初始调用
我们从controller开始看起，当我们发起一个request请求的时候，controller调用的是service，此处我们调用的dubbo引用服务的代理类
IUserService是一个接口，实际调用的是一个代理类，我们接着往下看：
@RestController
@RequestMapping("/view/user")
public class UserController {
@Resource
private IUserService userService;
@RequestMapping("/list")
public String getUserList(){
String list = userService.queryList();
return list;
}
}
实际上调用的是InvokerInvocationHandler的invoke方法，内部调用的成员变量invoker的invoke方法，并使用请求方法、参数封装了一个远程调用对象RpcInvocation，接下来我们看一下RpcInvocation对象都有什么？构建完RpcInvocation对象，继续执行invoke方法，如下
public class InvokerInvocationHandler implements InvocationHandler {
private final Invoker<?> invoker;
public InvokerInvocationHandler(Invoker<?> handler) {
this.invoker = handler;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
String methodName = method.getName();
Class<?>[] parameterTypes = method.getParameterTypes();
if (method.getDeclaringClass() == Object.class) {
return method.invoke(invoker, args);
}
if ("toString".equals(methodName) && parameterTypes.length == 0) {
return invoker.toString();
}
if ("hashCode".equals(methodName) && parameterTypes.length == 0) {
return invoker.hashCode();
}
if ("equals".equals(methodName) && parameterTypes.length == 1) {
return invoker.equals(args[0]);
}
//invoker = MockClusterInvoker
return invoker.invoke(new RpcInvocation(method, args)).recreate();
}
}
invoker.invoke
经过上一章节Dubbo发布过程中，消费者的初始化过程,我们知道此处的invoker是一个被装饰器包装了的invoker
public class MockClusterInvoker<T> implements Invoker<T> {
public MockClusterInvoker(Directory<T> directory, Invoker<T> invoker) {
this.directory = directory;
this.invoker = invoker;
}
public Result invoke(Invocation invocation) throws RpcException {
Result result = null;
// directory.getUrl() = zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?anyhost=true&application=user-consumer&check=false&dubbo=2.6.2&generic=false&getUserById.retries=3
//&getUserById.timeout=3000&interface=com.bail.user.service.IUserService&methods=getUserById,queryList&pid=9480
//®ister.ip=192.168.31.199&remote.timestamp=1638364136372&retries=2&revision=1.0.0&side=consumer&timeout=8000×tamp=1638364165215&version=1.0.0
//value = false,不是模拟请求
String value = directory.getUrl().getMethodParameter(invocation.getMethodName(), Constants.MOCK_KEY, Boolean.FALSE.toString()).trim();
if (value.length() == 0 || value.equalsIgnoreCase("false")) {
//no mock 此时的invoker去掉外层装饰，invoker = failoverClusterInovker
result = this.invoker.invoke(invocation);
} else if (value.startsWith("force")) {
if (logger.isWarnEnabled()) {
logger.info("force-mock: " + invocation.getMethodName() + " force-mock enabled , url : " + directory.getUrl());
}
//force:direct mock
result = doMockInvoke(invocation, null);
} else {
//fail-mock
try {
result = this.invoker.invoke(invocation);
} catch (RpcException e) {
if (e.isBiz()) {
throw e;
} else {
if (logger.isWarnEnabled()) {
logger.warn("fail-mock: " + invocation.getMethodName() + " fail-mock enabled , url : " + directory.getUrl(), e);
}
result = doMockInvoke(invocation, e);
}
}
}
return result;
}
}
FailoverClusterInovker
this.invoker.invoke(invocation)首先调用的是抽象父类AbstractClusterInvoker的invoke方法，调用list(invocation)从注册表中获取调用者列表，此处返回的是方法对应的invokers，此处有一个重要方法getMethodParameter，用来获取方法的不同配置，此处是根据方法名称获取方法调用的负载方式，如果没有配置，则走默认方式：random;拿到invoker及loadBalance之后，继续执行doInvoke方法
public abstract class AbstractClusterInvoker<T> implements Invoker<T> {
public Result invoke(final Invocation invocation) throws RpcException {
checkWhetherDestroyed();
LoadBalance loadbalance = null;
List<Invoker<T>> invokers = list(invocation);
if (invokers != null && !invokers.isEmpty()) {
//获取负载均衡的方式
loadbalance = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(invokers.get(0).getUrl()
.getMethodParameter(invocation.getMethodName(), Constants.LOADBALANCE_KEY, Constants.DEFAULT_LOADBALANCE));
}
