I've an issue using one-to-one mapping. I've searched internet and found many solutions but none was satisfying. Most of the examples carry overhead of storing parent instance in child class.
I want to use only parent Id in child class having foreign key constraint relationship but dont want to keep any parent instance in child.
When I try to load the records from database it throws exception "No row with the given identifier exists [AssemblyName.]". But, the record exists in Table "B" properly.
Any solutions for this issue?
The class structure:
class A {
public virtual string Id {get;set;}
public virtual B B {get;set;} // properties...... }
class B { public virtual string Id {get;set;} // properties......
public virtual string ParentId { get;set;} // class A Id }
The database structure:
CREATE TABLE [A](
[Id] [nvarchar](45) PRIMARY KEY
) ON [PRIMARY]
CREATE TABLE [B](
[Id] [nvarchar](45) PRIMARY KEY,
[ParentId] [nvarchar](45) NOT NULL
) ON [PRIMARY]
The mapping:
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="A,AssemblyName" table="A" lazy="true">
<id name="Id" column="Id" type="string">
<generator class="assigned"/>
</id>
<one-to-one name="_B" cascade="all" fetch="join" foreign-key="None" constrained="true" class="B"/>
</class>
</hibernate-mapping>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="B,AssemblyName" table="B" lazy="true">
<id name="Id" column="Id" type="string"> <generator class="assigned"/> </id>
<property name="_Name" column="Name"/> </class>
</hibernate-mapping>
One-to-one associations are always bidirectional in NHibernate. Mapping of class B is incomplete:
<class name="B,AssemblyName" table="B" lazy="true">
<id name="Id" column="Id" type="string">
<generator class="assigned"/>
</id>
<many-to-one name="A" unique="true" column="A" />
<property name="_Name" column="Name"/>
</class>
This is foreign key association. For more information see this detailed Ayende's blog post or NHibernate documentation.
Read this. A "real" one-to-one needs the same primary key in both tables (and no ParentId column).
Related
i want to do a left outer join from 2 table, but with 2 key that are not primary key.
This is the native sql query used:
Maybe there is a better way to do it?
SQLQuery query = session.createSQLQuery("
select {A.*},{B.*} from A_TABLE A left outer join B_TABLE B on A.QUOTE_ID = B.QUOTE_NUM ")
.addEntity("A", A_Class.class)
.addJoin("B", "A.bDocs");
for(Object result : query.list())
{
....
}
The mapping A file:
<class name="A_Class" table="A_TABLE" schema="S">
<id name="rowId" type="string">
<column name="ROW_ID" length="60" />
<generator class="assigned" />
</id>
<set name="BDocs" inverse="true" fetch="select" lazy="false">
<key>
<column name="QUOTE_NUM" length="60" not-null="true" />
</key>
<one-to-many class="B_Class" />
</set>
A_Class.java
public class A_Class implements java.io.Serializable
{
private String rowId;
private String QuoteId;
private Set BDocs= new HashSet(0);
// omitted all the set and get
}
The mapping B file:
<hibernate-mapping>
<class name="B" table="B_TABLE" schema="S">
<id name="rowId" type="string">
<column name="ROW_ID" length="60" />
<generator class="assigned" />
</id>
<many-to-one name="A" class="A_Class" fetch="select" lazy="false" outer-join="true" foreign-key="QuoteId" property-ref="QuoteId">
<column name="QUOTE_NUM" length="60" not-null="true" />
</many-to-one>
B_Class.java
public class B_Class implements java.io.Serializable
{
private String rowId;
private String quoteNum;
// omitted all the set and get
}
From this query i obtain 2 objects, one of A type and the other of B Type with a lot of correct datas but the set BDocs in the object of A type isn't filled. The goal is to get only the A Object with the variable BDocs filled with the B Objects.
I don't understand if the problem is in the query or in the mapping files. Anyone can help me?
I am trying to retrieve the count of items allocated to a container in my hbm file. I've done a bit of digging and managed to get my hbm code this far (below!). I want the count to be retrieved every time a container object is queried. I could use an interceptor but I assume there's a better way. Am I on the right track or should I use a different strategy to get the count loaded up?
Thanks.
