反射的简单使用

class Student{
    private Score score;
    @Resource
    private HandlerService handler;
    private Student(Score score) {
        this.score = score;
    }
}

Score score = new Score;
Class class = Student.class;
Constructor constructor = class.getConstructor(Score.class);
Student s = constructor.newInstance(score);

内部调用其他服务问题

问题说明

   开发中我们通常会使用Spring框架的注解来直接获取类的实例，因此在使用反射的时候就会习惯性还是用注解，如上面代码所示，这会导致handler为null。因为利用反射构造类的时候没有通过spring，那么该实例中的注解也不会生效。

问题解决

这种情况下，方法之一是将内部服务在构造函数中初始化以便获取实例。

class Student{
    private Score score;
    @Resource
    private HandlerService handler;
    private Student(Score score, ApplicationContext applicationContext) {
        this.score = score;
        this.handler = applicationContext.getBean(HandlerService.class);
    }
}

Class Main implements ApplicationContextAware {
     private ApplicationContext applicationContext;
     Score score = new Score;
public void test() {
     Class class = Student.class;
     Constructor constructor = class.getConstructor(Score.class, ApplicationContext.class);
     Student s = constructor.newInstance(score,applicationContext);
}
@Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }
}