Question

我正在尝试找到在id中生成Entity Spring的最佳做法符合以下要求：

必须是唯一的
必须有9位数字
必须是int
不能是序列

我无法使用uuid，因为它不符合要求。

我目前正在使用Hibernate版本4.3.1 - 但如果需要，我可能会更新。

Answer 1

您可以使用自定义ID生成器生成ID

@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "XyzIdGenerator")
@GenericGenerator(name = "XyzIdGenerator",
    strategy = "com.mycompany.myapp.id.BigIntegerSequenceGenerator",
    parameters = {
        @Parameter(name = "sequence", value = "xyz_id_sequence")
    })
public BigInteger getId()
{
   return id;
}


package com.mycompany.myapp.id;

import org.hibernate.id.SequenceGenerator;

public class BigIntegerSequenceGenerator
    extends SequenceGenerator
{
    @Override
    public Serializable generate(SessionImplementor session, Object obj)
    {
        ...
    }
}

并在generate函数中定义逻辑。

Answer 2

我用这种方式解决了问题：

 package com.project.generator;

import ...

public class IdGenerator extends SequenceGenerator
{
    Random r = new Random();
    private Logger log = LoggerFactory.getLogger(IdGenerator.class);
    Session session;

    int attempt = 0;

    public int generate9DigitNumber()
    {
        int aNumber = (int) ((Math.random() * 900000000) + 100000000); 
        return aNumber;
    }

    @Override
    public Serializable generate(SessionImplementor sessionImplementor, Object obj)
    {
        session = (Session) sessionImplementor;
        Integer id = generateRandomIndex();
        return id;
    }

    public Integer generateRandomIndex()
    {
            for (int i = 0; i < 3; i++)
    {
        log.info("attempt: " + i);
        Integer a = generate9DigitNumber();

        log.info("index: " + String.valueOf(a));
        if (session.get(Xyz.class, a) == null)
        {
            log.info("not found this id");
            return a;
        } else
        {
            log.info("found this id");
        }
    }

    for (int i = 100000000; i < 999999999; i++)
    {
        log.info("Is id free: " + i);
        if (session.get(Xyz.class, i) == null)
        {
            log.info("id is free: " + i);
            return i;
        }
    }
        return null;
    }
}

实体类：

@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "IdGenerator")
@GenericGenerator(name = "IdGenerator",
    strategy = "com.project.generator.IdGenerator",
    parameters = {
        @Parameter(name = "sequence", value = "xyz_id_sequence")
    })
private Integer id;

Spring唯一ID为整数，有9位数字 - 不是序列

2 个答案: