要说这个参数，就要所介绍ExecuteLimitFilter，他是这个参数使用者，看到Filter大家就应该懂了，就是在每个方法请求前后加上业务逻辑。下面贴出里面的代码：
@Activate(group = Constants.PROVIDER, value = Constants.EXECUTES_KEY)
public class ExecuteLimitFilter implements Filter {
public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
URL url = invoker.getUrl();
String methodName = invocation.getMethodName();
int max = url.getMethodParameter(methodName, Constants.EXECUTES_KEY, 0);
if (max > 0) {
RpcStatus count = RpcStatus.getStatus(url, invocation.getMethodName());
if (count.getActive() >= max) {
throw new RpcException("Failed to invoke method " + invocation.getMethodName() + " in provider " + url + ", cause: The service using threads greater than <dubbo:service executes=\"" + max + "\" /> limited.");
}
}
long begin = System.currentTimeMillis();
boolean isException = false;
RpcStatus.beginCount(url, methodName);
try {
Result result = invoker.invoke(invocation);
return result;
} catch (Throwable t) {
isException = true;
if(t instanceof RuntimeException) {
throw (RuntimeException) t;
}
else {
throw new RpcException("unexpected exception when ExecuteLimitFilter", t);
}
}
finally {
RpcStatus.endCount(url, methodName, System.currentTimeMillis() - begin, isException);
}
}
}
@Activate(group = Constants.CONSUMER, value = Constants.ACTIVES_KEY)
public class ActiveLimitFilter implements Filter {
public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
URL url = invoker.getUrl();
String methodName = invocation.getMethodName();
int max = invoker.getUrl().getMethodParameter(methodName, Constants.ACTIVES_KEY, 0);
RpcStatus count = RpcStatus.getStatus(invoker.getUrl(), invocation.getMethodName());
if (max > 0) {
long timeout = invoker.getUrl().getMethodParameter(invocation.getMethodName(), Constants.TIMEOUT_KEY, 0);
long start = System.currentTimeMillis();
long remain = timeout;
int active = count.getActive();
if (active >= max) {
synchronized (count) {
while ((active = count.getActive()) >= max) {
try {
count.wait(remain);
} catch (InterruptedException e) {
}
long elapsed = System.currentTimeMillis() - start;
remain = timeout - elapsed;
if (remain <= 0) {
throw new RpcException("Waiting concurrent invoke timeout in client-side for service: "
+ invoker.getInterface().getName() + ", method: "
+ invocation.getMethodName() + ", elapsed: " + elapsed
+ ", timeout: " + timeout + ". concurrent invokes: " + active
+ ". max concurrent invoke limit: " + max);
}
}
}
}
}
try {
long begin = System.currentTimeMillis();
RpcStatus.beginCount(url, methodName);
try {
Result result = invoker.invoke(invocation);
RpcStatus.endCount(url, methodName, System.currentTimeMillis() - begin, true);
return result;
} catch (RuntimeException t) {
RpcStatus.endCount(url, methodName, System.currentTimeMillis() - begin, false);
throw t;
}
} finally {
if(max>0){
synchronized (count) {
count.notify();
}
}
}
}
}上面代码大致上和executes一样，唯一不同的就是多了一个等待时间，当当前执行该方法的线程超出了最大限制，那么可以等待一个timeout时间，如果时间过了还是超出了最大限制，那么就抛出异常。这个相对余executes来说温柔那么点。这就是那点不同！ 要说这个参数，就要所介绍ExecuteLimitFilter，他是这个参数使用者，看到Filter大家就应该懂了，就是在每个方法请求前后加上业务逻辑。下面贴出里面的代码：
@Override
public void connected(Channel ch) throws RemotingException {
Collection<Channel> channels = getChannels();
if (accepts > 0 && channels.size() > accepts) {
logger.error("Close channel " + ch + ", cause: The server " + ch.getLocalAddress() + " connections greater than max config " + accepts);
ch.close();
return;
}
super.connected(ch);
}原文：http://blog.csdn.net/jdream314/article/details/44590937