Java注解Annotation学习笔记

//注解中的成员变量非常像定义接口
public @interface MyAnnotation {
    //不带有默认值
    String name();
    //带有默认值
    int age() default 20;
}

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface ValueBind {
    filedType type();
    String value() default "SUSU";
    enum filedType {
        STRING, INT
    }
}

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ValueBind {
    filedType type();
    String value() default "SUSU";
    enum filedType {
        STRING, INT
    }
}

public class Person implements Serializable {
    private String name;
    private int age;
    public String getName() {
        return name;
    }
    @ValueBind(type = ValueBind.filedType.STRING, value = "LCF")
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    @ValueBind(type = ValueBind.filedType.INT, value = "21")
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "Person{" +
                "name=‘" + name + ‘\‘‘ +
                ", age=" + age +
                ‘}‘;
    }
}

import java.lang.reflect.Method;
public class Main {
    public static void main(String[] args) throws Exception {
        Object person = Class.forName("Person").newInstance();
        //以下获取的是：类的注解
        // Annotation[] annotations = person.getClass().getAnnotations();
        Method[] methods = person.getClass().getMethods();
        for (Method method : methods) {
            //如果该方法上面具有ValueBind这个注解
            if (method.isAnnotationPresent(ValueBind.class)) {
                //通过这个注解可以获取到注解中定义的
                ValueBind annotation = method.getAnnotation(ValueBind.class);
                if (annotation.type().equals(ValueBind.filedType.STRING)) {
                    method.invoke(person, annotation.value());
                } else {
                    method.invoke(person, Integer.parseInt(annotation.value()));
                }
            }
        }
        System.out.println(person);
    }
}