org.jboss.netty.handler.execution

类 ExecutionHandler

java.lang.Object

org.jboss.netty.handler.execution.ExecutionHandler

所有已实现的接口:

ChannelDownstreamHandler, ChannelHandler, ChannelUpstreamHandler, ExternalResourceReleasable

@ChannelHandler.Sharable
public class ExecutionHandler
extends java.lang.Object
implements ChannelUpstreamHandler, ChannelDownstreamHandler, ExternalResourceReleasable

Forwards an upstream ChannelEvent to an Executor.

ExecutionHandler is often used when your ChannelHandler performs a blocking operation that takes long time or accesses a resource which is not CPU-bound business logic such as DB access. Running such operations in a pipeline without an ExecutionHandler will result in unwanted hiccup during I/O because an I/O thread cannot perform I/O until your handler returns the control to the I/O thread.

In most cases, an ExecutionHandler is coupled with an OrderedMemoryAwareThreadPoolExecutor because it guarantees the correct event execution order and prevents an OutOfMemoryError under load:

 public class DatabaseGatewayPipelineFactory implements ChannelPipelineFactory {

     private final ExecutionHandler executionHandler;

     public DatabaseGatewayPipelineFactory(ExecutionHandler executionHandler) {
         this.executionHandler = executionHandler;
     }

     public ChannelPipeline getPipeline() {
         return Channels.pipeline(
                 new DatabaseGatewayProtocolEncoder(),
                 new DatabaseGatewayProtocolDecoder(),
                 executionHandler, // Must be shared
                 new DatabaseQueryingHandler());
     }
 }
 ...

 public static void main(String[] args) {
     ServerBootstrap bootstrap = ...;
     ...
     ExecutionHandler executionHandler = new ExecutionHandler(
             new OrderedMemoryAwareThreadPoolExecutor(16, 1048576, 1048576))
     bootstrap.setPipelineFactory(
             new DatabaseGatewayPipelineFactory(executionHandler));
     ...
     bootstrap.bind(...);
     ...

     while (!isServerReadyToShutDown()) {
         // ... wait ...
     }

     bootstrap.releaseExternalResources();
     executionHandler.releaseExternalResources();
 }
 

Please refer to OrderedMemoryAwareThreadPoolExecutor for the detailed information about how the event order is guaranteed.

SEDA (Staged Event-Driven Architecture)

You can implement an alternative thread model such as SEDA by adding more than one ExecutionHandler to the pipeline.

Using other Executor implementation

Although it's recommended to use OrderedMemoryAwareThreadPoolExecutor, you can use other Executor implementations. However, you must note that other Executor implementation might break your application because they often do not maintain event execution order nor interact with I/O threads to control the incoming traffic and avoid OutOfMemoryError.

嵌套类概要

从接口继承的嵌套类/接口 org.jboss.netty.channel.ChannelHandler

ChannelHandler.Sharable

构造器概要

构造器

构造器和说明
ExecutionHandler(java.util.concurrent.Executor executor) Creates a new instance with the specified Executor.
ExecutionHandler(java.util.concurrent.Executor executor, boolean handleDownstream, boolean handleUpstream) Creates a new instance with the specified Executor.

方法概要

方法

限定符和类型	方法和说明
java.util.concurrent.Executor	getExecutor() Returns the Executor which was specified with the constructor.
void	handleDownstream(ChannelHandlerContext ctx, ChannelEvent e) Handles the specified downstream event.
protected boolean	handleReadSuspend(ChannelHandlerContext ctx, ChannelEvent e) Handle suspended reads
void	handleUpstream(ChannelHandlerContext context, ChannelEvent e) Handles the specified upstream event.
void	releaseExternalResources() Shuts down the Executor which was specified with the constructor and wait for its termination.

从类继承的方法 java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

构造器详细资料

ExecutionHandler

public ExecutionHandler(java.util.concurrent.Executor executor)

Creates a new instance with the specified Executor. Specify an OrderedMemoryAwareThreadPoolExecutor if unsure.

ExecutionHandler

public ExecutionHandler(java.util.concurrent.Executor executor,
                boolean handleDownstream,
                boolean handleUpstream)

Creates a new instance with the specified Executor. Specify an OrderedMemoryAwareThreadPoolExecutor if unsure.

方法详细资料

getExecutor

public java.util.concurrent.Executor getExecutor()

Returns the Executor which was specified with the constructor.

releaseExternalResources

public void releaseExternalResources()

Shuts down the Executor which was specified with the constructor and wait for its termination.

指定者:

releaseExternalResources 在接口中 ExternalResourceReleasable

handleUpstream

public void handleUpstream(ChannelHandlerContext context,
                  ChannelEvent e)
                    throws java.lang.Exception

从接口复制的说明: ChannelUpstreamHandler

Handles the specified upstream event.

指定者:

handleUpstream 在接口中 ChannelUpstreamHandler

参数:

context - the context object for this handler

e - the upstream event to process or intercept

抛出:

java.lang.Exception

handleDownstream

public void handleDownstream(ChannelHandlerContext ctx,
                    ChannelEvent e)
                      throws java.lang.Exception

从接口复制的说明: ChannelDownstreamHandler

Handles the specified downstream event.

指定者:

handleDownstream 在接口中 ChannelDownstreamHandler

参数:

ctx - the context object for this handler

e - the downstream event to process or intercept

抛出:

java.lang.Exception

handleReadSuspend

protected boolean handleReadSuspend(ChannelHandlerContext ctx,
                        ChannelEvent e)

Handle suspended reads