Java反射-继承关系
目錄
?
反射類型繼承關系圖
類
Type???
ParameterizedType
TypeVariable
WildcardType
GenericArrayType
Annotation
AnnotatedElement
GenericDeclaration
AnnotatedType
Parameter?
反射類型繼承關系圖
類
Type???
default String getTypeName() {
??????? return toString();
??? }
ParameterizedType
表達一個泛型類型。
Code：
public interface ParameterizedType extends Type {
?? ? //返回泛型類型的實際類型。如果是泛型類型的嵌套非泛型類型，則返回length=0的數組
?? ? //返回的類型是第一層嵌套類型，而不是遞歸的最基本類型。
?? ? //例如List<Map<String,String>> 返回的是Map<String,String>
??? Type[] getActualTypeArguments();
??? //返回原始類型，List<String>返回List
??? Type getRawType();
??? 返回類型的擁有者，可以理解嵌套類的外部類。
??? Type getOwnerType();
}
Sample
public class GenericTest {
?? ?public List<Map<String, String>> f =new ArrayList<Map<String, String>>();
?? ?public Map<String, String> m =new? HashMap<String, String> ();
?? ?
?? ?public static void main(String[] args) throws NoSuchMethodException, SecurityException, NoSuchFieldException {
?? ??? ?test2();
?? ?}
???
?? ?public static void test2() throws NoSuchMethodException, SecurityException, NoSuchFieldException
?? ?{
?? ??? ?List<Map<String, String>> list =new ArrayList<Map<String, String>>();
?? ??? ?list.add(new HashMap<String, String>());
?? ??? ?
?? ??? ?Class clazz = list.getClass();
?? ??? ?
?? ??? ?ParameterizedType t = (ParameterizedType) clazz.getGenericSuperclass();
?? ??? ?
?? ??? ?Type[] t2 = t.getActualTypeArguments();
?? ??? ?Type t3 = t.getRawType();
?? ??? ?Type t4 = t.getOwnerType();
?? ??? ?
?? ??? ?System.out.println("clazz : " + clazz.getTypeName());
?? ??? ?for(Type t0 : t2 )
?? ??? ?{
?? ??? ??? ?System.out.println("t2 : " + t0.getTypeName()? + " imp:" +?? t0.getClass().toString()? );
?? ??? ?}
?? ??? ?
?? ??? ?System.out.println("t3 : " + t3.toString());
?? ??? ?System.out.println("t4 is " + (t4 == null ? " ": " not ") + "null");
?? ??? ?
?? ??? ?
?? ??? ?Field f = GenericTest.class.getDeclaredField("f");
?? ? ?? ?Type tt = f.getGenericType();
?? ? ?? ?
?? ? ?? ?ParameterizedType pt = (ParameterizedType) tt;
?? ??? ?Type[] pt2 = pt.getActualTypeArguments();
?? ??? ?Type pt3 = pt.getRawType();
?? ??? ?Type pt4 = pt.getOwnerType();
?? ??? ?
?? ??? ?System.out.println("clazz : " + pt.getTypeName());
?? ??? ?for(Type t0 : pt2 )
?? ??? ?{
?? ??? ??? ?System.out.println("pt2 : " + t0.getTypeName()? + " imp:" +?? t0.getClass().toString()? );
?? ??? ?}
?? ??? ?
?? ??? ?System.out.println("pt3 : " + pt3.toString());
?? ??? ?System.out.println("pt4 is " + (pt4 == null ? " ": " not ") + "null");
?? ??? ?
?? ??? ?
?? ??? ?Field m = GenericTest.class.getDeclaredField("m");
?? ? ?? ?Type tm = m.getGenericType();
?? ? ?? ?
?? ? ?? ?ParameterizedType mpt = (ParameterizedType) tm;
?? ??? ?Type[] mpt2 = mpt.getActualTypeArguments();
?? ??? ?Type mpt3 = mpt.getRawType();
?? ??? ?Type mpt4 = mpt.getOwnerType();
?? ??? ?
