entity.merge 后如何获取主键答案

【问题标题】：How do I get the primary Key after entity.mergeentity.merge 后如何获取主键
【发布时间】：2016-09-29 09:25:44
【问题描述】：

我正在使用我的 SpringBoot JPA Hibernate 中的 entity.merge 将某些数据持久保存在 Oracle 数据库中，其中主键是序列生成的。但是在合并之后，我无法获得插入到 Oracle 表中的主键。对于这两种情况，它都返回 0

LOG.info("Inside InsertParts>>>>Before Merge Component-serialized_id>>>>" +webCrtPart.getSerializedComponentId()+ ">>>CSI>>" +webCrtPart.getCsInvSerialNumber());
    // Persist entity to database
    mergeEntity(webCrtPart);

    i++;
    // checking the batchsize so after every batch of batchsize , it
    // gets inserted to database
    if (i % batchSize == 0) {
        // Flush a batch of inserts and release memory.
        entityManager.flush();
        entityManager.clear();
    }

    LOG.info("Inside InsertParts>>>>After merge Component-serialized_id>>>>"+webCrtPart.getSerializedComponentId());
}

return webCrtPartList;

}

我的实体类看起来像：

@Table(name = "WEBCRT_CMPNT_SRLZD")
@Entity
public class WebCrtSerializedComponent {

    @Id 
    @SequenceGenerator(name="component_seq", sequenceName="WEBCRT_CMPNT_SRLZD_SEQ"  , allocationSize=1)
    @GeneratedValue(generator = "component_seq", strategy = GenerationType.SEQUENCE)
    @Column(name = "CMPNT_SRLZD_SEQ_ID")
    private Long serializedComponentId;

    @Column(name = "ITM")
    private String item;

    @Column(name = "SUB_CMPNT_SEQ_ID")
    private String subComponentSeqId;

    @Column(name = "PRT_NUM")
    private String partNumber;

    @Column(name = "INCMNG_SRL_NUM")
    private String incomingSerialNumber;

    @Column(name = "NUM_OF_PREV_RPRS")
    private String previousRepairCount;

请找到以下日志：

2016-09-28 15:42:19.861[0;39m [32m INFO[0;39m [35m63710[0;39m [2m---[0;39m [2m[nio-8080-exec-1][0;39m [36mo.s.web.servlet.DispatcherServlet       [0;39m [2m:[0;39m FrameworkServlet 'dispatcherServlet': initialization completed in 25 ms
[2m2016-09-28 15:42:19.934[0;39m [32m INFO[0;39m [35m63710[0;39m [2m---[0;39m [2m[nio-8080-exec-1][0;39m [36mc.g.p.b.m.impl.JobRetrievalManager      [0;39m [2m:[0;39m parameters to be passed : - 159693-----10
[2m2016-09-28 15:42:20.484[0;39m [32m INFO[0;39m [35m63710[0;39m [2m---[0;39m [2m[nio-8080-exec-1][0;39m [36mc.g.p.b.managers.impl.PartSynchManager  [0;39m [2m:[0;39m JobControllerV1 >>>>>>>1
[2m2016-09-28 15:42:20.491[0;39m [32m INFO[0;39m [35m63710[0;39m [2m---[0;39m [2m[nio-8080-exec-1][0;39m [36mc.g.p.b.r.PartSynchRepositoryImpl       [0;39m [2m:[0;39m Inside InsertParts>>>>Before Merge Component-serialized_id>>>>0>>>CSI>>null
Hibernate: select webcrtseri0_.cmpnt_srlzd_seq_id as cmpnt_srlzd_seq_id1_3_0_, webcrtseri0_.child_sys_asmbly_id as child_sys_asmbly_i2_3_0_, webcrtseri0_.crtd_by as crtd_by3_3_0_, webcrtseri0_.crtn_dt as crtn_dt4_3_0_, webcrtseri0_.csinv_sl_num as csinv_sl_num5_3_0_, webcrtseri0_.cust_supplied_ind as cust_supplied_ind6_3_0_, webcrtseri0_.incmng_dpm_ind as incmng_dpm_ind7_3_0_, webcrtseri0_.incmng_srl_num as incmng_srl_num8_3_0_, webcrtseri0_.itm as itm9_3_0_, webcrtseri0_.job_seq_id as job_seq_id10_3_0_, webcrtseri0_.lst_updtd_by as lst_updtd_by11_3_0_, webcrtseri0_.lst_updt_dt as lst_updt_dt12_3_0_, webcrtseri0_.outgng_dpm_ind as outgng_dpm_ind13_3_0_, webcrtseri0_.otgng_pn as otgng_pn14_3_0_, webcrtseri0_.otgng_sn as otgng_sn15_3_0_, webcrtseri0_.prt_num as prt_num16_3_0_, webcrtseri0_.prev_job_num as prev_job_num17_3_0_, webcrtseri0_.num_of_prev_rprs as num_of_prev_rprs18_3_0_, webcrtseri0_.repl_ind as repl_ind19_3_0_, webcrtseri0_.sub_cmpnt_seq_id as sub_cmpnt_seq_id20_3_0_, webcrtseri0_.set_sys_asmbly_id as set_sys_asmbly_id21_3_0_ from webcrt_cmpnt_srlzd webcrtseri0_ where webcrtseri0_.cmpnt_srlzd_seq_id=?
Hibernate: select WEBCRT_CMPNT_SRLZD_SEQ.nextval from dual
[2m2016-09-28 15:42:20.628[0;39m [32m INFO[0;39m [35m63710[0;39m [2m---[0;39m [2m[nio-8080-exec-1][0;39m [36mc.g.p.b.r.PartSynchRepositoryImpl       [0;39m [2m:[0;39m Inside InsertParts>>>>After merge Component-serialized_id>>>>0
Hibernate: insert into webcrt_cmpnt_srlzd (child_sys_asmbly_id, crtd_by, crtn_dt, csinv_sl_num, cust_supplied_ind, incmng_dpm_ind, incmng_srl_num, itm, job_seq_id, lst_updtd_by, lst_updt_dt, outgng_dpm_ind, otgng_pn, otgng_sn, prt_num, prev_job_num, num_of_prev_rprs, repl_ind, sub_cmpnt_seq_id, set_sys_asmbly_id, cmpnt_srlzd_seq_id) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)

【问题讨论】：

标签： java oracle hibernate jpa

【解决方案1】：

merge 方法返回一个持久对象，它不会将您发送给它的对象变成一个持久对象。

这是一个旧文档，但我相信我们在这里讨论的具体细节在最近的版本中保持不变： https://docs.jboss.org/hibernate/orm/3.5/javadocs/org/hibernate/Session.html#merge(java.lang.Object)

所以你应该这样做：

webCrtPart = session.merge(webCrtPart);

在您的 mergeEntity(webCrtPart) 方法中

【讨论】：

这和莫希特的回答很相似，我能拿到钥匙

【解决方案2】：

merge() 方法返回作为持久化上下文的一部分的实际实体，而不是传递给 merge() 方法的对象。可以通过merge()方法从返回的Entity对象中获取主键。

WebCrtSerializedComponent webCrtCom = entityManager.merge(webCrtPart);

'webCrtCom' 对象将具有主键。但要注意 webCrtCom 对象的持久化上下文。

【讨论】：

这个对象确实有主键，我的问题解决了

【解决方案3】：

根据示例的结构，webCrtPartList 很可能不是托管实体。您需要使用 EntityManager.merge() 的响应来获取托管实体（EntityManager.merge() 的参数不会[必要] 被托管）

【讨论】：