Spring整合MongoDB访问/save报500错误的排查与解决

访问http://localhost:8080/save返回500错误，控制台抛出如下异常：

java.lang.NullPointerException: Cannot invoke "team24.calender.service.mongo.MongoDBTestService.mongoInsert()" because "this.mongoDBTestService" is null
    at team24.calender.controller.UserController.test(UserController.java:46) ~[main/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:262) ~[spring-web-6.1.2.jar:6.1.2]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:190) ~[spring-web-6.1.2.jar:6.1.2]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:118) ~[spring-webmvc-6.1.2.jar:6.1.2]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:917) ~[spring-webmvc-6.1.2.jar:6.1.2]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:829) ~[spring-webmvc-6.1.2.jar:6.1.2]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-6.1.2.jar:6.1.2]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1089) ~[spring-webmvc-6.1.2.jar:6.1.2]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:979) ~[spring-webmvc-6.1.2.jar:6.1.2]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014) ~[spring-webmvc-6.1.2.jar:6.1.2]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:903) ~[spring-webmvc-6.1.2.jar:6.1.2]
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:564) ~[tomcat-embed-core-10.1.17.jar:6.0]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885) ~[spring-webmvc-6.1.2.jar:6.1.2]
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) ~[tomcat-embed-core-10.1.17.jar:6.0]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:205) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) ~[tomcat-embed-websocket-10.1.17.jar:10.1.17]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-6.1.2.jar:6.1.2]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.2.jar:6.1.2]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-6.1.2.jar:6.1.2]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.2.jar:6.1.2]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-6.1.2.jar:6.1.2]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.2.jar:6.1.2]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:482) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:340) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:391) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:896) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1744) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-10.1.17.jar:10.1.17]
    at java.base/java.lang.Thread.run(Thread.java:840) ~[na:na]

2024-01-28T01:10:04.655+09:00 DEBUG 61128 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : "ERROR" dispatch for GET "/error", parameters={}
2024-01-28T01:10:04.656+09:00 DEBUG 61128 --- [nio-8080-exec-1] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController#errorHtml(HttpServletRequest, HttpServletResponse)
2024-01-28T01:10:04.675+09:00 DEBUG 61128 --- [nio-8080-exec-1] o.s.w.s.v.ContentNegotiatingViewResolver : Selected 'text/html' given [text/html, text/html;q=0.8]
2024-01-28T01:10:04.679+09:00 DEBUG 61128 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Exiting from "ERROR" dispatch, status 500

相关代码 #

application.yml #

spring:
  data:
  mongodb:
    uri: mongodb+srv://jone:2344524@calendar.dthpjmz.mongodb.net/
    embedded:
      version: 4.0.21

MongoDBTestModel.java #

import lombok.*;
import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;

@Getter
@Setter
@ToString
@AllArgsConstructor
@Document(collection = "user")
public class MongoDBTestModel {

    @Id
    private Long id;
    private String uid;
}

MongoDBTestService.java #

import lombok.RequiredArgsConstructor;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.stereotype.Service;
import team24.calender.domain.mongo.MongoDBTestModel;

@RequiredArgsConstructor
@Service
public class MongoDBTestService {

    private final MongoTemplate mongoTemplate;

    public void mongoInsert(){
        MongoDBTestModel mongoDBTestModel=new MongoDBTestModel(2L,"jone");
        mongoTemplate.insert(mongoDBTestModel);
    }
}

UserController.java #

@RequiredArgsConstructor
@RestController
@Slf4j
public class UserController {

    private MongoDBTestService mongoDBTestService;

    @GetMapping("/save")
    public String test() {
        mongoDBTestService.mongoInsert();
        return "test";
    }
}

解决方法 #

核心问题 #

UserController使用了@RequiredArgsConstructor，但mongodbTestService字段未声明为final，导致Lombok无法生成对应构造方法，Spring无法完成依赖注入，最终触发空指针异常。

修复步骤 #

修改UserController.java的字段声明，添加final关键字：

@RequiredArgsConstructor
@RestController
@Slf4j
public class UserController {

    private final MongoDBTestService mongoDBTestService;

    @GetMapping("/save")
    public String test() {
        mongoDBTestService.mongoInsert();
        return "test";
    }
}

其他可选修复方式 #

若不想使用final字段，可改用@Autowired注解完成注入：

@RestController
@Slf4j
public class UserController {

    @Autowired
    private MongoDBTestService mongoDBTestService;

    @GetMapping("/save")
    public String test() {
        mongoDBTestService.mongoInsert();
        return "test";
    }
}

额外检查点 #

1. 确认MongoDBTestService上的@Service注解生效，且所在包在Spring Boot主类的扫描范围内
2. 修正application.yml的MongoDB配置：使用远程MongoDB Atlas时无需嵌入式MongoDB配置，建议指定具体数据库名

spring:
  data:
    mongodb:
      uri: mongodb+srv://jone:2344524@calendar.dthpjmz.mongodb.net/your-database-name

内容的提问来源于stack exchange，提问作者maje