JPA WrongArgumentException：SQL 字符串不能为 NULL：尽管 CrudRepository 保存函数接收填充的实体
JPA WrongArgumentException: SQL String cannot be NULL: despite CrudRepository save function recieving populated entity
我正在制作一个 Spring 引导程序 (2.1.9) api，并且正在使用 Postman POST 一些 JSON 到我的控制器中的一个函数将其转换为实体（作者）。我的控制器对象正确接收对象及其字段，将其传递到我的服务对象并将其传递到我的数据访问对象。
调用 CrudRepository save(S entity) 函数时出现问题，尽管打印字段并验证它们不为空，但我收到一个异常，声称我的字段确实为空。该实体未添加到数据库中。
我尝试添加 auto_increment，更改 generationType。我试过在 Postman 中为 Id 发送 null，我试过在 Postman 中不发送 Id。我不确定如何解决此问题，因为删除 @GeneratedValue 似乎可行，但并不理想，因为 save() 会根据
（注意：我还没有做任何适当的 http 状态，我想在那之前让它工作）
我的控制器：
@RestController
@RequestMapping(value = "/lms/admin*")
public class AdminController
{
@Autowired
AdminService admin;
@PostMapping(path = "/author", produces = "application/json", consumes="application/json")
public ResponseEntity<?> createAuthor(@RequestBody Author author)
{
return new ResponseEntity<>(admin.createAuthor(author),HttpStatus.OK);
}
/*other CRUD operations*/
}
我的服务：
@Component
public class AdminService
{
@Autowired
private AuthorDataAccess authorDao;
public Author createAuthor(Author author)
{
System.out.println(author.toString());
return authorDao.save(author);
}
/*other service functions*/
}
我的作者数据访问
@Component
public interface AuthorDataAccess extends CrudRepository<Author, Integer>
{
}
我的作者实体：
@Entity
@Table(name = "tbl_author", schema = "library")
public class Author implements Serializable
{
private static final long serialVersionUID = 3002288345129007776L;
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE)
@Column(updatable = false)
private Integer authorId;
private String authorName;
public Author(){}
public Author(String authorName)
{
this.authorName = authorName;
}
public Author(Integer authorId, String authorName)
{
this.authorId = authorId;
this.authorName = authorName;
}
/*hashcode, equals, toString, getters, setters*/
}
mySQL Table:
CREATE TABLE IF NOT EXISTS `library`.`tbl_author` (
`authorId` INT(11) NOT NULL,
`authorName` VARCHAR(45) NOT NULL,
PRIMARY KEY (`authorId`))
ENGINE = InnoDB
DEFAULT CHARACTER SET = latin1;
我的application.properties:
server.port=8100
spring.datasource.url=jdbc:mysql://localhost:3306/library
spring.datasource.username=root
spring.datasource.password=root
spring.application.name=admin
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5Dialect
spring.jpa.hibernate.naming.physical-strategy=org.hibernate.boot.model.naming.PhysicalNamingStrategyStandardImpl
spring.jpa.hibernate.use-new-id-generator-mappings= false
最后，我的 pom.xml:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.9.RELEASE</version>
<relativePath /> <!-- lookup parent from repository -->
</parent>
<groupId>com.ss</groupId>
<artifactId>lms</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>lms</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.17</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.19.1</version>
</plugin>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
这是我在 运行 后看到的确切错误消息：mvn clean package 和 java -jar ./taget/<something>.jar
2019-10-13 15:37:22.037 WARN 24581 --- [nio-8100-exec-1] o.h.engine.jdbc.spi.SqlExceptionHelper : SQL Error: 0, SQLState: S1009
2019-10-13 15:37:22.037 ERROR 24581 --- [nio-8100-exec-1] o.h.engine.jdbc.spi.SqlExceptionHelper : SQL String cannot be NULL
2019-10-13 15:37:22.073 ERROR 24581 --- [nio-8100-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.orm.jpa.JpaSystemException: could not prepare statement; nested exception is org.hibernate.exception.GenericJDBCException: could not prepare statement] with root cause
com.mysql.cj.exceptions.WrongArgumentException: SQL String cannot be NULL
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_222]
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_222]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_222]
at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_222]
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:85) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.AbstractPreparedQuery.checkNullOrEmptyQuery(AbstractPreparedQuery.java:159) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.jdbc.ClientPreparedStatement.<init>(ClientPreparedStatement.java:215) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.jdbc.ClientPreparedStatement.<init>(ClientPreparedStatement.java:193) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.jdbc.ClientPreparedStatement.getInstance(ClientPreparedStatement.java:134) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.jdbc.ConnectionImpl.clientPrepareStatement(ConnectionImpl.java:669) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.jdbc.ConnectionImpl.prepareStatement(ConnectionImpl.java:1653) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.jdbc.ConnectionImpl.prepareStatement(ConnectionImpl.java:1573) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.zaxxer.hikari.pool.ProxyConnection.prepareStatement(ProxyConnection.java:311) ~[HikariCP-3.2.0.jar!/:na]
