java - 无法从 Spring Boot 应用程序 Autowiring yml 配置类

Question

这个问题已经有答案了:

Why is my Spring @Autowired field null? (21 个回答)

已关闭 5 年前。

我无法@autowire spring boot中的一个类应用。以下是项目资源管理器快照:

来 self 的主课 CrmDisconnectionApplication ，我打电话DisconnectionConTrigger类(class)。在那堂课上我正在做@autowire对于 YamlConfig 。但我得到null pointer exception .

下面是代码:

<强> CrmDisconnectionApplication

package com.wpits.crm.disconnection;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import com.wpits.crm.disconnection.quartzJob.DisconnectionCronTrigger;

@SpringBootApplication(scanBasePackages = { "com.wpits.crm" })
public class CrmDisconnectionApplication {

    public static void main(String[] args) {
        SpringApplication.run(CrmDisconnectionApplication.class, args);
        DisconnectionCronTrigger disconnectionCronTrigger = DisconnectionCronTrigger.getInstance();
        disconnectionCronTrigger.initialize();
    }

}

<强> DisconnectionCronTrigger

package com.wpits.crm.disconnection.quartzJob;

import org.quartz.CronScheduleBuilder;
import org.quartz.JobBuilder;
import org.quartz.JobDetail;
import org.quartz.Scheduler;
import org.quartz.Trigger;
import org.quartz.TriggerBuilder;
import org.quartz.impl.StdSchedulerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.wpits.crm.disconnection.config.YamlConfig;
@Component
public class DisconnectionCronTrigger {

    @Autowired
    private YamlConfig myConfig;
    private static DisconnectionCronTrigger obj = null;

    private DisconnectionCronTrigger() {}

    public static DisconnectionCronTrigger getInstance() {
        if(obj == null) {
            obj = new DisconnectionCronTrigger();
        }
        return obj;
    }


    public void initialize() {
        System.out.println("using environment: " + myConfig.getEnvironment());
        System.out.println("name: " + myConfig.getName());
        System.out.println("servers: " + myConfig.getServers());
        System.out.println("hobies: "+myConfig.getHobies());

        JobDetail job = JobBuilder.newJob(DisconnectionJob.class).withIdentity("DisconnectionJob", "group1").build();

        Trigger trigger = TriggerBuilder.newTrigger().withIdentity("cronTrigger", "group1").withSchedule(CronScheduleBuilder.cronSchedule("0/10 * * * * ?")).build();
        try {
        Scheduler scheduler = new StdSchedulerFactory().getScheduler();
        scheduler.start();
        scheduler.scheduleJob(job, trigger);
        }catch(Exception ex) {
            ex.printStackTrace();
        }
    }
}

<强> YamlConfig

package com.wpits.crm.disconnection.config;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Configuration;
import java.util.*;

@Configuration
@EnableConfigurationProperties
@ConfigurationProperties


public class YamlConfig {
    private String name;
    private String environment;
    private List<String> servers = new ArrayList<>();
    private List<String> hobies = new ArrayList<>();

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getEnvironment() {
        return environment;
    }
    public void setEnvironment(String environment) {
        this.environment = environment;
    }
    public List<String> getServers() {
        return servers;
    }
    public void setServers(List<String> servers) {
        this.servers = servers;
    }
    public List<String> getHobies() {
        return hobies;
    }
    public void setHobies(List<String> hobies) {
        this.hobies = hobies;
    }    
}

我得到null pointer exception对于线 System.out.println("using environment: " + myConfig.getEnvironment());上课DisconnectionCronTrigger 。我哪里弄错了。请纠正我..

Answer 1

问题出在这一行

DisconnectionCronTrigger disconnectionCronTrigger = DisconnectionCronTrigger.getInstance();

在 getInstance 中，您将使用 new 创建一个新对象。您不应该新建，而应该 Autowiring bean 或从 Spring 应用程序上下文中获取它。

 public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(CrmDisconnectionApplication.class, args);
        DisconnectionCronTrigger disconnectionCronTrigger = (DisconnectionCronTrigger)context.getBean("disconnectionCronTrigger");
        disconnectionCronTrigger.initialize();
    }

如果你这样做，那么你将得到一个对象，该对象将 Autowiring bean 中的所有字段。如果你使用 new 创建一个对象，那么你就不会。