方法类 | Java中的 getAnnotatedReturnType() 方法

Java.lang.reflect.Method.getAnnotatedReturnType()方法返回一个 AnnotatedType 对象，该对象表示 AnnotatedType 来指定方法对象的返回类型。如果为构造函数创建 Method 对象，则 AnnotatedType 对象指定构造对象的类型。如果为方法创建Method对象，则AnnotatedType对象指定使用类型来指定源代码中指定的方法的返回类型。

返回的 AnnotatedType 表示 AnnotatedType 本身或其任何子接口（如 AnnotatedArrayType、AnnotatedParameterizedType、AnnotatedTypeVariable、AnnotatedWildcardType）的实现。 AnnotatedType 表示任何类型的潜在注释使用，包括数组类型、参数化类型、类型变量或当前在Java虚拟机中运行的通配符类型。

句法：

public AnnotatedType getAnnotatedReturnType()

返回值：该方法返回一个 AnnotatedType 对象，该对象表示 AnnotatedType 来指定 Method Object 的返回类型。

下面的程序说明了 Method 类的 getAnnotatedReturnType() 方法：

示例 1：对作为 Input 给出的特定方法使用 AnnotatedType()。

该程序包含一个方法名称 getAddressMethod，其中包含 AnnotatedType。所以这个程序将获取 AnnotatedType 的详细信息，它包含在 getAddressMethod 方法中。

// Java program to demonstrate how to
// apply getAnnotatedReturnType() method
// of Method Class.
  
import java.lang.annotation.*;
import java.lang.reflect.AnnotatedType;
import java.lang.reflect.Method;
import java.util.Arrays;
  
public class GFG {
  
    // Creating custom AnnotatedType
    @Target({ ElementType.TYPE_USE })
    @Retention(RetentionPolicy.RUNTIME)
    private @interface customAnnotatedType {
    }
  
    // a sample method with return type String and
    // AnnotatedType is @customAnnotatedType
    public @customAnnotatedType String getAddress()
    {
        return null;
    }
  
    // main method
    public static void main(String[] args)
    {
  
        try {
            // create class object
            Class classobj = GFG.class;
  
            // create method object of getAddress
            Method getAddressMethod = null;
  
            Method[] methods = classobj.getMethods();
            for (Method m : methods) {
                if (m.getName().equals("getAddress"))
                    getAddressMethod = m;
            }
  
            // get AnnotatedType for return type
            AnnotatedType annotatedType = getAddressMethod
                                              .getAnnotatedReturnType();
  
            // print AnnotatedType details with Method name
            System.out.println("Method Name: "
                               + getAddressMethod.getName());
  
            System.out.println("Type: "
                               + annotatedType.getType().getTypeName());
  
            System.out.println("Annotations: "
                               + Arrays.toString(annotatedType.getAnnotations()));
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
}

输出：

Method Name: getAddress
Type: java.lang.String
Annotations: [@GFG$customAnnotatedType()]

示例 2：为 GFG 类的方法打印数组类型或多维数组或 Generic 的注释。

// Java program to demonstrate how to
// apply getAnnotatedReturnType() method
// of Method Class.
  
import java.lang.annotation.*;
import java.lang.reflect.*;
import java.util.List;
  
public class systemUTCMethodDemo {
  
    // Creating custom AnnotatedType
    @Target({ ElementType.TYPE_USE })
    @Retention(RetentionPolicy.RUNTIME)
    private @interface customAnnotatedType {
    }
  
    // a sample method with Annotation on array type
    public @customAnnotatedType String[] getAddress()
    {
        return null;
    }
  
    // a sample method on Annotation on multidimensional array
    public String[] @customAnnotatedType[] getvalues()
    {
        return null;
    }
  
    // a sample method on Annotation on a type with generic
    public @customAnnotatedType List getWords()
    {
        return null;
    }
  
    // main method
    public static void main(String[] args)
    {
  
        try {
            // create class object
            Class classobj = systemUTCMethodDemo.class;
  
            // create method object of getAddress and getValues
            Method[] methods = classobj.getMethods();
  
            for (Method m : methods) {
  
                // if method object is for getAddress and getValues
                // then print @customAnnotatedType for both
                if (m.getName().equals("getAddress")
                    || m.getName().equals("getvalues")
                    || m.getName().equals("getWords")) {
                    printDetails(m);
                }
            }
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
  
    public static void printDetails(Method m)
    {
  
        // get AnnotatedType for return type
        AnnotatedType annotatedType = m.getAnnotatedReturnType();
  
        // print AnnotatedType details with Method name
  
        System.out.println("Method Name: " + m.getName());
        System.out.println("Type: " + annotatedType.getType().getTypeName());
        System.out.println("Annotations: " + annotatedType);
        System.out.println();
    }
}

输出：

Method Name: getWords
Type: java.util.List
Annotations: sun.reflect.annotation.AnnotatedTypeFactory$AnnotatedParameterizedTypeImpl@12a3a380

Method Name: getvalues
Type: java.lang.String[][]
Annotations: sun.reflect.annotation.AnnotatedTypeFactory$AnnotatedArrayTypeImpl@29453f44

Method Name: getAddress
Type: java.lang.String[]
Annotations: sun.reflect.annotation.AnnotatedTypeFactory$AnnotatedArrayTypeImpl@5cad8086

参考： https: Java