獲取註解資訊

package com.reflection;

import java.lang.annotation.*;
import java.lang.reflect.Field;

public class Test08 {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException {

        Class c1 = Class.forName("com.reflection.Student02");

        //通過反射獲得註解
        Annotation[] annotations = c1.getAnnotations();
        
 
for (Annotation annotation : annotations) {
            System.out.println(annotation);
        }

        //獲得註解的value值
        TableXue tableXue = (TableXue)c1.getAnnotation(TableXue.class);
        String value = tableXue.value();
        System.out.println(value);

        //獲得類指定的註解
        Field name = c1.getDeclaredField("name");
        FieldXue annotation 
 
= name.getAnnotation(FieldXue.class);
        System.out.println(annotation.columnName());
        System.out.println(annotation.type());
        System.out.println(annotation.length());
    }
}

@TableXue("db_student")
class Student02{

    @FieldXue(columnName = "db_id",type = "int",length = 10)
    
 
private int id;
    @FieldXue(columnName = "db_age",type = "int",length = 10)
    private int age;
    @FieldXue(columnName = "db_name",type = "varchar",length = 3)
    private String name;

    public Student02(){}
    public Student02(int id,int age, String name){
        this.id = id;
        this.age = age;
        this.name = name;
    }

    public int getId() {
        return id;
    }

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

    public int getAge() {
        return age;
    }

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

    public String getName() {
        return name;
    }

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

    @Override
    public String toString() {
        return "Student02{" +
                "id=" + id +
                ", age=" + age +
                ", name='" + name + '\'' +
                '}';
    }
}

//類名的註解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface TableXue{
    String value();
}

//屬性的註解
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface FieldXue{
    String columnName();//列名
    String type();//型別
    int length();//長度
}