本文中我们会讲解如何在Spring Boot JPA中实现class和数据表格的映射。
默认实现
Spring Boot JPA底层是用Hibernate实现的，默认情况下，数据库表格的名字是相应的class名字的首字母大写。命名的定义是通过接口ImplicitNamingStrategy来定义的：
/** * Determine the implicit name of an entity's primary table. * * @param source The source information * * @return The implicit table name. */ public Identifier determinePrimaryTableName(ImplicitEntityNameSource source);
我们看下它的实现ImplicitNamingStrategyJpaCompliantImpl：
@Override
public Identifier determinePrimaryTableName(ImplicitEntityNameSource source) {
if ( source == null ) {
// should never happen, but to be defensive...
throw new HibernateException( "Entity naming information was not provided." );
}
String tableName = transformEntityName( source.getEntityNaming() );
if ( tableName == null ) {
// todo : add info to error message - but how to know what to write since we failed to interpret the naming source
throw new HibernateException( "Could not determine primary table name for entity" );
}
return toIdentifier( tableName, source.getBuildingContext() );
}
如果我们需要修改系统的默认实现，则可以实现接口PhysicalNamingStrategy：
public interface PhysicalNamingStrategy {
public Identifier toPhysicalCatalogName(Identifier name, JdbcEnvironment jdbcEnvironment);
public Identifier toPhysicalSchemaName(Identifier name, JdbcEnvironment jdbcEnvironment);
public Identifier toPhysicalTableName(Identifier name, JdbcEnvironment jdbcEnvironment);
public Identifier toPhysicalSequenceName(Identifier name, JdbcEnvironment jdbcEnvironment);
public Identifier toPhysicalColumnName(Identifier name, JdbcEnvironment jdbcEnvironment);
}
使用@Table自定义表格名字
我们可以在@Entity中使用@Table来自定义映射的表格名字：
@Entity
@Table(name = "ARTICLES")
public class Article {
// ...
}
当然，我们可以将整个名字写在静态变量中：
@Entity
@Table(name = Article.TABLE_NAME)
public class Article {
public static final String TABLE_NAME= "ARTICLES";
// ...
}
在JPQL Queries中重写表格名字
通常我们在@Query中使用JPQL时可以这样用：
@Query(“select * from Article”)
其中Article默认是Entity类的Class名称，我们也可以这样来修改它：
@Entity(name = "MyArticle")
这时候我们可以这样定义JPQL：
@Query(“select * from MyArticle”)
