聊聊puma的Dispatcher

序

本文主要研究一下 puma 的 Dispatcher

Dispatcher

puma/puma/src/main/java/com/dianping/puma/sender/dispatcher/Dispatcher.java

public interface Dispatcher extends LifeCycle {String getName();

    void dispatch(ChangedEvent event, PumaContext context) throws DispatcherException;

    List<Sender> getSenders();}

• Dispatcher 定义了 getName、dispatch、getSenders 方法

AbstractDispatcher

puma/puma/src/main/java/com/dianping/puma/sender/dispatcher/AbstractDispatcher.java

public abstract class AbstractDispatcher implements Dispatcher {
    private String name;

    /*
     * (non-Javadoc)
     *
     * @see com.dianping.puma.common.LifeCycle#start()
     */
    @Override
    public void start() {}

    /*
     * (non-Javadoc)
     *
     * @see com.dianping.puma.common.LifeCycle#stop()
     */
    @Override
    public void stop() {}

    /*
     * (non-Javadoc)
     *
     * @see com.dianping.puma.sender.dispatcher.Dispatcher#getName()
     */
    @Override
    public String getName() {return name;}

    public void setName(String name) {this.name = name;}

    protected void throwExceptionIfNeeded(List<Throwable> exceptionList) throws DispatcherException {if (exceptionList != null && !exceptionList.isEmpty()) {StringWriter buffer = new StringWriter();
            PrintWriter out = null;
            try {out = new PrintWriter(buffer);

                for (Throwable exception : exceptionList) {exception.printStackTrace(out);
                }
            } finally {if (out != null) {out.close();
                }
            }

            throw new DispatcherException(buffer.toString());
        }

    }

}

• AbstractDispatcher 定义了 throwExceptionIfNeeded 方法，它将 exceptionList 转换为 DispatcherException

SimpleDispatcherImpl

puma/puma/src/main/java/com/dianping/puma/sender/dispatcher/SimpleDispatcherImpl.java

public class SimpleDispatcherImpl extends AbstractDispatcher {private static final Logger log = Logger.getLogger(SimpleDispatcherImpl.class);

    private List<Sender> senders;

    /**
     * @return the senders
     */
    public List<Sender> getSenders() {return senders;}

    /**
     * @param senders
     *           the senders to set
     */
    public void setSenders(List<Sender> senders) {this.senders = senders;}

    @Override
    public void start() {for (Sender sender : senders) {sender.start();
        }
        super.start();}

    @Override
    public void stop() {for (Sender sender : senders) {sender.stop();
        }
        super.stop();}

    @Override
    public void dispatch(ChangedEvent event, PumaContext context) throws DispatcherException {if (senders != null && senders.size() > 0) {List<Throwable> exceptionList = new ArrayList<Throwable>();
            for (Sender sender : senders) {
                try {sender.send(event, context);
                } catch (Exception e) {log.error("Exception occurs in sender" + sender.getName());
                    exceptionList.add(e);
                }
            }

            throwExceptionIfNeeded(exceptionList);
        } else {log.warn("No senders in dispatcher" + getName());
        }
    }

}

• SimpleDispatcherImpl 继承了 AbstractDispatcher，其 start 方法遍历 senders，挨个执行 sender.start()；其 stop 方法遍历 senders，挨个执行 sender.stop()；其 dispatch 方法遍历 senders，挨个执行 sender.send(event, context)

小结

Dispatcher 定义了 getName、dispatch、getSenders 方法；AbstractDispatcher 定义了 throwExceptionIfNeeded 方法，它将 exceptionList 转换为 DispatcherException；SimpleDispatcherImpl 继承了 AbstractDispatcher，实现了 start、stop、dispatch 方法

doc

• Dispatcher