不成功：alter table XXX在Hibernate / JPA / HSQLDB独立版中删除约束YYY

Question

我正在尝试使用内存中的HSQL DB运行一些Hibernate / JPA示例。我得到的错误消息如下：

13:54:21,427 ERROR SchemaExport:425 - HHH000389: Unsuccessful: alter table ReferringItem_map drop constraint FK5D4A98E0361647B8
13:54:21,427 ERROR SchemaExport:426 - user lacks privilege or object not found: PUBLIC.REFERRINGITEM_MAP
13:54:21,427 ERROR SchemaExport:425 - HHH000389: Unsuccessful: alter table ReferringItem_myCollection drop constraint FK75BA3266361647B8
13:54:21,427 ERROR SchemaExport:426 - user lacks privilege or object not found: PUBLIC.REFERRINGITEM_MYCOLLECTION
13:54:21,428 ERROR SchemaExport:425 - HHH000389: Unsuccessful: alter table ReferringItem_myList drop constraint FK6D37AA66361647B8
13:54:21,428 ERROR SchemaExport:426 - user lacks privilege or object not found: PUBLIC.REFERRINGITEM_MYLIST
13:54:21,428 ERROR SchemaExport:425 - HHH000389: Unsuccessful: alter table ReferringItem_mySet drop constraint FK3512699A361647B8
13:54:21,429 ERROR SchemaExport:426 - user lacks privilege or object not found: PUBLIC.REFERRINGITEM_MYSET

相应的课程是：

@Entity
public class ReferringItem implements Serializable {

    @Id
    private long id;

    @ElementCollection
    private Collection<AnEmbeddable> myCollection
        = new ArrayList<AnEmbeddable>();

    @ElementCollection(fetch=FetchType.EAGER)
    private Set<Long> mySet = new HashSet<Long>();

    @ElementCollection(targetClass=String.class)
    private List myList = new ArrayList();

    @ElementCollection
    private Map<String,AnEmbeddable> map
        = new HashMap<String,AnEmbeddable>();

    public ReferringItem() { }

    // Setters & Getters

}

嵌入式是：

@Embeddable
public class AnEmbeddable implements Serializable {

    private String s;

    public AnEmbeddable() { }

    public String getS() {
        return s;
    }

    public void setS(String s) {
        this.s = s;
    }

}

我的persistence.xml：

<persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd" version="2.0">

    <persistence-unit name="JPA" transaction-type="RESOURCE_LOCAL">

        <provider>org.hibernate.ejb.HibernatePersistence</provider>

        <class>com.jverstry.jpa.AuthorizedTypes.AuthorizedTypes</class>
        <class>com.jverstry.jpa.AuthorizedTypes.OtherEntity</class>
        <class>com.jverstry.jpa.AuthorizedTypes.SomeEmbeddable</class>

        <properties>
            <property name="javax.persistence.jdbc.driver" value="org.hsqldb.jdbcDriver"/>
            <property name="javax.persistence.jdbc.url" value="jdbc:hsqldb:mem:testdb"/>
            <property name="javax.persistence.jdbc.user" value="sa"/>
            <property name="javax.persistence.jdbc.password" value=""/>
            <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
            <property name="hibernate.hbm2ddl.auto" value="create-drop"/>
        </properties>

    </persistence-unit>

</persistence>

我正在使用Hibernate 4.1.5.Final和HSQLDB 2.2.8。

有谁知道造成这个问题的原因以及如何解决？

Answer 1

您可以忽略这些错误。 create-drop和内存数据库的组合为它尝试删除的每个数据库对象生成这些。原因是没有要删除的数据库对象 - DROP语句是针对空数据库执行的。

另外，对于普通的永久数据库，这样的错误确实会发生，因为Hibernate在执行DROP语句之前没有弄明白，数据库中是否存在添加的对象，还是新的。

Answer 2

这个解决方案对我有用，而不是给出的其他解决方案。里程数显然不同。

这是我的确切错误：

HHH000389: Unsuccessful: alter table ... drop constraint FK_g1uebn6mqk9qiaw45vnacmyo2 if exists
Table "..." not found; SQL statement: ...

