java - 使用构造函数注入(inject)的 spring @RestController 中的空异常 @Service

Question

这是我的第三个个人 spring-boot 项目，我所做的配置与之前的 99% 相同，所以不知道为什么我会在这个项目上遇到此错误。

项目启动得很好，但是一旦我对我拥有的唯一的 @RestController 进行任何请愿，它就会立即收到 null 错误。该端点接收一个 alpha 2 国家/地区代码 + 城市名称 + 所需的 ip 地址，如果未提供 ip 地址，它将采用客户端 ip 地址，该地址用作我从中获取 null 的 @Service 的参数。之后， Controller 应该在将预期输出发送到客户端之前执行许多其他操作，但由于此 @Service 上出现 null 异常，它永远不会达到该点。

这是我正在尝试的请愿书:

http://localhost:8080/apiv1/get-distance?country=af&city=Qalat&ip=150.135.184.38

There was an unexpected error (type=Internal Server Error, status=500).
Cannot invoke "me.givo.distancebetweenus.getdistance.services.CurrentLocationService.getCurrentLocation(String)" because "this.currentLocationService" is null
java.lang.NullPointerException: Cannot invoke "me.givo.distancebetweenus.getdistance.services.CurrentLocationService.getCurrentLocation(String)" because "this.currentLocationService" is null
    at me.givo.distancebetweenus.getdistance.controllers.DistanceController.getDistance(DistanceController.java:53)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:655)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:96)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:895)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1722)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:833)

这是我的 Controller :

package me.givo.distancebetweenus.getdistance.controllers;

import javax.servlet.http.HttpServletRequest;
import javax.validation.constraints.Max;
import javax.validation.constraints.Min;

import me.givo.distancebetweenus.getdistance.dtos.CityDto;
import me.givo.distancebetweenus.getdistance.dtos.CountryDto;
import me.givo.distancebetweenus.getdistance.entities.CityEntity;
import me.givo.distancebetweenus.getdistance.entities.CountryEntity;
import me.givo.distancebetweenus.getdistance.models.ApiCurrentLocationResponse;
import me.givo.distancebetweenus.getdistance.models.Coordinate;
import me.givo.distancebetweenus.getdistance.models.DistanceResponse;
import me.givo.distancebetweenus.getdistance.repositories.ICitiesRepository;
import me.givo.distancebetweenus.getdistance.repositories.ICountriesRepository;
import me.givo.distancebetweenus.getdistance.services.CurrentLocationService;
import org.modelmapper.ModelMapper;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.*;

@RequestMapping("/apiv1")
@Validated
@RestController
public class DistanceController {

    private final CurrentLocationService currentLocationService;
    private final ICitiesRepository citiesRepository;
    private final ICountriesRepository countriesRepository;
    private final ModelMapper modelMapper;

    public DistanceController(CurrentLocationService currentLocationService, ICitiesRepository citiesRepository,
                              ICountriesRepository countryRepository, ModelMapper modelMapper) {
        this.currentLocationService = currentLocationService;
        this.citiesRepository = citiesRepository;
        this.countriesRepository = countryRepository;
        this.modelMapper = modelMapper;
    }

    @GetMapping("/get-distance")
    @ResponseBody
    private ResponseEntity<Object> getDistance(
            @RequestParam(required = true, name = "country") @Min(2) @Max(2) String country,
            @RequestParam(required = true, name = "city") String city,
            @RequestParam(required = false, name = "ip") @Min(7) @Max(15) String ip,
            HttpServletRequest request) {

        ApiCurrentLocationResponse currentLocation;
        if (ip == null || ip.isEmpty()) {
            String requestIP = request.getRemoteAddr();
            System.out.println(requestIP);
            try {
                currentLocation = currentLocationService.getCurrentLocation(requestIP);
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }
        } else {
            try {
                currentLocation = currentLocationService.getCurrentLocation(ip);
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }
        }

        CountryEntity countryEntity = countriesRepository.getById(country);
        CityEntity cityEntity = citiesRepository.getByNameAndCode(city, country);

