聊聊如何利用spring实现服务隔离

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前言

假设我们有个场景，我们需要实现服务之间的数据隔离、配置隔离、依赖的spring bean之间隔离。大家会有什么实现思路？今天给大家介绍spring-cloud-context里面有个NamedContextFactory可以达到上面的效果

NamedContextFactory简介

NamedContextFactory可以实现子容器，通过它创建子容器，然后通过NamedContextFactory.Specification可以定制子容器会用到的bean。

所以为什么通过NamedContextFactory可以达到数据隔离、配置隔离、依赖的spring bean之间隔离，本质就是利用NamedContextFactory为不同的服务，创建出不同的子容器，子容器之间彼此不共享，从而达到隔离的效果。

下面通过一个示例来讲解

示例

注：示例就模拟一个用户注册成功后发送华为云短信，下单成功后发送阿里云短信为例子

模拟定义短信接口

public interface SmsService {

    void send(String phone, String content);
}

模拟定义相应短信实现类

public class DefaultSmsService implements SmsService {
    @Override
    public void send(String phone, String content) {
        System.out.printf("send to %s content %s used default sms%n", phone, content);
    }
}

public class AliyunSmsService implements SmsService {
    @Override
    public void send(String phone, String content) {
        System.out.printf("send to %s content %s used aliyun sms%n", phone, content);
    }
}

public class HuaWeiSmsService implements SmsService {
    @Override
    public void send(String phone, String content) {
        System.out.printf("send to %s content %s used huawei sms%n", phone, content);
    }
}

自定义短信默认配置类

@Configuration
public class DefaultSmsClientConfiguration {


    @Bean
    @ConditionalOnMissingBean
    public SmsService smsService(){
        return new DefaultSmsService();
    }

}

定制短信需要的子容器NamedContextFactory.Specification

public class SmsClientSpecification implements NamedContextFactory.Specification{
    private String name;

    private Class<?>[] configuration;

    public SmsClientSpecification() {
    }

    public SmsClientSpecification(String name, Class<?>[] configuration) {
        this.name = name;
        this.configuration = configuration;
    }

    @Override
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public Class<?>[] getConfiguration() {
        return configuration;
    }

    public void setConfiguration(Class<?>[] configuration) {
        this.configuration = configuration;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        SmsClientSpecification that = (SmsClientSpecification) o;
        return Arrays.equals(configuration, that.configuration)
                && Objects.equals(name, that.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(configuration, name);
    }

    @Override
    public String toString() {
        return new StringBuilder("SmsSpecification{").append("name='")
                .append(name).append("', ").append("configuration=")
                .append(Arrays.toString(configuration)).append("}").toString();
    }
}

属性讲解

name： 子容器的名称（示例中我们会把用户服务名和订单服务名当成子容器名称）

configuration： name子容器需要的configuration

NamedContextFactory.Specification的作用是当创建子容器时，如果容器的name匹配了Specification的name，则会加载 Specification对应Configuration类，并将Configuration类里面标注@Bean的返回值注入到子容器中

为不同的服务创建不同的SmsClientSpecification并注入到spring容器中

@Configuration
@Import(SmsClientConfigurationRegistrar.class)
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface SmsClient {

    /**
     * Synonym for name (the name of the client).
     *
     * @see #name()
     * @return name of the Sms client
     */
    String value() default "";

    /**
     * The name of the sms client, uniquely identifying a set of client resources,
     * @return name of the Sms client
     */
    String name() default "";

    /**
     * A custom <code>@Configuration</code> for the sms client. Can contain override
     * <code>@Bean</code> definition for the pieces that make up the client
     */
    Class<?>[] configuration() default {};
}

@Configuration
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.TYPE })
@Documented
@Import(SmsClientConfigurationRegistrar.class)
public @interface SmsClients {

  SmsClient[] value() default {};

  Class<?>[] defaultConfiguration() default {};

}

注：利用import机制，将SmsClientSpecification注入到spring容器

public class SmsClientConfigurationRegistrar implements ImportBeanDefinitionRegistrar {

  @Override
  public void registerBeanDefinitions(AnnotationMetadata metadata,
      BeanDefinitionRegistry registry) {
    Map<String, Object> attrs = metadata
        .getAnnotationAttributes(SmsClients.class.getName(), true);
    if (attrs != null && attrs.containsKey("value")) {
      AnnotationAttributes[] clients = (AnnotationAttributes[]) attrs.get("value");
      for (AnnotationAttributes client : clients) {
        registerClientConfiguration(registry, getClientName(client),
            client.get("configuration"));
      }
    }
    if (attrs != null && attrs.containsKey("defaultConfiguration")) {
      String name;
      if (metadata.hasEnclosingClass()) {
        name = "default." + metadata.getEnclosingClassName();
      }
      else {
        name = "default." + metadata.getClassName();
      }
      registerClientConfiguration(registry, name,
          attrs.get("defaultConfiguration"));
    }
    Map<String, Object> client = metadata
        .getAnnotationAttributes(SmsClient.class.getName(), true);
    String name = getClientName(client);
    if (name != null) {
      registerClientConfiguration(registry, name, client.get("configuration"));
    }
  }

