接下來(lái)說(shuō)一下我遇到的問(wèn)題，在spring boot中創(chuàng)建了一個(gè)UDP客戶(hù)端，用于監(jiān)聽(tīng)UDP服務(wù)端發(fā)送到數(shù)據(jù)。在實(shí)現(xiàn)這一功能時(shí)遇到主要遇到了兩個(gè)難題

1.由于之前都是通過(guò)controller調(diào)用service層來(lái)實(shí)現(xiàn)訪(fǎng)問(wèn)

現(xiàn)在要建立一個(gè)持久的連接來(lái)實(shí)現(xiàn)監(jiān)聽(tīng)某一端口的數(shù)據(jù)，由于做的項(xiàng)目不多，經(jīng)驗(yàn)不足，spring也沒(méi)怎么學(xué)過(guò)所以困擾了很久。

只是在main方法中開(kāi)啟一個(gè)線(xiàn)程簡(jiǎn)單的new創(chuàng)建實(shí)例解決了該問(wèn)題，雖然不知道這樣做對(duì)不對(duì)，但是能實(shí)現(xiàn)功能。（如有更好的辦法請(qǐng)告訴小白，謝謝）

@SpringBootApplication
@MapperScan("com.example.net.udpservicertest.mapper") 
public class UdpServicerTestApplication { 
    public static void main(String[] args) throws Exception {
        SpringApplication.run(UdpServicerTestApplication.class, args);
        new Thread(()->{
 
            try {
                UDPService udpService = new UDPService();
                udpService.startSocketServer();
 
            } catch (Exception e) {
                e.printStackTrace();
            }
        }).start();   
    } 
}

客戶(hù)端雖然能夠啟動(dòng)，但是新的問(wèn)題又來(lái)了

2.在拿到數(shù)據(jù)之后，掉service時(shí)出現(xiàn)空指針

這又困擾了小白兩天，通過(guò)這篇文章得到了這樣的解決方案

（1）首先需要新建一個(gè)類(lèi)，實(shí)現(xiàn) ApplicationContextAware 接口。

要@Conponment注解

   @Component
        public class SpringUtils implements ApplicationContextAware { 
            private static ApplicationContext applicationContext = null; 
            @Override
            public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
                if(SpringUtils.applicationContext == null){
                    SpringUtils.applicationContext  = applicationContext;
                }
            }
 
            //獲取applicationContext
            public static ApplicationContext getApplicationContext() {
                return applicationContext;
            }
 
            //通過(guò)name獲取 Bean.
            public static Object getBean(String name){
                return getApplicationContext().getBean(name);
            }
 
            //通過(guò)class獲取Bean.
            public static <T> T getBean(Class<T> clazz){
                return getApplicationContext().getBean(clazz);
            }
 
            //通過(guò)name,以及Clazz返回指定的Bean
            public static <T> T getBean(String name,Class<T> clazz){
                return getApplicationContext().getBean(name, clazz);
            }
        }

（2）在UDP類(lèi)中獲取ApplicationContext對(duì)象，然后去獲取需要的service 或者 dao。

@Service注解，將自動(dòng)注冊(cè)到Spring容器，不需要再在applicationContext.xml文件定義bean了，類(lèi)似的還包括@Component、@Repository、@Controller。

ApplicationContext又是spring管理bean的容器，加載配置文件的時(shí)候，就會(huì)將Spring管理的類(lèi)都實(shí)例化。所以就能夠注入到該實(shí)例。

public class UDPService {
    private ApplicationContext applicationContext=SpringUtils.getApplicationContext();
    private UserServiceImpl userService=applicationContext.getBean(UserServiceImpl.class);
    public void startSocketServer() throws Exception {
        DatagramSocket ds = new DatagramSocket(10000);
        while (true) {
            // 2.創(chuàng)建數(shù)據(jù)包
            byte[] buf = new byte[1024];
            DatagramPacket dp = new DatagramPacket(buf, buf.length);
 