        CountryDto countryDto = convertToCountryDto(countryEntity);
        CityDto cityDto = convertToCityDto(cityEntity);

        Coordinate currentLocationCoordinate = new Coordinate(currentLocation);
        Coordinate destinationCoordinate = new Coordinate(cityDto);

        Double distance = currentLocationCoordinate.distanceBetweenUsKm(destinationCoordinate);

        DistanceResponse response = new DistanceResponse(countryDto, cityDto, distance);

        return ResponseEntity.status(HttpStatus.OK).body(response);
    }

    private CityDto convertToCityDto(CityEntity cityEntity) {
        return modelMapper.map(cityEntity, CityDto.class);
    }

    private CountryDto convertToCountryDto(CountryEntity countryEntity) {
        return modelMapper.map(countryEntity, CountryDto.class);
    }
}

这是“null”@Service:

package me.givo.distancebetweenus.getdistance.services;

import me.givo.distancebetweenus.getdistance.models.ApiCurrentLocationResponse;
import org.springframework.stereotype.Service;
import org.springframework.web.reactive.function.client.WebClient;

@Service
public class CurrentLocationService {

    private final WebClient.Builder webClient;

    private final String key = "fakekey347834834892923fake";

    public CurrentLocationService(WebClient.Builder webClient) {
        this.webClient = webClient;
    }

    public ApiCurrentLocationResponse getCurrentLocation(String requestIP) {

        String url = "https://api.fakeapi.app/json/";
        return webClient.baseUrl(url).build().get()
                .uri(uriBuilder -> uriBuilder
                        .path(requestIP)
                        .queryParam("apikey", key)
                        .build())
                .retrieve()
                .bodyToMono(ApiCurrentLocationResponse.class)
                .block();
    }
}

非常感谢您的帮助。如果需要任何其他信息，请告诉我。谢谢你! - - - - - - - - 编辑 - - - - - - - - - - shivam 的评论给了我在注入(inject)中使用 @Autowired 标记的想法，所以我这样做了，并且我不再在 @Service 中收到 null 异常，它位于 ICountriesRepository 中，而这只是我的 @RestController 中的下一行代码..这些是我所做的更改:

public class DistanceController {

    private final CurrentLocationService currentLocationService;
    private final ICitiesRepository citiesRepository;
    private final ICountriesRepository countriesRepository;
    private final ModelMapper modelMapper;

    @Autowired
    public DistanceController(CurrentLocationService currentLocationService, ICitiesRepository citiesRepository,
                              ICountriesRepository countriesRepository, ModelMapper modelMapper) {
        this.currentLocationService = currentLocationService;
        this.citiesRepository = citiesRepository;
        this.countriesRepository = countriesRepository;
        this.modelMapper = modelMapper;
    }

这是"new"错误日志:

There was an unexpected error (type=Internal Server Error, status=500).
Cannot invoke "me.givo.distancebetweenus.getdistance.repositories.ICountriesRepository.getById(Object)" because "this.countriesRepository" is null
java.lang.NullPointerException: Cannot invoke "me.givo.distancebetweenus.getdistance.repositories.ICountriesRepository.getById(Object)" because "this.countriesRepository" is null
    at me.givo.distancebetweenus.getdistance.controllers.DistanceController.getDistance(DistanceController.java:72)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:655)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:96)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:895)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1722)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:833)

这是 ICountriesRepository 的代码:

package me.givo.distancebetweenus.getdistance.repositories;


import me.givo.distancebetweenus.getdistance.entities.CountryEntity;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;


@Repository
public interface ICountriesRepository extends JpaRepository<CountryEntity, String> {

}

另外，我添加了为 ModelMapper 制作的 @Configuration 代码:

package me.givo.distancebetweenus.getdistance.config;

import org.modelmapper.ModelMapper;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class Config {

    @Bean
    public ModelMapper modelMapper() {
        return new ModelMapper();
    }

}

Answer 1

我在工作日有点忙，所以直到现在才能够检查我的代码，我发现我的 Controller 拥有的唯一 GetMapping 方法是私有(private)。我刚刚将其公开，并且一切都已按预期运行。感谢大家抽出时间。