Spring Boot @Autowired injects static variables or static methods

Note: Use static to define an injection method or configuration file value variable, there will be no exception during compilation, and a null pointer will be reported during runtime.

Spring officials do not recommend this method.

 principle:

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

Solution

Use spring's set injection method to inject static variables through non-static setter methods. We can change it so that the static variables can get the information you configured.

Remove the static modifier of the get and set methods, and then add @Autowired to the set method.

/** 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;
}

Reference documents

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

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

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

 

After trying, there are two ways to achieve

Method 1: Declare a static variable or method, and then inject a corresponding variable and method accordingly. Finally, the PostConstruct annotation is implemented in init.

code show as below

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);
        }
        
    }

}

 

Method 2: (Pro-test is feasible)

Inject during set

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);
        }
    }

}

Pro test example:

@Component
public class NetEleUtil {

    private static WirelessResourceProperties resProps;

    public WirelessResourceProperties getResProps() {
        return resProps;
    }

//    @Autowired
    public void setResProps(WirelessResourceProperties resProps) {
        NetEleUtil.resProps = resProps;
    }

    /**
     * 根据网元英文简称获取网元中文名称
     *
     * @param obj
     * @return java.util.Map<java.lang.String,java.lang.Object>
     * @author liangzhaolin
     * @date 2020/10/22 11:00
     */
    public static String getNetEleTableCnName(String netEleType) {
        Map<String, String> tableMap = resProps.getTableCnName();
        String netEleTableCnName = tableMap.get(netEleType);

        return netEleTableCnName;
    }
}