我正在使用hbmddl.auto设置在hibernate配置文件中创建并使用它以网络模式连接到derby数据库（未嵌入，不知道是否相关）。
这是我的hibernate.cfg.xml
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- Database connection settings -->
<property name="connection.driver_class">org.apache.derby.jdbc.ClientDriver</property>
<property name="connection.url">jdbc:derby://localhost:1527/HibernateDb;create=true</property>
<property name="connection.username">admin</property>
<property name="connection.password">admin</property>
<!-- JDBC connection pool (use the built-in) -->
<property name="connection.pool_size">1</property>
<!-- SQL dialect -->
<property name="dialect">org.hibernate.dialect.DerbyDialect</property>
<!-- Disable the second-level cache -->
<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
<!-- Echo all executed SQL to stdout -->
<property name="show_sql">true</property>
<!-- Drop and re-create the database schema on startup -->
<property name="hbm2ddl.auto">create-drop</property>
<!-- Names the annotated entity class -->
<mapping class="org.asif.javabrains.dto.UserDetails"/>
</session-factory>
</hibernate-configuration>
但是当我运行使用这个名为服务类的java程序时，我似乎不会丢弃数据库并重新创建它。正如评论所说（我从hibernate示例中获取了配置文件）。
~~~~ UPDATE ~~~~
我得出结论，hbm2ddl没有根据以下行为删除架构
我有两个类如下所示
@Entity
public class UserDetails {
@Id @GeneratedValue(strategy=GenerationType.AUTO)
private int userId;
private String userName;
@OneToMany
@JoinTable(name="USER_VEHICLE",
joinColumns=@JoinColumn(name="USER_ID"),
inverseJoinColumns = @JoinColumn(name="VEHICLE_ID")
)
private Collection<Vehicle> vehicles = new ArrayList<Vehicle>() ;
/* getters and setters */
}
和
@Entity
public class Vehicle {
@Id @GeneratedValue
private int vehicleId;
private String vehicleName;
@ManyToOne
@JoinColumn(name="USER_ID")
private UserDetails user;
/* getters and setters */
}
并且相应的hibernate配置是
<!--boiler plate-->
<!-- Drop and re-create the database schema on startup -->
<property name="hbm2ddl.auto">create</property>
<!-- Names the annotated entity class -->
<mapping class="org.asif.javabrains.dto.UserDetails"/>
<mapping class="org.asif.javabrains.dto.Vehicle"/>
<!--boiler plate-->
现在我将上述课程改为
@Entity
public class UserDetails {
@Id @GeneratedValue(strategy=GenerationType.AUTO)
private int userId;
private String userName;
@OneToMany(mappedBy="user")
private Collection<Vehicle> vehicles = new ArrayList<Vehicle>() ;
//rest is same
和
@Entity
public class Vehicle {
@Id @GeneratedValue
private int vehicleId;
private String vehicleName;
@ManyToOne
@JoinColumn(name="USER_ID")
private UserDetails user;
//rest is same
以下内容将打印到控制台
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
Hibernate: insert into UserDetails (userId, userName) values (default, ?)
Hibernate: values identity_val_local()
Hibernate: insert into Vehicle (vehicleId, USER_ID, vehicleName) values (default, ?, ?)
Exception in thread "main" org.hibernate.exception.SQLGrammarException: could not insert: [org.asif.javabrains.dto.Vehicle]
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:92)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
at org.hibernate.id.insert.AbstractSelectingDelegate.performInsert(AbstractSelectingDelegate.java:64)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2345)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2852)
at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)
at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:273)
at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:320)
at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:203)
at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:129)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:713)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:701)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:697)
at org.asif.javabrains.hibernate.HibernateTest.main(HibernateTest.java:33)
Caused by: java.sql.SQLSyntaxErrorException: 'USER_ID' is not a column in table or VTI 'ADMIN.VEHICLE'.