?? ??? ?System.out.println("clazz : " + mpt.getTypeName());
?? ??? ?for(Type t0 : mpt2 )
?? ??? ?{
?? ??? ??? ?System.out.println("mpt2 : " + t0.getTypeName() + " imp:" +?? t0.getClass().toString()? );
?? ??? ?}
?? ??? ?
?? ??? ?System.out.println("mpt3 : " + mpt3.toString());
?? ??? ?System.out.println("mpt4 is " + (mpt4 == null ? " ": " not ") + "null");
?? ?}
}
Result：
clazz : java.util.ArrayList
t2 : E imp:class sun.reflect.generics.reflectiveObjects.TypeVariableImpl
t3 : class java.util.AbstractList
t4 is? null
clazz : java.util.List<java.util.Map<java.lang.String, java.lang.String>>
pt2 : java.util.Map<java.lang.String, java.lang.String> imp:class sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl
pt3 : interface java.util.List
pt4 is? null
clazz : java.util.Map<java.lang.String, java.lang.String>
mpt2 : java.lang.String imp:class java.lang.Class
mpt2 : java.lang.String imp:class java.lang.Class
mpt3 : interface java.util.Map
mpt4 is? null
?
TypeVariable
表示類型變量或者又叫類型參數，泛型定義中，<>內的即為類型變量。
Code
public interface TypeVariable<D extends GenericDeclaration> extends Type, AnnotatedElement {
??? //返回表示此類型變量上邊界的 Type 對象的數組
?? ?//如果未顯式聲明上邊界，則上邊界為 Object
?? ?//對于每個上邊界 B：
??? //如果 B 是一個參數化類型(ParameterizedType) 或一個類型變量(TypeVariable)，則會創建它
??? //否則，B 將被解析。
??? Type[] getBounds();
??? // 返回 GenericDeclaration 對象，該對象表示聲明此類型變量的一般聲明
??? D getGenericDeclaration();
??? //返回此類型變量的名稱，它出現在源代碼中
??? String getName();
??? //Jdk1.8新增的方法，用于獲得注解類型的上限，若未明確聲明上邊界則默認為長度為0的數組。
???? AnnotatedType[] getAnnotatedBounds();
}
?
Sample
public class GenericTest {
?? ?public List<Map<String, String>> f =new ArrayList<Map<String, String>>();
?? ?public Map<String, String> m =new? HashMap<String, String> ();
?? ?
?? ?public <T extends Map<String, Integer> & Serializable & Cloneable & Runnable,U extends List<String>> T m2()
?? ?{
?? ??? ?return null;
?? ?}
?? ?
?? ?public static void main(String[] args) throws NoSuchMethodException, SecurityException, NoSuchFieldException {
?? ??? ?test3();
?? ?}
???public static void test3() throws NoSuchMethodException, SecurityException
?? ?{
?? ??? ?Method m = GenericTest.class.getDeclaredMethod("m2");
?? ??? TypeVariable<Method>[] vlist =?? ?? m.getTypeParameters();
?? ?? ?
?? ?? for(TypeVariable<Method> v : vlist)
?? ?? {
?? ??? ?? System.out.println("getName:" +v.getName());
?? ??? ? Method vm =? v.getGenericDeclaration();
?? ??? ? System.out.println("getGenericDeclaration:" + vm.getName());
?? ??? ?
?? ??? ? Type[] bs = v.getBounds() ;
?? ??? ? for( Type b : bs )
?? ??? ? {
?? ??? ??? ? System.out.println("Bound:" + b.getTypeName());
?? ??? ? }
?? ??? ?
?? ??? ?AnnotatedType[] alist = v.getAnnotatedBounds();
?? ??? ?for(AnnotatedType a : alist )
?? ??? ?{
?? ??? ??? ?java.lang.annotation.Annotation[] annotations = a.getAnnotations();
??????????? for (java.lang.annotation.Annotation annotation : annotations) {
?????????? ??? ?System.out.println("AnnotatedType" + annotation.toString());
??????????? }
?????????? ?
?? ??? ??? ?
