使用反射来使用注解的一个小案例

掌握一个知识点：怎么使用被注解修饰的类或者方法的对象工具（对象工具是个人理解，具体介绍在反射博文）获得注解对象，一节获得注解的value值

案例：获得被指定注解修饰的类并创建其对象封装进一个Map集合中：

未被修饰的Person类：

package com.neima;

import java.io.File;
import java.util.HashMap;

public class zhujie01 {
    public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InstantiationException {
        HashMap<String, Object> beans = new HashMap<>();
        File pathfile = new File("E:\\code\\Myproject02\\ZhuJie\\src\\com\\neima");
        File[] files = pathfile.listFiles();
        for (File file : files) {
            String classname = file.getName();
            String[] split = classname.split("\\.");
            String name = split[0];
            String thePath = "com.neima." + name;
            Class<?> clazz = Class.forName(thePath);
            boolean result = clazz.isAnnotationPresent(Container.class);
            if (result) {
                Object o = clazz.newInstance();
                Container annotation = clazz.getAnnotation(Container.class);//获得指定注解
                String value = annotation.value();
                beans.put(value, o);
            }
        }
        System.out.println(beans);
    }
}

 被修饰的学生类：

 

package com.neima;
@Container("student")
public class Student {
    private String name;
    private  int age;
    private String sex;

    public Student() {
    }

    public Student(String name, int age, String sex) {
        this.name = name;
        this.age = age;
        this.sex = sex;
    }

    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;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Student student = (Student) o;

        if (age != student.age) return false;
        if (name != null ? !name.equals(student.name) : student.name != null) return false;
        return sex != null ? sex.equals(student.sex) : student.sex == null;
    }

    @Override
    public int hashCode() {
        int result = name != null ? name.hashCode() : 0;
        result = 31 * result + age;
        result = 31 * result + (sex != null ? sex.hashCode() : 0);
        return result;
    }

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

 

 

 被修饰的老师类：

package com.neima;
@Container("teacher")
public class Teacher {
    private String name;
    private int age;
    private String sex;

    public Teacher() {
    }

    public Teacher(String name, int age, String sex) {
        this.name = name;
        this.age = age;
        this.sex = sex;
    }

    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;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Teacher teacher = (Teacher) o;

        if (age != teacher.age) return false;
        if (name != null ? !name.equals(teacher.name) : teacher.name != null) return false;
        return sex != null ? sex.equals(teacher.sex) : teacher.sex == null;
    }

    @Override
    public int hashCode() {
        int result = name != null ? name.hashCode() : 0;
        result = 31 * result + age;
        result = 31 * result + (sex != null ? sex.hashCode() : 0);
        return result;
    }

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

 

 

 指定的自定义注解类：

package com.neima;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@Retention(RetentionPolicy.RUNTIME) //定义该注解的生命周期
public @interface Container {
    public String value();








}

 

 

 测试类：

package com.neima;

import java.io.File;
import java.util.HashMap;

public class zhujie01 {
    public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InstantiationException {
        HashMap<String, Object> beans = new HashMap<>();
        File pathfile = new File("E:\\code\\Myproject02\\ZhuJie\\src\\com\\neima");
        File[] files = pathfile.listFiles();
        for (File file : files) {
            String classname = file.getName();
            String[] split = classname.split("\\.");
            String name = split[0];
            String thePath = "com.neima." + name;
            Class<?> clazz = Class.forName(thePath);
            boolean result = clazz.isAnnotationPresent(Container.class);  //判断是否被指定注解修饰
            if (result) {
                Object o = clazz.newInstance();
                Container annotation = clazz.getAnnotation(Container.class);//获得指定注解
                String value = annotation.value();
                beans.put(value, o);
            }
        }
        System.out.println(beans);
    }
}

 

 没什么大的只是，注意加红两个方法就行了