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EurekaClientAutoConfiguration

2021-05-16 12:58:11   0  举报

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EurekaClient 自动化配置

后端开发

系统架构

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源码

@EnableConfigurationProperties

源码

/**
* Convenient way to quickly register {@link ConfigurationProperties} annotated beans
* with Spring. Standard Spring Beans will also be scanned regardless of this value.
* @return {@link ConfigurationProperties} annotated beans to register
*/
Class<?>[] value() default {};

@Import(EnableConfigurationPropertiesImportSelector.class)

源码

源码注释

@ConditionalOnClass(EurekaClientConfig.class)

@ConditionalOnClass是指当classpath下有某个类时才装配。@ConditionalOnMissingClass是指当classpath下没有某个类时才装配

因为 EurekaClientConfig类在 com.netflix.eureka:eureka-client 包下面，所以也就是说只有当有这个jar 依赖的时候才会起作用

@ConditionalOnBean(EurekaDiscoveryClientConfiguration.Marker.class)

@ConditionalOnBean是指当spring容器中有某个bean时才装配。@ConditionalOnMissingBean当spring容器中不存在某个bean时才装配

首先我们看Eureka-client 端

主启动类

@EnableEurekaClient

源码

@EnableDiscoveryClient

源码

@Import(EnableDiscoveryClientImportSelector.class)

源码

子主题

EurekaDiscoveryClientConfiguration

源码

@ConditionalOnProperty(value = "eureka.client.enabled", matchIfMissing = true)

@ConditionalOnProperty是指当某个配置项为某个值时才装配。@ConditionalOnMissingProperty是指当某个配置项不等于某个值时才装配

我们看这个如果没有配置的话默认就是 true

@AutoConfigureBefore({ NoopDiscoveryClientAutoConfiguration.class,
CommonsClientAutoConfiguration.class, ServiceRegistryAutoConfiguration.class })

源码

源码说明

@AutoConfigureAfter(name = "org.springframework.cloud.autoconfigure.RefreshAutoConfiguration")

源码

源码说明

@Autowired
private ConfigurableEnvironment env

什么时候初始化的？

SpringBoot main 方法 run 源码中

@Autowired(required = false)
private HealthCheckHandler healthCheckHandler

什么时候初始化的？

首先这个对象不一定会被创建（从注解看 required= false 他也不是必须的）

首先如果我们如果想要初始化必须添加pom 依赖

首先它是一个接口，我们可以发现这个接口只有两个实现类

EurekaHealthCheckHandler

HealthCheckCallbackToHandlerBridge

因为：HealthCheckCallbackToHandlerBridge 是废弃的，所以我们这个接口的对象一定注入的是EurekaHealthCheckHandler的实例

我们发现 EurekaDiscoveryClientConfiguration这个配置类中创建了我们要找的Bean 对象

源码

核心方法：

我们可以发现只有当我们在配置文件中配置了：eureka.client.healthcheck.enabled 对象才会创建

源码

public EurekaClientConfigBean eurekaClientConfigBean()

核心代码

注解说只有IOC 容器没有EurekaClientConfig bean 对象的时候才会创建当前bean

@ImplementedBy(DefaultEurekaClientConfig.class)

@ImplementedBy注解的作用是指定默认接口的实现类

DefaultEurekaClientConfig

源码

@Singleton

源码

源码说明

@ProvidedBy(DefaultEurekaClientConfigProvider.class)

源码

源码说明

指向提供者

DefaultEurekaClientConfigProvider

源码

源码说明

源码

说明：客户端的配置bean对象，我们可以通过这个类看到很多的客户端的默认配置

public EurekaInstanceConfigBean eurekaInstanceConfigBean(InetUtils inetUtils)

核心代码

源码

该Bean 是Eureka 客户端的实例bean

InetUtils

我们可以根据这个配置我们客户端指定的网卡等

public DiscoveryClient discoveryClient(EurekaInstanceConfig config,
EurekaClient client)

核心代码

对象源码

我们可以通过这个Bean 获取服务实例列表等

示例

public EurekaServiceRegistry eurekaServiceRegistry()

