我尝试使用 ObjectMapper 的 convertValue 方法将 DTO（Student）映射到 DAO（StudentEntity）：
new ObjectMapper().convertValue(student, StudentEntity.class);
但是，我遇到了以下异常：
2024-09-20T20:48:01.063+05:30 INFO 10444 --- [nio-8080-exec-2] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet 'dispatcherServlet'
2024-09-20T20:48:01.064+05:30 INFO 10444 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'
2024-09-20T20:48:01.065+05:30 INFO 10444 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : Completed initialization in 1 ms
2024-09-20T20:48:01.210+05:30 ERROR 10444 --- [nio-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed: java.lang.IllegalArgumentException: Unrecognized field "firstName" (class com.icet.dao.StudentEntity), not marked as ignorable (0 known properties: ])
at [Source: UNKNOWN; byte offset: #UNKNOWN] (through reference chain: com.icet.dao.StudentEntity["firstName"])] with root cause
com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "firstName" (class com.icet.dao.StudentEntity), not marked as ignorable (0 known properties: ])
at [Source: UNKNOWN; byte offset: #UNKNOWN] (through reference chain: com.icet.dao.StudentEntity["firstName"])
但是在StudentEntity类上添加@JsonIgnoreProperties(ignoreUnknown = true)注解之后，并没有出现异常。
我的问题是：导致此异常的可能原因是什么，以及为什么添加可以@JsonIgnoreProperties(ignoreUnknown = true)解决问题？
实体类：
package com.icet.dao;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import jakarta.persistence.*;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.NoArgsConstructor;
import lombok.ToString;
@Builder
@Entity
@Table(name = "student")
@NoArgsConstructor
@AllArgsConstructor
@ToString
public class StudentEntity {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
Long id;
private String firstName;
private String lastName;
private String address;
private String phoneNumber;
private String nic;
private String email;
private String batch;
private String age;
}
学生班级:
package com.icet.model;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
@Data
@AllArgsConstructor
@Builder
public class Student {
private String firstName;
private String lastName;
private String address;
private String phoneNumber;
private String nic;
private String email;
private String batch;
private String age;
}
对象映射的服务类方法：
public void registerStudent(Student student) {
StudentEntity entity1 = new ObjectMapper()
.convertValue(student,StudentEntity.class);
//log.info(entity1.toString());
repository.save(entity1);
}
完整堆栈跟踪：
2024-09-20T20:48:01.063+05:30 INFO 10444 --- [nio-8080-exec-2] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet 'dispatcherServlet'
2024-09-20T20:48:01.064+05:30 INFO 10444 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'
2024-09-20T20:48:01.065+05:30 INFO 10444 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : Completed initialization in 1 ms
2024-09-20T20:48:01.210+05:30 ERROR 10444 --- [nio-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed: java.lang.IllegalArgumentException: Unrecognized field "firstName" (class com.icet.dao.StudentEntity), not marked as ignorable (0 known properties: ])
at [Source: UNKNOWN; byte offset: #UNKNOWN] (through reference chain: com.icet.dao.StudentEntity["firstName"])] with root cause
com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "firstName" (class com.icet.dao.StudentEntity), not marked as ignorable (0 known properties: ])
at [Source: UNKNOWN; byte offset: #UNKNOWN] (through reference chain: com.icet.dao.StudentEntity["firstName"])
at com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.from(UnrecognizedPropertyException.java:61) ~[jackson-databind-2.17.2.jar:2.17.2]
at com.fasterxml.jackson.databind.DeserializationContext.handleUnknownProperty(DeserializationContext.java:1153) ~[jackson-databind-2.17.2.jar:2.17.2]
at com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:2241) ~[jackson-databind-2.17.2.jar:2.17.2]
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownProperty(BeanDeserializerBase.java:1793) ~[jackson-databind-2.17.2.jar:2.17.2]
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownVanilla(BeanDeserializerBase.java:1771) ~[jackson-databind-2.17.2.jar:2.17.2]
at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:316) ~[jackson-databind-2.17.2.jar:2.17.2]
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:177) ~[jackson-databind-2.17.2.jar:2.17.2]
at com.fasterxml.jackson.databind.ObjectMapper._convert(ObjectMapper.java:4619) ~[jackson-databind-2.17.2.jar:2.17.2]
at com.fasterxml.jackson.databind.ObjectMapper.convertValue(ObjectMapper.java:4555) ~[jackson-databind-2.17.2.jar:2.17.2]
at com.icet.service.impl.StudentServiceImpl.registerStudent(StudentServiceImpl.java:27) ~[classes/:na]
at com.icet.controller.StudentController.registerStudent(StudentController.java:20) ~[classes/:na]
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:580) ~[na:na]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:255) ~[spring-web-6.1.12.jar:6.1.12]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:188) ~[spring-web-6.1.12.jar:6.1.12]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:118) ~[spring-webmvc-6.1.12.jar:6.1.12]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:926) ~[spring-webmvc-6.1.12.jar:6.1.12]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:831) ~[spring-webmvc-6.1.12.jar:6.1.12]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-6.1.12.jar:6.1.12]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1089) ~[spring-webmvc-6.1.12.jar:6.1.12]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:979) ~[spring-webmvc-6.1.12.jar:6.1.12]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014) ~[spring-webmvc-6.1.12.jar:6.1.12]
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:914) ~[spring-webmvc-6.1.12.jar:6.1.12]
at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:590) ~[tomcat-embed-core-10.1.28.jar:6.0]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885) ~[spring-webmvc-6.1.12.jar:6.1.12]
at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) ~[tomcat-embed-core-10.1.28.jar:6.0]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:195) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) ~[tomcat-embed-websocket-10.1.28.jar:10.1.28]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-6.1.12.jar:6.1.12]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.12.jar:6.1.12]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-6.1.12.jar:6.1.12]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.12.jar:6.1.12]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-6.1.12.jar:6.1.12]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.12.jar:6.1.12]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:483) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:344) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:384) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:904) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1741) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1190) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:63) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
at java.base/java.lang.Thread.run(Thread.java:1583) ~[na:na]
3
最佳答案
2
简单回答：
在进行转换时，Jackson ObjectMapper 需要 Setter 和 getter，但您的实体类中缺少这两个函数。
请在实体类顶部添加@Getter和来自 Lombok。@Setter
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首先我要说的是，这不是将业务领域映射到实体的理想设计。有更适合此任务的库可以内置到应用程序的持久层设计中，以高效的方式自动进行映射。（但如果这只是一个基本项目，我认为没有理由改变您的实现）
至于您的问题，转换失败是因为实体类上没有 setter。在实体上添加注释或为字段添加单独的 setter，它将按预期工作。请注意，转换回@Data实体类也需要 getter。@SetterStudent
忽略未知属性时它起作用的原因是，由于实体上没有 setter，因此 上的每个属性Student对于 来说都是未知的StudentEntity。使用此注释执行转换时，实际上没有任何属性会映射到实体类。
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