RpcUtils.attachInvocationIdIfAsync(getUrl(), invocation);
return doInvoke(invocation, invokers, loadbalance);
}
protected List<Invoker<T>> list(Invocation invocation) throws RpcException {
//directory = RegistryDirectory
List<Invoker<T>> invokers = directory.list(invocation);
return invokers;
}
}
- 调用AbstractDirectory的list方法
此处从容器拿到invokers后，有一个路由的处理
public abstract class AbstractDirectory<T> implements Directory<T> {
public List<Invoker<T>> list(Invocation invocation) throws RpcException {
if (destroyed) {
throw new RpcException("Directory already destroyed .url: " + getUrl());
}
List<Invoker<T>> invokers = doList(invocation);
List<Router> localRouters = this.routers; // local reference
if (localRouters != null && !localRouters.isEmpty()) {
for (Router router : localRouters) {
try {
if (router.getUrl() == null || router.getUrl().getParameter(Constants.RUNTIME_KEY, false)) {
invokers = router.route(invokers, getConsumerUrl(), invocation);
}
} catch (Throwable t) {
logger.error("Failed to execute router: " + getUrl() + ", cause: " + t.getMessage(), t);
}
}
}
return invokers;
}
}
public class RegistryDirectory<T> extends AbstractDirectory<T> implements NotifyListener {
private volatile Map<String, List<Invoker<T>>> methodInvokerMap; //方法对应的invoker
public List<Invoker<T>> doList(Invocation invocation) {
if (forbidden) {
// 1. No service provider 2. Service providers are disabled
throw new RpcException(RpcException.FORBIDDEN_EXCEPTION,
"No provider available from registry " + getUrl().getAddress() + " for service " + getConsumerUrl().getServiceKey() + " on consumer " + NetUtils.getLocalHost()
+ " use dubbo version " + Version.getVersion() + ", please check status of providers(disabled, not registered or in blacklist).");
}
List<Invoker<T>> invokers = null;
Map<String, List<Invoker<T>>> localMethodInvokerMap = this.methodInvokerMap; // local reference
if (localMethodInvokerMap != null && localMethodInvokerMap.size() > 0) {
String methodName = RpcUtils.getMethodName(invocation);
Object[] args = RpcUtils.getArguments(invocation);
if (args != null && args.length > 0 && args[0] != null
&& (args[0] instanceof String || args[0].getClass().isEnum())) {
invokers = localMethodInvokerMap.get(methodName + "." + args[0]); // The routing can be enumerated according to the first parameter
}
if (invokers == null) {
//从容器中返回方法对应的invoker
invokers = localMethodInvokerMap.get(methodName);
}
if (invokers == null) {
invokers = localMethodInvokerMap.get(Constants.ANY_VALUE);
}
if (invokers == null) {
Iterator<List<Invoker<T>>> iterator = localMethodInvokerMap.values().iterator();
if (iterator.hasNext()) {
invokers = iterator.next();
}
}
}
return invokers == null ? new ArrayList<Invoker<T>>(0) : invokers;
}
}
doInvoke
在方法中，根据加载的负载均衡策略选择invoker，继续调用RegistryDirectory invoker的invoke方法 ->invoker(ProtocolFilterWrapper).invoke->经过多个Filter的调用（ConsumerContextFilter、ProtocolFilterWrapper、FutureFilter、PFW、MonitorFilter）-LitenerInvokerWrapper DubboInvoker.invoke->abstractInvoker.invoke()->abstractInvoker.doInvoke() ->dubboInvoker.doInvoke ->client.request
最后通过clinet发起dubbo协议的netty请求，请求服务端。服务端接收请求，进行处理。
2.远程对象RpcInvocation
public class RpcInvocation implements Invocation, Serializable {
public RpcInvocation(Method method, Object[] arguments) {
this(method.getName(), method.getParameterTypes(), arguments, null, null);
}
public RpcInvocation(String methodName, Class<?>[] parameterTypes, Object[] arguments, Map<String, String> attachments, Invoker<?> invoker) {
this.methodName = methodName;
this.parameterTypes = parameterTypes == null ? new Class<?>[0] : parameterTypes;
this.arguments = arguments == null ? new Object[0] : arguments;
//此处的attachments invoker为空
this.attachments = attachments == null ? new HashMap<String, String>() : attachments;
this.invoker = invoker;
}
}