java - org.hibernate.id.IdentifierGenerationException : ids for this class must be manually assigned before calling save(): com. app.entities.Details

Question

我多次尝试使用下面的代码在表中插入 id 值，但它总是抛出 org.hibernate.id.IdentifierGenerationException: 此类的 ids 必须在调用 save() 之前手动分配:com.app.entites。 L详情

以下是实体类中的代码

@Column(name="LID")
@GenericGenerator(name="generatedId", strategy="com.app.common.IdGenerator")
@GeneratedValue(generator="generatedId", strategy=GenerationType.SEQUENCE)
@NotNull
private String lId;

我已经使用 IdentifierGenerator 实现了 id 生成器，如下所示

public class IdGenerator implements IdentifierGenerator{

private static String id;

@Override
public Serializable generate(SharedSessionContractImplementor session, Object object) throws HibernateException {
    Connection con = session.connection();
    try {
        Statement statement = con.createStatement();
        ResultSet rs = statement.executeQuery("select count(ID) from L_DETAILS");
        if(rs.next()) {
            int i = rs.getInt(1)+1;
            this.id="ll"+i;
            System.out.println("generated id is "+id);
            return "l"+i;
        }
    }catch(SQLException e) {
        e.printStackTrace();
    }
    return null;
}

}

Answer 1

使用以下方法在实体类中自动生成主键:-

 import javax.persistence.GenerationType;
 import javax.persistence.Id;
 import javax.persistence.Entity;

        @Entity
        @Table(name = "your_table_name")
        public class YourEntityClass{

            @Id
            @GeneratedValue(strategy = GenerationType.AUTO)
            @Column(name = "id")
            private long id;

            //other column names

           // setter & getter methods

        }

此后，每当您在表中保存新记录时，都不必生成新的 ID