学习使用SpringBoot创建微服务时遇到错误

Question

使用 Spring 书籍创建了一个产品服务，这里是模型 Product,java:

package com.scalermasterclass.productservice.models;

import com.fasterxml.jackson.annotation.JsonProperty;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;


public class Product {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String title;
    private String description;
    private String category;
    private double price;
    private String imageUrl;
    private boolean isPublic;
}

这是产品控制器文件：

package com.scalermasterclass.productservice.controllers;

import com.scalermasterclass.productservice.models.Product;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;


@RestController
@RequestMapping(path="/products", produces= MediaType.TEXT_PLAIN_VALUE)//localhost:8081/products

public class ProductController {
    @GetMapping("/details")  //GET /products/details
    public Product getProductDetails(@RequestParam("user_Id") Long userId,@RequestParam("product_Id") Long productId){
        return new Product();
    }
}

面对错误：

{
    "timestamp": "2024-01-24T19:46:39.475+00:00",
    "status": 500,
    "error": "Internal Server Error",
    "trace": "org.springframework.http.converter.HttpMessageNotWritableException: No converter for [class com.scalermasterclass.productservice.models.Product] with preset Content-Type 'null'\r\n\tat org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:319)\r\n\tat org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:190)\r\n\tat org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:78)\r\n\tat org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:136)\r\n\tat org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:917)\r\n\tat org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:829)\r\n\tat org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)\r\n\tat org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1089)\r\n\tat org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:979)\r\n\tat org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014)\r\n\tat org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:903)\r\n\tat jakarta.servlet.http.HttpServlet.service(HttpServlet.java:564)\r\n\tat org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885)\r\n\tat jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658)\r\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:205)\r\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)\r\n\tat org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)\r\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174)\r\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)\r\n\tat org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)\r\n\tat org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)\r\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174)\r\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)\r\n\tat org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)\r\n\tat org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)\r\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174)\r\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)\r\n\tat org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)\r\n\tat org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)\r\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174)\r\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)\r\n\tat org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167)\r\n\tat org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90)\r\n\tat org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:482)\r\n\tat org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115)\r\n\tat org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93)\r\n\tat org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)\r\n\tat org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:340)\r\n\tat org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:391)\r\n\tat org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63)\r\n\tat org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:896)\r\n\tat org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1744)\r\n\tat org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)\r\n\tat org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)\r\n\tat org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)\r\n\tat org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)\r\n\tat java.base/java.lang.Thread.run(Thread.java:1623)\r\n",
    "message": "No converter for [class com.scalermasterclass.productservice.models.Product] with preset Content-Type 'null'",
    "path": "/products/details"
}

我尝试使用 Postman GUI 发送 get 请求 localhost:8081/products/details?user_Id=1&product_Id=1 ，但是面对上述错误，请帮助我解决此错误，以便我可以学习 SpringBoot。

Answer 1

问题出在你的

Entity

public class Product {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String title;
    private String description;
    private String category;
    private double price;
    private String imageUrl;
    private boolean isPublic;
}

在这个类中，您必须为字段添加构造函数、getter、setter 方法。