            // 3.使用接受方法將數(shù)據(jù)存儲(chǔ)到數(shù)據(jù)包中
            ds.receive(dp);// 阻塞式的
 
            // 4.通過(guò)數(shù)據(jù)包對(duì)象的方法，解析其中的數(shù)據(jù) 數(shù)據(jù)內(nèi)容
        //    String ip = dp.getAddress().getHostAddress();
        //    int port = dp.getPort();
             String text = new String(dp.getData(), 0, dp.getLength());
             System.out.println(""+text.length());
            System.out.println(""+text);
           // byte[] data = dp.getData();
 
            String[] split = text.split("#");
            System.out.println(split[0]);
            userService.updateUser(split[0],split[1]);
            Thread.sleep(3000L); 
        } 
    }
}
@SpringBootApplication
@MapperScan("com.example.net.udpservicertest.mapper")
@ComponentScan("com.example.net.udpservicertest")
public class UdpServicerTestApplication { 
    public static void main(String[] args) throws Exception {
        SpringApplication.run(UdpServicerTestApplication.class, args);
        new Thread(()->{
 
            try {
                UDPService udpService = new UDPService();
                udpService.startSocketServer();
 
            } catch (Exception e) {
                e.printStackTrace();
            }
        }).start(); 
    } 
}

頭疼的問(wèn)題終于解決了！開(kāi)心~

springboot 普通類(lèi)怎么使用注入

需要自定義方法：

package com.example.demo.util;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;
/**
 * @author Mikey
 * @Title:
 * @Description:用于普通類(lèi)也能使用Bean
 * @Email:1625017540@qq.com
 * @date 2018/12/3 21:57
 * @Version 1.0
 */
@Component
public class SpringUtil implements ApplicationContextAware {
    private static ApplicationContext applicationContext = null;
    public SpringUtil() {
    }
    public void setApplicationContext(ApplicationContext arg0) throws BeansException {
        if (applicationContext == null) {
            applicationContext = arg0;
        }
    }
    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }
    public static void setAppCtx(ApplicationContext webAppCtx) {
        if (webAppCtx != null) {
            applicationContext = webAppCtx;
        }
    }
    /**
     * 拿到ApplicationContext對(duì)象實(shí)例后就可以手動(dòng)獲取Bean的注入實(shí)例對(duì)象
     */
    public static <T> T getBean(Class<T> clazz) {
        return getApplicationContext().getBean(clazz);
    }
    public static <T> T getBean(String name, Class<T> clazz) throws ClassNotFoundException {
        return getApplicationContext().getBean(name, clazz);
    }
    public static final Object getBean(String beanName) {
        return getApplicationContext().getBean(beanName);
    }
    public static final Object getBean(String beanName, String className) throws ClassNotFoundException {
        Class clz = Class.forName(className);
        return getApplicationContext().getBean(beanName, clz.getClass());
    }
    public static boolean containsBean(String name) {
        return getApplicationContext().containsBean(name);
    }
    public static boolean isSingleton(String name) throws NoSuchBeanDefinitionException {
        return getApplicationContext().isSingleton(name);
    }
    public static Class<?> getType(String name) throws NoSuchBeanDefinitionException {
        return getApplicationContext().getType(name);
    }
    public static String[] getAliases(String name) throws NoSuchBeanDefinitionException {
        return getApplicationContext().getAliases(name);
    }
}

使用：

package com.example.demo.util;
import com.example.demo.Controller.login.JwtAuthenticator;
import com.example.demo.Dao.userandroleandpermissionDao.HRUserDao;
import com.example.demo.Entity.userandroleandpermission.HRUser;
import org.apache.shiro.SecurityUtils;
import org.apache.shiro.subject.Subject;
public class MethodUtils {
    public HRUser findUserByToken(){
        Subject subject = SecurityUtils.getSubject();
        String token = subject.getPrincipal().toString();
        String code = JwtAuthenticator.getUsername(token);
        HRUserDao hrUserDao = SpringUtil.getBean(HRUserDao.class);//此處根據(jù)類(lèi).class來(lái)獲取bean
        HRUser user = hrUserDao.findByCode(code);
        if(user != null){
            return user;
        }else{
            return  null;
        }
    }
}

以上為個(gè)人經(jīng)驗(yàn)，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。

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