通过反射获取注解参数,并进行对象封装

首先可以先理清思路
1.创建注解类,实体类
2.应该判断实体类是否有该注解
3.通过反射获取实体类上注解参数
4.通过反射调用set方法进行参数封装

注解类

//创建一个注解
@Target(ElementType.TYPE)//指改注解能在什么地方使用
@Retention(RetentionPolicy.RUNTIME)//该注解在什么条件下存在
public @interface AnnBeanTitle {
    String[] value() default {};
}

实体类

//用于学习注解反射,就按照固定位置
@AnnBeanTitle(value = {"1","张三","11"})
public class User implements Serializable {
    private String id;
    private String name;
    private String age;

    public User() {
    }

    public User(String id, String name, String age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

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

反射类

public class MyClassLoader {
 /**
     * 通过注解获取传入参数
     * @param aClass 传入class对象
     * @return 返回对象
     * @throws Exception
     */
public static Object getObjectAnn(Class<?> aClass) throws Exception {
		//判断是否有改注解
        boolean flag = aClass.isAnnotationPresent(AnnBeanTitle.class);
        Field[] fields = aClass.getDeclaredFields();
        PropertyDescriptor descriptor = null;
        if (flag) {
            //实例化对象
            Object object = aClass.newInstance();
            //获取注解对象
            AnnBeanTitle ann1 = aClass.getDeclaredAnnotation(AnnBeanTitle.class);
            //获取反射中方法 ann1.xxxx();
            String[] value = ann1.value();
            if (value.length == fields.length) {
                List<String> list = new ArrayList<>(Arrays.asList(value));
                for (int i = 0; i < fields.length; i++) {
                    //遍历所有方法
                    descriptor = new PropertyDescriptor(fields[i].getName(), aClass);
                    //得到set方法
                    Method setMethod = descriptor.getWriteMethod();
                    //执行set方法
                    setMethod.invoke(object, list.get(i));
                }
                return object;
            } else {
                return null;
            }
        }
        return null;
    }
  }

执行

public class MyTest01 {
    public static void main(String[] args) throws Exception {
        User ann = (User)MyClassLoader.getObjectAnn(User.class);
        System.out.println(ann);
    }
}

执行结果