在使用 PostgreSQL 和 Spring Boot 时，是不是有禁止将其实体类命名为“用户”的规则？
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【中文标题】在使用 PostgreSQL 和 Spring Boot 时，是不是有禁止将其实体类命名为“用户”的规则？【英文标题】：Is there a rule that forbids to name its entity class "User" when working with PostgreSQL and Spring Boot?在使用 PostgreSQL 和 Spring Boot 时，是否有禁止将其实体类命名为“用户”的规则？ 【发布时间】：2020-09-10 20:58:42 【问题描述】：伙计们。我遇到了 Spring boot 2.3.0 和 PostgreSQL 12 项目的问题。我有一个名为 User 的实体类，其代码如下：
@Entity
@NoArgsConstructor
@Data
@AllArgsConstructor
@Builder
public class User
@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String username;
private String email;
private String firstName;
private String lastName;
private int age;
我的 application.properties 文件如下所示：
spring.jpa.hibernate.ddl-auto=create-drop
spring.jpa.hibernate.show-sql=true
spring.datasource.url=jdbc:postgresql://localhost:5432/dbname
spring.datasource.username=postgres
spring.datasource.password=*********
担心的是，当我执行我的项目时，我会遇到这样的错误：
org.hibernate.tool.schema.spi.CommandAcceptanceException: Error executing DDL "drop table if exists user cascade" via JDBC Statement
at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:67) ~[hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.internal.SchemaDropperImpl.applySqlString(SchemaDropperImpl.java:375) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.internal.SchemaDropperImpl.applySqlStrings(SchemaDropperImpl.java:359) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.internal.SchemaDropperImpl.dropFromMetadata(SchemaDropperImpl.java:241) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.internal.SchemaDropperImpl.performDrop(SchemaDropperImpl.java:154) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.internal.SchemaDropperImpl.doDrop(SchemaDropperImpl.java:126) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.internal.SchemaDropperImpl.doDrop(SchemaDropperImpl.java:112) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.performDatabaseAction(SchemaManagementToolCoordinator.java:145) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.process(SchemaManagementToolCoordinator.java:73) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:314) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:468) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1249) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:58) [spring-orm-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) [spring-orm-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:391) [spring-orm-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_252]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[na:1.8.0_252]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[na:1.8.0_252]
at java.lang.Thread.run(Thread.java:748) ~[na:1.8.0_252]
Caused by: org.postgresql.util.PSQLException: ERREUR: erreur de syntaxe sur ou près de « user »
Position : 22
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2533) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2268) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:313) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:448) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:369) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:310) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.jdbc.PgStatement.executeCachedSql(PgStatement.java:296) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:273) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:268) ~[postgresql-42.2.12.jar:42.2.12]
at com.zaxxer.hikari.pool.ProxyStatement.execute(ProxyStatement.java:95) ~[HikariCP-3.4.5.jar:na]
at com.zaxxer.hikari.pool.HikariProxyStatement.execute(HikariProxyStatement.java) ~[HikariCP-3.4.5.jar:na]
at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:54) ~[hibernate-core-5.4.15.Final.jar:5.4.15.Final]
... 18 common frames omitted
2020-05-24 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
org.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
at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:67) ~[hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.internal.SchemaCreatorImpl.applySqlString(SchemaCreatorImpl.java:439) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.internal.SchemaCreatorImpl.applySqlStrings(SchemaCreatorImpl.java:423) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.internal.SchemaCreatorImpl.createFromMetadata(SchemaCreatorImpl.java:314) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.internal.SchemaCreatorImpl.performCreation(SchemaCreatorImpl.java:166) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.internal.SchemaCreatorImpl.doCreation(SchemaCreatorImpl.java:135) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.internal.SchemaCreatorImpl.doCreation(SchemaCreatorImpl.java:121) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.performDatabaseAction(SchemaManagementToolCoordinator.java:156) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.process(SchemaManagementToolCoordinator.java:73) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:314) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:468) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1249) [hibernate-core-5.4.15.Final.jar:5.4.15.Final]
at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:58) [spring-orm-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) [spring-orm-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:391) [spring-orm-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_252]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[na:1.8.0_252]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[na:1.8.0_252]
at java.lang.Thread.run(Thread.java:748) ~[na:1.8.0_252]
Caused by: org.postgresql.util.PSQLException: ERREUR: erreur de syntaxe sur ou près de « user »
Position : 14
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2533) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2268) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:313) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:448) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:369) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:310) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.jdbc.PgStatement.executeCachedSql(PgStatement.java:296) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:273) ~[postgresql-42.2.12.jar:42.2.12]
at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:268) ~[postgresql-42.2.12.jar:42.2.12]
at com.zaxxer.hikari.pool.ProxyStatement.execute(ProxyStatement.java:95) ~[HikariCP-3.4.5.jar:na]
at com.zaxxer.hikari.pool.HikariProxyStatement.execute(HikariProxyStatement.java) ~[HikariCP-3.4.5.jar:na]
at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:54) ~[hibernate-core-5.4.15.Final.jar:5.4.15.Final]
... 18 common frames omitted
但是，当我更改班级名称时，例如对人
@Entity
@NoArgsConstructor
@Data
@AllArgsConstructor
@Builder
public class Person
@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String username;
private String email;
private String firstName;
private String lastName;
private int age;
我没有收到任何错误。有人可以通过以下方式帮助我，或者至少向我解释实体类 User 有什么问题。 我还想补充一点，当有疑问时，我用 mysql 作为 PostgreSQL 的替代品测试了这段代码，没有出错。
【问题讨论】：
【参考方案1】：在 PostgreSQL 中，user 是保留关键字。使用 "user" 之类的引号作为表名，使用 @Table
@Table(name = "\"user\"")
public class User
更好的表名命名是使用复数形式，如users。
@Table(name = "users")
public class User
【讨论】：
【参考方案2】：user 是 SQL 和 Postgres 中的保留字。为避免这种情况，要么更改表名，要么将表名定义为@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
【讨论】：
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