to
*/
public AcceptorOperationFuture(List localAddresses) {
this.localAddresses = new ArrayList<>(localAddresses);
}
/**
* @return The list of local addresses we listen to
*/
public final List getLocalAddresses() {
return Collections.unmodifiableList(localAddresses);
}
/**
* @see Object#toString()
*/
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("Acceptor operation : ");
if (localAddresses != null) {
boolean isFirst = true;
for (SocketAddress address : localAddresses) {
if (isFirst) {
isFirst = false;
} else {
sb.append(", ");
}
sb.append(address);
}
}
return sb.toString();
}
}
}
总结；
IoAcceptor与IoService不同的是，添加了监听连接请求和地址绑定功能。抽象Io监听器AbstractIoAcceptor绑定地址首先要检查绑定的socket地址与传输元数据的地址类型是否相同，相同则通过bindInternal完成实际的绑定，然后通知Service监听器，Service已激活fireServiceActivated。解绑地址方法，主要是委托unbind0方法完成实际解绑工作，清空绑定地址集合boundAddresses，触发Service监听器无效事件fireServiceDeactivated。