java - null not allowed for column in join table with one entity extending another -

i have situation have entity vcenterdistributedvirtualportgroup extends vcenternetwork , both entities in onetomany relationship inside entity vcenterfolder. i'm getting following error:

caused by: org.h2.jdbc.jdbcsqlexception: null not allowed column "network_type"; sql statement: insert folder_network (folder_type, folder_val, distributedvirtualportgroups_type, distributedvirtualportgroups_val) values (?, ?, ?, ?) [23502-182]

vcenternetwork:

@entity @embeddable @table(name="network") @discriminatorcolumn(name="discriminator") @discriminatorvalue("network") public class vcenternetwork {     @transient     private network network;      @transient     private static map<mor, vcenternetwork> networkmap = new treemap<mor, vcenternetwork>();      @embeddedid     private mor id;     public mor getid() {return this.id;}     public void setid(mor id) {this.id = id;}     ... } 

vcenterdistributedvirtualportgroup:

@entity @table(name="distributedvirtualportgroup") @discriminatorcolumn(name="discriminator") @discriminatorvalue("distributedvirtualportgroup") public class vcenterdistributedvirtualportgroup extends vcenternetwork {     @transient     private distributedvirtualportgroup distributedvirtualportgroup;      @transient     private static map<mor, vcenterdistributedvirtualportgroup> distributedvirtualportgroupmap = new treemap<mor, vcenterdistributedvirtualportgroup>();     ... } 

vcenterfolder:

@entity @table(name="folder") public class vcenterfolder {     @transient     private folder folder;      @transient     private static map<mor, vcenterfolder> foldermap = new treemap<mor, vcenterfolder>();      @embeddedid     private mor id;     public mor getid() {return this.id;}     public void setid(mor id) {this.id = id;}      @embedded     @onetomany(cascade=cascadetype.all)     private list<vcenternetwork> network = new arraylist<vcenternetwork>();     public list<vcenternetwork> getnetwork() {return this.network;}     public void getvirtualnetwork(list<vcenternetwork> network) {this.network = network;}      @embedded     @onetomany(cascade=cascadetype.all)     private list<vcenterdistributedvirtualportgroup> distributedvirtualportgroups = new arraylist<vcenterdistributedvirtualportgroup>();     public list<vcenterdistributedvirtualportgroup> getdistributedvirtualportgroups() {return this.distributedvirtualportgroups;}     public void setdistributedvirtualportgroups(list<vcenterdistributedvirtualportgroup> distributedvirtualportgroups){this.distributedvirtualportgroups = distributedvirtualportgroups;}     .... } 

this results in join table looks following:

folder_network     folder_type - varchar(255) not null     folder_val - varchar(255) not null     network_type - varchar(255) not null     network_val - varchar(255) not null     distributedvirtualportgroup_type - varchar(255) not null     distributedvirtualportgroup_type - varchar(255) not null 

i'm new jpa, guess join table needed both vcenterfolder-vcenternetwork , vcenterfolder-vcenterdistributedvirtualportgroup, since vcenterdistributedvirtualportgroup extends vcenternetwork, it's building 1 join table both relations using different type/val pair each relation. assume 1 pair used @ time other being null. seems problem. seem me fields should either nullable or 2 sets of type/val pairs should merged one.

i assume there way round this, sure don't know is.

mor happens have members type & val, names in join table.

i solved problem adding folloing jointable on both network , distributedvirtualportgroups fields:

    @jointable     (             name="folder_network",             joincolumns= {@joincolumn(name="type", referencedcolumnname="type"), @joincolumn(name="val", referencedcolumnname="val")},             inversejoincolumns= {@joincolumn(name="network_type", referencedcolumnname="type"), @joincolumn(name="network_val", referencedcolumnname="val")}     )