为什么我的 Spring Boot 转换器在其他人工作时不起作用

【问题标题】：Why is my Spring Boot converter not working when others are为什么我的 Spring Boot 转换器在其他人工作时不起作用
【发布时间】：2021-05-27 20:52:31
【问题描述】：

我无法弄清楚为什么我的一些 Spring Boot 转换器无法正常工作。我已经制作了几个正在工作的转换器，它们实现了 convert 方法，扩展了 WebMvcConfigurer 覆盖了 addFormatters 方法并在那里添加了所有转换器。一些转换器正在工作，但我必须在转换器类中包含我的一些存储库，因为来自它们的数据用于转换。 一些示例代码

    //this one does work
@Component
class ReviewToDtoConverter: Converter<Review, ReviewDto> {
    override fun convert(review: Review): ReviewDto {
        return ReviewDto(review)
    }
}

//this one does not work
@Component
class DtoToReviewConverter: Converter<ReviewDto,Review> {

    @field:Autowired
    lateinit var userRepo: UserRepo

    @field:Autowired
    lateinit var productRepo: ProductRepo

    override fun convert(reviewDto: ReviewDto): Review? {

        return Review(
            reviewDto = reviewDto,
            user = try {userRepo.findByIdUser(reviewDto.userId ?: throw UserNotProvidedException("The User was not provided"))}
            catch (e: EmptyResultDataAccessException)
            { throw UserNotFoundException("The user could not be found")},
            product = try {productRepo.findByUpc(reviewDto.upc)}
            catch (e: EmptyResultDataAccessException)
            {throw ProductNotFoundException("The product could not be found")}
        )
    }
}

以及我在哪里添加转换器

@Configuration
class MvcConfig: WebMvcConfigurer {
    override fun addFormatters(registry: FormatterRegistry) {
        registry.addConverter(DtoToOrderConverter())
        registry.addConverter(OrderToDtoConverter())
        registry.addConverter(UserToDtoConverter())
        registry.addConverter(DtoToUserConverter())
        registry.addConverter(DtoToProductConverter())
        registry.addConverter(ProductToDtoConverter())
        registry.addConverter(ReviewToDtoConverter())
        registry.addConverter(DtoToReviewConverter())
        super.addFormatters(registry)

    }

}

@Component
class MyConversionService:DefaultConversionService(), ConversionService{

}

我不得不添加 MyConversionService 类，因为我在 spring 中遇到了一个错误，不知道要使用哪个 bean，这是我发现的唯一可行的解​​决方案

以及我在哪里使用转换服务

    @RestController
@RequestMapping("/review")
class ReviewController(val reviewService: ReviewService, val conversionService: MyConversionService) {

    @PutMapping(params = ["upc", "userId"])
    fun updateReview(@RequestParam("upc") upc: Int, @RequestParam("userId") userId: Int, @RequestBody reviewDto: ReviewDto): ReviewDto {
        reviewDto.userId = userId
        reviewDto.upc = upc
        conversionService.addConverter(DtoToReviewConverter())
        println("can convert " + conversionService.canConvert(ReviewDto::class.java, Review::class.java))

        return conversionService.convert(reviewService.updateReview(upc, userId, conversionService.convert(reviewDto, Review::class.java) ?: throw CustomConversionException("There was a problem")), ReviewDto::class.java) ?: throw CustomConversionException("There was a problem")

    }

    @PostMapping(params = ["upc", "userId"])
    fun saveReview(@RequestParam("upc") upc: Int, @RequestParam("userId") userId: Int, @RequestBody reviewDto: ReviewDto): ReviewDto {
        reviewDto.userId = userId
        reviewDto.upc = upc
        return conversionService.convert(reviewService.saveReview(
            upc = upc,
            userId = userId,
            review = conversionService.convert(reviewDto, Review::class.java) ?: throw CustomConversionException("There was a problem")
        ), ReviewDto::class.java) ?: throw CustomConversionException("There was a problem")
    }