P.S. We're using NH v2.2
<?xml version="1.0" encoding="utf-8"?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-lazy="false" assembly="MyEntities" namespace="Entities.Containers"> <class name="Container" table="[Container]" xmlns="urn:nhibernate-mapping-2.2">
<id name="Id" column="Id" type="Int32" unsaved-value="0">
<generator class="native" />
</id>
<property name="Capacity" column="Capacity">
<column name="Capacity" />
</property>
<property name="Description" column="Description" length="50" type="String">
<column name="Description" />
</property>
<loader query-ref="sqCurrentContainerAllocation"/> </class>
<sql-query name="sqCurrentContainerAllocation">
<return-scalar column="AllocatedItemsCount" type="int"></return-scalar>
SELECT COUNT(*) FROM [ContainerTracking]
WHERE [ContainerId] = :Id </sql-query>
</hibernate-mapping>
If you need to get some calculated property, you can use mapping with formula.
Let's extend your C# class:
public class Container
{
... // ID, Capacity, Description
public virtual int MyCount { get; set; }
And extend your mapping
<class name="Container" table="[Container]"
...
<property name="MyCount" insert="false" update="false" >
<formula>
(
SELECT count(*)
FROM [ContainerTracking] as ct
WHERE ct.[ContainerId] = Id
)
</formula>
</property>
the Id will be replaced with somethink like '_this.Id', the name of the column Id and its alias
This will of course load the count all the time (except projections) so think twice before use it
I need a HQL Query but I just dont get it.
SELECT * FROM Poll WHERE pid NOT IN (
SELECT pid FROM votes WHERE uid = 'theuserid')
I want all List of Poll´s back where the uid not in the table votes exists.
Also helpfull would be the hql query where the uid in the table votes exists, but I guess this is very similar ;-)
These are the 2 classes:
public class Poll {
private int pid;
private String name;
private String description;
private Date deadline;
private Set<Team> teams = new HashSet<Team>(0);
//some getter & setter
}
public class Vote {
private int vid;
private String uid;
private int pid;
private int tid;
private int votes;
//some getter & setter
}
Can smbdy please help me. I guess it is a join with a WHERE and NOT LIKE but I just dont get it.
Merci!
This is btw the hibernate mapping:
<hibernate-mapping>
<class name="package.model.Poll" table="poll">
<id name="pid" column="pid" >
<generator class="increment"/>
</id>
<property name="name" column="name" />
<property name="description" column="description" />
<property name="deadline" type="timestamp" column="deadline" />
<set name="teams" table="pollchoice"
inverse="false" lazy="false" fetch="select" cascade="all" >
<key>
<column name="pid" not-null="true" />
</key>
<many-to-many entity-name="knt.exceedvote.model.Team">
<column name="tid" not-null="true" />
</many-to-many>
</set>
</class>
</hibernate-mapping>
<hibernate-mapping>
<class name="package.model.Vote" table="votes">
<id name="vid" column="vid" >
<generator class="increment"/>
</id>
<property name="pid" column="pid" />
<property name="uid" column="uid" />
<property name="tid" column="tid" />
<property name="votes" column="votes" />
</class>
</hibernate-mapping>
Please keep in mind, Hibernate is designed using the notion of Object Graph, which is a name given to the relational objects.
That core concept is missing in your mapping (Poll and Vote seem to be isolated) hence I doubt you can use HQL in its current state.
In my opinion, you have two options:
Define the relationship between Poll, pid and Vote, uid. Then you should be able to write simple HQL.
Use native SQL through Hibernate session itself.
Hey,
I have to map the following entities:
class Document
{
public int DocumentId { get; set; }
public DocumentList ContainingList { get; set; }
}
class DocumentList
{
public int DocumentListId { get; set; }
public DateTime LastUpdateTime { get; set; }
public IList<Doucment> Documents { get; set; }
}
With the constraint that only one DocumentList can own a specific document (altough a collection-table exists here).
Mapping has to rely on the following tables (which cannot be changed, for the sake of simplicity):
TB_DOC
------
DOC_ID (int, PK)
DOC_CONTENT (blob)
TB_DOC_LIST
-----------
DOC_LIST_ID (int, PK)
DOC_LIST_UPDATE_TIME (datetime)
TB_LIST_AND_DOCS
----------------
DOC_LIST_ID
DOC_ID
So the mapping i tohught of would be like this:
enter code here
<class name="DocumentList" table="TB_DOC_LIST">
<id name="DocumentListId">
<column name="DOC_LIST_ID"/>
<generator class="assigned" />
</id>
<property name="LastUpdateTime" column="DOC_LIST_UPDATE_TIME ">
<set name="Documents" table="TB_LIST_AND_DOCS">
<key column="DOC_ID"></key>
<one-to-many class="Document" />
</set>
</class>
and:
<class name="Document" table="TB_DOC">
<id name="DocumentId">
<column name="DOC_ID"/>
<generator class="assigned" />
</id>
[ ??? ] - property to reference the "owner" document list
</class>
Now, following the known patterns, i can't figure out how should the back-link from Document to the DocumentList be mapped, since i have a "weired| one-to-many relation here, broken by a third table.
I also don't want a Document object to reference an IList to solve this with back-referencing many-to-many, since each Document has only one such "owner" DocumentList.
Any elegant idea? what am i mispercepting here?
cant test it right now, but a join could be used to get the reference id.
<class name="Document" table="TB_DOC">
<id name="DocumentId">
<column name="DOC_ID"/>
<generator class="assigned" />
</id>
<join table="TB_LIST_AND_DOCS">
<key column="DOC_ID"/>
<many-to-one class="DocumentList">
<column name="DOC_LIST_ID" />
</many-to-one>
</join>
</class>
Hi
I have parent and child table like below
<?xml version="1.0" encoding="utf-8"?>
------- parent --------------
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="HibernateSample.StudMarks,HibernateSample" table="StudMarks" lazy="false">
<id name="Sno" column="SNO" type="int">
<generator class="assigned"/>
</id>
<many-to-one name="Student" column="ID" not-null="true"/>
<property name="Marks" column="Marks" type="int" not-null="true" />
<property name="Rank" column="Rank" type="int" not-null="true" />
</class>
</hibernate-mapping>
------- child --------------
<?xml version="1.0" encoding="utf-8"?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="HibernateSample.Student,HibernateSample" table="Student" lazy="false">
<id name="Id" column="ID" type="int">
<generator class="native" />
</id>
<property name="Name" column="Name" type="string" not-null="true" />
<property name="Standard" column="Standard" type="string" not-null="true" />
<bag name="StudMarks" cascade="all" lazy="false">
<key column="ID" not-null="true"/>
<one-to-many class="HibernateSample.StudMarks,HibernateSample" />
</bag>
</class>
</hibernate-mapping>
and in .cs file i have like written code like below to insert into parent and child.
StudMarks sm = new StudMarks();
Student st = new Student();
List<StudMarks> sms = new List<StudMarks>();
st.Id = 9;
st.Name = "stud 999";
st.Standard = "99";
sm.Sno = 9;
sm.Marks = 99;
sm.Rank = 9;
sm.Student = st; ------ **Line 1**
st.StudMarks = sms; ------ **Line 2**
session.Save(sm);
session.Flush();
If i commENT "Line 1" in above code only child is inserting. If i comment "Line 2" foreign key constraint error is throwing.
Tables:
CREATE TABLE [dbo].[Student](
[ID] [int] IDENTITY(1,1) NOT NULL, -- PRIMARY KEY
[Name] [varchar](50) NOT NULL,
[Standard] [varchar](50) NOT NULL,
CREATE TABLE [dbo].[StudMarks](
[SNO] [int] NOT NULL, -- PRIMARY KEY
[ID] [int] NOT NULL, -- FOREIGN KEY
[Marks] [int] NOT NULL,
[Rank] [int] NOT NULL,)
Please let me know how to insert in parent and child at a time in single save operation.
You have a cascade relation from Student->StudentMarks. So you should be saving st...
session.Save(st);
You should also specify inverse="true" on the bag so you don't get double updates of the foreign key and a cascade="all-delete-orphan" is probably appropriate here as you want all StudentMarks to be deleted when the Student is deleted.
I believe you need to specify inverse="true" on the Student mapping of the StudMarks collection property, indicating that the StudMark mapping is the owner of the relationship.