问题：
组织。postgresql。util。PSQLException：错误：关系“app\u user”不存在
申高卓
我有一个使用spring boot和postgres的应用程序。我在尝试创建用户时遇到此错误。
当我在我的数据库上运行此查询时，我得到相同的错误：
select * from APP_USER
ERROR: relation "app_user" does not exist
LINE 1: select * from APP_USER
^
********** Error **********
ERROR: relation "app_user" does not exist
SQL state: 42P01
但如果我将其更改为：
select * from "APP_USER"
它起作用了。
如何在我的spring boot应用程序上配置它？
pom中的依赖项。xml：
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-security</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<dependency>
<groupId>org.thymeleaf.extras</groupId>
<artifactId>thymeleaf-extras-tiles2</artifactId>
<version>2.1.1.RELEASE</version>
</dependency>
<dependency>
<groupId>org.postgresql</groupId>
<artifactId>postgresql</artifactId>
<version>9.4-1201-jdbc41</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
application.properties：
spring.datasource.driverClassName=org.postgresql.Driver
spring.datasource.url=jdbc:postgresql://localhost:5432/boek
spring.datasource.username=postgres
spring.datasource.password=ABCD123$
spring.jpa.database-platform=org.hibernate.dialect.PostgreSQLDialect
spring.jpa.generate-ddl=false
#spring.jpa.hibernate.ddl-auto=create
spring.jpa.show-sql=true
我的实体：
@Entity
@Table(name = "APP_USER")
public class User implements Serializable {
private static final long serialVersionUID = -1152779434213289790L;
@Id
@Column(name="ID", nullable = false, updatable = false)
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;
@Column(name="NAME", nullable = false)
private String name;
@Column(name="USER_NAME", nullable = false, unique = true)
private String username;
@Column(name="PASSWORD", nullable = false)
private String password;
@Column(name="EMAIL", nullable = false, unique = true)
private String email;
@Column(name="ROLE", nullable = false)
private RoleEnum role;
我从表单中调用此操作：
<form role="form" action="#" th:action="@{/user/create}" th:object="${userDTO}" method="post">
这是我的控制器：
@RequestMapping(value = "/user/create", method = RequestMethod.POST)
public String handleUserCreateForm(@Valid @ModelAttribute("form") UserDTO form, BindingResult bindingResult) {
if (bindingResult.hasErrors()) {
return "user_create";
}
try {
userService.create(form);
} catch (DataIntegrityViolationException e) {
bindingResult.reject("email.exists", "Email already exists");
return "user_create";
}
return "redirect:/users";
}
记录错误的验证器：
private void validateEmail(Errors errors, UserDTO form) {
if (userService.getUserByEmail(form.getEmail()).isPresent()) {
errors.reject("email.exists", "User with this email already exists");
}
}
UserServiceImpl（@服务）：
@Override
public Optional<User> getUserByEmail(String email) {
return userRepository.findOneByEmail(email);
}
存储库是一个粗糙的存储接口，没有实现：
@Repository
public interface UserRepository extends CrudRepository<User, Serializable> {
Optional<User> findOneByEmail(String email);
}
通过调试验证器，我可以得到以下堆栈：
org.springframework.dao.InvalidDataAccessResourceUsageException: could not extract ResultSet; SQL [n/a]; nested exception is org.hibernate.exception.SQLGrammarException: could not extract ResultSet
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:238)
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:221)
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:417)
at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:59)
at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:213)
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:147)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodIntercceptor.invoke(CrudMethodMetadataPostProcessor.java:122)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)
at com.sun.proxy.$Proxy75.findOneByEmail(Unknown Source)
at com.myapp.service.impl.UserServiceImpl.getUserByEmail(UserServiceImpl.java:32)
at com.myapp.model.validator.UserValidator.validateEmail(UserValidator.java:40)
at com.myapp.model.validator.UserValidator.validate(UserValidator.java:30)
at org.springframework.validation.DataBinder.validate(DataBinder.java:785)
at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.validateIfApplicable(ModelAttributeMethodProcessor.java:164)
at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.resolveArgument(ModelAttributeMethodProcessor.java:111)
at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:77)
at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:162)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:129)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:869)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.boot.actuate.autoconfigure.EndpointWebMvcAutoConfiguration$ApplicationContextHeaderFilter.doFilterInternal(EndpointWebMvcAutoConfiguration.java:295)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:102)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:154)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:110)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.csrf.CsrfFilter.doFilterInternal(CsrfFilter.java:105)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:57)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:50)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:85)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.boot.actuate.autoconfigure.MetricsFilter.doFilterInternal(MetricsFilter.java:68)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1521)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1478)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.hibernate.exception.SQLGrammarException: could not extract ResultSet
at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:123)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:126)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:112)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:91)
at org.hibernate.loader.Loader.getResultSet(Loader.java:2066)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1863)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1839)
at org.hibernate.loader.Loader.doQuery(Loader.java:910)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:355)
at org.hibernate.loader.Loader.doList(Loader.java:2554)
at org.hibernate.loader.Loader.doList(Loader.java:2540)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2370)
at org.hibernate.loader.Loader.list(Loader.java:2365)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:497)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:387)
at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:236)
at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1300)
at org.hibernate.internal.QueryImpl.list(QueryImpl.java:103)
at org.hibernate.jpa.internal.QueryImpl.list(QueryImpl.java:573)
at org.hibernate.jpa.internal.QueryImpl.getSingleResult(QueryImpl.java:495)
at org.hibernate.jpa.criteria.compile.CriteriaQueryTypeQueryAdapter.getSingleResult(CriteriaQueryTypeQueryAdapter.java:71)
at org.springframework.data.jpa.repository.query.JpaQueryExecution$SingleEntityExecution.doExecute(JpaQueryExecution.java:202)
at org.springframework.data.jpa.repository.query.JpaQueryExecution.execute(JpaQueryExecution.java:74)
at org.springframework.data.jpa.repository.query.AbstractJpaQuery.doExecute(AbstractJpaQuery.java:99)
at org.springframework.data.jpa.repository.query.AbstractJpaQuery.execute(AbstractJpaQuery.java:90)
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:415)
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:393)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.data.repository.core.support.RepositoryFactorySupport$DefaultMethodInvokingMethodInterceptor.invoke(RepositoryFactorySupport.java:506)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136)
... 98 more
Caused by: org.postgresql.util.PSQLException: ERROR: relation "app_user" does not exist
Posição: 177
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2270)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1998)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:255)
at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:570)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:420)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:305)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:82)
... 129 more
谢谢你的帮助！
共有3个答案
归泽宇
也可能是由于hibernate配置中缺少默认模式声明。
Properties jpaProperties = new Properties();
..