这是我的解决方案，覆盖H2方言：

package com.totaalsoftware.incidentmanager;

import org.hibernate.dialect.H2Dialect;

/**
 * Workaround.
 * 
 * @see https://hibernate.atlassian.net/browse/hhh-7002
 * 
 */
public class ImprovedH2Dialect extends H2Dialect {
    @Override
    public String getDropSequenceString(String sequenceName) {
        // Adding the "if exists" clause to avoid warnings
        return "drop sequence if exists " + sequenceName;
    }

    @Override
    public boolean dropConstraints() {
        // We don't need to drop constraints before dropping tables, that just
        // leads to error messages about missing tables when we don't have a
        // schema in the database
        return false;
    }
}

Answer 3

上面提供的解决方案@Sander也适用于MYSQL。只需扩展MySQL5InnoDBDialect，如下所示：

import org.hibernate.dialect.MySQL5InnoDBDialect;

public class ImprovedMySQLDialect extends MySQL5InnoDBDialect {
    @Override
    public String getDropSequenceString(String sequenceName) {
        // Adding the "if exists" clause to avoid warnings
        return "drop sequence if exists " + sequenceName;
    }

    @Override
    public boolean dropConstraints() {
        // We don't need to drop constraints before dropping tables, that just leads to error
        // messages about missing tables when we don't have a schema in the database
        return false;
    }
}

然后在您的数据源文件中更改以下行：

dialect = org.hibernate.dialect.MySQL5InnoDBDialect

到

dialect = my.package.name.ImprovedMySQLDialect

Answer 4

只需设置dbCreate="update"，错误就会立即消失。

请参阅：https://stackoverflow.com/a/31257468/715608

Answer 5

使用带有HSQLDB和hbm2ddl.auto = create-drop的内存数据库，在每次测试开始时，恼人的错误消息变得更加令人讨厌的堆栈跟踪。

对HSQLDB bug report的响应建议使用DROP TABLE ... CASCADE而不是DROP CONSTRAINT IF EXISTS。不幸的是，丢弃表的HSQLDB语法是DROP TABLE <table> [IF EXISTS] [RESTRICT | CASCADE]; Hibernate Dialect没有为Dialect提供一个简单的机制，可以在最终的IF EXISTS子句之后指定CASCADE。我为此限制写了a bug。

但是，我能够通过创建自定义Dialect来解决这个问题，如下所示：

public class HsqlDialectReplacement extends HSQLDialect {

  @Override
  public String getDropTableString( String tableName ) {
    // Append CASCADE to formatted DROP TABLE string
    final String superDrop = super.getDropTableString( tableName );
    return superDrop + " cascade";
  }

  @Override
  public boolean dropConstraints() {
      // Do not explicitly drop constraints, use DROP TABLE ... CASCADE
      return false;
  }

  @Override
  public Exporter<Table> getTableExporter() {
    // Must override TableExporter because it also formulates DROP TABLE strings
    synchronized( this ) {
      if( null == overrideExporter ) {
        overrideExporter = new HsqlExporter( super.getTableExporter() );
      }
    }

    return overrideExporter;
  }

  private Exporter<Table> overrideExporter = null;

  private static class HsqlExporter implements Exporter<Table> {
    HsqlExporter( Exporter<Table> impl ) {
      this.impl = impl;
    }

    @Override
    public String[] getSqlCreateStrings( Table exportable, Metadata metadata ) {
      return impl.getSqlCreateStrings( exportable, metadata );
    }

    @Override
    public String[] getSqlDropStrings( Table exportable, Metadata metadata ) {
      final String[] implDrop = impl.getSqlDropStrings( exportable, metadata );
      final String[] dropStrings = new String[implDrop.length];
      for( int i=0; i<implDrop.length; ++i ) {
        dropStrings[i] = implDrop[i] + " cascade";
      }
      return dropStrings;
    }

    private final Exporter<Table> impl;
  };
}

Answer 6

我们在尝试在Spring中创建一个简单的登录窗口时遇到了同样的问题。有两个表user和role都具有主键id类型的BIGINT。这些我们将（Many-to-Many）映射到另一个表user_roles，其中两列user_id和role_id作为外键。

问题是role_id表中的user_roles列，它是int类型，与role的外键不兼容。将类型修改为BIGINT后，错误得到纠正。