核心代码

源码

服务注册，服务注销，设置状态，获取状态

public EurekaRegistration eurekaRegistration(EurekaClient eurekaClient, CloudEurekaInstanceConfig instanceConfig, ApplicationInfoManager applicationInfoManager)

核心方法

类源码

作用就是我们可以通过这个Bean 拿到

EurekaClient

CloudEurekaInstanceConfig

ApplicationInfoManager

HealthCheckHandler

public EurekaAutoServiceRegistration eurekaAutoServiceRegistration(ApplicationContext context, EurekaServiceRegistry registry, EurekaRegistration registration)

方法

核心方法 start()

源码

public class EurekaAutoServiceRegistration implements AutoServiceRegistration, SmartLifecycle, Ordered

SmartLifecycle

SmartLifecycle 是一个接口。当Spring容器加载所有bean并完成初始化之后，会接着回调实现该接口的类中对应的方法（start()方法）

测试代码示例

经过测试发现，start 方法在InitializingBean 方法的 afterPropertiesSet() 方法之后执行

总结：就是在IOC 容器启动完成之后，注册监控检查，设置状态，发布事件

public MutableDiscoveryClientOptionalArgs discoveryClientOptionalArgs()

代码

@Configuration
@ConditionalOnMissingRefreshScope
protected static class EurekaClientConfiguration

代码

CloudEurekaClient

核心代码

public CloudEurekaClient(ApplicationInfoManager applicationInfoManager,
EurekaClientConfig config,
DiscoveryClientOptionalArgs args,
ApplicationEventPublisher publisher) {
super(applicationInfoManager, config, args);
this.applicationInfoManager = applicationInfoManager;
this.publisher = publisher;
this.eurekaTransportField = ReflectionUtils.findField(DiscoveryClient.class, "eurekaTransport");
ReflectionUtils.makeAccessible(this.eurekaTransportField);
}

super(applicationInfoManager, config, args);

DiscoveryClient

源码

/**
* @deprecated use the version that take {@link com.netflix.discovery.AbstractDiscoveryClientOptionalArgs} instead
*/
@Deprecated
public DiscoveryClient(ApplicationInfoManager applicationInfoManager, final EurekaClientConfig config, DiscoveryClientOptionalArgs args) {
this(applicationInfoManager, config, (AbstractDiscoveryClientOptionalArgs) args);
}

this(applicationInfoManager, config, (AbstractDiscoveryClientOptionalArgs) args);

public DiscoveryClient(ApplicationInfoManager applicationInfoManager, final EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs args) {
this(applicationInfoManager, config, args, new Provider<BackupRegistry>() {
private volatile BackupRegistry backupRegistryInstance;

@Override
public synchronized BackupRegistry get() {
if (backupRegistryInstance == null) {
String backupRegistryClassName = config.getBackupRegistryImpl();
if (null != backupRegistryClassName) {
try {
backupRegistryInstance = (BackupRegistry) Class.forName(backupRegistryClassName).newInstance();
logger.info("Enabled backup registry of type " + backupRegistryInstance.getClass());
} catch (InstantiationException e) {
logger.error("Error instantiating BackupRegistry.", e);
} catch (IllegalAccessException e) {
logger.error("Error instantiating BackupRegistry.", e);
} catch (ClassNotFoundException e) {
logger.error("Error instantiating BackupRegistry.", e);
}
}

if (backupRegistryInstance == null) {
logger.warn("Using default backup registry implementation which does not do anything.");
backupRegistryInstance = new NotImplementedRegistryImpl();
}
}

return backupRegistryInstance;
}
});
}

核心源码

源码

@Configuration
@ConditionalOnRefreshScope
protected static class RefreshableEurekaClientConfiguration

代码

@interface ConditionalOnMissingRefreshScope

代码

就是在当前类定义一个条件刷新注解，上面EurekaClientConfiguration 配置是否会起作用会判断这个条件是否满足

@interface ConditionalOnRefreshScope

代码

就是在当前类定义一个条件刷新注解，上面RefreshableEurekaClientConfiguration 配置是否会起作用会判断这个条件是否满足

@ConditionalOnClass(RefreshScope.class)

@RefreshScope 注解