我遇到的问题是启动定时器,然后在跟数据库交互的地方报错,Exception in thread "Timer-1" java.lang.NullPointerException。后来检查了一下是因为,dataAcquisitionVoMapper没有正常注入,原始代码如下:

package com.hqgd.pms.controller.Timer;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.HashMap;
import java.util.Map;
import java.util.TimerTask;

import javax.annotation.Resource;

import com.hqgd.pms.common.SpringContextUtil;
import com.hqgd.pms.dao.dataAcquisition.DataAcquisitionVoMapper;

public class UpdateTableTimer extends TimerTask {
    @Resource
    private DataAcquisitionVoMapper dataAcquisitionVoMapper;

//    public UpdateTableTimer() {//从bean工厂里拿个实例
//        this.dataAcquisitionVoMapper = SpringContextUtil.getBean(DataAcquisitionVoMapper.class);
//    }

    @Override
    public void run() {
        // 获取当前时间
        Calendar calendar = Calendar.getInstance();
        calendar.add(Calendar.MINUTE, -1460);
        String lastTime = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(calendar.getTime());
        Map<String, Object> param = new HashMap<>();
        
        for (int i = 1; i <= 4; i++) {
            param.put("lastTime", lastTime);
            param.put("table", "hq_equipment_monitor_data_r" + i);
            dataAcquisitionVoMapper.deleter(param);//此处报空指针异常,是因为dataAcquisitionVoMapper没有正常注入
        }
        for (int i = 1; i <= 4; i++) {
            param.put("tabler", "hq_equipment_monitor_data_r" + i);
            param.put("tablef", "hq_equipment_monitor_data_f" + i);
            dataAcquisitionVoMapper.insertt(param);

        }
    }

}

报错提示如下:

在线程中为了线程安全,是防注入的,如果要用到这个类,只能从bean工厂里拿个实例。和上面的代码对比,需要添加下面框框里的代码,就是上面代码注释掉的部分,

SpringContextUtil工具类的代码如下:

package com.hqgd.pms.common;

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

/**
 * @Description: 获取bean对象的工具类
 * @Author: yaorong
 * @CreateDate: 2018/12/10
 */

@Component
public class SpringContextUtil implements ApplicationContextAware {
    /**
     * 上下文对象实例
     */
    private static ApplicationContext applicationContext;

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

    /**
     * 获取applicationContext
     *
     * @return
     */
    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    /**
     * 通过name获取 Bean.
     *
     * @param name
     * @return
     */
    public static Object getBean(String name) {
        return getApplicationContext().getBean(name);
    }

    /**
     * 通过class获取Bean.
     *
     * @param clazz
     * @param <T>
     * @return
     */
    public static <T> T getBean(Class<T> clazz) {
        return getApplicationContext().getBean(clazz);
    }

    /**
     * 通过name,以及Clazz返回指定的Bean
     *
     * @param name
     * @param clazz
     * @param <T>
     * @return
     */
    public static <T> T getBean(String name, Class<T> clazz) {
        return getApplicationContext().getBean(name, clazz);
    }
}

好了,问题解决!!!

小小菜鸟,如有不正确之处,请指正!


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