迁移到 Hibernate 5

Question

我正在将应用程序从 Hibernate 4.3 迁移到 Hibernate 5.0.1-Final 我在 Postgres 9.4.4 中使用 ImplicitNamingStrategyComponentPathImpl 作为我的 hibernate.implicit_naming_strategy，我的公司使用 hibernate.hbm2ddl.auto = update 进行部署（我知道这是一种不好的做法，但无能为力）

会话工厂初始化时，抛出以下错误。显然生成的别名对于 Postgres 来说太长了。我们如何处理这种情况？我已经尝试分配 @Table(name=..) 注释来解决这个问题，但随着从那一点开始的每个关系都变得糟糕，情况变得更糟。

Caused by: org.hibernate.tool.schema.spi.SchemaManagementException: Unable to execute schema management to JDBC target [create table public.ReferenceDocumentVersion_ReferenceDocumentSourceFilesStoreDescriptor (ReferenceDocumentVersion_unid uuid not null, sourceFilesStore_filesDescriptorMap_unid uuid not null, filesDescriptorMap_KEY text not null, primary key (ReferenceDocumentVersion_unid, filesDescriptorMap_KEY))]
    at org.hibernate.tool.schema.internal.TargetDatabaseImpl.accept(TargetDatabaseImpl.java:59)
    at org.hibernate.tool.schema.internal.SchemaMigratorImpl.applySqlString(SchemaMigratorImpl.java:371)
    at org.hibernate.tool.schema.internal.SchemaMigratorImpl.applySqlStrings(SchemaMigratorImpl.java:360)
    at org.hibernate.tool.schema.internal.SchemaMigratorImpl.createTable(SchemaMigratorImpl.java:181)
    at org.hibernate.tool.schema.internal.SchemaMigratorImpl.doMigrationToTargets(SchemaMigratorImpl.java:134)
    at org.hibernate.tool.schema.internal.SchemaMigratorImpl.doMigration(SchemaMigratorImpl.java:59)
    at org.hibernate.tool.hbm2ddl.SchemaUpdate.execute(SchemaUpdate.java:129)
    at org.hibernate.tool.hbm2ddl.SchemaUpdate.execute(SchemaUpdate.java:97)
    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:481)
    at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:444)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:802)
    ... 29 more
Caused by: org.postgresql.util.PSQLException: ERROR: relation "referencedocumentversion_referencedocumentsourcefilesstoredescr" already exists
    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2182)
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1911)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:173)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:618)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:454)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.executeUpdate(AbstractJdbc2Statement.java:382)
    at org.apache.tomcat.dbcp.dbcp.DelegatingStatement.executeUpdate(DelegatingStatement.java:228)
    at org.apache.tomcat.dbcp.dbcp.DelegatingStatement.executeUpdate(DelegatingStatement.java:228)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at net.bull.javamelody.JdbcWrapper.doExecute(JdbcWrapper.java:404)
    at net.bull.javamelody.JdbcWrapper$StatementInvocationHandler.invoke(JdbcWrapper.java:129)
    at net.bull.javamelody.JdbcWrapper$DelegatingInvocationHandler.invoke(JdbcWrapper.java:286)
    at com.sun.proxy.$Proxy93.executeUpdate(Unknown Source)
    at org.hibernate.tool.schema.internal.TargetDatabaseImpl.accept(TargetDatabaseImpl.java:56)
    ... 39 more

Answer 1

尝试遵循此 link

中 Hibernate 文档中的迁移指南

https://github.com/hibernate/hibernate-orm/blob/5.0/migration-guide.adoc

Answer 2

我已经通过自定义 ImplicitNamingStrategy 解决了这种情况，该自定义将 Hibernate 生成的标识符截断为 64 个字符（Postgres 的最大长度）。

以前版本的 Hibernate(4.x) 遇到了同样的错误，但他们只是忽略它并继续初始化 SessionFactory。但是，Hibernate 5.x 有一个新的引导程序 API，它会在这种情况下抛出 SchemaManagementException 并中止。下面粘贴了我的测试场景中的 Hibernate 日志以供参考。