?? ??? ?}
?? ?? }
Result：
getName:T
getGenericDeclaration:m2
Bound:java.util.Map<java.lang.String, java.lang.Integer>
Bound:java.io.Serializable
Bound:java.lang.Cloneable
Bound:java.lang.Runnable
getName:U
getGenericDeclaration:m2
Bound:java.util.List<java.lang.String>
?
WildcardType
Code
public interface WildcardType extends Type {
??? Type[] getUpperBounds();
??? Type[] getLowerBounds();
}
Sample
??? public? <T,U>? Map<T, U> m3(List<? super T> r1,List<? extends U> r2)
?? ?{
?? ??? ?return null;
?? ?}
???
??? Method m = GenericTest.class.getDeclaredMethod("m3",List.class,List.class);
?? ??? TypeVariable<Method>[] vlist =?? ?? m.getTypeParameters();
?? ?? ?
?? ?? for(TypeVariable<Method> v : vlist)
?? ?? {
?? ??? ?? System.out.println("getName:" +v.getName());
?? ??? ? Method vm =? v.getGenericDeclaration();
?? ??? ? System.out.println("getGenericDeclaration:" + vm.getName());
?? ??? ?
?? ??? ? Type[] bs = v.getBounds() ;
?? ??? ? for( Type b : bs )
?? ??? ? {
?? ??? ??? ? System.out.println("Bound:" + b.getTypeName());
?? ??? ? }
?? ??? ?
?? ?? }
?? ? ?
?? ? ?
?? ??? Type[] genericParameterTypes = m.getGenericParameterTypes();
?????? for (Type type : genericParameterTypes) {
?????????? if (type instanceof ParameterizedType) {
?????????????? ParameterizedType parameterizedType = (ParameterizedType) type;
?????????????? Type[] actualTypeArguments = parameterizedType.getActualTypeArguments();
?????????????? for (Type actualType : actualTypeArguments) {
?????????????????? if (actualType instanceof WildcardType) {
?????????????????????? WildcardType wildcardType = (WildcardType) actualType;
?????????????????????? System.out.println("WildcardType --> " + wildcardType + " getUpperBounds--> "
?????????????????????????????? + Arrays.toString(wildcardType.getUpperBounds()) + " getLowerBounds--> " + Arrays.toString(wildcardType.getLowerBounds()));
?????????????????? } else {
?????????????????????? System.out.println("Not WildcardType --> " + actualType);
?????????????????? }
?????????????? }
?????????? }
?????? }
??????
Result：
getName:T
getGenericDeclaration:m3
Bound:java.lang.Object
getName:U
getGenericDeclaration:m3
Bound:java.lang.Object
WildcardType --> ? super T getUpperBounds--> [class java.lang.Object] getLowerBounds--> [T]
WildcardType --> ? extends U getUpperBounds--> [U] getLowerBounds--> []
?
GenericArrayType
也就是泛型數組，也就是元素類型為泛型類型的數組實現了該接口。它要求元素的類型是ParameterizedType或TypeVariable(實際中發現元素是GenericArrayType也是允許的)
//返回元素類型
Type getGenericComponentType();
Annotation
//返回注解的Class?
Class<? extends Annotation> annotationType();
AnnotatedElement
public interface AnnotatedElement {
??? default <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) {
???????? Objects.requireNonNull(annotationClass);
???????? // Loop over all directly-present annotations looking for a matching one
???????? for (Annotation annotation : getDeclaredAnnotations()) {
???????????? if (annotationClass.equals(annotation.annotationType())) {
???????????????? // 做一次強制轉化確保確實是同一個Class。
???????????????? return annotationClass.cast(annotation);
???????????? }
???????? }
???????? return null;
???? }
? ?
??? default <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass) {
??????? Objects.requireNonNull(annotationClass);
??????? return AnnotationSupport.
??????????? getDirectlyAndIndirectlyPresent(Arrays.stream(getDeclaredAnnotations()).
