RabbitMQ-java-client版本

1. com.rabbitmq:amqp-client:4.3.0
2. RabbitMQ版本宣告: 3.6.15

BlockingCell

1. BlockingCell，程式碼文件註釋描述為”簡單的一次性IPC機制“，其實就是一個Future物件，大多數長連線裡非同步處理獲取響應值都會採用Future模式。

2. uml關聯

   

BlockingCell原始碼分析

1. 完整程式碼，我們從程式碼結構來看其實就是一個Future

   /**
    * Simple one-shot IPC mechanism. Essentially a one-place buffer that cannot be emptied once filled.
    * 簡單的一次性IPC機制。 基本上是一個緩衝區，一旦填滿就不能清空。
    * 從程式碼上來看其實就是一個Future物件
    */
    
   
   public class BlockingCell<T> {
       /** Indicator of not-yet-filledness
        *  尚未填充滿的標示
        * */
       private boolean _filled = false;
   
       /** Will be null until a value is supplied, and possibly still then. */
       private T _value;
   
       private static final long NANOS_IN_MILLI = 1000 * 1000;
   
       private
    
    static final long INFINITY = -1;
   
       /** Instantiate a new BlockingCell waiting for a value of the specified type. */
       public BlockingCell() {
           // no special handling required in default constructor
       }
   
       /**
        * Wait for a value, and when one arrives, return it (without clearing it). If there's already a value present, there's no need to wait - the existing value
        * is returned.
        * 一直等待，直到拿到響應資料之後呼叫set(T newValue)，設定值之後呼叫notifyAll()，此時get()不再阻塞。
        * @return the waited-for value
        *
        * @throws InterruptedException if this thread is interrupted
        */
    
   
       public synchronized T get() throws InterruptedException {
           while (!_filled) {
               wait();
           }
           return _value;
       }
   
       /**
        * Wait for a value, and when one arrives, return it (without clearing it). If there's
        * already a value present, there's no need to wait - the existing value is returned.
        * If timeout is reached and value hasn't arrived, TimeoutException is thrown.
        * 
        * @param timeout timeout in milliseconds. -1 effectively means infinity
        * @return the waited-for value
        * @throws InterruptedException if this thread is interrupted
        */
       public synchronized T get(long timeout) throws InterruptedException, TimeoutException {
           //如果設定為-1，則表示一直等待下去
           if (timeout == INFINITY) return get();
   
           if (timeout < 0) {
               throw new AssertionError("Timeout cannot be less than zero");
           }
   
           long now = System.nanoTime() / NANOS_IN_MILLI;
           long maxTime = now + timeout;
           while (!_filled && (now = (System.nanoTime() / NANOS_IN_MILLI)) < maxTime) {
               wait(maxTime - now);
           }
   
           if (!_filled)
               throw new TimeoutException();
   
           return _value;
       }
   
       /**
        * As get(), but catches and ignores InterruptedException, retrying until a value appears.
        * @return the waited-for value
        */
       public synchronized T uninterruptibleGet() {
           boolean wasInterrupted = false;
           try {
               while (true) {
                   try {
                       return get();
                   } catch (InterruptedException ex) {
                       // no special handling necessary
                       wasInterrupted = true;
                   }
               }
           } finally {
               if (wasInterrupted) {
                   Thread.currentThread().interrupt();
               }
           }
       }
   
       /**
        * As get(long timeout), but catches and ignores InterruptedException, retrying until
        * a value appears or until specified timeout is reached. If timeout is reached,
        * TimeoutException is thrown.
        * We also use System.nanoTime() to behave correctly when system clock jumps around.
        * 
        * @param timeout timeout in milliseconds. -1 means 'infinity': never time out
        * @return the waited-for value
        */
       public synchronized T uninterruptibleGet(int timeout) throws TimeoutException {
           long now = System.nanoTime() / NANOS_IN_MILLI;
           long runTime = now + timeout;
           boolean wasInterrupted = false;
           try {
               do {
                   try {
                       return get(runTime - now);
                   } catch (InterruptedException e) {
                       // Ignore.
                       wasInterrupted = true;
                   }
               } while ((timeout == INFINITY) || ((now = System.nanoTime() / NANOS_IN_MILLI) < runTime));
           } finally {
               if (wasInterrupted) {
                   Thread.currentThread().interrupt();
               }
           }
   
