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• Am I using EJBs properly?

  - by kgrad

  I am using a JEE6 stack including JPA 2.0, JSF 2.0, EJB 3.1 etc. The way my architecture is setup is the following: I have JPA annotated DAOs using hibernate as my JPA provider. I have JSF Managed beans which correspond to my facelet/xhtml pages. I have EJBs that handle all of my database requests. My XHTML pages have JSF EL which make calls to my Managed beans. My managed beans contain references to my DAO entities which are managed by EJBs. For example, I have a user entity which is mapped to a db table. I have a user EJB which handles all CRUD operations that return Users. I have a page that edits a user. The highlevel workflow would be: navigate to user edit page - EL calls a method located in the managed bean that loads a user. The method calls userEJB.loadUser(user) from the EJB to get the user from the database. The user is edited and submit - a function is called in the managed bean which calls a function in the EJB to save the user. etc. I am running into issues accessing my data within my JSF pages using EJBs. I am having a lot of problems with lazy initialization errors, which I believe is due to how I have set things up. For example, I have a Client entity that has a List of users which are lazily loaded. In order to get a client I call a method in my EJB which goes to the database, finds a client and returns it. Later on i wish to access this clients list of users, in order to do so i have to go back to the EJB by calling some sort of method in order to load those users (since they are lazily loaded). This means that I have to create a method such as public List<User> getUserListByClient(Client c) { c = em.merge(c); return c.getUserList(); } The only purpose of this method is to load the users (and I'm not even positive this approach is good or works). If i was doing session management myself, I would like just leave the session open for the entire request and access the property directly, this would be fine as the session would be open anyway, there seems to be this one extra layer of indirection in EJBs which is making things difficult for me. I do like EJBs as I like the fact that they are controlled by the container, pooled, offer transaction management for free etc. However, I get the feeling that I am using them incorrectly, or I have set up my JSF app incorrectly. Any feedback would be greatly appreciated. thanks,

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• SQLSTATE[HY093]: Invalid parameter number: mixed named and positional parameters

  - by Gremo

  Weird error and this is driving me crazy all the day. To me it seems a bug because there are no positional parameters in my query. Here is the method: public function getAll(User $user, DateTime $start = null, DateTime $end = null) { $params = array('user_id' => $user->getId()); $rsm = new \Doctrine\ORM\Query\ResultSetMapping(); // Result set mapping $rsm->addScalarResult('subtype', 'subtype'); $rsm->addScalarResult('count', 'count'); $sms_sql = "SELECT CONCAT('sms_', IF(is_auto = 0, 'user' , 'auto')) AS subtype, " . "SUM(messages_count * (customers_count + recipients_count)) AS count " . "FROM outgoing_message AS m INNER JOIN small_text_message AS s ON " . "m.id = s.id WHERE status <> 'pending' AND user_id = :user_id"; $news_sql = "SELECT CONCAT('news_', IF(is_auto = 0, 'user' , 'auto')) AS subtype, " . "SUM(customers_count + recipients_count) AS count " . "FROM outgoing_message AS m JOIN newsletter AS n ON m.id = n.id " . "WHERE status <> 'pending' AND user_id = :user_id"; if($start) : $sms_sql .= " AND sent_at >= :start"; $news_sql .= " AND sent_at >= :start"; $params['start'] = $start->format('Y-m-d'); endif; $sms_sql .= ' GROUP BY type, is_auto'; $news_sql .= ' GROUP BY type, is_auto'; return $this->_em->createNativeQuery("$sms_sql UNION ALL $news_sql", $rsm) >setParameters($params)->getResult(); } And this throws the exception: SQLSTATE[HY093]: Invalid parameter number: mixed named and positional parameters Array $arams is OK and so generated SQL: var_dump($params); array (size=2) 'user_id' => int 1 'start' => string '2012-01-01' (length=10) Strangest thing is that it works with "$sms_sql" only! Any help would make my day, thanks. Update Found another strange thing. If i change only the name (to start_date instead of start): if($start) : $sms_sql .= " AND sent_at >= :start_date"; $news_sql .= " AND sent_at >= :start_date"; $params['start_date'] = $start->format('Y-m-d'); endif; What happens is that Doctrine/PDO says: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'sent1rt_date' in 'where clause' ... as string 1rt was added in the middle of the column name! Crazy...

