环境：springboot2.3.10

需求：有这么一个Bean它被注册的条件是需要满足多个条件下才能被注册。如下

pack:
  datasource:
    enabled: true
---
pack:
  cache:
	  enabled: true

只有在这两个属性都为true时才注册Bean。

方法1 @ConditionalOnExpression

注解说明：

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

  /**
   * The SpEL expression to evaluate. Expression should return {@code true} if the
   * condition passes or {@code false} if it fails.
   * @return the SpEL expression
   */
  String value() default "true";

}

表达式SpEL表达式要么返回true，要么返回false。

使用内置的@ConditionalOnExpression表达式条件注解。

@Bean
@ConditionalOnExpression("${pack.datasource.enabled:true} and ${pack.cache.enabled:true}")
public Animal animal() {
  return new Animal() ;
}

pack:
  datasource:
    enabled: true
---    
pack:
  cache:
    enabled: false

只有这两个属性都配置为true时Animal Bean才会被注册。

方式2 AllNestedConditions & AnyNestedCondition

使用AllNestedConditions所有条件都满足的情况下才会注册Bean

public class DataSourceAllCondition extends AllNestedConditions {
	
  public DataSourceAllCondition() {
    super(ConfigurationPhase.REGISTER_BEAN) ;
  }
  public DataSourceAllCondition(ConfigurationPhase configurationPhase) {
    super(configurationPhase);
  }
  @ConditionalOnBean(UsersController.class)
  static class ExistClass {
  }
  @ConditionalOnProperty(prefix = "pack.datasource", name = "enabled", havingValue = "true", matchIfMissing = false)
  static class PropertyEnabled {
  }
  @ConditionalOnProperty(prefix = "pack.cache", name = "enabled", havingValue = "true", matchIfMissing = false)
  static class PropertyEnabled {
  }
}

@Bean
@Conditional(DataSourceAnyCondition.class)
public Animal animal() {
  return new Animal() ;
}

这里只有3个条件都满足了才会注册。当前上下文中存在UsersController Bean，pack.datasource.enabled=true, pack.cache.enabled=true 3个条件同时成立才会被注册。

AnyNestedCondition 只要有一个条件成立就会注册Bean。

public class DataSourceAnyCondition extends AnyNestedCondition {
	public DataSourceAnyCondition() {
		super(ConfigurationPhase.REGISTER_BEAN) ;
	}
	public DataSourceAnyCondition(ConfigurationPhase configurationPhase) {
		super(configurationPhase);
	}
	@ConditionalOnProperty(prefix = "pack.datasource", name = "enabled", havingValue = "true", matchIfMissing = false)
	static class PropertyEnabled {
	}
  @ConditionalOnProperty(prefix = "pack.cache", name = "enabled", havingValue = "true", matchIfMissing = false)
  static class PropertyEnabled {
  }
}

两个条件只要有一个成立即可。

完毕！！！

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