           throw new TimeoutException();
       }
   
       /**
        * Store a value in this BlockingCell, throwing AssertionError if the cell already has a value.
        *
        * @param newValue the new value to store
        */
       public synchronized void set(T newValue) {
           if (_filled) {
               throw new AssertionError("BlockingCell can only be set once");
           }
           _value = newValue;
           _filled = true;
           notifyAll();
       }
   
       /**
        * Store a value in this BlockingCell if it doesn't already have a value.
        * @return true if this call to setIfUnset actually updated the BlockingCell; false if the cell already had a value.
        * @param newValue the new value to store
        */
       public synchronized boolean setIfUnset(T newValue) {
           if (_filled) {
               return false;
           }
           set(newValue);
           return true;
       }
   }
   
   

ValueOrException

1. ValueOrException值與異常的包裝。

   public class ValueOrException<V, E extends Throwable & SensibleClone<E>> {
       private final boolean _useValue;
       private final V _value;
       private final E _exception;
       ......
   }
   
   

BlockingValueOrException

1. BlockingValueOrException是BlockingCell的擴充套件類，泛型引數是ValueOrException

   public class BlockingValueOrException<V, E extends Throwable & SensibleClone<E>>
       extends BlockingCell<ValueOrException<V, E>>
   {
       public void setValue(V v) {
           super.set(ValueOrException.<V, E>makeValue(v));
       }
   
       public void setException(E e) {
           super.set(ValueOrException.<V, E>makeException(e));
       }
   
       public V uninterruptibleGetValue() throws E {
           return uninterruptibleGet().getValue();
       }
   
       public V uninterruptibleGetValue(int timeout) throws E, TimeoutException {
       	return uninterruptibleGet(timeout).getValue();
       }
   }
   

RpcContinuation

1. rpc配置介面

    public interface RpcContinuation {
       void handleCommand(AMQCommand command);
       void handleShutdownSignal(ShutdownSignalException signal);
   }
   
   public static abstract class BlockingRpcContinuation<T> implements RpcContinuation {
       public final BlockingValueOrException<T, ShutdownSignalException> _blocker =
           new BlockingValueOrException<T, ShutdownSignalException>();
   
       //將響應的結果存入到Future物件中(BlockingCell)
       @Override
       public void handleCommand(AMQCommand command) {
           _blocker.setValue(transformReply(command));
       }
   
       @Override
       public void handleShutdownSignal(ShutdownSignalException signal) {
           _blocker.setException(signal);
       }
   
       public T getReply() throws ShutdownSignalException
       {
           return _blocker.uninterruptibleGetValue();
       }
   
       public T getReply(int timeout)
           throws ShutdownSignalException, TimeoutException
       {
           return _blocker.uninterruptibleGetValue(timeout);
       }
       //獲取響應的結果
       public abstract T transformReply(AMQCommand command);
   }
   
   public static class SimpleBlockingRpcContinuation
       extends BlockingRpcContinuation<AMQCommand>
   {
       @Override
       public AMQCommand transformReply(AMQCommand command) {
           return command;
       }
   }
   

擴充套件

自己寫一個

1. 這裡是我之前學習netty時候寫的一個Future物件以及實現，供參考

2. ResponseFuture介面

   public interface ResponseFuture<T> {
   
       T get()  throws InterruptedException;
   
