如何在Hibernate中将字符串映射到数据库序列

实现一个自定义的IdentifierGenerator类；从博客文章：

import java.io.Serializable;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import org.hibernate.HibernateException;import org.hibernate.engine.spi.SessionImplementor;import org.hibernate.id.IdentifierGenerator;public class StringKeyGenerator implements IdentifierGenerator {    @Override    public Serializable generate(SessionImplementor session, Object collection) throws HibernateException {        Connection connection = session.connection();        PreparedStatement ps = null;        String result = "";        try { // Oracle-specific pre to query a sequence ps = connection.prepareStatement("SELECt TABLE_SEQ.nextval AS TABLE_PK FROM dual"); ResultSet rs = ps.executeQuery(); if (rs.next()) {     int pk = rs.getInt("TABLE_PK");     // Convert to a String     result = Integer.toString(pk); }        } catch (SQLException e) { throw new HibernateException("Unable to generate Primary Key");        } finally { if (ps != null) {     try {         ps.close();     } catch (SQLException e) {         throw new HibernateException("Unable to close prepared statement.");     } }        }        return result;    }}

像这样注释实体PK：

@Id@GenericGenerator(name="seq_id", strategy="my.package.StringKeyGenerator")@GeneratedValue(generator="seq_id")@Column(name = "TABLE_PK", unique = true, nullable = false, length = 20)public String getId() {    return this.id;}

由于Eclipse中的错误，可能会引发一个错误，即

seq_id

1. 选择 窗口»首选项
2. 展开 Java持久性»JPA»错误/警告
3. 点击 查询和生成器
4. 在持久性单元中未 将Set Generator定义 为：

   Warning

5. 单击 确定 以应用更改并关闭对话框