??????????????????????????????????????????? collect(Collectors.toMap(Annotation::annotationType,
???????????????????????????????????????????????????????????????????? Function.identity(),
???????????????????????????????????????????????????????????????????? ((first,second) -> first),
???????????????????????????????????????????????????????????????????? LinkedHashMap::new)),
??????????????????????????????????????????? annotationClass);
??? }
?? ?//返回定義在類上的注解，包括直接和間接
?? ?Annotation[] getAnnotations();
?? ??? ?
??? //返回直接定義在類上的注解
??? Annotation[] getDeclaredAnnotations();
?? ?
?? ?<T extends Annotation> T getAnnotation(Class<T> annotationClass);
?? ?
?? ?default boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) {
??????? return getAnnotation(annotationClass) != null;
??? }
?? ?default <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) {
?? ? T[] result = getDeclaredAnnotationsByType(annotationClass);
?? ? if (result.length == 0 && // Neither directly nor indirectly present
?? ??? ? this instanceof Class && // the element is a class
?? ??? ? AnnotationType.getInstance(annotationClass).isInherited()) { // Inheritable
?? ??? ? Class<?> superClass = ((Class<?>) this).getSuperclass();
?? ??? ? if (superClass != null) {
?? ??? ??? ? // Determine if the annotation is associated with the
?? ??? ??? ? // superclass
?? ??? ??? ? result = superClass.getAnnotationsByType(annotationClass);
?? ??? ? }
?? ? }
?? ? return result;
?}
}
GenericDeclaration
表明可以聲明泛型，派生類：Class，Method，Constructor
//返回泛型聲明中聲明的類型變量
public TypeVariable<?>[] getTypeParameters();
AnnotatedType
泛型相關的類型
public interface AnnotatedType extends AnnotatedElement {
??? public Type getType();
}
Sample
public <T, U> Map<T, U> m4(List<? super T> r1, List<? extends U> r2) {
?? ??? ?return null;
?? ?}
?? ?public <T, U> Map<String, String> m5(List<? super T> r1, List<? extends U> r2) {
?? ??? ?return null;
?? ?}
?? ?public static void test5() throws NoSuchMethodException, SecurityException {
?? ??? ?Method m4 = GenericTest.class.getDeclaredMethod("m4", List.class, List.class);
?
?? ??? ?AnnotatedType xx = m4.getAnnotatedReturnType();
?? ??? ?Type yyy = xx.getType();
?? ??? ?Type ttt = m4.getReturnType();
?? ??? ?System.out.println("getAnnotatedReturnType:" + xx.toString()? );
?? ??? ?System.out.println("getAnnotatedReturnType.getType:" + yyy.toString()? );
?? ??? ?System.out.println("getReturnType:" + ttt.toString()? );
?? ??? ?
?? ??? ?Method m5 = GenericTest.class.getDeclaredMethod("m5", List.class, List.class);
?
?? ??? ?AnnotatedType xx5 = m5.getAnnotatedReturnType();
?? ??? ?Type yyy5 = xx5.getType();
?? ??? ?Type ttt5 = m5.getReturnType();
?? ??? ?
?? ??? ?System.out.println("getAnnotatedReturnType:" + xx5.toString()? );
?? ??? ?System.out.println("getAnnotatedReturnType.getType:" + yyy5.toString()? );
?? ??? ?System.out.println("getReturnType:" + ttt5.toString()? );
?? ??? ?
?? ??? ?
?? ?}
Result
getAnnotatedReturnType:sun.reflect.annotation.AnnotatedTypeFactory$AnnotatedParameterizedTypeImpl@6d06d69c
getAnnotatedReturnType.getType:java.util.Map<T, U>
getReturnType:interface java.util.Map
getAnnotatedReturnType:sun.reflect.annotation.AnnotatedTypeFactory$AnnotatedParameterizedTypeImpl@7852e922
getAnnotatedReturnType.getType:java.util.Map<java.lang.String, java.lang.String>
getReturnType:interface java.util.Map
?
Parameter?
定義Executable中的參數
??? private final String name;
??? private final int modifiers;
??? private final Executable executable;
??? private final int index;
?
總結
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