Java 休眠一对多映射完整性约束冲突

错误。

错误相同的ACC\u ID在调节中为空。默认情况下，长变量具有空值

Caused by: org.hsqldb.HsqlException: integrity constraint violation: NOT NULL check constraint; SYS_CT_10115 table: ACCOMMODATION_CATEGORY column: ACC_ID
    at org.hsqldb.error.Error.error(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]
    at org.hsqldb.Table.enforceRowConstraints(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]
    at org.hsqldb.Table.insertSingleRow(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]
    at org.hsqldb.StatementDML.insertRowSet(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]
    at org.hsqldb.StatementInsert.getResult(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]
    at org.hsqldb.StatementDMQL.execute(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]
    at org.hsqldb.Session.executeCompiledStatement(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]
    at org.hsqldb.Session.execute(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]

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我如何自动生成acc_id？绝对地看这个。声明性的，直截了当的。

Caused by: org.hsqldb.HsqlException: integrity constraint violation: NOT NULL check constraint; SYS_CT_10115 table: ACCOMMODATION_CATEGORY column: ACC_ID
    at org.hsqldb.error.Error.error(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]
    at org.hsqldb.Table.enforceRowConstraints(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]
    at org.hsqldb.Table.insertSingleRow(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]
    at org.hsqldb.StatementDML.insertRowSet(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]
    at org.hsqldb.StatementInsert.getResult(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]
    at org.hsqldb.StatementDMQL.execute(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]
    at org.hsqldb.Session.executeCompiledStatement(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]
    at org.hsqldb.Session.execute(Unknown Source) ~[hsqldb-2.3.0.jar:2.3.0]

 @Column(name = "ACC_ID", unique = true, nullable = false)
 public Long getId() {
    return id;
 }