Question

请参阅我的Model类：

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="STUDENT")
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name="student_id")
    private String studentId;

    @Column(name="student_name")
    private String studentName;

    public String getStudentId() {
        return studentId;
    }
    public void setStudentId(String studentId) {
        this.studentId = studentId;
    }
    public String getStudentName() {
        return studentName;
    }
    public void setStudentName(String studentName) {
        this.studentName = studentName;
    }
}

并将其保存到DB，如下所示：

public static void test4()
{
    Student st = new Student();
    st.setStudentName("Bitt");

    SessionFactory sessionF = new Configuration().configure().buildSessionFactory();
    Session session = sessionF.openSession();
    session.beginTransaction();
    session.save(st);

    st = new Student();
    st.setStudentName("Rock");
    session.save(st);
    session.getTransaction().commit();
    session.close();
}

后台DB是Oracle11g，Hibernate版本是hibernate-core-5.2.10.Final.jar。

从我看来，如果studentId是String数据类型，hibernate应该生成一个随机字符串，如果studentId是int数据类型，hibernate应该生成一个唯一的数字，以确保它在DB中不重复，但是我收到了以下错误消息：

Jun 06, 2017 9:20:10 AM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {5.2.10.Final}
Jun 06, 2017 9:20:10 AM org.hibernate.cfg.Environment <clinit>
INFO: HHH000206: hibernate.properties not found
Jun 06, 2017 9:20:10 AM org.hibernate.annotations.common.reflection.java.JavaReflectionManager <clinit>
INFO: HCANN000001: Hibernate Commons Annotations {5.0.1.Final}
Jun 06, 2017 9:20:10 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
WARN: HHH10001002: Using Hibernate built-in connection pool (not for production use!)
Jun 06, 2017 9:20:10 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001005: using driver [oracle.jdbc.driver.OracleDriver] at URL [jdbc:oracle:thin:@16.165.180.124:1521:orcl]
Jun 06, 2017 9:20:10 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001001: Connection properties: {user=hibernate, password=****}
Jun 06, 2017 9:20:10 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001003: Autocommit mode: false
Jun 06, 2017 9:20:10 AM org.hibernate.engine.jdbc.connections.internal.PooledConnections <init>
INFO: HHH000115: Hibernate connection pool size: 20 (min=1)
Jun 06, 2017 9:20:11 AM org.hibernate.dialect.Dialect <init>
INFO: HHH000400: Using dialect: org.hibernate.dialect.Oracle10gDialect
Hibernate: select hibernate_sequence.nextval from dual
Jun 06, 2017 9:20:12 AM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
WARN: SQL Error: 2289, SQLState: 42000
Jun 06, 2017 9:20:12 AM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
ERROR: ORA-02289: sequence does not exist

Exception in thread "main" org.hibernate.exception.SQLGrammarException: could not extract ResultSet
    at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:63)
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:111)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:97)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:80)
    at org.hibernate.id.enhanced.SequenceStructure$1.getNextValue(SequenceStructure.java:95)
    at org.hibernate.id.enhanced.NoopOptimizer.generate(NoopOptimizer.java:40)
    at org.hibernate.id.enhanced.SequenceStyleGenerator.generate(SequenceStyleGenerator.java:432)
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:105)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:192)
    at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:38)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:177)
    at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:32)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:73)
    at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:689)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:681)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:676)
    at org.dxc.java.hibernate.main.HibernateDriver.test4(HibernateDriver.java:73)
    at org.dxc.java.hibernate.main.HibernateDriver.main(HibernateDriver.java:19)
Caused by: java.sql.SQLSyntaxErrorException: ORA-02289: sequence does not exist

    at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:447)
    at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:396)
    at oracle.jdbc.driver.T4C8Oall.processError(T4C8Oall.java:951)
    at oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:513)
    at oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:227)
    at oracle.jdbc.driver.T4C8Oall.doOALL(T4C8Oall.java:531)
    at oracle.jdbc.driver.T4CPreparedStatement.doOall8(T4CPreparedStatement.java:208)
    at oracle.jdbc.driver.T4CPreparedStatement.executeForDescribe(T4CPreparedStatement.java:886)
    at oracle.jdbc.driver.OracleStatement.executeMaybeDescribe(OracleStatement.java:1175)
    at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1296)
    at oracle.jdbc.driver.OraclePreparedStatement.executeInternal(OraclePreparedStatement.java:3613)
    at oracle.jdbc.driver.OraclePreparedStatement.executeQuery(OraclePreparedStatement.java:3657)
    at oracle.jdbc.driver.OraclePreparedStatementWrapper.executeQuery(OraclePreparedStatementWrapper.java:1495)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:71)
    ... 14 more

那么，我怎样才能让hibernate自动为我生成主键值？

Answer 1

请将您的代码更改为此并检查一次，

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name="student_id")
private Integer studentId;

@GeneratedValue（strategy = GenerationType.AUTO）

这为您提供了一个数字长值，可自动更新studentId，您添加的每条记录。

在Hibernate中使用Generation注释时，Sequence不存在异常

1 个答案: