一、前言

　　spring為開發人員提供了兩個搜尋註解的工具類，分別是AnnotatedElementUtils和AnnotationUtils。在使用的時候，總是傻傻分不清，什麼情況下使用哪一個。於是我做了如下的整理和總結。

二、AnnotationUtils官方解釋

　　功能

　　用於處理註解，處理元註解，橋接方法（編譯器為通用宣告生成）以及超級方法（用於可選註解繼承）的常規實用程式方法。請注意，JDK的內省工具本身並不提供此類的大多數功能。作為執行時保留註解的一般規則（例如，用於事務控制，授權或服務公開），始終在此類上使用查詢方法（例如，findAnnotation（Method，Class），getAnnotation（Method，Class）和getAnnotations（方法））而不是JDK中的普通註解查詢方法。您仍然可以在給定類級別的get查詢（getAnnotation（Method，Class））和給定方法的整個繼承層次結構中的查詢查詢（findAnnotation（Method，Class））之間明確選擇。

　　術語

　　直接呈現，間接呈現和呈現的術語與AnnotatedElement的類級別javadoc中定義的含義相同（在Java 8中）。如果註解被宣告為元素上存在的其他註解上的元註解，則註解在元素上是元存在的。如果A在另一個註解上直接存在或元存在，則註解A在另一個註解上存在元。

　　元註解支援

　　大多數find *（）方法和此類中的一些get *（）方法都支援查詢用作元註解的註解。有關詳細資訊，請參閱此類中每個方法的javadoc。對於在組合註解中使用屬性覆蓋的元註解的細粒度支援，請考慮使用AnnotatedElementUtils的更具體的方法。

　　屬性別名

　　此類中返回註解，註解陣列或AnnotationAttributes的所有公共方法都透明地支援通過@AliasFor配置的屬性別名。有關詳細資訊，請參閱各種synthesizeAnnotation *（..）方法。

　　搜尋範圍

　　一旦找到指定型別的第一個註解，此類中的方法使用的搜尋演算法將停止搜尋註解。因此，將默默忽略指定型別的其他註解。

三、AnnotatedElementUtils官方解釋

　　功能

 　　用於在AnnotatedElements上查詢註解，元註解和可重複註解的常規實用程式方法。AnnotatedElementUtils為Spring的元註解程式設計模型定義了公共API，並支援註解屬性覆蓋。如果您不需要支援註解屬性覆蓋，請考慮使用AnnotationUtils。請注意，JDK的內省工具本身不提供此類的功能。

　　註解屬性覆蓋

　　getMergedAnnotationAttributes（），getMergedAnnotation（），getAllMergedAnnotations（），getMergedRepeatableAnnotations（），findMergedAnnotationAttributes（），findMergedAnnotation（），findAllMergedAnnotations（）和findMergedRepeatableAnnotations（）的所有變體都支援組合註解中帶有屬性覆蓋的元註解的方法。

　　查詢與獲取語義

　　獲取語​​義（Get semantics）僅限於搜尋AnnotatedElement上存在的註解（即本地宣告或繼承）或在AnnotatedElement上方的註解層次結構中宣告的註解。
　　查詢語義（Find semantics）更加詳盡，提供了語義加上對以下內容的支援：

• 如果帶註解的元素是類，則在介面上搜索
• 如果帶註解的元素是類，則在超類上搜索
• 解析橋接方法，如果帶註解的元素是方法
• 如果帶註解的元素是方法，則在介面中搜索方法
• 如果帶註解的元素是方法，則在超類中搜索方法

　　支援@Inherited

　　get語義之後的方法將遵循Java的@Inherited批註的約定，除了本地宣告的註解（包括自定義組合註解）將優於繼承註解。相反，查詢語義之後的方法將完全忽略@Inherited的存在，因為查詢搜尋演算法手動遍歷型別和方法層次結構，從而隱式支援註解繼承而不需要@Inherited。

四、準備兩個測試的註解

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@interface RequestMapping {

    String name() default "";

    @AliasFor("path")
    String[] value() default {};


    @AliasFor("value")
    String[] path() default {};
}


@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@RequestMapping
@interface PostMapping {

    @AliasFor(annotation = RequestMapping.class)
    String name() default "";

    @AliasFor(annotation = RequestMapping.class)
    String[] value() default {};

