SpringDataJPA笔记(12)-Table注解详解

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发布于 2020-03-25 15:00:10

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发布于 2020-03-25 15:00:10

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SpringDataJPA笔记(12)-Table注解详解

由于在实际使用中，有时候会遇到需要访问同一台服务器上别的数据库，但是又不想配置多数据源的情况，Table注解给我们提供了这种便利的操作

JPA在根据实体自动生成数据表关联的时候，如果实体类与其映射的数据库表名不同名时，则需要使用到Table注解来标注映射的表名，除此之外还可以指定表所属的数据库目录或模式

首先来看一下Table注解的属性

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface Table {
    String name() default "";

    String catalog() default "";

    String schema() default "";

    UniqueConstraint[] uniqueConstraints() default {};

    Index[] indexes() default {};
}

name

name属性用于指定数据库表名称

若不指定则以实体类名称作为表名

例如如下代码

@Entity
@Table
public class TableEntity extends AnimalEntity<Long> {
}

生成的数据库名为table_entity

catalog

catalog属性用于指定数据库实例名

一般来说数据库实例在数据源配置的时候指定了，不配置就默认使用数据源配置的默认库

如果使用catalog属性设置名称时，若数据库存在和指定名称一致的实例，新创建的表将出现在该实例中

若不存在，则会在启动的时候抛出异常

 WARN 3304 --- [           main] o.h.t.s.i.ExceptionHandlerLoggedImpl     : GenerationTarget encountered exception accepting command : Error executing DDL "create table aaaadb.table_entity (id bigint not null auto_increment, age integer, gmt_create datetime not null, gmt_update datetime, height integer, name varchar(255), pid bigint, sex varchar(255), weight integer, primary key (id)) engine=InnoDB" via JDBC Statement

org.hibernate.tool.schema.spi.CommandAcceptanceException: Error executing DDL "create table aaaadb.table_entity (id bigint not null auto_increment, age integer, gmt_create datetime not null, gmt_update datetime, height integer, name varchar(255), pid bigint, sex varchar(255), weight integer, primary key (id)) engine=InnoDB" via JDBC Statement
	at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:67) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
	at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.applySqlString(AbstractSchemaMigrator.java:559) [hibernate-core-5.4.12.Final.jar:5.4.12.Final]
	at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.applySqlStrings(AbstractSchemaMigrator.java:504) [hibernate-core-5.4.12.Final.jar:5.4.12.Final]
	at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.createTable(AbstractSchemaMigrator.java:277) [hibernate-core-5.4.12.Final.jar:5.4.12.Final]
	at org.hibernate.tool.schema.internal.GroupedSchemaMigratorImpl.performTablesMigration(GroupedSchemaMigratorImpl.java:71) [hibernate-core-5.4.12.Final.jar:5.4.12.Final]
	at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.performMigration(AbstractSchemaMigrator.java:207) [hibernate-core-5.4.12.Final.jar:5.4.12.Final]
	at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.doMigration(AbstractSchemaMigrator.java:114) [hibernate-core-5.4.12.Final.jar:5.4.12.Final]
	at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.performDatabaseAction(SchemaManagementToolCoordinator.java:184) [hibernate-core-5.4.12.Final.jar:5.4.12.Final]
	at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.process(SchemaManagementToolCoordinator.java:73) [hibernate-core-5.4.12.Final.jar:5.4.12.Final]
	at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:314) [hibernate-core-5.4.12.Final.jar:5.4.12.Final]
	at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:468) [hibernate-core-5.4.12.Final.jar:5.4.12.Final]
	at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1237) [hibernate-core-5.4.12.Final.jar:5.4.12.Final]
	at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:58) [spring-orm-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) [spring-orm-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:391) [spring-orm-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:378) [spring-orm-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.afterPropertiesSet(LocalContainerEntityManagerFactoryBean.java:341) [spring-orm-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1855) [spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1792) [spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:595) [spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) [spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) [spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) [spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) [spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1108) ~[spring-context-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:868) ~[spring-context-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at com.mt.demo.jpa.SpringBootJpaDemoApplication.main(SpringBootJpaDemoApplication.java:10) ~[classes/:na]
Caused by: java.sql.SQLSyntaxErrorException: Unknown database 'aaaadb'
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:120) ~[mysql-connector-java-8.0.19.jar:8.0.19]
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) ~[mysql-connector-java-8.0.19.jar:8.0.19]
	at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) ~[mysql-connector-java-8.0.19.jar:8.0.19]
	at com.mysql.cj.jdbc.StatementImpl.executeInternal(StatementImpl.java:764) ~[mysql-connector-java-8.0.19.jar:8.0.19]
	at com.mysql.cj.jdbc.StatementImpl.execute(StatementImpl.java:648) ~[mysql-connector-java-8.0.19.jar:8.0.19]
	at com.zaxxer.hikari.pool.ProxyStatement.execute(ProxyStatement.java:95) ~[HikariCP-3.4.2.jar:na]
	at com.zaxxer.hikari.pool.HikariProxyStatement.execute(HikariProxyStatement.java) ~[HikariCP-3.4.2.jar:na]
	at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:54) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
	... 34 common frames omitted

uniqueConstraints

uniqueConstraints属性用于设定约束条件

例如

@Table(uniqueConstraints={@UniqueConstraint(name = "name_key", columnNames={"name"})})

查看数据库，对应SQL语句

UNIQUE KEY `name_key` (`name`)

这里建议指定name属性，以防止在不同情况下生成的name不同，引起一些问题

联合约束

@Table(uniqueConstraints={@UniqueConstraint(name = "name_age_key", columnNames={"name", "age"})})

对应数据库语句

UNIQUE KEY `name_age_key` (`name`,`age`)

indexes

表的索引，通过使用 @Index 注解来声明，仅在允许自动更新数据库表结构的场景中起到作用，默认没有其他额外的索引

例如，默认是不唯一的

@Table(indexes={@Index(name = "name_index", columnList="name")})

数据库对应SQL语句

KEY `name_index` (`name`)

如果添加了unique = true，则和约束的效果是一样的

@Table(indexes={@Index(name = "name_index", columnList="name", unique = true)})

数据库语句为

UNIQUE KEY `name_index` (`name`)

联合索引

@Table(indexes={@Index(name = "name_age_index", columnList="name, age", unique = true)})

同样和约束时一样的SQL

UNIQUE KEY `name_age_index` (`name`,`age`)

schema

目前schema在mysql中的作用未知，怎么设置好像都没有什么用处，后续有空再研究看看

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