Write it at the front

Before , A lot of friends sent me private letters : How to quickly master Dubbo The core principle and source code of . therefore , I wrote an article 《 How can I quickly grasp Dubbo The principle and source code of ( Dry only )?》. about Dubbo Source code analysis series article , I'm also thinking about how to make the article of source code analysis easier to understand , therefore , I adjusted my writing Dubbo Source code analysis article strategy , Try to make it easier for your friends 、 Easy to understand way to master thoroughly Dubbo Source code . today , Let's talk about Dubbo How to realize the unified contract in .

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I have to say URL

URL The full name is the uniform resource locator , It can locate a unique network address in the Internet .URL The format of is as follows .


among , A brief description of each part is as follows .

  • protocol:URL The agreement . The most common protocol is HTTP and HTTPS, Others are FTP、WS、FILE、SMTP etc. .
  • username: user name .
  • password: password .
  • host: host , It's usually a domain name or IP Address .
  • port: Host port number .
  • path: The path of the requested target file .
  • parameters: Request specific parameter information , Here for key=value&key=value.

This is what we see on the Internet URL Brief description .

that , stay Dubbo Inside , A large number of methods receive parameters in the form of URL Encapsulated , that ,URL stay Dubbo What role does the interior play ? Let's move on .

Dubbo Medium URL

in general , stay Dubbo Inside , Service providers Provider Will encapsulate their own information into URL Sign up to Zookeeper Or other registries , So as to expose the services they provide . And service consumers Consumer Also through URL In the form of Zookeeper Or other registries subscribe to the services they want to call . And in the Dubbo Of SPI In the implementation ,URL And will participate in the logic processing of extension implementation . So ,URL stay Dubbo Is very important in the implementation of . It can also be said that ,Dubbo Medium URL Namely Dubbo The unified contract of .

So let's see Dubbo Medium URL What does it look like , By debugging Dubbo Bring their own Provider Sample source code , We can see in the Dubbo Medium URL As shown below .


This is also Provider Sign up to Zookeeper Or other registry information . The description of each part is as follows .

  • dubbo: It uses dubbo agreement .
  • host: The host IP The address is
  • port: The port number is 20880.
  • path: The request path here is :org.apache.dubbo.demo.DemoService
  • parameters: Requested parameter information , Here for :anyhost=true&application=dubbo-demo-annotation-provider&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&interface=org.apache.dubbo.demo.DemoService&methods=sayHello,sayHelloAsync&pid=15012&release=&side=provider&timestamp=1610857629484.

since Dubbo Is to Zookeeper Or other registries to register this information , that Dubbo How does the interior respond to URL It's packaged .

stay dubbo-common Module , There is one URL Class is designed to encapsulate URL, As shown below .

stay URL Class , Let's look at a core constructor , As shown below .

public URL(String protocol,
String username,
String password,
String host,
int port,
String path,
Map<String, String> parameters,
Map<String, Map<String, String>> methodParameters) {
if (StringUtils.isEmpty(username)
&& StringUtils.isNotEmpty(password)) {
throw new IllegalArgumentException("Invalid url, password without username!");
this.protocol = protocol;
this.username = username;
this.password = password;
this.host = host;
this.port = Math.max(port, 0);
this.address = getAddress(this.host, this.port); // trim the beginning "/"
while (path != null && path.startsWith("/")) {
path = path.substring(1);
this.path = path;
if (parameters == null) {
parameters = new HashMap<>();
} else {
parameters = new HashMap<>(parameters);
this.parameters = Collections.unmodifiableMap(parameters);
this.methodParameters = Collections.unmodifiableMap(methodParameters);

You can see ,Dubbo about URL The core encapsulation of , It's basically the same as in the Internet URL Encapsulation is consistent .

stay Dubbo Of dubbo-common The module provides processing URL Tool class of :URLBuilder and URLStrParser. As shown below .

The implementation of these two classes is relatively simple , Friends can read by themselves Dubbo Source code .

Next , Let's see Dubbo Inside ,URL How to realize the unified contract ?

