注解ConditionalOnClass的处理类在哪里？

Question

最近在看spring boot中的starter， 想知道注解@ConditionalOnClass的处理类是什么， 能介绍下相关的类如何协作那最好。

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

    /**
     * The classes that must be present. Since this annotation is parsed by loading class
     * bytecode, it is safe to specify classes here that may ultimately not be on the
     * classpath, only if this annotation is directly on the affected component and
     * <b>not</b> if this annotation is used as a composed, meta-annotation. In order to
     * use this annotation as a meta-annotation, only use the {@link #name} attribute.
     * @return the classes that must be present
     */
    Class<?>[] value() default {};

    /**
     * The classes names that must be present.
     * @return the class names that must be present.
     */
    String[] name() default {};

}

Answer 1

http://www.jianshu.com/p/1d0f... 推荐查看这个文章，写的比较清晰

Answer 2

就在 @Conditional(OnClassCondition.class)，其中OnClassCondition.class 为具体实现！