    @AliasFor(annotation = RequestMapping.class)
    String[] path() default {};
}

五、測試例子

　　父類擁有註解@RequestMapping，子類沒有註解

public class AnnotationTest {
    public static void main(String[] args) {
        System.out.println("ParentController getAnnotation @RequestMapping: " + AnnotationUtils.getAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ChildController getAnnotation @RequestMapping: " +AnnotationUtils.getAnnotation(ChildController.class, RequestMapping.class));
        System.out.println();

        System.out.println("ParentController findAnnotation @RequestMapping: " + AnnotationUtils.findAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ParentController findAnnotation @RequestMapping: " + AnnotationUtils.findAnnotation(ChildController.class, RequestMapping.class));
        System.out.println();

        System.out.println("ParentController isAnnotated @RequestMapping: " + AnnotatedElementUtils.isAnnotated(ParentController.class, RequestMapping.class));
        System.out.println("ParentController getMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.getMergedAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ChildController isAnnotated @RequestMapping: " + AnnotatedElementUtils.isAnnotated(ChildController.class, RequestMapping.class));
        System.out.println("ChildController getMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.getMergedAnnotation(ChildController.class, RequestMapping.class));
        System.out.println();

        System.out.println("ParentController hasAnnotation @RequestMapping: " + AnnotatedElementUtils.hasAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ParentController findMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.findMergedAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ChildController hasAnnotation @RequestMapping: " + AnnotatedElementUtils.hasAnnotation(ChildController.class, RequestMapping.class));
        System.out.println("ChildController findMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.findMergedAnnotation(ChildController.class, RequestMapping.class));
    }
}

@RequestMapping(value = "parent/controller")
class ParentController {
}

class ChildController extends ParentController {
}

　　輸出結果如下。

ParentController getAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])
ChildController getAnnotation @RequestMapping: null

ParentController findAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])
ChildController findAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])

ParentController isAnnotated @RequestMapping: true
ParentController getMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])
ChildController isAnnotated @RequestMapping: false
ChildController getMergedAnnotation @RequestMapping: null

ParentController hasAnnotation @RequestMapping: true
ParentController findMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])
ChildController hasAnnotation @RequestMapping: true
ChildController findMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])

　　父類沒有註解，子類擁有註解@RequestMapping

　　輸出結果如下。

ParentController getAnnotation @RequestMapping: null
ChildController getAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])

ParentController findAnnotation @RequestMapping: null
ChildController findAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])

ParentController isAnnotated @RequestMapping: false
ParentController getMergedAnnotation @RequestMapping: null
ChildController isAnnotated @RequestMapping: true
ChildController getMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])

ParentController hasAnnotation @RequestMapping: false
ParentController findMergedAnnotation @RequestMapping: null
ChildController hasAnnotation @RequestMapping: true
ChildController findMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])

　　父類擁有註解@PostMapping，子類沒有註解

public class AnnotationTest {
    public static void main(String[] args) {
        System.out.println("ParentController getAnnotation @RequestMapping: " + AnnotationUtils.getAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ChildController getAnnotation @RequestMapping: " +AnnotationUtils.getAnnotation(ChildController.class, RequestMapping.class));
        System.out.println("ParentController getAnnotation @PostMapping: " + AnnotationUtils.getAnnotation(ParentController.class, PostMapping.class));
        System.out.println("ChildController getAnnotation @PostMapping: " +AnnotationUtils.getAnnotation(ChildController.class, PostMapping.class));
        System.out.println();

        System.out.println("ParentController findAnnotation @RequestMapping: " + AnnotationUtils.findAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ParentController findAnnotation @RequestMapping: " + AnnotationUtils.findAnnotation(ChildController.class, RequestMapping.class));
        System.out.println("ParentController findAnnotation @PostMapping: " + AnnotationUtils.findAnnotation(ParentController.class, PostMapping.class));
        System.out.println("ParentController findAnnotation @PostMapping: " + AnnotationUtils.findAnnotation(ChildController.class, PostMapping.class));
        System.out.println();