       T get(final long timeoutMillis)  throws InterruptedException;
       
       boolean isCancelled();
   
       boolean isDone();
   
       boolean isSuccess();
   
       void setResult(T result);
   
       void setFailure(Throwable err);
   
       boolean isTimeout();
       
       public long getCreateTime();
   
       public long getTimeoutInMillis();
       
       public void executeAsyncInvokeCallback();
       
       public void setAsyncInvokeCallback(AsyncInvokeCallback<T> invokeCallback);
       
       public boolean hasCallback();
   }
   

3. AbstractResponseFuture抽象類

   package cn.jananl.netty.transport;
   
   import java.util.concurrent.CountDownLatch;
   public abstract class AbstractResponseFuture<T> implements ResponseFuture<T>{
   
       public enum FutureState {
           /**新建任務 **/
           NEW(0),
           /** 任務完成 **/
           DONE(1),
           /** 任務取消**/
           CANCELLED(2),
           /**
            * 任務超時
            */
           TIMEOUT(3);
           private int state;
           FutureState(int state) {
               this.state = state;
           }
       }
       protected final CountDownLatch countDownLatch = new CountDownLatch(1);
       
       
       protected volatile FutureState state = FutureState.NEW; //狀態
       
       protected final long createTime = System.currentTimeMillis();//處理開始時間
   
       /**
        * 本地呼叫的超時時間
        */
       protected long timeoutInMillis;
   
       public AbstractResponseFuture(long timeoutInMillis) {
           this.timeoutInMillis = timeoutInMillis;
       }
   
       @Override
       public boolean isCancelled() {
           return this.state == FutureState.CANCELLED;
       }
   
       @Override
       public boolean isDone() {
           return this.state == FutureState.DONE;
       }
   
       @Override
       public boolean isTimeout() {
           return createTime + timeoutInMillis < System.currentTimeMillis();
       }
   
       public long getCreateTime() {
           return createTime;
       }
   
       public long getTimeoutInMillis() {
           return timeoutInMillis;
       }
   }
   

4. DefaultResponseFuture具體實現

   package cn.jananl.netty.transport;
   
   import java.util.concurrent.TimeUnit;
   /**
    * 預設響應future
    * @author jannal
    * @param <T>
    */
   public class DefaultResponseFuture<T> extends AbstractResponseFuture<T>{
   
       private volatile T result;
       private volatile Throwable throwable;
       private  AsyncInvokeCallback<T> invokeCallback;
       
       public DefaultResponseFuture(long timeoutInMillis) {
           super(timeoutInMillis);
       }
   
       @Override
       public T get() throws InterruptedException {
           if(!this.isDone()) {
               this.countDownLatch.await(super.timeoutInMillis, TimeUnit.MILLISECONDS);
           }
           if(this.throwable!=null){
               if(this.state==FutureState.CANCELLED){
                   throw new RuntimeException("任務被取消");
               }else{
                   throw new RuntimeException(this.throwable);
               }
           }else{
               return this.result;
           }
          
       }
   
       @Override
       public T get(long timeout) throws InterruptedException {
           if(!this.isDone()) {
               this.countDownLatch.await(timeout, TimeUnit.MILLISECONDS);
           }
           return result; 
       }
   
       @Override
       public boolean isSuccess() {
           return isDone()&&throwable==null;
       }
   
   
       @Override
       public void setFailure(Throwable cause) {
           if(!this.isDone()) {
               this.setFailure(cause);
               this.state = FutureState.DONE;
               this.countDownLatch.countDown();
           }
       }
   
       @Override
       public void setResult(T result) {
           if(!this.isDone()){
               this.result = result;
               this.state = FutureState.DONE;
               this.countDownLatch.countDown();
           }
           
       }
   
       @Override
       public void executeAsyncInvokeCallback() {
           if(invokeCallback!=null){
               invokeCallback.operationComplete(this);
           }
           
       }
   
       @Override
       public void setAsyncInvokeCallback(AsyncInvokeCallback<T> invokeCallback) {
          this.invokeCallback =  invokeCallback;
           
       }
   
       @Override
       public boolean hasCallback() {
           if(invokeCallback!=null){
               return true;
           }
           return false;
       }
   }