at com.zaxxer.hikari.pool.HikariProxyConnection.prepareStatement(HikariProxyConnection.java) ~[HikariCP-3.2.0.jar!/:na]
at org.hibernate.engine.jdbc.internal.StatementPreparerImpl.doPrepare(StatementPreparerImpl.java:90) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$StatementPreparationTemplate.prepareStatement(StatementPreparerImpl.java:176) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.engine.jdbc.internal.StatementPreparerImpl.prepareStatement(StatementPreparerImpl.java:75) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.id.SequenceGenerator.generateHolder(SequenceGenerator.java:114) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.id.SequenceHiLoGenerator.getNextValue(SequenceHiLoGenerator.java:71) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.id.enhanced.LegacyHiLoAlgorithmOptimizer.generate(LegacyHiLoAlgorithmOptimizer.java:60) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.id.SequenceHiLoGenerator.generate(SequenceHiLoGenerator.java:67) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:119) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:192) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:135) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:62) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:804) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:789) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_222]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_222]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_222]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_222]
at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:351) ~[spring-orm-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at com.sun.proxy.$Proxy83.persist(Unknown Source) ~[na:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_222]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_222]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_222]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_222]
at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:310) ~[spring-orm-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at com.sun.proxy.$Proxy83.persist(Unknown Source) ~[na:na]
at org.springframework.data.jpa.repository.support.SimpleJpaRepository.save(SimpleJpaRepository.java:535) ~[spring-data-jpa-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_222]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_222]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_222]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_222]
at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:359) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:200) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:644) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:608) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.lambda$invoke(RepositoryFactorySupport.java:595) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:595) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:59) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:295) ~[spring-tx-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:98) ~[spring-tx-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139) ~[spring-tx-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:144) ~[spring-data-jpa-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$ExposeRepositoryInvocationInterceptor.invoke(CrudMethodMetadataPostProcessor.java:364) ~[spring-data-jpa-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:93) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:61) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at com.sun.proxy.$Proxy85.save(Unknown Source) ~[na:na]
at com.ss.lms.service.AdminService.createAuthor(AdminService.java:48) ~[classes!/:0.0.1-SNAPSHOT]
at com.ss.lms.controller.AdminController.createAuthor(AdminController.java:54) ~[classes!/:0.0.1-SNAPSHOT]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_222]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_222]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_222]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_222]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:893) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:798) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:660) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:94) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:526) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1589) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_222]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_222]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_222]
更新
向控制器发送一个 ID 不存在的作者，仍然不起作用，这里是 sql：
Author [authorId=4, authorName=myName]
Hibernate: select author0_.authorId as authorId1_0_0_, author0_.authorName as authorNa2_0_0_ from tbl_author author0_ where author0_.authorId=?
