java - 使用 JPA 的 Spring Boot - 无法从 h2 数据库返回对象
问题描述
我正在学习 Spring Boot，并尝试实现一个简单的保存和获取数据库 Web 应用程序。这是我的控制器类：
package com.example.demo;
import java.util.Optional;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.servlet.ModelAndView;
@Controller
public class WebsiteClass
{
@Autowired
PersonDBHandler personDBHandlerObj;
@RequestMapping("index")
public String index()
{
return "home.jsp";
}
@RequestMapping("addPerson")
public String addObject(Person obj)
{
personDBHandlerObj.save(obj);
return "home.jsp";
}
@RequestMapping("getPerson")
public ModelAndView getObject(@RequestParam int id)
{
ModelAndView mv = new ModelAndView("showPerson.jsp");
Person person = personDBHandlerObj.findById(id).orElse(new Person());
mv.addObject(person);
return mv;
}
}
数据正在保存到 h2 数据库中，但是当我尝试通过 id 获取 person 对象时，我在 line 处遇到错误Person person = personDBHandlerObj.findById(id).orElse(new Person());。错误 -
org.hibernate.TypeMismatchException: Provided id of the wrong type for class com.example.demo.Person. Expected: class java.lang.String, got class java.lang.Integer
at org.hibernate.event.internal.DefaultLoadEventListener.checkIdClass(DefaultLoadEventListener.java:155) ~[hibernate-core-5.4.20.Final.jar:5.4.20.Final]
at org.hibernate.event.internal.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:71) ~[hibernate-core-5.4.20.Final.jar:5.4.20.Final]
at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:113) ~[hibernate-core-5.4.20.Final.jar:5.4.20.Final]
at org.hibernate.internal.SessionImpl.fireLoadNoChecks(SessionImpl.java:1187) ~[hibernate-core-5.4.20.Final.jar:5.4.20.Final]
at org.hibernate.internal.SessionImpl.fireLoad(SessionImpl.java:1176) ~[hibernate-core-5.4.20.Final.jar:5.4.20.Final]
at org.hibernate.internal.SessionImpl.access$2100(SessionImpl.java:194) ~[hibernate-core-5.4.20.Final.jar:5.4.20.Final]
at org.hibernate.internal.SessionImpl$IdentifierLoadAccessImpl.doLoad(SessionImpl.java:2787) ~[hibernate-core-5.4.20.Final.jar:5.4.20.Final]
at org.hibernate.internal.SessionImpl$IdentifierLoadAccessImpl.lambda$load$1(SessionImpl.java:2768) ~[hibernate-core-5.4.20.Final.jar:5.4.20.Final]
at org.hibernate.internal.SessionImpl$IdentifierLoadAccessImpl.perform(SessionImpl.java:2724) ~[hibernate-core-5.4.20.Final.jar:5.4.20.Final]
at org.hibernate.internal.SessionImpl$IdentifierLoadAccessImpl.load(SessionImpl.java:2768) ~[hibernate-core-5.4.20.Final.jar:5.4.20.Final]
at org.hibernate.internal.SessionImpl.find(SessionImpl.java:3323) ~[hibernate-core-5.4.20.Final.jar:5.4.20.Final]
at org.hibernate.internal.SessionImpl.find(SessionImpl.java:3290) ~[hibernate-core-5.4.20.Final.jar:5.4.20.Final]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:366) ~[spring-orm-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at com.sun.proxy.$Proxy76.find(Unknown Source) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:314) ~[spring-orm-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at com.sun.proxy.$Proxy76.find(Unknown Source) ~[na:na]
at org.springframework.data.jpa.repository.support.SimpleJpaRepository.findById(SimpleJpaRepository.java:281) ~[spring-data-jpa-2.3.3.RELEASE.jar:2.3.3.RELEASE]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
at org.springframework.data.repository.core.support.ImplementationInvocationMetadata.invoke(ImplementationInvocationMetadata.java:72) ~[spring-data-commons-2.3.3.RELEASE.jar:2.3.3.RELEASE]
at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:382) ~[spring-data-commons-2.3.3.RELEASE.jar:2.3.3.RELEASE]
at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:205) ~[spring-data-commons-2.3.3.RELEASE.jar:2.3.3.RELEASE]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:549) ~[spring-data-commons-2.3.3.RELEASE.jar:2.3.3.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:155) ~[spring-data-commons-2.3.3.RELEASE.jar:2.3.3.RELEASE]