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• What was "The Next Big Thing" when you were just starting out in programming?

  - by Andrew

  I'm at the beginning of my career and there are lots of things which are being touted as "The Next Big Thing". For example: Dependency Injection (Spring, etc) MVC (Struts, ASP.NET MVC) ORMs (Linq To SQL, Hibernate) Agile Software Development These things have probably been around for some time, but I've only just started out. And don't get me wrong, I think these things are great! So, what was "The Next Big Thing" when you were starting out? When was it? Were people sceptical of it at first? Why? Did you think it would catch on? Did it pan out and become widely accepted/used? If not, why not? EDIT It's been nearly a week since I first posted this question and I can safely say that I did not expect such explosive interest. I asked the question so that I could gain a perspective of what kinds of innovations in programming people thought were most important when they were starting out. At the time of writing this I have read ~95% of all answers. To answer a few questions, the "Next Big Things" I listed are ones that I am currently really excited about and that I had not really been exposed to until I started working. I'm hoping to implement some or all of these in the near future at my current workplace. To many people they are probably old news. In regards to the "is this a real question" debate, I can see that obviously hasn't been settled yet. I feel bad whenever I read a comment saying that these kinds of questions take away from the real meaning of SO. I'm not wholly convinced that it doesn't. On the other hand, I have seen a lot of comments saying what a great question it is. Anyway, I have chosen "The Internet!" as my answer to this question. I don't think (in my very humble opinion, and, it seems many SOers opinions) that many things related to programming can compare. Nowadays every business and their dog has a website which can do anything from simply supplying information to purchasing goods halfway around the world to updating your blog. And of course, all these businesses need people like us. Thanks to everyone for all the great answers!

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• Storing simulation results in a persistent manner for Python?

  - by Az

  Background: I'm running multiple simuations on a set of data. For each session, I'm allocating projects to students. The difference between each session is that I'm randomising the order of the students such that all the students get a shot at being assigned a project they want. I was writing out some of the allocations in a spreadsheet (i.e. Excel) and it basically looked like this (tiny snapshot, actual table extends to a few thousand sessions, roughly 100 students). | | Session 1 | Session 2 | Session 3 | |----------|-----------|-----------|-----------| |Stu1 |Proj_AA |Proj_AB |Proj_AB | |----------|-----------|-----------|-----------| |Stu2 |Proj_AB |Proj_AA |Proj_AC | |----------|-----------|-----------|-----------| |Stu3 |Proj_AC |Proj_AC |Proj_AA | |----------|-----------|-----------|-----------| Now, the code that deals with the allocation currently stores a session in an object. The next time the allocation is run, the object is over-written. Thus what I'd really like to do is to store all the allocation results. This is important since I later need to derive from the data, information such as: which project Stu1 got assigned to the most or perhaps how popular Proj_AC was (how many times it was assigned / number of sessions). Question(s): What methods can I possibly use to basically store such session information persistently? Basically, each session output needs to add itself to the repository after ending and before beginning the next allocation cycle. One solution that was suggested by a friend was mapping these results to a relational database using SQLAlchemy. I kind of like the idea since this does give me an opportunity to delve into databases. Now the database structure I was recommended was: |----------|-----------|-----------| |Session |Student |Project | |----------|-----------|-----------| |1 |Stu1 |Proj_AA | |----------|-----------|-----------| |1 |Stu2 |Proj_AB | |----------|-----------|-----------| |1 |Stu3 |Proj_AC | |----------|-----------|-----------| |2 |Stu1 |Proj_AB | |----------|-----------|-----------| |2 |Stu2 |Proj_AA | |----------|-----------|-----------| |2 |Stu3 |Proj_AC | |----------|-----------|-----------| |3 |Stu1 |Proj_AB | |----------|-----------|-----------| |3 |Stu2 |Proj_AC | |----------|-----------|-----------| |3 |Stu3 |Proj_AA | |----------|-----------|-----------| Here, it was suggested that I make the Session and Student columns a composite key. That way I can access a specific record for a particular student for a particular session. Or I can merely get the entire allocation run for a particular session. Questions: Is the idea a good one? How does one implement and query a composite key using SQLAlchemy? What happens to the database if a particular student is not assigned a project (happens if all projects that he wants are taken)? In the code, if a student is not assigned a project, instead of a proj_id he simply gets None for that field/object. I apologise for asking multiple questions but since these are closely-related, I thought I'd ask them in the same space.

