java中沒有@Id注解的序列生成器，Postgres中的休眠在一定范圍內

Question

我有一個 REST API，它有一個人，現在我有一個數字范圍 (40000 - 99999)，我必須在最后填充並將其保存到數據庫中，我不會在請求正文中獲取它。 但是我仍然必須按順序堅持這個數字

例如：Postgres 中的 40001、40002、40003 等，因為它不是@Id字段，所以我無法找到將它持久化到數據庫中的方法，有沒有辦法用 Java、JPA 做到這一點？

CREATE SEQUENCE public.certificate
    INCREMENT 1
    START 40000
    MINVALUE 40000
    MAXVALUE 99999999
    CACHE 1;

create table CertificateNumber (c_number integer default nextval(‘certificate’));

@Generated(value = GenerationTime.INSERT)
@Column(name = "c_number", insertable = false,updatable = false)
Integer certificateNumber;

 Resolved [org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [certificate_number]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement]
2020-03-06 16:33:13.167  INFO 864 --- [nio-8080-exec-2] i.StatisticalLoggingSessionEventListener : Session Metrics {
    714213 nanoseconds spent acquiring 1 JDBC connections;
    0 nanoseconds spent releasing 0 JDBC connections;
    3037131 nanoseconds spent preparing 1 JDBC statements;
    18543560 nanoseconds spent executing 1 JDBC statements;
    0 nanoseconds spent executing 0 JDBC batches;
    0 nanoseconds spent performing 0 L2C puts;
    0 nanoseconds spent performing 0 L2C hits;
    0 nanoseconds spent performing 0 L2C misses;
    67929213 nanoseconds spent executing 1 flushes (flushing a total of 1 entities and 0 collections);
    0 nanoseconds spent executing 0 partial-flushes (flushing a total of 0 entities and 0 collections)
}

作為對 API 的回應，下面也提到了我所得到的。

{
    "apierror": {
        "status": "INTERNAL_SERVER_ERROR",
        "timestamp": "06-03-2020 04:33:13",
        "message": "Unexpected error",
        "debugMessage": "could not execute statement; SQL [n/a]; constraint [certificate_number]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement",
        "subErrors": null
    }
}

Answer 1

我建議在你的數據庫中使用觸發器，首先你創建你的序列：

CREATE SEQUENCE certificateNumber_table_seq
INCREMENT 1
START 1; 

然后創建這個函數：

CREATE OR REPLACE FUNCTION trigger_function()
RETURNS trigger AS
$BODY$
BEGIN
New.c_number:=nextval('certificateNumber_table_seq');
Return NEW;
END;
$BODY$

最后你的觸發器將執行你創建的函數

DROP TRIGGER IF EXISTS trigg_auto_increment ON table_name;
CREATE TRIGGER trigg_auto_increment
BEFORE INSERT
ON table_name //the name of your table
FOR EACH ROW
EXECUTE PROCEDURE trigger_function();