at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:130) ~[spring-data-commons-2.3.3.RELEASE.jar:2.3.3.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:367) ~[spring-tx-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:118) ~[spring-tx-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139) ~[spring-tx-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:178) ~[spring-data-jpa-2.3.3.RELEASE.jar:2.3.3.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:95) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at com.sun.proxy.$Proxy79.findById(Unknown Source) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:205) ~[spring-aop-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at com.sun.proxy.$Proxy58.findById(Unknown Source) ~[na:na]
at com.example.demo.WebsiteClass.getPerson(WebsiteClass.java:35) ~[classes/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[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:564) ~[na:na]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:878) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:792) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:626) ~[tomcat-embed-core-9.0.37.jar:4.0.FR]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) ~[tomcat-embed-core-9.0.37.jar:4.0.FR]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.37.jar:9.0.37]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1589) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
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-9.0.37.jar:9.0.37]
at java.base/java.lang.Thread.run(Thread.java:832) ~[na:na]
JSP 文件包含以下形式。
home.jsp -
<body>
<form action="addPerson">
<input type="text" name="name">
<input type="number" name="id">
<input type="submit">
</form>
<br>
<form action="getPerson">
<input type="number" name="id">
<input type="submit">
</form>
</body>
showPerson.jsp -
<body>
${person}
</body>
</html>
编辑：在下面添加了类
人 -
package com.example.demo;
import javax.persistence.Id;
import org.hibernate.annotations.Entity;
import org.springframework.stereotype.Component;
@javax.persistence.Entity
public class Person
{
@Id
private String name;
private int id;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
/*@Override
public String toString()
{
return "Person - "+name+", ID - "+id;
}*/
}
PersonDBHandler -
package com.example.demo;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Component;
public interface PersonDBHandler extends CrudRepository<Person, Integer>
{
}
我究竟做错了什么？
解决方案
正如错误消息所说
org.hibernate.TypeMismatchException：为类 com.example.demo.Person 提供了错误类型的 id。预期：类 java.lang.String，得到类 java.lang.Integer
你应该传递一个字符串 id 而不是一个整数。尝试将您的代码更改为
@RequestMapping("getPerson")
public ModelAndView getObject(@RequestParam String id)
{
ModelAndView mv = new ModelAndView("showPerson.jsp");
Person person = personDBHandlerObj.findById(id).orElse(new Person());
mv.addObject(person);
return mv;
}
如果这不起作用，您将希望在此处共享您的 Person 类定义和您的 personDBHandlerObj。
编辑：
现在您共享了其余代码，我们看到问题在于 Person 类。
@Id
private String name;
@Id 注释将名称定义为 id - 它是字符串类型。id 字段包含什么并不重要。
（a）在 id 上方注释 @Id （我认为如果你有一个 id 字段，你实际上不需要注释）或（b）使用名称作为 id 然后使用名称而不是整数进行查询。
推荐阅读
- c# - 如何从数据库中获取用户角色以填充 AuthorizeAttribute
- asp.net-core - asp.net core 2.x - 在哪里以及如何放置中央控制器功能？
- identityserver4 - 在 IdentityServer4 中，您可以在 client_credentials 身份验证中使用“*”作为请求的范围吗？
- powershell - 需要在不使用tail函数的情况下从文件末尾读取内容直到文件中的指定字符串
- angular - 由于更新导致的 Ionic v3 本机键盘使用问题
- java - 我可以在不执行测试的情况下计算测试总数吗？
- python - 如何使用 relativedelta 计算日期之间月份的差异
- google-cloud-platform - 谷歌云视觉类别检测
- design-patterns - 任何可用于订单管理的通用设计模式
- javascript - 获取 keydown 或 input 的值