Spring Boot邮件REST API无法访问，求正确调用方案

开发一个带REST API的Spring Boot应用，该API可通过传入包含邮箱凭证的JSON发送邮件，应用不涉及数据库操作。已编写MailController、MailPojo及MailServiceImpl实现邮件发送逻辑，启动后控制台显示Tomcat在8080端口启动，上下文路径为空。但使用Postman调用http://localhost:8080/mailsend/mailService/sendMail时无法访问API，请问如何成功调用该API？

MailController #

@RestController
@RequestMapping("/mailService")
public class MailController{
    @Autowired
    private MailService mailService;
    
    @PostMapping("/sendMail")
    public ResponseEntity<Long>  sendMail(@RequestBody MailPojo pojo){
        System.out.println("POST Request ....");
        MailResponse resp = mailService.sendMail(pojo);
        
        return new ResponseEntity(resp, HttpStatus.CREATED);
    }
    
}

MailPojo #

public class MailPojo {
    
    private String smtpServer;  
    private String userName;    
    private String password;
    private String smtpPort;    
    private String emailFrom;  
    private String emailTo;     
    private String emailCC;    
    private String emailSubject;    
    private String emailText;  
    ...
    ......

}

MailServiceImpl #

@Service
@Slf4j
public class MailServiceImpl implements MailService {
    
    @Override
    public MailResponse sendMail(MailPojo pojo) {
        
        String srvrResp = "";
        String retn = "";
        String SMTP_SERVER = pojo.getSmtpServer();    
        final String USERNAME =  pojo.getUserName();  
        final String PASSWORD = pojo.getPassword();   
        String TLS = "Y";
        String smtpPort = pojo.getSmtpPort();         
        String EMAIL_FROM = pojo.getEmailFrom();      
        String EMAIL_TO = pojo.getEmailTo();          
        String EMAIL_CC = pojo.getEmailCC();         
        String EMAIL_SUBJECT = pojo.getEmailSubject();   
        String EMAIL_TEXT = pojo.getEmailText();         

        Properties prop = System.getProperties();
        prop.put("mail.smtp.host", SMTP_SERVER); // optional, defined in SMTPTransport
        prop.put("mail.smtp.auth", "true");
        prop.put("mail.smtp.port", smtpPort);    // default port 25 (TLS)
        prop.put("mail.smtp.socketFactory.port", "465"); //SSL Port
        prop.put("mail.smtp.socketFactory.class",
                "javax.net.ssl.SSLSocketFactory"); //SSL Factory Class
        
        Authenticator auth = new Authenticator() {
            //override the getPasswordAuthentication method
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(USERNAME, PASSWORD);
            }
        };

        Session session = Session.getInstance(prop, auth);

        System.out.println("Session created");
        Message msg = new MimeMessage(session);

        try {

            ...
            ....
            ......

            t.sendMessage(msg, msg.getAllRecipients());

            System.out.println("Response: " + t.getLastServerResponse());
            srvrResp = t.getLastServerResponse();
            
            retn ="SUCCESS";
            t.close();

        } catch (MessagingException e) {
            retn = "FAILED";
            e.printStackTrace();
        }
        
        .....
        ........

        return respObj;     
    }

   
}

.   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::               (v2.7.12)

2023-06-11 22:53:10.535  INFO 3048 --- [  restartedMain] in.issac.mailsend.MailsendApplication    : Starting MailsendApplication using Java 17.0.7 on DESKTOP-QU763SD with PID 3048 (F:\STS_Workspace\mailsend\target\classes started by Jayanta Pramanik in F:\STS_Workspace\mailsend)
2023-06-11 22:53:10.551  INFO 3048 --- [  restartedMain] in.issac.mailsend.MailsendApplication    : No active profile set, falling back to 1 default profile: "default"
2023-06-11 22:53:10.680  INFO 3048 --- [  restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : Devtools property defaults active! Set 'spring.devtools.add-properties' to 'false' to disable
2023-06-11 22:53:10.680  INFO 3048 --- [  restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : For additional web related logging consider setting the 'logging.level.web' property to 'DEBUG'
2023-06-11 22:53:12.816  INFO 3048 --- [  restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2023-06-11 22:53:12.838  INFO 3048 --- [  restartedMain] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2023-06-11 22:53:12.839  INFO 3048 --- [  restartedMain] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.75]
2023-06-11 22:53:12.969  INFO 3048 --- [  restartedMain] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2023-06-11 22:53:12.971  INFO 3048 --- [  restartedMain] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 2289 ms
2023-06-11 22:53:13.927  INFO 3048 --- [  restartedMain] o.s.b.d.a.OptionalLiveReloadServer       : LiveReload server is running on port 35729
2023-06-11 22:53:14.017  INFO 3048 --- [  restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2023-06-11 22:53:14.055  INFO 3048 --- [  restartedMain] in.issac.mailsend.MailsendApplication    : Started MailsendApplication in 4.256 seconds (JVM running for 5.13)

1. 修正请求URL #

从启动日志可知，应用的上下文路径为空（context path ''），而MailController的请求映射是/mailService，接口的POST映射是/sendMail，因此正确的请求URL应该是：
http://localhost:8080/mailService/sendMail
当前调用的URL多了/mailsend（项目文件夹名称），但Spring Boot并未将其设为上下文路径，因此需要去掉。

2. 确保请求方式与参数正确 #

• 请求方式必须为POST，在Postman中选择POST方法。
• 请求体必须是符合MailPojo结构的JSON数据，同时要将Content-Type设置为application/json。示例JSON如下：

{
    "smtpServer": "smtp.example.com",
    "userName": "your-email@example.com",
    "password": "your-password",
    "smtpPort": "465",
    "emailFrom": "sender@example.com",
    "emailTo": "recipient@example.com",
    "emailCC": "cc-recipient@example.com",
    "emailSubject": "Test Email",
    "emailText": "This is a test email content."
}

3. 验证Controller是否被Spring扫描 #

检查启动类MailsendApplication的包路径（in.issac.mailsend），确保MailController所在的包是其子包（比如in.issac.mailsend.controller）。Spring Boot默认会扫描启动类所在包及其子包下的组件，如果Controller在其他包，需要在启动类上添加@ComponentScan(basePackages = "your.controller.package")指定扫描路径。

4. 排查拦截/安全配置 #

如果项目中引入了Spring Security或自定义拦截器，需要确保/mailService/sendMail接口被允许访问，避免被拦截。

5. 开启日志排查问题 #

在application.properties或application.yml中添加配置，开启Web层的DEBUG日志，查看请求是否到达Spring框架，以及是否存在映射错误：

logging.level.web=DEBUG

启动应用后重新调用接口，查看控制台日志，确认请求的URL、方法是否与Controller的映射匹配。

内容的提问来源于stack exchange，提问作者Jayanta Pramanik