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• Any tool(s) for knowing the layout (segments) of running process in Windows?

  - by claws

  I've always been curious about How exactly the process looks in memory? What are the different segments(parts) in it? How exactly will be the program (on the disk) & process (in the memory) are related? My previous question: http://stackoverflow.com/questions/1966920/more-info-on-memory-layout-of-an-executable-program-process In my quest, I finally found a answer. I found this excellent article that cleared most of my queries: http://www.linuxforums.org/articles/understanding-elf-using-readelf-and-objdump_125.html In the above article, author shows how to get different segments of the process (LINUX) & he compares it with its corresponding ELF file. I'm quoting this section here: Courious to see the real layout of process segment? We can use /proc//maps file to reveal it. is the PID of the process we want to observe. Before we move on, we have a small problem here. Our test program runs so fast that it ends before we can even dump the related /proc entry. I use gdb to solve this. You can use another trick such as inserting sleep() before it calls return(). In a console (or a terminal emulator such as xterm) do: $ gdb test (gdb) b main Breakpoint 1 at 0x8048376 (gdb) r Breakpoint 1, 0x08048376 in main () Hold right here, open another console and find out the PID of program "test". If you want the quick way, type: $ cat /proc/`pgrep test`/maps You will see an output like below (you might get different output): [1] 0039d000-003b2000 r-xp 00000000 16:41 1080084 /lib/ld-2.3.3.so [2] 003b2000-003b3000 r--p 00014000 16:41 1080084 /lib/ld-2.3.3.so [3] 003b3000-003b4000 rw-p 00015000 16:41 1080084 /lib/ld-2.3.3.so [4] 003b6000-004cb000 r-xp 00000000 16:41 1080085 /lib/tls/libc-2.3.3.so [5] 004cb000-004cd000 r--p 00115000 16:41 1080085 /lib/tls/libc-2.3.3.so [6] 004cd000-004cf000 rw-p 00117000 16:41 1080085 /lib/tls/libc-2.3.3.so [7] 004cf000-004d1000 rw-p 004cf000 00:00 0 [8] 08048000-08049000 r-xp 00000000 16:06 66970 /tmp/test [9] 08049000-0804a000 rw-p 00000000 16:06 66970 /tmp/test [10] b7fec000-b7fed000 rw-p b7fec000 00:00 0 [11] bffeb000-c0000000 rw-p bffeb000 00:00 0 [12] ffffe000-fffff000 ---p 00000000 00:00 0 Note: I add number on each line as reference. Back to gdb, type: (gdb) q So, in total, we see 12 segment (also known as Virtual Memory Area--VMA). But I want to know about Windows Process & PE file format. Any tool(s) for getting the layout (segments) of running process in Windows? Any other good resources for learning more on this subject? EDIT: Are there any good articles which shows the mapping between PE file sections & VA segments?

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• Translate Java class with static attributes and Annotation to Scala equivalent