休眠4.X

INFO: HHH000396: Updating schema
Oct 04, 2015 1:38:00 PM org.hibernate.tool.hbm2ddl.DatabaseMetadata getTableMetadata
INFO: HHH000262: Table not found: ReferenceDocumentVersionEntityWithAReallyReallyReallyLongNameBeyondPostGres
Oct 04, 2015 1:38:00 PM org.hibernate.tool.hbm2ddl.DatabaseMetadata getTableMetadata
INFO: HHH000262: Table not found: ReferenceDocumentVersionEntityWithAReallyReallyReallyLongNameBeyondPostGres
Oct 04, 2015 1:38:00 PM org.hibernate.tool.hbm2ddl.DatabaseMetadata getTableMetadata
INFO: HHH000262: Table not found: ReferenceDocumentVersionEntityWithAReallyReallyReallyLongNameBeyondPostGres
Oct 04, 2015 1:38:00 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute
ERROR: HHH000388: Unsuccessful: create table ReferenceDocumentVersionEntityWithAReallyReallyReallyLongNameBeyondPostGres (unid uuid not null, path text, primary key (unid))
Oct 04, 2015 1:38:00 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute
ERROR: ERROR: relation "referencedocumentversionentitywithareallyreallyreallylongnamebe" already exists
Oct 04, 2015 1:38:00 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute
INFO: HHH000232: Schema update complete

休眠 5.0.2.Final

Oct 04, 2015 1:39:16 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute
INFO: HHH000228: Running hbm2ddl schema update
Oct 04, 2015 1:39:16 PM org.hibernate.tool.schema.extract.internal.InformationExtractorJdbcDatabaseMetaDataImpl processGetTableResults
INFO: HHH000262: Table not found: ReferenceDocumentVersionEntityWithAReallyReallyReallyLongNameBeyondPostGres
Oct 04, 2015 1:39:16 PM org.hibernate.tool.schema.extract.internal.InformationExtractorJdbcDatabaseMetaDataImpl processGetTableResults
INFO: HHH000262: Table not found: ReferenceDocumentVersionEntityWithAReallyReallyReallyLongNameBeyondPostGres
Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.813 sec <<< FAILURE!
testApp(org.foobar.AppTest)  Time elapsed: 0.788 sec  <<< ERROR!
javax.persistence.PersistenceException: [PersistenceUnit: org.foobar.persistence.default] Unable to build Hibernate SessionFactory
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.persistenceException(EntityManagerFactoryBuilderImpl.java:877)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:805)
    at org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:58)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:39)
    at org.foobar.AppTest.testApp(AppTest.java:18)

解决方案

自定义隐式命名策略

package org.foobar.persistence;
import org.hibernate.boot.model.naming.Identifier;
import org.hibernate.boot.model.naming.ImplicitNamingStrategyComponentPathImpl;
import org.hibernate.boot.spi.MetadataBuildingContext;

public class PGConstrainedImplicitNamingStrategy extends ImplicitNamingStrategyComponentPathImpl {
private static final int POSTGRES_IDENTIFIER_MAXLENGTH = 63;
public static final PGConstrainedImplicitNamingStrategy INSTANCE = new PGConstrainedImplicitNamingStrategy();

public PGConstrainedImplicitNamingStrategy() {

}

@Override
protected Identifier toIdentifier(String stringForm, MetadataBuildingContext buildingContext) {
    return buildingContext.getMetadataCollector()
            .getDatabase()
            .getJdbcEnvironment()
            .getIdentifierHelper()
            .toIdentifier( stringForm.substring( 0, Math.min( POSTGRES_IDENTIFIER_MAXLENGTH, stringForm.length() ) ) );

}}

persistence.xml

<properties>
    <property name="hibernate.implicit_naming_strategy" value="org.foobar.persistence.PGConstrainedImplicitNamingStrategy"/>
</properties>

这根本不是一个可扩展的解决方案，但有助于保持表现运行。永久解决方案是 ~~显式提供标识符，这样休眠就不会生成很长的标识符。~~ - 请参阅

撰写的答案

Answer 3

OP 的解决方案可能会导致冲突（这就是他称之为不可扩展的原因，对吧？）。明确提供 all 标识符对我来说听起来是个糟糕的主意。我建议以下之一

提供 Map<String, String> 将所有超长名称映射到更短的名称
将所有超长的名称缩短为 POSTGRES_IDENTIFIER_MAXLENGTH - N 并附加 N 从切掉部分的哈希生成的字符，因此冲突的可能性得到最小化
使用一些标识符缩写函数，例如 {"Reference" -> "Ref", "Document" -> "Doc", ...}，并在标识符被处理之前将其应用于您的标识符，这样您就可以得到 RefDocVersion_RefDocSourceFileDescr... 而不是 referencedocumentversion_referencedocumentsourcefilesstoredescr...。
考虑在您的代码中使用缩写名称。通常建议不要这样做，因为它很容易导致难以理解的废话，但恕我直言，如果使用得当增加可读性（仅使用几个缩写并系统地使用它们；提供一个列表他们）。

迁移到 Hibernate 5

Migrating to Hibernate 5

java

postgresql

hibernate

hibernate-5.x