jpaProperties.put("hibernate.default_schema", "my_default_schema");
entityManagerFactoryBean.setJpaProperties(jpaProperties);
奚瑾瑜
同时提供架构名称和表名称。它为我解决了这个问题。
@Entity
@Table(name = "APP_USER",schema="xxxxx")
public class User implements Serializable {
private static final long serialVersionUID = -1152779434213289790L;
@Id
@Column(name="ID", nullable = false, updatable = false)
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;
@Column(name="NAME", nullable = false)
private String name;
@Column(name="USER_NAME", nullable = false, unique = true)
private String username;
@Column(name="PASSWORD", nullable = false)
private String password;
@Column(name="EMAIL", nullable = false, unique = true)
private String email;
@Column(name="ROLE", nullable = false)
private RoleEnum role;
陆宏壮
PostgreSQL遵循SQL标准，在这种情况下，这意味着标识符（表名、列名等）被强制为小写，除非它们被引用。因此，当您创建这样的表时：
CREATE TABLE APP_USER ...
您实际上得到了一个表app\u user。你显然做到了：
CREATE TABLE "APP_USER" ...
然后你会得到一个表"APP_USER"。
在Spring中，您为表名指定一个常规字符串，用大写字母表示，但它会拼接成对PostgreSQL服务器的查询，不带引号。您可以通过读取PostgreSQL日志文件来检查这一点：它应该显示Spring生成的查询，然后在消息顶部显示错误。
由于您几乎无法控制Spring如何从实体构造查询，因此最好使用SQL标准小写标识符。
类似资料：
-
由于一些奇怪的原因，hibernate生成的查询不适用于postgres，它告诉它无法找到关系/表，即使在架构中有有效的表？这个答案没有帮助。 例外情况： HQL公司 生成SQL 此查询工作正常： 基于胶片实体注释的映射： 解决方案/黑客： 评论后，问题消失了。
-
问题内容： 我正在尝试在PostgreSQL 8.4.2 DB上运行hibernate模式。每当我尝试运行一个简单的Java代码，例如： 我收到以下错误： 由于我将选项hibernate.show_sql选项设置为true，因此可以看到hibernate尝试运行以下SQL命令： 实际上，它至少应运行以下命令： 有谁知道我需要进行哪些更改才能使Hibernate为PostgreSQL生成正确的SQL
-
我使用PostgreSQL 10、Spring Boot 2.2.7.Release和pgAdmin 4来实现Postgres GUI 我有以下实体类： 我已经使用GUI PGADMIN4为ID列“TB03_TABLE_A_SEQ”创建了表“TB03_TABLE_A”和序列 我哪里出问题了？请救命！ 提前感谢！
-
我正在使用java web服务（apache axis）和JDBC连接来连接postgres数据库，以获取数据。但突然间，在大多数情况下，我都遇到了
-
我在heroku上创建了java（Spring）应用程序，并将postgreql连接到它。当我在应用程序上发出请求时，日志显示 WARN 4-[io-14883-exec-3]o . h . engine . JDBC . SPI . sqlexception helper:SQL错误:0，SQLState:42p 01 app[web.1]:2016-12-11 12:13:09.942错误4-
-
我得到了这个例外 在下面的方法中，身份验证是使用ldap完成的。如果发生不正确的用户名或密码或连接异常，将捕获以下异常之一。 我的问题是这个。我将异常发送到下面的方法，并将异常转换为String并将其添加到我的实体类中。 这是我的实体类： 但是当操作发生时，我得到以下异常。 我研究了一些东西，上面说是这样的。 但我不明白的是，我在这里得到的值是空的？我知道在调试时，Entity类会将异常消息放在l