java 反射 获取字段、方法、构造

ClassA

package com.huawei.ywj.reflect;

public class ClassA {
    private String name = "defaultName";
    private int age = 16;

    private ClassA() {
    }

    private ClassA(String name) {
        this.name = name;
    }

    private void setName(String name) {
        this.name = name;
    }

    private String getName() {
        return name;
    }

    @Override
    public String toString() {
        return "ClassA{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

调用类 ExampleUnitTest

public class ExampleUnitTest {

    @Test
    public void test() throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InstantiationException, InvocationTargetException, NoSuchFieldException {
//        reflectMethod();
//        reflectMethod2();
//        reflectMethod3();
//        reflectField();
        reflectConstructor();
    }

    private void reflectMethod() throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InstantiationException, InvocationTargetException {
        Class<?> clazz = Class.forName("com.huawei.ywj.reflect.ClassA");

        Constructor<?> declaredConstructor = clazz.getDeclaredConstructor(String.class);
        declaredConstructor.setAccessible(true);
        ClassA instance = (ClassA) declaredConstructor.newInstance("xiaoming");

        Method method = clazz.getDeclaredMethod("getName");
        method.setAccessible(true);
        Object result = method.invoke(instance);

        System.out.println(result);

    }

    private void reflectMethod2() throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InstantiationException, InvocationTargetException {
        Class<?> clazz = Class.forName("com.huawei.ywj.reflect.ClassA");
        Constructor<?> declaredConstructor = clazz.getDeclaredConstructor();
        declaredConstructor.setAccessible(true);
        Object instance = declaredConstructor.newInstance();

        Method setName = clazz.getDeclaredMethod("setName", String.class);
        setName.setAccessible(true);
        setName.invoke(instance, "xiaoming");

        Method getName = clazz.getDeclaredMethod("getName");
        getName.setAccessible(true);
        Object result = getName.invoke(instance);
        System.out.println(result);

    }

    private void reflectMethod3() throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InstantiationException, InvocationTargetException {
        Class<ClassA> clazz = ClassA.class;

        Constructor declaredConstructor = clazz.getDeclaredConstructor();
        declaredConstructor.setAccessible(true);
        Object instance = declaredConstructor.newInstance();

        Method method = clazz.getDeclaredMethod("getName", null);
        method.setAccessible(true);
        Object result = method.invoke(instance);

        System.out.println(result);

    }

    private void reflectField() throws ClassNotFoundException, NoSuchFieldException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
        Class<?> clazz = Class.forName("com.huawei.ywj.reflect.ClassA");

        Constructor<?> declaredConstructor = clazz.getDeclaredConstructor(String.class);
        declaredConstructor.setAccessible(true);
        Object instance = declaredConstructor.newInstance("xiaoming");

        Field field = clazz.getDeclaredField("name");
        field.setAccessible(true);
        field.set(instance, "xiaoming2");

        System.out.println(field.get(instance));

    }

    private void reflectConstructor() throws ClassNotFoundException, NoSuchFieldException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
        Class<?> clazz = Class.forName("com.huawei.ywj.reflect.ClassA");

        Constructor<?> declaredConstructor = clazz.getDeclaredConstructor(String.class);
        declaredConstructor.setAccessible(true);
        Object instance = declaredConstructor.newInstance("xiaoming");

        System.out.println(instance.toString());

    }
}