获取注解信息

package edu.wtbu;

import java.lang.annotation.*;

//练习反射操作注解
public class Demo01 {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException {
        Class<?> c1 = Class.forName("edu.wtbu.Student1");
        //通过反射获得注解
        Annotation[] annotations = c1.getAnnotations();
        for (Annotation annotation : annotations) {
            System.out.println(annotation);//@edu.wtbu.Table("dh_Student")
        }

        //获得注解的value的值
        Table table = (Table) c1.getAnnotation(Table.class);
        String value = table.value();
        System.out.println(value);//dh_Student

        //获得类指定的注解
        java.lang.reflect.Field name = c1.getDeclaredField("name");
        Field annotation = name.getAnnotation(Field.class);
        System.out.println(annotation.columnName());//db_name
        System.out.println(annotation.type());//String
        System.out.println(annotation.length());//3
    }

}

@Table("db_Student")
class Student1{
    @Field(columnName = "db_id",type = "int",length = 10)
    private int id;
    @Field(columnName = "db_age",type = "int",length = 10)
    private int age;
    @Field(columnName = "db_name",type = "String",length = 3)
    private String name;

    public Student1() {

    }

    public Student1(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 "Student1{" +
                "id=" + id +
                ", age=" + age +
                ", name='" + name + '\'' +
                '}';
    }
}

//类名的注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface Table{
    String value();
}

//属性的注解
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface Field{
    String columnName();
    String type();
    int length();
}