前言

本文我们来解析OnEnabledEndpointCondition的实现,这个还是很简单的.目的是为了做下缓冲,后面的内容比较复杂.好了,开始吧.

解析

@ConditionalOnEnabledEndpoint

代码如下:

@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.METHOD, ElementType.TYPE })
@Conditional(OnEnabledEndpointCondition.class)
@Documented
public @interface ConditionalOnEnabledEndpoint {

    // endpoint的名字
    String value();

    // 返回endpoint是否可用,默认是可用的
    boolean enabledByDefault() default true;

}

其处理类为OnEnabledEndpointCondition.

OnEnabledEndpointCondition

OnEnabledEndpointCondition 继承自SpringBootCondition.

1. getMatchOutcome 实现如下:

   public ConditionOutcome getMatchOutcome(ConditionContext context,
           AnnotatedTypeMetadata metadata) {
       // 1. 获得@ConditionalOnEnabledEndpoint配置的Endpoint的名字和enabledByDefault的值
       AnnotationAttributes annotationAttributes = AnnotationAttributes.fromMap(metadata
               .getAnnotationAttributes(ConditionalOnEnabledEndpoint.class.getName()));
       String endpointName = annotationAttributes.getString("value");
       boolean enabledByDefault = annotationAttributes.getBoolean("enabledByDefault");
       // 2. 获得endpoints.endpointName.enabled 的配置.然后进行返回,如此时传入的是env,则读取endpoints.env.enabled 的配置
       ConditionOutcome outcome = determineEndpointOutcome(endpointName,
               enabledByDefault, context);
       if (outcome != null) {
           return outcome;
       }
       // 3.读取endpoints.enabled的配置,如果没有配置的话,则默认匹配
       return determineAllEndpointsOutcome(context);
   }

   1. 获得@ConditionalOnEnabledEndpoint配置的Endpoint的名字和enabledByDefault的值

   2. 获得endpoints.endpointName.enabled 的配置.如果有配置的化则进行返回.如此时传入的是env,则读取endpoints.env.enabled 的配置.代码如下:

      private ConditionOutcome determineEndpointOutcome(String endpointName,
              boolean enabledByDefault, ConditionContext context) {
          RelaxedPropertyResolver resolver = new RelaxedPropertyResolver(
                  context.getEnvironment(), "endpoints." + endpointName + ".");
          if (resolver.containsProperty("enabled") || !enabledByDefault) {
              boolean match = resolver.getProperty("enabled", Boolean.class,
                      enabledByDefault);
              ConditionMessage message = ConditionMessage
                      .forCondition(ConditionalOnEnabledEndpoint.class,
                              "(" + endpointName + ")")
                      .because(match ? "enabled" : "disabled");
              return new ConditionOutcome(match, message);
          }
          return null;
      }

      1. 实例化RelaxedPropertyResolver,读取endpoints.endpointName. 开头的配置

      2. 如果配置有endpoints.endpointName.enabled 或者 默认该endpoint不默认生效

         1. 获得有endpoints.endpointName.enabled的值,构造ConditionOutcome,然后返回
      3. 返回null

   3. 读取endpoints.enabled的配置,如果没有配置的话,则默认匹配.代码如下:

      private ConditionOutcome determineAllEndpointsOutcome(ConditionContext context) {
          RelaxedPropertyResolver resolver = new RelaxedPropertyResolver(
                  context.getEnvironment(), "endpoints.");
          boolean match = Boolean.valueOf(resolver.getProperty("enabled", "true"));
          ConditionMessage message = ConditionMessage
                  .forCondition(ConditionalOnEnabledEndpoint.class)
                  .because("All endpoints are " + (match ? "enabled" : "disabled")
                          + " by default");
          return new ConditionOutcome(match, message);
      }

      1. 实例化RelaxedPropertyResolver,读取endpoints. 开头的配置
      2. 获取endpoints.enabled 的配置,如果没有配置,则返回true
      3. 构造ConditionOutcome进行返回

2. 使用案例:

   在EndpointWebMvcManagementContextConfiguration中有如下方法:

   @Bean
   @ConditionalOnMissingBean
   @ConditionalOnBean(EnvironmentEndpoint.class)
   @ConditionalOnEnabledEndpoint("env")
   public EnvironmentMvcEndpoint environmentMvcEndpoint(EnvironmentEndpoint delegate) {
       return new EnvironmentMvcEndpoint(delegate);
   }

   其中使用到了@ConditionalOnEnabledEndpoint注解,意思是当配置有endpoints. env.enabled=true或者配置有endpoints.enabled=true或者没有配置endpoints.enabled,endpoints. env.enabled时默认生效