如何使用Hibernate实现自定义字符串序列标识符生成器
我正在使用spring，h2和liquibase的hibernate，我试图通过这个博客文章的示例为我的实体创建一个自定义的String id生成器，但是我收到一个错误： Caused by: org.hibernate.id.IdentifierGenerationException: Unknown integral data type for ids : java.lang.String
这是我的SequenceStyleGenerator代码：
public class CTCIDGenerator extends SequenceStyleGenerator { @Override public Serializable generate(SessionImplementor session, Object obj) { if (obj instanceof Identifiable) { Identifiable identifiable = (Identifiable) obj; Serializable id = identifiable.getId(); if (id != null) { return id; } } return "CTC"+super.generate(session, obj); } }
我的实体代码：
@Entity @Table(name = "contact") public class Contact implements Serializable, Identifiable { private static final long serialVersionUID = 1L; @Id @GenericGenerator( name = "assigned-sequence", strategy = "net.atos.seirich.support.domain.idgenerator.CTCIDGenerator", parameters = @org.hibernate.annotations.Parameter( name = "sequence_name", value = "hibernate_sequence" ) ) @GeneratedValue(generator = "assigned-sequence", strategy = GenerationType.SEQUENCE) private String id; public String getId() { return id; } public void setId(String id) { this.id = id; } }
而liquibase XML：
顺便说一句，是否有可能避免参数sequence_name，所以hibernate可以自己处理这个？
如果有人可以帮助我，谢谢！
问题是SequenceStyleGenerator期望返回一个数值，而不是String 。
我已经尝试过这个问题的解决方案，它就像一个魅力 。 因此，您需要像这样更改您的生成器：
public class StringSequenceIdentifier implements IdentifierGenerator, Configurable { private String sequenceCallSyntax; @Override public void configure(Type type, Properties params, ServiceRegistry serviceRegistry) throws MappingException { final JdbcEnvironment jdbcEnvironment = serviceRegistry.getService(JdbcEnvironment.class); final Dialect dialect = jdbcEnvironment.getDialect(); final String sequencePerEntitySuffix = ConfigurationHelper.getString(CONFIG_SEQUENCE_PER_ENTITY_SUFFIX, params, DEF_SEQUENCE_SUFFIX); final String defaultSequenceName = ConfigurationHelper.getBoolean(CONFIG_PREFER_SEQUENCE_PER_ENTITY, params, false) ? params.getProperty(JPA_ENTITY_NAME) + sequencePerEntitySuffix : DEF_SEQUENCE_NAME; sequenceCallSyntax = dialect.getSequenceNextValString(ConfigurationHelper.getString(SEQUENCE_PARAM, params, defaultSequenceName)); } @Override public Serializable generate(SessionImplementor session, Object obj) { if (obj instanceof Identifiable) { Identifiable identifiable = (Identifiable) obj; Serializable id = identifiable.getId(); if (id != null) { return id; } } long seqValue = ((Number) Session.class.cast(session) .createSQLQuery(sequenceCallSyntax) .uniqueResult()).longValue(); return "CTC" + seqValue; } }
您的映射变为：
@Entity(name = "Post") @Table(name = "post") public static class Post implements Identifiable { @Id @GenericGenerator( name = "assigned-sequence", strategy = "com.vladmihalcea.book.hpjp.hibernate.identifier.StringSequenceIdentifier", parameters = @org.hibernate.annotations.Parameter(name = "sequence_name", value = "hibernate_sequence") ) @GeneratedValue(generator = "assigned-sequence", strategy = GenerationType.SEQUENCE) private String id; @Version private Integer version; public Post() { } public Post(String id) { this.id = id; } @Override public String getId() { return id; } }
现在，当您插入以下实体时：
doInJPA(entityManager -> { entityManager.persist(new Post()); entityManager.persist(new Post("ABC")); entityManager.persist(new Post()); entityManager.persist(new Post("DEF")); });
Hibernate生成正确的标识符：
Query:["select nextval ('hibernate_sequence')"], Params:[()] Query:["select nextval ('hibernate_sequence')"], Params:[()] Query:["insert into post (version, id) values (?, ?)"], Params:[(0, CTC1)] Query:["insert into post (version, id) values (?, ?)"], Params:[(0, ABC)] Query:["insert into post (version, id) values (?, ?)"], Params:[(0, CTC2)] Query:["insert into post (version, id) values (?, ?)"], Params:[(0, DEF)]
GitHub上提供的代码。
是的，hibernate有预构建的String生成器。 只需将@GenericGenerator定义替换为另一种策略即可。
@Entity @Table(name = "contact") public class Contact implements Serializable, Identifiable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(generator = "uuid") @GenericGenerator(name = "uuid", strategy = "uuid2") private String id; public String getId() { return id; } public void setId(String id) { this.id = id; } }
有关不同hibernate生成器的更多信息，您可以查看文档 。