Many to many relation ship gives null - mysql

Question

using spring data and mysql as persistence layer getting some issues in Many to many mappings
#Getter
#Setter
public class BusinessUnitEntitiy extends AbstractTenantEntity implements Auditable{
private static final long serialVersionUID = -1123383144979037984L;
#Column(name = "NAME")
String name;
#Column(name = "DESCRIPTION")
String description;
#ManyToMany(fetch = FetchType.LAZY,mappedBy = "businessUnits" )
private Set<User> businessUsers;
public Set<User> fetchBusinessUsers() {
return businessUsers;
}
#Column(name = "DISPLAY_SEQUENCE_NUM")
protected Long displaySequenceNum;
#Column(name = "UNIQUE_SEQUENCE_ID",unique = true)
protected String uniqueSequenceId;
}
#Getter
#Setter
public class User extends AbstractTenantEntity {
private static final long serialVersionUID = 65981149772133526L;
#Column(name = "PROVIDER_USER_ID")
private String providerUserId;
private String email;
#Column(name = "enabled", columnDefinition = "BIT", length = 1)
private boolean enabled;
#Column(name = "DISPLAY_NAME")
private String displayName;
private String password;
private String provider;
#Column(name = "DISPLAY_SEQUENCE_NUM")
protected Long displaySequenceNum;
#Column(name = "UNIQUE_SEQUENCE_ID",unique = true)
protected String uniqueSequenceId;
#ManyToMany(fetch = FetchType.EAGER)
#JoinTable(
name = "business_unit_user",
joinColumns={#JoinColumn(name ="user_id")},
inverseJoinColumns = { #JoinColumn(name="business_unit_id") }
)
Set<BusinessUnitJpaEntitiy> businessUnits;
}
fetching the user from businessunit works perfectly
but fetching businessunits from users gives null set even updating the same user is persisiting only the newly linked businessunit older values vanishes

Answer 1

If you persisted the user within the transaction without initializing the businessUnits fields, that's what you get. Either you also initialize the set correctly before persisting, or you detach the user after persisting, so that the user is reloaded from the database and the set is properly initialized.

Answer 2

you can try this
#ManyToMany
#JoinTable(
name = "business_unit_user",
joinColumns={#JoinColumn(name ="user_id",referencedColumnName = "id")},
inverseJoinColumns = { #JoinColumn(name="business_unit_id",referencedColumnName = "id") }
)
Set<BusinessUnitJpaEntitiy> businessUnits;
and you must have setter and getter for each property