Hibernate: null
已解决
我使用以下方法解决了我的问题：
@GeneratedValue(strategy = GenerationType.IDENTITY)
并使用 auto_incrememnt 约束。虽然据我了解，这并不理想，因为要获取创建的实体的 ID，需要再次遍历 table。如果有人知道如何避免这种情况，请告诉我！
the database existed before I started creating the api
要使 strategy = GenerationType.SEQUENCE 正常工作，必须存在可用于 authorId 列的数据库序列。此外，您需要使用 @SequenceGenerator 注释指定其名称，以便 JPA 知道如何找到它：
@GeneratedValue(generator = "authorIdGenerator", strategy = GenerationType.SEQUENCE)
@SequenceGenerator(name = "authorIdGenerator", sequenceName = <existing_sequence_name_in_the_db>, allocationSize=<correct_allocation_size_for_the_sequence>)
to get the ID of the created entity, it requires the table to be traversed again
为了获取 ID，Hibernate 需要将更改刷新到 DB，因为它是生成 ID 的 DB。如果您使用 JpaRepository 而不是 CrudRepository 作为基本接口，您将能够改为调用 saveAndFlush 并读取生成的 ID。
我正在制作一个 Spring 引导程序 (2.1.9) api，并且正在使用 Postman POST 一些 JSON 到我的控制器中的一个函数将其转换为实体（作者）。我的控制器对象正确接收对象及其字段，将其传递到我的服务对象并将其传递到我的数据访问对象。
调用 CrudRepository save(S entity) 函数时出现问题，尽管打印字段并验证它们不为空，但我收到一个异常，声称我的字段确实为空。该实体未添加到数据库中。
我尝试添加 auto_increment，更改 generationType。我试过在 Postman 中为 Id 发送 null，我试过在 Postman 中不发送 Id。我不确定如何解决此问题，因为删除 @GeneratedValue 似乎可行，但并不理想，因为 save() 会根据
（注意：我还没有做任何适当的 http 状态，我想在那之前让它工作）
我的控制器：
@RestController
@RequestMapping(value = "/lms/admin*")
public class AdminController
{
@Autowired
AdminService admin;
@PostMapping(path = "/author", produces = "application/json", consumes="application/json")
public ResponseEntity<?> createAuthor(@RequestBody Author author)
{
return new ResponseEntity<>(admin.createAuthor(author),HttpStatus.OK);
}
/*other CRUD operations*/
}
我的服务：
@Component
public class AdminService
{
@Autowired
private AuthorDataAccess authorDao;
public Author createAuthor(Author author)
{
System.out.println(author.toString());
return authorDao.save(author);
}
/*other service functions*/
}
我的作者数据访问
@Component
public interface AuthorDataAccess extends CrudRepository<Author, Integer>
{
}
我的作者实体：
@Entity
@Table(name = "tbl_author", schema = "library")
public class Author implements Serializable
{
private static final long serialVersionUID = 3002288345129007776L;
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE)
@Column(updatable = false)
private Integer authorId;
private String authorName;
public Author(){}
public Author(String authorName)
{
this.authorName = authorName;
}
public Author(Integer authorId, String authorName)
{
this.authorId = authorId;
this.authorName = authorName;
}
/*hashcode, equals, toString, getters, setters*/
}
mySQL Table:
CREATE TABLE IF NOT EXISTS `library`.`tbl_author` (
`authorId` INT(11) NOT NULL,
`authorName` VARCHAR(45) NOT NULL,
PRIMARY KEY (`authorId`))
ENGINE = InnoDB
DEFAULT CHARACTER SET = latin1;
我的application.properties:
server.port=8100
spring.datasource.url=jdbc:mysql://localhost:3306/library
spring.datasource.username=root
spring.datasource.password=root
spring.application.name=admin
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5Dialect
spring.jpa.hibernate.naming.physical-strategy=org.hibernate.boot.model.naming.PhysicalNamingStrategyStandardImpl
spring.jpa.hibernate.use-new-id-generator-mappings= false
最后，我的 pom.xml:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.9.RELEASE</version>
<relativePath /> <!-- lookup parent from repository -->
</parent>
<groupId>com.ss</groupId>
<artifactId>lms</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>lms</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.17</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.19.1</version>
</plugin>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
这是我在 运行 后看到的确切错误消息：mvn clean package 和 java -jar ./taget/<something>.jar
2019-10-13 15:37:22.037 WARN 24581 --- [nio-8100-exec-1] o.h.engine.jdbc.spi.SqlExceptionHelper : SQL Error: 0, SQLState: S1009
2019-10-13 15:37:22.037 ERROR 24581 --- [nio-8100-exec-1] o.h.engine.jdbc.spi.SqlExceptionHelper : SQL String cannot be NULL
2019-10-13 15:37:22.073 ERROR 24581 --- [nio-8100-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.orm.jpa.JpaSystemException: could not prepare statement; nested exception is org.hibernate.exception.GenericJDBCException: could not prepare statement] with root cause
com.mysql.cj.exceptions.WrongArgumentException: SQL String cannot be NULL
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_222]
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_222]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_222]
at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_222]
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:85) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.AbstractPreparedQuery.checkNullOrEmptyQuery(AbstractPreparedQuery.java:159) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.jdbc.ClientPreparedStatement.<init>(ClientPreparedStatement.java:215) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.jdbc.ClientPreparedStatement.<init>(ClientPreparedStatement.java:193) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.jdbc.ClientPreparedStatement.getInstance(ClientPreparedStatement.java:134) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.jdbc.ConnectionImpl.clientPrepareStatement(ConnectionImpl.java:669) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.jdbc.ConnectionImpl.prepareStatement(ConnectionImpl.java:1653) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.mysql.cj.jdbc.ConnectionImpl.prepareStatement(ConnectionImpl.java:1573) ~[mysql-connector-java-8.0.17.jar!/:8.0.17]
at com.zaxxer.hikari.pool.ProxyConnection.prepareStatement(ProxyConnection.java:311) ~[HikariCP-3.2.0.jar!/:na]
at com.zaxxer.hikari.pool.HikariProxyConnection.prepareStatement(HikariProxyConnection.java) ~[HikariCP-3.2.0.jar!/:na]
