SpringBoot 中@Autowired 注入失效原因及解决方法

Posted 2023-04-07

参考技术A

通过@Autowired注入的类所在的包路径不在Application启动类所在的包/子包路径下。
Spring Boot项目的Bean装配 默认规则 是根据Application类(指项目入口类)所在的包位置从上往下扫描。
eg: Application启动类 在包com.alibaba.taobao下，则只会扫描 com.alibaba.taobao 包及其所有子包，如果需要自动装载的类所在包不在 com.alibaba.taobao 及其子包下，而是在 com.alibaba.tmall 下，则不会被扫描，自然就没法被注入！

若类A中包含成员属性B, B是通过@Autowired自动注入，而类 A的实例 是通过 new的方式 产生，则自动注入会失效的。

在启动类中定义分别扫描两个包 ，即在@SpringBootApplication注解的类中添加：
@ComponentScan("com.alibaba.taobao","com.alibaba.tmall")
或
@ComponentScan("com.alibaba")

定义一个SpringUtil类

然后在类A中通过如下调用获取Spring容器中的B实例
ClassBInterface b = (ClassBInterfaceImpl) SpringUtil.getBean("classBInterfaceImpl");

SpringBoot @Autowired中注入静态方法或者静态变量

https://www.cnblogs.com/huanghongbo/p/10890025.html

注：用static去定义一个注入的方法或者配置文件值变量，编译时不会有任何异常，运行时会报空指针。

Spring官方不推荐此种方法。

 原理：

https://www.cnblogs.com/chenfeng1122/p/6270217.html

解决办法

利用spring的set注入方法，通过非静态的setter方法注入静态变量 ，我们可以改成这样就静态变量可以获取到你配置的信息了。

把get,set方法的static 修饰符去掉，然后在set方法上面加@Autowired即可

/** 阿里云OSS配置查询 */
private static OSSConfMapper ossConfMapper;
/** 阿里云OSS图片上传 */
private static UploadImgOSS uploadImgOSS;

public  OSSConfMapper getOssConfMapper() {
    return ossConfMapper;
}
@Autowired
public  void setOssConfMapper(OSSConfMapper ossConfMapper) {
    UploadUtil.ossConfMapper = ossConfMapper;
}
public  UploadImgOSS getUploadImgOSS() {
    return uploadImgOSS;
}
@Autowired
public  void setUploadImgOSS(UploadImgOSS uploadImgOSS) {
    UploadUtil.uploadImgOSS = uploadImgOSS;
}

参考文档

https://blog.csdn.net/kongrun12/article/details/76246369

https://blog.csdn.net/zxl646801924/article/details/81738231

https://blog.csdn.net/u014079773/article/details/66973830

 

经过尝试，有两种实现方式

方式一：声明一个静态的变量或方法，再相应的注入一个对应的变量和方法，最后PostConstruct注解在init时实现。

代码如下

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.mail.SimpleMailMessage;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.stereotype.Component;
import tylin.paas.transfers.util.DateUtil;

import javax.annotation.PostConstruct;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.LinkedList;
import java.util.List;

@Slf4j
@Component
public class ErrorHandler {


    @Value("${customer.mail.bankMail.sender}")
    private String configSender;

    private static String sender;

    @Value("${customer.mail.bankMail.receiver}")
    private String configReceiver;

    private static String receiver;

    public static ErrorHandler errorHandler;

    @Autowired
    JavaMailSender autoJavaMailSender;

    private static JavaMailSender javaMailSender;


    @PostConstruct
    public void init() {
        sender = configSender;
        receiver = configReceiver;
        javaMailSender = autoJavaMailSender;
        errorHandler = this;
    }


    public static void sendMail() {
        
        SimpleMailMessage message = new SimpleMailMessage();
        message.setFrom(sender);
        message.setTo(receiver.split(";"));
        message.setSubject("your subject");
        message.setText("your content text");

        try {
            javaMailSender.send(message);
            log.info("发送邮件成功！");
        } catch (Exception e) {
            log.error("发送邮件时发生异常！", e);
        }
        
    }

}

 

方式二：

在set时注入

import lombok.extern.slf4j.Slf4j;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.mail.SimpleMailMessage;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.stereotype.Component;
import org.springframework.test.context.junit4.SpringRunner;
import org.tylin.TylinERPApplication;

import java.text.SimpleDateFormat;
import java.util.Date;


@Slf4j
@Component
@SpringBootTest(classes = TylinERPApplication.class)
@RunWith(SpringRunner.class)
public class MailAutoSendTest {
    private static String sender;

    //可以不要
    public  String getSender() {
        return sender;
    }
    @Value("${customer.mail.bankMail.sender}")
    public void setSender(String sender) {
        MailAutoSendTest.sender = sender;
    }

    private static String receiver;

    //可以不要
    public  String getReceiver() {
        return receiver;
    }

    @Value("${customer.mail.bankMail.receiver}")
    public void setReceiver(String receiver) {
        MailAutoSendTest.receiver = receiver;
    }


    private static JavaMailSender javaMailSender;

    public JavaMailSender getJavaMailSender(){
        return javaMailSender;
    }

    @Autowired
    public void setJavaMailSender(JavaMailSender javaMailSender){
        MailAutoSendTest.javaMailSender = javaMailSender;
    }


    @Test
    public void sendMail() {
        SimpleMailMessage message = new SimpleMailMessage();
        message.setFrom(sender);
        log.info(sender);
        log.info(receiver);
        message.setTo(receiver.split(";"));
        message.setSubject("xxxx");

        Date date = new Date();
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd  HH:mm:ss");

        message.setText("xxxx"+dateFormat.format(date));

        try {
            javaMailSender.send(message);
            log.info("简单邮件已经发送。");
        } catch (Exception e) {
            log.error("发送简单邮件时发生异常！", e);
        }
    }

}

 

 

分类: Java, SpringBoot