        System.out.println("ParentController isAnnotated @RequestMapping: " + AnnotatedElementUtils.isAnnotated(ParentController.class, RequestMapping.class));
        System.out.println("ParentController getMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.getMergedAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ParentController isAnnotated @PostMapping: " + AnnotatedElementUtils.isAnnotated(ParentController.class, PostMapping.class));
        System.out.println("ParentController getMergedAnnotation @PostMapping: " + AnnotatedElementUtils.getMergedAnnotation(ParentController.class, PostMapping.class));
        System.out.println("ChildController isAnnotated @RequestMapping: " + AnnotatedElementUtils.isAnnotated(ChildController.class, RequestMapping.class));
        System.out.println("ChildController getMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.getMergedAnnotation(ChildController.class, RequestMapping.class));
        System.out.println("ChildController isAnnotated @PostMapping: " + AnnotatedElementUtils.isAnnotated(ChildController.class, PostMapping.class));
        System.out.println("ChildController getMergedAnnotation @PostMapping: " + AnnotatedElementUtils.getMergedAnnotation(ChildController.class, PostMapping.class));
        System.out.println();

        System.out.println("ParentController hasAnnotation @RequestMapping: " + AnnotatedElementUtils.hasAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ParentController findMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.findMergedAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ParentController hasAnnotation @PostMapping: " + AnnotatedElementUtils.hasAnnotation(ParentController.class, PostMapping.class));
        System.out.println("ParentController findMergedAnnotation @PostMapping: " + AnnotatedElementUtils.findMergedAnnotation(ParentController.class, PostMapping.class));
        System.out.println("ChildController hasAnnotation @RequestMapping: " + AnnotatedElementUtils.hasAnnotation(ChildController.class, RequestMapping.class));
        System.out.println("ChildController findMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.findMergedAnnotation(ChildController.class, RequestMapping.class));
        System.out.println("ChildController hasAnnotation @PostMapping: " + AnnotatedElementUtils.hasAnnotation(ChildController.class, PostMapping.class));
        System.out.println("ChildController findMergedAnnotation @PostMapping: " + AnnotatedElementUtils.findMergedAnnotation(ChildController.class, PostMapping.class));
    }
}

@PostMapping(value = "parent/controller")
class ParentController {
}

class ChildController extends ParentController {
}

　　輸出結果如下。

ParentController getAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[], path=[])
ChildController getAnnotation @RequestMapping: null
ParentController getAnnotation @PostMapping: @com.hjzgg.apigateway.test.service.main.PostMapping(name=, value=[parent/controller], path=[parent/controller])
ChildController getAnnotation @PostMapping: null

ParentController findAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[], path=[])
ChildController findAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[], path=[])
ParentController findAnnotation @PostMapping: @com.hjzgg.apigateway.test.service.main.PostMapping(name=, value=[parent/controller], path=[parent/controller])
ChildController findAnnotation @PostMapping: @com.hjzgg.apigateway.test.service.main.PostMapping(name=, value=[parent/controller], path=[parent/controller])

ParentController isAnnotated @RequestMapping: true
ParentController getMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])
ParentController isAnnotated @PostMapping: true
ParentController getMergedAnnotation @PostMapping: @com.hjzgg.apigateway.test.service.main.PostMapping(name=, value=[parent/controller], path=[parent/controller])
ChildController isAnnotated @RequestMapping: false
ChildController getMergedAnnotation @RequestMapping: null
ChildController isAnnotated @PostMapping: false
ChildController getMergedAnnotation @PostMapping: null

ParentController hasAnnotation @RequestMapping: true
ParentController findMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])
ParentController hasAnnotation @PostMapping: true
ParentController findMergedAnnotation @PostMapping: @com.hjzgg.apigateway.test.service.main.PostMapping(name=, value=[parent/controller], path=[parent/controller])
ChildController hasAnnotation @RequestMapping: true
ChildController findMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])
ChildController hasAnnotation @PostMapping: true
ChildController findMergedAnnotation @PostMapping: @com.hjzgg.apigateway.test.service.main.PostMapping(name=, value=[parent/controller], path=[parent/controller])　　

　　父類沒有註解，子類擁有註解@PostMapping

ParentController getAnnotation @RequestMapping: null
ChildController getAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[], path=[])
ParentController getAnnotation @PostMapping: null
ChildController getAnnotation @PostMapping: @com.hjzgg.apigateway.test.service.main.PostMapping(name=, value=[parent/controller], path=[parent/controller])

