通过反射调用内部类的方法

柔光的暖阳◎ 2023-06-19 07:19 10阅读 0赞

**背景：JDK13、IDEA2019.2.4**

**一、创建一个外部类**

package com.zsx.reflect;
    
    public class OutClass {
    
        private void print() {
            System.out.println("Calling the OutClass print method" );
        }
    
        class InnerClass {
    
            private void print() {
                System.out.println("Calling the InnerClass print method" );
            }
        }
    
        private class InnerClass1 {
    
            private void print() {
                System.out.println("Calling the InnerClass1 print method" );
            }
        }
    
        private class InnerClass2 {
    
            private void print() {
                System.out.println("Calling the InnerClass2 print method" );
            }
        }
    
    }

**二、编写测试案例**

package com.zsx.test.reflect;
    
    import com.zsx.reflect.OutClass;
    import org.junit.jupiter.api.DisplayName;
    import org.junit.jupiter.api.Test;
    
    import java.lang.reflect.Constructor;
    import java.lang.reflect.InvocationTargetException;
    import java.util.Arrays;
    
    public class ReflectTest {
    
        @Test
        @DisplayName("Calling methods of inner classes via reflection")
        void testReflectInnerClass() {
            OutClass entity = new OutClass();
            Class<?>[] declaredClasses = OutClass.class.getDeclaredClasses();
            Arrays.stream(declaredClasses).forEach(clazz->{
                Arrays.stream(clazz.getDeclaredMethods()).forEach(method -> {
                    try {
                        method.setAccessible(true);
                        // 获取内部类的构造方法，内部类的构造只能通过外部类来获取
                        Constructor declaredConstructor = clazz.getDeclaredConstructor(OutClass.class);
                        declaredConstructor.setAccessible(true);
                        // 由外部类对象来反射获取内部类的对象
                        Object obj = declaredConstructor.newInstance(entity);
                        method.invoke(obj);
                    } catch (IllegalAccessException | NoSuchMethodException
                            | InstantiationException | InvocationTargetException e) {
                        e.printStackTrace();
                    }
                });
            });
    
        }
    
    }

**三、运行测试方法、查看控制台测试结果**

Calling the InnerClass2 print method
    Calling the InnerClass1 print method
    Calling the InnerClass print method

**从以上结果可以看出调用成功**