at org.hibernate.engine.jdbc.internal.StatementPreparerImpl.doPrepare(StatementPreparerImpl.java:90) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$StatementPreparationTemplate.prepareStatement(StatementPreparerImpl.java:176) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.engine.jdbc.internal.StatementPreparerImpl.prepareStatement(StatementPreparerImpl.java:75) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.id.SequenceGenerator.generateHolder(SequenceGenerator.java:114) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.id.SequenceHiLoGenerator.getNextValue(SequenceHiLoGenerator.java:71) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.id.enhanced.LegacyHiLoAlgorithmOptimizer.generate(LegacyHiLoAlgorithmOptimizer.java:60) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.id.SequenceHiLoGenerator.generate(SequenceHiLoGenerator.java:67) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:119) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:192) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:135) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:62) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:804) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:789) ~[hibernate-core-5.3.12.Final.jar!/:5.3.12.Final]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_222]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_222]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_222]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_222]
at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:351) ~[spring-orm-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at com.sun.proxy.$Proxy83.persist(Unknown Source) ~[na:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_222]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_222]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_222]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_222]
at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:310) ~[spring-orm-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at com.sun.proxy.$Proxy83.persist(Unknown Source) ~[na:na]
at org.springframework.data.jpa.repository.support.SimpleJpaRepository.save(SimpleJpaRepository.java:535) ~[spring-data-jpa-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_222]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_222]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_222]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_222]
at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:359) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:200) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:644) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:608) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.lambda$invoke(RepositoryFactorySupport.java:595) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:595) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:59) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:295) ~[spring-tx-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:98) ~[spring-tx-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139) ~[spring-tx-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:144) ~[spring-data-jpa-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$ExposeRepositoryInvocationInterceptor.invoke(CrudMethodMetadataPostProcessor.java:364) ~[spring-data-jpa-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:93) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:61) ~[spring-data-commons-2.1.11.RELEASE.jar!/:2.1.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at com.sun.proxy.$Proxy85.save(Unknown Source) ~[na:na]
at com.ss.lms.service.AdminService.createAuthor(AdminService.java:48) ~[classes!/:0.0.1-SNAPSHOT]
at com.ss.lms.controller.AdminController.createAuthor(AdminController.java:54) ~[classes!/:0.0.1-SNAPSHOT]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_222]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_222]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_222]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_222]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:893) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:798) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:660) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:94) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.10.RELEASE.jar!/:5.1.10.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:526) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1589) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_222]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_222]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.26.jar!/:9.0.26]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_222]
更新
向控制器发送一个 ID 不存在的作者，仍然不起作用，这里是 sql：
Author [authorId=4, authorName=myName]
Hibernate: select author0_.authorId as authorId1_0_0_, author0_.authorName as authorNa2_0_0_ from tbl_author author0_ where author0_.authorId=?
Hibernate: null
已解决
我使用以下方法解决了我的问题：
@GeneratedValue(strategy = GenerationType.IDENTITY)
并使用 auto_incrememnt 约束。虽然据我了解，这并不理想，因为要获取创建的实体的 ID，需要再次遍历 table。如果有人知道如何避免这种情况，请告诉我！
the database existed before I started creating the api
要使 strategy = GenerationType.SEQUENCE 正常工作，必须存在可用于 authorId 列的数据库序列。此外，您需要使用 @SequenceGenerator 注释指定其名称，以便 JPA 知道如何找到它：
@GeneratedValue(generator = "authorIdGenerator", strategy = GenerationType.SEQUENCE)
@SequenceGenerator(name = "authorIdGenerator", sequenceName = <existing_sequence_name_in_the_db>, allocationSize=<correct_allocation_size_for_the_sequence>)
to get the ID of the created entity, it requires the table to be traversed again
为了获取 ID，Hibernate 需要将更改刷新到 DB，因为它是生成 ID 的 DB。如果您使用 JpaRepository 而不是 CrudRepository 作为基本接口，您将能够改为调用 saveAndFlush 并读取生成的 ID。