    @GetMapping(params = ["userId"])
    fun getReviewsByUser(@RequestParam("userId") userId: Int): List<ReviewDto> {
        return reviewService.getReviewsByUser(userId).map { conversionService.convert(it, ReviewDto::class.java) ?: throw CustomConversionException("There was a problem") }
    }

    @GetMapping(params = ["upc"])
    fun getReviewsByProduct(@RequestParam("upc") upc: Int): List<ReviewDto> {
        return reviewService.getReviewsByProduct(upc).map { conversionService.convert(it, ReviewDto::class.java) ?: throw CustomConversionException("There was a problem") }
    }
}

这是堆栈跟踪

org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [com.example.demo.datatranferobjects.ReviewDto] to type [com.example.demo.entities.Review]
    at org.springframework.core.convert.support.GenericConversionService.handleConverterNotFound(GenericConversionService.java:322) ~[spring-core-5.3.6.jar:5.3.6]
    at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:195) ~[spring-core-5.3.6.jar:5.3.6]
    at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:175) ~[spring-core-5.3.6.jar:5.3.6]
    at com.example.demo.controllers.ReviewController.updateReview(ReviewController.kt:18) ~[classes/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78) ~[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:567) ~[na:na]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197) ~[spring-web-5.3.6.jar:5.3.6]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141) ~[spring-web-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1060) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:962) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.FrameworkServlet.doPut(FrameworkServlet.java:920) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:655) ~[tomcat-embed-core-9.0.45.jar:4.0.FR]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) ~[tomcat-embed-core-9.0.45.jar:4.0.FR]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.6.jar:5.3.6]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.6.jar:5.3.6]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.6.jar:5.3.6]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.6.jar:5.3.6]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:93) ~[spring-boot-actuator-2.4.5.jar:2.4.5]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.6.jar:5.3.6]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.6.jar:5.3.6]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.6.jar:5.3.6]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1707) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) ~[na:na]
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) ~[na:na]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at java.base/java.lang.Thread.run(Thread.java:831) ~[na:na]

我尝试将存储库添加到其中一个正在工作的转换器类中，认为它可能会停止工作，但它仍然可以工作

不知道该去哪里，因为堆栈跟踪对我没有帮助

更新我认为我已经取得了一些进展，我很确定问题与 spring 实例化 bean 的顺序有关。我只是不确定现在如何正确设置所有内容。好像如果我可以改变 spring 进行自动装配的方式，我可以解决这个问题

【问题讨论】：

  • 你能发布转换器的定义吗？
  • 不确定你的意思。你在找什么？我以为我把定义放在第一个代码块中
  • 您已经发布了适用于订单的OrderToDtoConverter和DtoToOrderConverter，但错误是关于Review，因此我们需要查看Review相关转换器。我相信您的代码中称为ReviewToDtoConverter。
  • 哇，我真的没注意。发布的订单和评论的实现和错误基本相同。谢谢

标签： java spring-boot kotlin


【解决方案1】：

我认为可能的原因是DtoToReviewConverter: Converter&lt;ReviewDto,Review&gt; 类的签名与转换器的返回类型不匹配。因此，即使您已将 Converter 定义为返回 Review 类型的对象，您的转换器方法也将返回 Review? 类型的对象。可空类型与 Kotlin 中的不可空类型根本不同。要解决此问题，您可以将转换器的泛型类型更新为 Review? 或确保转换器函数的返回类型为 Review。

本文讨论了 Kotlin 中的可空性和泛型，看看是否有帮助：https://medium.com/@igorwojda/kotlin-deep-dive-into-generics-nullability-9853d9a9f50d

【讨论】：

  • 所以我也对此提出质疑，并尝试使用转换器返回一个可选值和一个非可选值。我得到了相同的结果。查看我的最新更新。我认为这个问题与 bean 实例化的顺序以及 spring 如何自动装配它们有关
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