package test;

import java.lang.annotation.Annotation;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

import java.lang.reflect.Field;

//通过反射操作注解

public class Test{

    public static void main(String[] args) {

        Class c1 = Student.class;

        //利用反射获取注解

        Annotation[] annotations = c1.getAnnotations();

        for(Annotation annotation : annotations) {

            System.out.println(annotation);

        }

        //获取注解的value的值

        TableHgqin tableHgqin = (TableHgqin) c1.getAnnotation(TableHgqin.class);

        String value = tableHgqin.value();

        System.out.println(value);

        //获得类指定的注解

        Field[] fields = c1.getDeclaredFields();

        for(Field field : fields) {

            System.out.println("#字段为： "+field);

            annotations = field.getAnnotations();

            for(Annotation annotation : annotations) {

                System.out.println(annotation);

            }

            //获取注解对应的值

            FieldHgqin fieldHgqin = (FieldHgqin)field.getAnnotation(FieldHgqin.class);

            System.out.println(fieldHgqin.columnName());

            System.out.println(fieldHgqin.type());

            System.out.println(fieldHgqin.length());

        }

    }

}

@TableHgqin("db_student")

class Student{

    @FieldHgqin(columnName="db_id",type="int",length=10)

    private int id;

    @FieldHgqin(columnName="db_name",type="int",length=10)

    private String name;

    @FieldHgqin(columnName="db_age",type="varchar",length=3)

    private int age;

    public Student() {

        super();

        // TODO Auto-generated constructor stub

    }

    public Student(int id, String name, int age) {

        super();

        this.id = id;

        this.name = name;

        this.age = age;

    }

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public int getAge() {

        return age;

    }

    public void setAge(int age) {

        this.age = age;

    }

    @Override

    public String toString() {

        return "student [id=" + id + ", name=" + name + ", age=" + age + "]";

    }

}

//类名的注解

@Target(ElementType.TYPE)

@Retention(RetentionPolicy.RUNTIME)

@interface TableHgqin{

    String value();

}

//属性的注解

@Target(ElementType.FIELD)

@Retention(RetentionPolicy.RUNTIME)

@interface FieldHgqin{

    String columnName();

    String type();

    int length();

}