使用 PostgreSQL 和 Spring Boot 时是否有规则禁止将其实体类命名为“User”？

Question

伙计们。我在 Spring boot 2.3.0 和 PostgreSQL 12 项目中遇到问题。我有一个名为User的实体类，其代码如下：

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@Entity\n@NoArgsConstructor\n@Data\n@AllArgsConstructor\n@Builder\npublic class User {\n    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)\n    private Long id;\n    private String username;\n    private String email;\n    private String firstName;\n    private String lastName;\n    private int age;\n}\n

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我的 application.properties 文件如下所示：

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spring.jpa.hibernate.ddl-auto=create-drop\nspring.jpa.hibernate.show-sql=true\nspring.datasource.url=jdbc:postgresql://localhost:5432/dbname\nspring.datasource.username=postgres\nspring.datasource.password=*********\n

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担心的是，当我执行我的项目时，我会遇到这样的错误：

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org.hibernate.tool.schema.spi.CommandAcceptanceException: Error executing DDL "drop table if exists user cascade" via JDBC Statement\n    at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:67) ~[hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.internal.SchemaDropperImpl.applySqlString(SchemaDropperImpl.java:375) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.internal.SchemaDropperImpl.applySqlStrings(SchemaDropperImpl.java:359) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.internal.SchemaDropperImpl.dropFromMetadata(SchemaDropperImpl.java:241) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.internal.SchemaDropperImpl.performDrop(SchemaDropperImpl.java:154) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.internal.SchemaDropperImpl.doDrop(SchemaDropperImpl.java:126) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.internal.SchemaDropperImpl.doDrop(SchemaDropperImpl.java:112) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.performDatabaseAction(SchemaManagementToolCoordinator.java:145) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.process(SchemaManagementToolCoordinator.java:73) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:314) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:468) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1249) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:58) [spring-orm-5.2.6.RELEASE.jar:5.2.6.RELEASE]\n    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) [spring-orm-5.2.6.RELEASE.jar:5.2.6.RELEASE]\n    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:391) [spring-orm-5.2.6.RELEASE.jar:5.2.6.RELEASE]\n    at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_252]\n    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[na:1.8.0_252]\n    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[na:1.8.0_252]\n    at java.lang.Thread.run(Thread.java:748) ~[na:1.8.0_252]\nCaused by: org.postgresql.util.PSQLException: ERREUR: erreur de syntaxe sur ou pr\xc3\xa8s de \xc2\xab user \xc2\xbb\n  Position\xc2\xa0: 22\n    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2533) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2268) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:313) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:448) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:369) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:310) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.jdbc.PgStatement.executeCachedSql(PgStatement.java:296) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:273) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:268) ~[postgresql-42.2.12.jar:42.2.12]\n    at com.zaxxer.hikari.pool.ProxyStatement.execute(ProxyStatement.java:95) ~[HikariCP-3.4.5.jar:na]\n    at com.zaxxer.hikari.pool.HikariProxyStatement.execute(HikariProxyStatement.java) ~[HikariCP-3.4.5.jar:na]\n    at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:54) ~[hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    ... 18 common frames omitted\n\n2020-05-24 06:16:33.429  WARN 13636 --- [         task-1] o.h.t.s.i.ExceptionHandlerLoggedImpl     : GenerationTarget encountered exception accepting command : Error executing DDL "create table user (id int8 generated by default as identity, age int4 not null, email varchar(255), first_name varchar(255), last_name varchar(255), username varchar(255), primary key (id))" via JDBC Statement\n\norg.hibernate.tool.schema.spi.CommandAcceptanceException: Error executing DDL "create table user (id int8 generated by default as identity, age int4 not null, email varchar(255), first_name varchar(255), last_name varchar(255), username varchar(255), primary key (id))" via JDBC Statement\n    at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:67) ~[hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.internal.SchemaCreatorImpl.applySqlString(SchemaCreatorImpl.java:439) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.internal.SchemaCreatorImpl.applySqlStrings(SchemaCreatorImpl.java:423) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.internal.SchemaCreatorImpl.createFromMetadata(SchemaCreatorImpl.java:314) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.internal.SchemaCreatorImpl.performCreation(SchemaCreatorImpl.java:166) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.internal.SchemaCreatorImpl.doCreation(SchemaCreatorImpl.java:135) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.internal.SchemaCreatorImpl.doCreation(SchemaCreatorImpl.java:121) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.performDatabaseAction(SchemaManagementToolCoordinator.java:156) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.process(SchemaManagementToolCoordinator.java:73) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:314) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:468) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1249) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:58) [spring-orm-5.2.6.RELEASE.jar:5.2.6.RELEASE]\n    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) [spring-orm-5.2.6.RELEASE.jar:5.2.6.RELEASE]\n    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:391) [spring-orm-5.2.6.RELEASE.jar:5.2.6.RELEASE]\n    at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_252]\n    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[na:1.8.0_252]\n    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[na:1.8.0_252]\n    at java.lang.Thread.run(Thread.java:748) ~[na:1.8.0_252]\nCaused by: org.postgresql.util.PSQLException: ERREUR: erreur de syntaxe sur ou pr\xc3\xa8s de \xc2\xab user \xc2\xbb\n  Position\xc2\xa0: 14\n    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2533) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2268) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:313) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:448) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:369) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:310) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.jdbc.PgStatement.executeCachedSql(PgStatement.java:296) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:273) ~[postgresql-42.2.12.jar:42.2.12]\n    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:268) ~[postgresql-42.2.12.jar:42.2.12]\n    at com.zaxxer.hikari.pool.ProxyStatement.execute(ProxyStatement.java:95) ~[HikariCP-3.4.5.jar:na]\n    at com.zaxxer.hikari.pool.HikariProxyStatement.execute(HikariProxyStatement.java) ~[HikariCP-3.4.5.jar:na]\n    at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:54) ~[hibernate-core-5.4.15.Final.jar:5.4.15.Final]\n    ... 18 common frames omitted\n

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但是，当我将班级名称更改为 Person 时

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@Entity\n@NoArgsConstructor\n@Data\n@AllArgsConstructor\n@Builder\npublic class Person {\n    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)\n    private Long id;\n    private String username;\n    private String email;\n    private String firstName;\n    private String lastName;\n    private int age;\n}\n

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我没有收到任何错误。有人可以通过以下方式帮助我解决这个问题，或者至少向我解释实体类 User 有什么问题。\n我还想补充一点，当有疑问时，我使用 MySQL 作为 PostgreSQL 的替代品测试了这段代码，并且没有错误。

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Answer 1

在 PostgreSQL 中user是一个保留关键字。使用引号，例如"user"表名使用@Table

@Table(name = "\"user\"")
public class User {

更好的表名命名是使用复数形式，例如users.

@Table(name = "users")
public class User {

Answer 2

user 是 SQL 和 Postgres 中的保留字。为了避免这种情况，您可以更改表名称或将表名称定义为@Table(name="`user`")

请检查 https://github.com/hibernate/hibernate-orm/blob/master/hibernate-core/src/test/java/org/hibernate/test/quote/User.java#L31