Zuul correlation analysis

Zuul's working mechanism

Zuul in SpringBoot

一般情况我们在springboot工程中使用
@EnableZuulProxy
或者 
@EnableZuulServer
Set up the application to act as a generic Zuul server without any built-in reverse proxy features
两个注解中一个来启动zuul网关
还有一些配置文件，这里先忽略

Being in EnableZuulServer

Take EnableZuulServer as an example to see how zuul works.

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(ZuulConfiguration.class)
public @interface EnableZuulServer {

}

ZuulConfiguration Class was imported in the EnableZuulServer annotation. Let's take a look at the ZuulConfiguration class.

@Configuration
@EnableConfigurationProperties({ ZuulProperties.class })
@ConditionalOnClass(ZuulServlet.class)
只有classpath中存在ZuulServlet类才生效。
// Make sure to get the ServerProperties from the same place as a normal web app would
@Import(ServerPropertiesAutoConfiguration.class)
public class ZuulConfiguration {
...
}

We see that the loading of the configuration file is defined in ZuulConfiguration, and we haven't seen where is the entrance of the runner zuul gateway? Continue to look down, a bean ZuulController is defined in ZuulConfiguration.

	@Bean
	public ZuulController zuulController() {
		return new ZuulController();
	}

The confusing name ZuulController, this is not our normal use of the Controller in the spring web framework. Let's look at the details:

public class ZuulController extends ServletWrappingController {

	public ZuulController() {
		setServletClass(ZuulServlet.class);
		setServletName("zuul");
		setSupportedMethods((String[]) null); // Allow all
	}
	...
}

ZuulController inherits ServletWrappingController, which originally wrapped ZuulServlet into a bean. by

public class ServletWrappingController extends AbstractController
		implements BeanNameAware, InitializingBean, DisposableBean {
		...
	@Override
	public void afterPropertiesSet() throws Exception {
		if (this.servletClass == null) {
			throw new IllegalArgumentException("'servletClass' is required");
		}
		if (this.servletName == null) {
			this.servletName = this.beanName;
		}
		this.servletInstance = this.servletClass.newInstance();
		this.servletInstance.init(new DelegatingServletConfig());
	}
	...
	}

Pass this.servletInstance.init(new DelegatingServletConfig());to initialize ZuulServlet. When ZuulController processes a request, it is handled by super.handleRequestInternal(request, response);ZuulServlet.

summary

The above briefly analyzes how springboot handles zuul. The source code path (the initialization of the parent class is not repeated here.):

EnableZuulServer --> ZuulConfiguration -->ZuulController--> ZuulServlet