Java 注解与反射（七）反射获取注解信息

Java 注解与反射（七）反射获取注解信息

package com.zzz.reflection;

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

public class Test05 {

    public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException {
        Class c1 = Class.forName("com.zzz.reflection.Studentdb");

        Annotation[] annotations = c1.getAnnotations(); //获取类的注解
        for (Annotation annotation : annotations) {
            System.out.println(annotation);
        }

        Tablezzz tablezzz = (Tablezzz)c1.getAnnotation(Tablezzz.class); //获取类注解参数value的具体值
        String value = tablezzz.value();
        System.out.println(value);

        Field field = c1.getDeclaredField("name");
        Annotation[] fieldAnnotations = field.getAnnotations(); //获取属性的注解
        for (Annotation fieldAnnotation : fieldAnnotations) {
            System.out.println(fieldAnnotation);
        }

        Fieldzzz fieldzzz = field.getAnnotation(Fieldzzz.class);    //获取属性注解参数的具体值
        System.out.println(fieldzzz.columnName());
        System.out.println(fieldzzz.type());
        System.out.println(fieldzzz.length());
    }

}

@Tablezzz("db_student")
class Studentdb{
    @Fieldzzz(columnName = "db_id",type = "int",length = 10)
    private int id;

    @Fieldzzz(columnName = "db_age",type = "int",length = 3)
    private int age;

    @Fieldzzz(columnName = "db_name",type = "varchar",length = 10)
    private String name;

    public Studentdb() {
    }

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

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface Tablezzz{
    String value();
}

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface Fieldzzz{
    String columnName();
    String type();
    int length();
}