ParentController findAnnotation @RequestMapping: null
ChildController findAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[], path=[])
ParentController findAnnotation @PostMapping: null
ChildController findAnnotation @PostMapping: @com.hjzgg.apigateway.test.service.main.PostMapping(name=, value=[parent/controller], path=[parent/controller])

ParentController isAnnotated @RequestMapping: false
ParentController getMergedAnnotation @RequestMapping: null
ParentController isAnnotated @PostMapping: false
ParentController getMergedAnnotation @PostMapping: null
ChildController isAnnotated @RequestMapping: true
ChildController getMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])
ChildController isAnnotated @PostMapping: true
ChildController getMergedAnnotation @PostMapping: @com.hjzgg.apigateway.test.service.main.PostMapping(name=, value=[parent/controller], path=[parent/controller])

ParentController hasAnnotation @RequestMapping: false
ParentController findMergedAnnotation @RequestMapping: null
ParentController hasAnnotation @PostMapping: false
ParentController findMergedAnnotation @PostMapping: null
ChildController hasAnnotation @RequestMapping: true
ChildController findMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[parent/controller], path=[parent/controller])
ChildController hasAnnotation @PostMapping: true
ChildController findMergedAnnotation @PostMapping: @com.hjzgg.apigateway.test.service.main.PostMapping(name=, value=[parent/controller], path=[parent/controller])

　　@PostMapping 注有 @RequestMapping，AnnotationUtils和AnnotatedElementUtils區別

public class AnnotationTest {
    public static void main(String[] args) {
        System.out.println("ParentController getAnnotation @RequestMapping: " + AnnotationUtils.getAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ChildController getAnnotation @RequestMapping: " + AnnotationUtils.getAnnotation(ChildController.class, RequestMapping.class));
        System.out.println("ParentController findAnnotation @RequestMapping: " + AnnotationUtils.findAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ChildController findAnnotation @RequestMapping: " + AnnotationUtils.findAnnotation(ChildController.class, RequestMapping.class));
        System.out.println();

        System.out.println("ParentController getMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.getMergedAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ChildController getMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.getMergedAnnotation(ChildController.class, RequestMapping.class));
        System.out.println("ParentController findMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.findMergedAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ChildController findMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.findMergedAnnotation(ChildController.class, RequestMapping.class));
    }
}

@RequestMapping(name = "parent", path="parent/controller")
class ParentController {
}

@PostMapping(name="child", value = "child/controller", consume = "application/json")
class ChildController extends ParentController {
}


@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@interface RequestMapping {

    String name() default "";

    @AliasFor("path")
    String[] value() default {};


    @AliasFor("value")
    String[] path() default {};

    String[] consume() default {};
}


@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@RequestMapping
@interface PostMapping {

    @AliasFor(annotation = RequestMapping.class)
    String name() default "";

    @AliasFor(annotation = RequestMapping.class)
    String[] value() default {};

    @AliasFor(annotation = RequestMapping.class)
    String[] path() default {};

    @AliasFor(annotation = RequestMapping.class)
    String[] consume() default "";
}

　　輸出結果如下。

ParentController getAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=parent, value=[parent/controller], path=[parent/controller], consume=[])
ChildController getAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[], path=[], consume=[])
ParentController findAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=parent, value=[parent/controller], path=[parent/controller], consume=[])
ChildController findAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=, value=[], path=[], consume=[])

ParentController getMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=parent, value=[parent/controller], path=[parent/controller], consume=[])
ChildController getMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=child, value=[child/controller], path=[child/controller], consume=[application/json])
ParentController findMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=parent, value=[parent/controller], path=[parent/controller], consume=[])
ChildController findMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=child, value=[child/controller], path=[child/controller], consume=[application/json])

　　@PostMapping 和 @RequestMapping各自獨立，AnnotationUtils和AnnotatedElementUtils區別

public class AnnotationTest {
    public static void main(String[] args) {
        System.out.println("ParentController getAnnotation @RequestMapping: " + AnnotationUtils.getAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ChildController getAnnotation @RequestMapping: " + AnnotationUtils.getAnnotation(ChildController.class, RequestMapping.class));
        System.out.println("ParentController findAnnotation @RequestMapping: " + AnnotationUtils.findAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ChildController findAnnotation @RequestMapping: " + AnnotationUtils.findAnnotation(ChildController.class, RequestMapping.class));
        System.out.println();

