微服务之SpringCloud实战（四）：SpringCloud Eureka源码分析

Eureka源码解析：

　　搭建Eureka服务的时候，我们会再SpringBoot启动类加上@EnableEurekaServer的注解，这个注解做了一些什么，我们一起来看。

点进@EnableEurekaServer这个注解就会看到下面代码：

/*
* Copyright 2013-2017 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*      http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package org.springframework.cloud.netflix.eureka.server;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.context.annotation.Import;

/**
* Annotation to activate Eureka Server related configuration {@link EurekaServerAutoConfiguration}
*
* @author Dave Syer
* @author Biju Kunjummen
*
*/

@EnableDiscoveryClient
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(EurekaServerMarkerConfiguration.class)
public @interface EnableEurekaServer {

}

大家可以清楚的看到@EnableEurekaServer引用了@EnableDiscoveryClient这个注解，源码如下：

/*
* Copyright 2013-2015 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*      http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package org.springframework.cloud.client.discovery;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.springframework.context.annotation.Import;

/**
* Annotation to enable a DiscoveryClient implementation.
* @author Spencer Gibb
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Import(EnableDiscoveryClientImportSelector.class)
public @interface EnableDiscoveryClient {

/**
* If true, the ServiceRegistry will automatically register the local server.
*/
boolean autoRegister() default true;
}

从这个注解我们可以知道，它主要是用来开启DiscoveryClient实例的，通过搜索DiscoveryClient我们可以看到一个类和一个接口，得到下图关系：

 待补充................