静态变量setter注入

1.java中静态方法调用非静态成员变量、非静态方法

public class Circle {
  private double radius = 1.0;

  double getAre() {
    return radius * radius * Math.PI;
  }

  public static void main(String[] args) {
    Circle myCircle = new Circle();
    System.out.println("radius is " + myCircle.radius); //radius不是静态的，静态方法可以通过类对象调用非静态成员变量、非静态方法
  }
}

2.不new对象，只能访问静态成员变量。而静态成员变量注入只能使用set注入，原因是静态变量/类变量不是对象的属性,而是一个类的属性,spring则是基于对象层面上的依赖注入. 

private static MqttServerProxy mProxy;

 

    private static DeviceStateService devStateService;

 

    public static void main(String[] args) {

       SpringApplication.run(App.class, args);

       //启动，自动连接mqtt

       LOGGER.info("APP: run().start to connect mqtt...");

       devStateService.setMqttProxy(mProxy);

       devStateService.startService();

    }

 

    @Autowired

    public void setMqttServerProxy(MqttServerProxy proxy) {

       mProxy = proxy;

    }

 

    @Autowired

    public void setDeviceStateService(DeviceStateService service) {

       devStateService = service;

    }