at org.apache.derby.client.am.SQLExceptionFactory40.getSQLException(Unknown Source)
at org.apache.derby.client.am.SqlException.getSQLException(Unknown Source)
at org.apache.derby.client.am.Connection.prepareStatement(Unknown Source)
at org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:534)
at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:116)
at org.hibernate.id.insert.AbstractSelectingDelegate.performInsert(AbstractSelectingDelegate.java:54)
... 16 more
Caused by: org.apache.derby.client.am.SqlException: 'USER_ID' is not a column in table or VTI 'ADMIN.VEHICLE'.
at org.apache.derby.client.am.Statement.completeSqlca(Unknown Source)
at org.apache.derby.client.net.NetStatementReply.parsePrepareError(Unknown Source)
at org.apache.derby.client.net.NetStatementReply.parsePRPSQLSTTreply(Unknown Source)
at org.apache.derby.client.net.NetStatementReply.readPrepareDescribeOutput(Unknown Source)
at org.apache.derby.client.net.StatementReply.readPrepareDescribeOutput(Unknown Source)
at org.apache.derby.client.net.NetStatement.readPrepareDescribeOutput_(Unknown Source)
at org.apache.derby.client.am.Statement.readPrepareDescribeOutput(Unknown Source)
at org.apache.derby.client.am.PreparedStatement.readPrepareDescribeInputOutput(Unknown Source)
at org.apache.derby.client.am.PreparedStatement.flowPrepareDescribeInputOutput(Unknown Source)
at org.apache.derby.client.am.PreparedStatement.prepare(Unknown Source)
at org.apache.derby.client.am.Connection.prepareStatementX(Unknown Source)
... 20 more
当我手动删除表并再次执行时，这似乎消失了。可能导致这种行为的原因。
答案 0 :(得分：4)
该评论实际上是不正确的。从quite a long time ago开始，与“创建”相比，“create-drop”的真实行为是，当SessionFactory关闭时，前者会丢弃模式。 “创建”本身就是评论所说的，即删除模式并在启动时重新创建模式。要进行验证，将“org.hibernate”日志记录设置为trace将显示使用“create”或“create-drop”，架构将被删除，然后在启动时创建：
INFO - Running hbm2ddl schema export
DEBUG - import file not found: /import.sql
INFO - exporting generated schema to database
TRACE - total checked-out connections: 0
TRACE - using pooled JDBC connection, pool size: 0
DEBUG - alter table Bar drop constraint FK103F39E150191
DEBUG - Unsuccessful: alter table Bar drop constraint FK103F39E150191
DEBUG - Table "BAR" not found; SQL statement:
alter table Bar drop constraint FK103F39E150191 [42102-149]
DEBUG - drop table Bar if exists
DEBUG - drop table Foo if exists
DEBUG - create table Bar (id integer generated by default as identity, foo_id integer, primary key (id))
DEBUG - create table Foo (id integer generated by default as identity, primary key (id))
DEBUG - alter table Bar add constraint FK103F39E150191 foreign key (foo_id) references Foo
INFO - schema export complete
但是，在关闭（SessionFactory.close（））时，“create”给出
INFO - closing
INFO - cleaning up connection pool: jdbc:h2:file:D:/dev/projects/testbed/test-db-for-hibernate-create-drop
而使用“create-drop”，你会看到
INFO - closing
INFO - Running hbm2ddl schema export
DEBUG - import file not found: /import.sql
INFO - exporting generated schema to database
TRACE - total checked-out connections: 0
TRACE - using pooled JDBC connection, pool size: 0
DEBUG - alter table Bar drop constraint FK103F39E150191
DEBUG - drop table Bar if exists
DEBUG - drop table Foo if exists
INFO - schema export complete
TRACE - returning connection to pool, pool size: 1
INFO - cleaning up connection pool: jdbc:h2:file:D:/dev/projects/testbed/test-db-for-hibernate-create-drop
您可以自己尝试一下：
git clone git@github.com:zzantozz/testbed tmp
cd tmp
mvn compile exec:java -Dexec.mainClass=rds.hibernate.Main -pl hibernate-create-drop
答案 1 :(得分：2)
您可能忘记拨打sessionFactory.close()，就像我犯的错误一样。突然的退出不会优雅地完成清洁工作。
使用
create-drop时，SessionFactory显式关闭时将删除数据库架构。- Hibernate Community Documentation, Chapter 3. Configuration。