解决多线程无法@Autowired注入，手动获取Bean对象

解决多线程无法@Autowired注入，手动获取Bean对象

问题

当我们使用多线程时，又想注入一个service给我们使用，但是我们发现service总是为null。

代码示例：

//例1
public class TaskComments implements Callable<List<String>> {
    //注入不进去，总是为null
    @Autowired
    private RedisClient redisClient;
    
    @Override
    public List<String> call() throws Exception {
        //业务代码
    }
    
}

//例2
public class TaskComments implements Runnable {
     //注入不进去，总是为null
    @Autowired
    private RedisClient redisClient;
    
    @Override
    public void run() {
        //业务代码
    }
}

原因

new Thread不在spring容器中，也就无法获得spring中的bean对象。

解决方案

1.最简单的方法 把要注入的service通过构造方法传过去

public class TaskComments implements Callable<List<String>> {

    private RedisClient redisClient;
    private TaskComments(RedisClient redisClient){
        this.redisClient = redisClient;
    }
    
    @Override
    public List<String> call() throws Exception {
        //业务代码
    }
    
}


PS:不推荐这样的话有NEW对象了，没有用Spring去管理

2.通过ApplicationContext手动获取Bean(Springboot版本，其他自行百度)

• 1.配置Config

package cn.pconline.config;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

/**
 * 手动获取Bean
 * https://blog.csdn.net/tiger0709/article/details/78270768
 * https://blog.csdn.net/u011493599/article/details/78522315
 */
@Component
public class BeanContext implements ApplicationContextAware {

    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        BeanContext.applicationContext = applicationContext;
    }

    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    @SuppressWarnings("unchecked")
    public static <T> T getBean(String name) throws BeansException {
        return (T) applicationContext.getBean(name);
    }

    public static <T> T getBean(Class<T> clz) throws BeansException {
        return (T) applicationContext.getBean(clz);
    }
}

• 2.使用

package cn.pconline.modules.toutiao.task;

import cn.pconline.config.BeanContext;
import cn.pconline.redis.client.RedisClient;
import lombok.NoArgsConstructor;
import lombok.extern.slf4j.Slf4j; 

import java.util.ArrayList; 
import java.util.List; 
import java.util.concurrent.Callable;

/**
 * @Description 多线程无法@Autowired注入，手动获取
 * @Author jie.zhao
 * @Date 2019/7/24 15:52
 */
@Slf4j
@NoArgsConstructor
public class TaskComments implements Callable<List<String>> {

   
    private RedisClient redisClient = BeanContext.getBean(RedisClient.class);
    
    @Override
    public List<String> call() throws Exception {
        //业务代码
    }
    
}