  private String getClientName(Map<String, Object> client) {
    if (client == null) {
      return null;
    }
    String value = (String) client.get("value");
    if (!StringUtils.hasText(value)) {
      value = (String) client.get("name");
    }
    if (StringUtils.hasText(value)) {
      return value;
    }
    throw new IllegalStateException(
        "Either 'name' or 'value' must be provided in @SmsClient");
  }

  private void registerClientConfiguration(BeanDefinitionRegistry registry, Object name,
      Object configuration) {
    BeanDefinitionBuilder builder = BeanDefinitionBuilder
        .genericBeanDefinition(SmsClientSpecification.class);
    builder.addConstructorArgValue(name);
    builder.addConstructorArgValue(configuration);
    registry.registerBeanDefinition(name + ".SmsClientSpecification",
        builder.getBeanDefinition());
  }

}

创建短信NameContextFactory

public class SmsClientNameContextFactory extends NamedContextFactory<SmsClientSpecification> {

    public SmsClientNameContextFactory() {
        super(DefaultSmsClientConfiguration.class, "sms", "sms.client.name");
    }

    public SmsService getSmsService(String serviceName) {
        return getInstance(serviceName, SmsService.class);
    }
}

注： super三个参数讲解

public NamedContextFactory(Class<?> defaultConfigType, String propertySourceName,
      String propertyName) {
    this.defaultConfigType = defaultConfigType;
    this.propertySourceName = propertySourceName;
    this.propertyName = propertyName;
  }

defaultConfigType： 默认配置类，NamedContextFactory创建子容器时，默认就会加载该配置类，该配置类主要用来做兜底，当找不到容器为name的configuration，则会使用该配置类
propertySourceName： 给propertySource取个名称
propertyName： 子容器可以通过读取配置propertyName来获取容器名。当创建子容器时通常会提供子容器的容器name。子容器中的Environment会被写入一条配置，sms.client.name=容器name

将SmsClientNameContextFactory注入到spring容器

@Bean
    @ConditionalOnMissingBean
    public SmsClientNameContextFactory smsClientNameContextFactory(@Autowired(required = false) List<SmsClientSpecification> smsSpecifications){
        SmsClientNameContextFactory smsClientNameContextFactory = new SmsClientNameContextFactory();
        smsClientNameContextFactory.setConfigurations(smsSpecifications);
        return smsClientNameContextFactory;
    }

创建不同的短信配置类

public class AliyunSmsClientConfiguration {

    @ConditionalOnMissingBean
    @Bean
    public SmsService smsService() {
       return new AliyunSmsService();
    }
}

public class HuaWeiSmsClientConfiguration {

    @ConditionalOnMissingBean
    @Bean
    public SmsService smsService() {
       return new HuaWeiSmsService();
    }
}

注：因为上述配置只需被子容器加载，因此不需要加 @Configuration

为用户服务和订单服务指定NamedContextFactory.Specification

@Configuration
@SmsClients(value = {@SmsClient(name = OrderService.SERVICE_NAME, configuration = AliyunSmsClientConfiguration.class),
        @SmsClient(name = UserService.SERVICE_NAME, configuration = HuaWeiSmsClientConfiguration.class)})
public class SmsClientAutoConfiguration {
}

测试

模拟用户注册

@Service
@RequiredArgsConstructor
public class UserService {

    private final ApplicationContext applicationContext;

    public static final String SERVICE_NAME = "userService";

    public void registerUser(String userName, String password,String mobile){
        System.out.println("注册用户"+userName+"成功");
        UserRegisterEvent event = new UserRegisterEvent(userName,password,mobile);
        applicationContext.publishEvent(event);
    }
}

@Component
@RequiredArgsConstructor
public class UserRegisterListener {

    private final SmsClientNameContextFactory smsClientNameContextFactory;


    @EventListener
    @Async
    public void listener(UserRegisterEvent event) {
        SmsService smsService = smsClientNameContextFactory.getSmsService(UserService.SERVICE_NAME);
        smsService.send(event.getMobile(), "恭喜您注册成功！初始密码为："+event.getPassword()+"，请尽快修改密码！");
    }
}

核心：

SmsService smsService = smsClientNameContextFactory.getSmsService(UserService.SERVICE_NAME);

和 @SmsClient(name = UserService.SERVICE_NAME）对应起来

运行查看控制台

当服务名不匹配时，再观察控制台

发现此时是走默认配置

总结

本文主要是聊下通过NamedContextFactory来实现服务隔离，核心点就是通过创建不同子容器进行隔离。这种方式在ribbon、openfeign、以及loadbalancer都有类似的实现，感兴趣朋友可以查阅其源码。不过这边有细节点需要注意，因为NamedContextFactory默认是懒加载创建子容器，所以可能第一次调用会比较慢。这也是ribbon第一次调用慢的原因

demo链接

https://github.com/lyb-geek/springboot-learning/tree/master/springboot-named-context-factory

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