        System.out.println("ParentController getMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.getMergedAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ChildController getMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.getMergedAnnotation(ChildController.class, RequestMapping.class));
        System.out.println("ParentController findMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.findMergedAnnotation(ParentController.class, RequestMapping.class));
        System.out.println("ChildController findMergedAnnotation @RequestMapping: " + AnnotatedElementUtils.findMergedAnnotation(ChildController.class, RequestMapping.class));
    }
}

@RequestMapping(name = "parent", path="parent/controller")
class ParentController {
}

@PostMapping(name="child", value = "child/controller", consume = "application/json")
class ChildController extends ParentController {
}


@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@interface RequestMapping {

    String name() default "";

    @AliasFor("path")
    String[] value() default {};


    @AliasFor("value")
    String[] path() default {};

    String[] consume() default {};
}


@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@interface PostMapping {

    @AliasFor(annotation = RequestMapping.class)
    String name() default "";

    @AliasFor(annotation = RequestMapping.class)
    String[] value() default {};

    @AliasFor(annotation = RequestMapping.class)
    String[] path() default {};

    @AliasFor(annotation = RequestMapping.class)
    String[] consume() default "";
}

　　輸出結果如下。

ParentController getAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=parent, value=[parent/controller], path=[parent/controller], consume=[])
ChildController getAnnotation @RequestMapping: null
ParentController findAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=parent, value=[parent/controller], path=[parent/controller], consume=[])
ChildController findAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=parent, value=[parent/controller], path=[parent/controller], consume=[])

ParentController getMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=parent, value=[parent/controller], path=[parent/controller], consume=[])
ChildController getMergedAnnotation @RequestMapping: null
ParentController findMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=parent, value=[parent/controller], path=[parent/controller], consume=[])
ChildController findMergedAnnotation @RequestMapping: @com.hjzgg.apigateway.test.service.main.RequestMapping(name=parent, value=[parent/controller], path=[parent/controller], consume=[])

　　此時@PostMapping沒注有@RequestMapping，所以AnnotationUtis.getAnnotation()和AnnotatedElementUtils.getMergeAnnotation()方法獲取@RequestMapping資訊為空，對應的find*()方法獲取到的都是父類@RequestMapping資訊。

六、相關方法解釋

　　AnnotationUtils.getAnnotation

　　從提供的AnnotatedElement獲取annotationType的單個Annotation，其中註解在AnnotatedElement上存在或元存在。請注意，此方法僅支援單級元註解。要支援任意級別的元註解，請使用findAnnotation（AnnotatedElement，Class）。　　

　　AnnotationUtils.findAnnotation

　　在提供的AnnotatedElement上查詢annotationType的單個Annotation。如果註解不直接出現在提供的元素上，則將搜尋元註解。

　　AnnotatedElementUtils.isAnnotated

　　確定在提供的AnnotatedElement上或指定元素上方的註解層次結構中是否存在指定annotationType的註解。如果此方法返回true，則getMergedAnnotationAttributes方法將返回非null值。

　　AnnotatedElementUtils.hasAnnotation

　　確定指定的annotationType的註解是否在提供的AnnotatedElement上或在指定元素上方的註解層次結構中可用。如果此方法返回true，則findMergedAnnotationAttributes方法將返回非null值。

　　AnnotatedElementUtils.getMergedAnnotation

　　在提供的元素上方的註解層次結構中獲取指定註解型別的第一個註解，將註解的屬性與註解層次結構的較低級別中的註解的匹配屬性合併，並將結果合成回指定註解型別的註解。完全支援@AliasFor語義，包括單個註解和註解層次結構。此方法委託給getMergedAnnotationAttributes（AnnotatedElement，Class）和AnnotationUtils.synthesizeAnnotation（Map，Class，AnnotatedElement）。

　　AnnotatedElementUtils.findMergedAnnotation

　　在提供的元素上方的註解層次結構中查詢指定註解型別的第一個註解，將註解的屬性與註解層次結構的較低級別中的註解的匹配屬性合併，並將結果合成回指定註解型別的註解。完全支援@AliasFor語義，包括單個註解和註解層次結構。