Dubbo in URL Practical application of

here , We mainly talk about it from three aspects URL stay Dubbo Internal applications :

  • URL stay SPI Application in .
  • URL Applications in service registration .
  • URL Applications in service discovery .

URL stay SPI Application in

I know a little about Dubbo Everyone knows that ,Dubbo With a high degree of scalability , And this scalability is based on Dubbo Self SPI To achieve . stay Dubbo Realized SPI in ,URL And played a very important role .

stay Dubbo SPI In the implementation of , A typical scene is being @Adaptive Annotation decorated interface method , for example , stay dubbo-registry-api Module RegistryFactory Interface getRegistry() The method is @Adaptive({"protocol"}) To modify . As shown below .

explain RegistryFactory Interface getRegistry() Method is an adapter method ,Dubbo In the process of running , Would be getRegistry() Methods are generated dynamically RegistryFactory$Adaptive type . for example , Generated RegistryFactory$Adaptive The types are as follows .

public class RegistryFactory$Adaptive
implements RegistryFactory {
public Registry getRegistry(org.apache.dubbo.common.URL arg0) {
if (arg0 == null) throw new IllegalArgumentException("");
org.apache.dubbo.common.URL url = arg0;
String extName = (url.getProtocol() == null ? "dubbo" : url.getProtocol());
if (extName == null)
throw new IllegalStateException("");
RegistryFactory extension = (RegistryFactory) ExtensionLoader.getExtensionLoader(RegistryFactory.class).getExtension(extName);
return extension.getRegistry(arg0);

This code is relatively easy to understand , Generated RegistryFactory$Adaptive It's automatic getRegistry() Method , stay getRegistry() In the method , Will get URL Medium protocol Parameters to determine URL The agreement , If you get protocol It's empty , Use the default dubbo agreement , With this Agreement , I can get through SPI Load specific extension implementation classes dynamically .

We are Dubbo Of dubbo-registry-api Found in module RegistryProtocol class , As shown below .

Find one getRegistry() Method and hit the breakpoint , As shown below .

Next ,debug start-up Dubbo Of Provider Example , As shown below .

You can see , Used at this time protocol Agreement for zookeeper. of Dubbo in SPI The implementation of the , We will analyze it in detail later , today , Let's have a general understanding .

URL Applications in service registration

stay Dubbo The implementation of service registration in ,URL Also played a very important role . here , The registry I use is Zookeeper, therefore , We are dubbo-registry-zookeeper Found in module ZookeeperRegistry class , As shown below .

Find one doRegister() Method , Set a breakpoint , As shown below .

debug start-up Dubbo Self contained provider Example , As shown below .

You can see , Register to Zookeeper Medium URL in , Contains protocol agreement 、host Host name 、port Port number 、path Request path ,parameters Parameter information .

URL Applications in service discovery

Dubbo Consumers of services in the market Consumer When it starts , Will send to Zookeeper The registry subscribes to the services it needs to call , That's how to get through URL What about the subscription ? We are also in dubbo-registry-zookeeper Module ZookeeperRegistry Find in class doSubscribe() Method . stay doSubscribe() Method , As shown below .

start-up Dubbo Self contained Consumer Example , As shown below .

We can see ,Dubbo Of Consumer Will send to Zookeeper Pass in the following parameters to subscribe to the service .


Among them protocol by consumer, Represents a subscription agreement .category Represents the category to subscribe to , Here is providers,configurators,routers Three categories .interface Represents the interface service to subscribe to , Here is org.apache.dubbo.demo.DemoService.methods Represents the method to subscribe to , Here is sayHello,sayHelloAsync.

Another thing to note is : In the process of service registration ,Dubbo Will URL Turn into Zookeeper Path to register information to Zookeeper in ; In the process of service discovery ,Dubbo Will URL Turn into Zookeeper route , To monitor Zookeeper Change the directory to subscribe to related services .

All in all , stay Dubbo Through internal URL The realization of a unified contract . Have you learned ?

Recommended reading

Okay , That's all for today , I'm glacier , If you have any questions, please leave a message below , I can also add wechat :sun_shine_lyz, Exchange technology together , Step up together , Let's fight together ~~

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