最近建了個技術交流群，然後好多小夥伴都問關於Netty的問題，尤其今天的問題最特殊，功能大概是要在Netty接收訊息時把資料寫入資料庫，那個小夥伴用的是 Spring Boot + MyBatis + Netty，所以就碰到了Handler中@Autowired註解為空的問題

參考了一些大神的博文，Spring Boot非controller使用@Autowired註解注入為null的問題，得到結論:

三個要素

• 1、用@Component註解把類設定為元件

@Component
public ClassName class; 

• 2、在方法上面加@PostConstruct註解

	@PostConstruct
    public void init() {
        mclass = this;
    }

然後就可以用ServerImpl的介面了

 @Autowired
 ServerImpl serviceImpl
 mclass.serviceImpl.add(Pojo pojo);

但是，在這個case裡面，這一套不好用了！！！就這麼神奇…
那最後還是要自己去Spring容器獲取Bean
首先改造一下Application，實現ApplicationContextAware介面，這裡這樣寫是考慮到使用完還要釋放，所以寫的比較複雜

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

@SpringBootApplication
public class SpbNettyApplication implements ApplicationContextAware {

    private static ApplicationContext applicationContext;
    private static DefaultListableBeanFactory defaultListableBeanFactory;

    public static void main(String[] args) {
        SpringApplication.run(SpbNettyApplication.class, args);
        new EchoServer().start(1234);
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
        defaultListableBeanFactory = (DefaultListableBeanFactory)applicationContext.getAutowireCapableBeanFactory();
    }

    public static <T> T getBean(Class<T> clazz) {
        BeanDefinitionBuilder beanDefinitionBuilder = BeanDefinitionBuilder.genericBeanDefinition(clazz);
        String className = clazz.getName();
        defaultListableBeanFactory.registerBeanDefinition(className, beanDefinitionBuilder.getBeanDefinition());
        return (T) applicationContext.getBean(className);
    }

    public static void destroy(String className){
        defaultListableBeanFactory.removeBeanDefinition(className);
        System.out.println("destroy " + className);
    }

}
 

這時候就可以在Netty的Handler中為所欲為啦！

import com.avanty.spbnetty.pojo.Car;
import com.avanty.spbnetty.service.CarServiceImpl;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

public class EchoHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) {

    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg){
        System.out.println(ctx.channel().remoteAddress() + "  " + msg.toString());
        ctx.channel().write("recv : " + msg.toString());
        ctx.channel().flush();

        Car car = new Car();
        car.setCarBrand("Mustang");
        car.setCarNum("789632");

        CarServiceImpl carServiceImpl = SpbNettyApplication.getBean(CarServiceImpl.class);
        carServiceImpl.addCar(car);
        SpbNettyApplication.destroy(CarServiceImpl.class.getName());

    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {

    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {

    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) {
        System.out.println("offline " + ctx.channel().remoteAddress());
    }

}

搞定！

Demo【SpbNetty】地址 https://gitee.com/ichampion/Public-Project-Demo.git

#寫在最後
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