  - by ifischer

  I'm currently trying to "translate" the following Java class to an equivalent Scala class. It's part of a JavaEE6-application and i need it to use the JPA2 MetaModel. import javax.persistence.metamodel.SingularAttribute; import javax.persistence.metamodel.StaticMetamodel; @StaticMetamodel(Person.class) public class Person_ { public static volatile SingularAttribute<Person, String> name; } A dissassembling of the compiled class file reveals the following information for the compiled file: > javap Person_.class : public class model.Person_ extends java.lang.Object{ public static volatile javax.persistence.metamodel.SingularAttribute name; public model.Person_(); } So now i need an equivalent Scala file that has the same structure, as JPA depends on it, cause it resolves the attributes by reflection to make them accessible at runtime. So the main problem i think is that the attribute is static, but the Annotation has to be on an (Java)Object (i guess) My first naive attempt to create a Scala equivalent is the following: @StaticMetamodel(classOf[Person]) class Person_ object Person_ { @volatile var name:SingularAttribute[Person, String] = _; } But the resulting classfile is far away from the Java one, so it doesn't work. When trying to access the attributes at runtime, e.g. "Person_.firstname", it resolves to null, i think JPA can't do the right reflection magic on the compiled classfile (the Java variant resolves to an instance of org.hibernate.ejb.metamodel.SingularAttributeImpl at runtime). > javap Person_.class : public class model.Person_ extends java.lang.Object implements scala.ScalaObject{ public static final void name_$eq(javax.persistence.metamodel.SingularAttribute); public static final javax.persistence.metamodel.SingularAttribute name(); public model.Person_(); } > javap Person_$.class : public final class model.Person__$ extends java.lang.Object implements scala.ScalaObject public static final model.Person__$ MODULE$; public static {}; public javax.persistence.metamodel.SingularAttribute name(); public void name_$eq(javax.persistence.metamodel.SingularAttribute); } So now what i'd like to know is if it's possible at all to create a Scala equivalent of the Java class? It seems to me that it's absolutely not, but maybe there is a workaround or something (except just using Java, but i want my app to be in Scala where possible) Any ideas, anyone? Thanks in advance!

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• What are the benefits of using ORM over XML Serialization/Deserialization?

  - by Tequila Jinx

  I've been reading about NHibernate and Microsoft's Entity Framework to perform Object Relational Mapping against my data access layer. I'm interested in the benefits of having an established framework to perform ORM, but I'm curious as to the performance costs of using it against standard XML Serialization and Deserialization. Right now, I develop stored procedures in Oracle and SQL Server that use XML Types for either input or output parameters and return or shred XML depending on need. I use a custom database command object that uses generics to deserialize the XML results into a specified serializable class. By using a combination of generics, xml (de)serialization and Microsoft's DAAB, I've got a process that's fairly simple to develop against regardless of the data source. Moreover, since I exclusively use Stored Procedures to perform database operations, I'm mostly protected from changes in the data structure. Here's an over-simplified example of what I've been doing. static void main() { testXmlClass test = new test(1); test.Name = "Foo"; test.Save(); } // Example Serializable Class ------------------------------------------------ [XmlRootAttribute("test")] class testXmlClass() { [XmlElement(Name="id")] public int ID {set; get;} [XmlElement(Name="name")] public string Name {set; get;} //create an instance of the class loaded with data. public testXmlClass(int id) { GenericDBProvider db = new GenericDBProvider(); this = db.ExecuteSerializable("myGetByIDProcedure"); } //save the class to the database... public Save() { GenericDBProvider db = new GenericDBProvider(); db.AddInParameter("myInputParameter", DbType.XML, this); db.ExecuteSerializableNonQuery("mySaveProcedure"); } } // Database Handler ---------------------------------------------------------- class GenericDBProvider { public T ExecuteSerializable<T>(string commandText) where T : class { XmlSerializer xml = new XmlSerializer(typeof(T)); // connection and command code is assumed for the purposes of this example. // the final results basically just come down to... return xml.Deserialize(commandResults) as T; } public void ExecuteSerializableNonQuery(string commandText) { // once again, connection and command code is assumed... // basically, just execute the command along with the specified // parameters which have been serialized. } public void AddInParameter(string name, DbType type, object value) { StringWriter w = new StringWriter(); XmlSerializer x = new XmlSerializer(value.GetType()); //handle serialization for serializable classes. if (type == DbType.Xml && (value.GetType() != typeof(System.String))) { x.Serialize(w, value); w.Close(); // store serialized object in a DbParameterCollection accessible // to my other methods. } else { //handle all other parameter types } } } I'm starting a new project which will rely heavily on database operations. I'm very curious to know whether my current practices will be sustainable in a high-traffic situation and whether or not I should consider switching to NHibernate or Microsoft's Entity Framework to perform what essentially seems to boil down to the same thing I'm currently doing. I appreciate any advice you may have.

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• NHibernate GenericADO Exception

  - by Ris90

  Hi, I'm trying to make simple many-to-one association, using NHibernate.. I have class Recruit with this mapping: <class name="Recruit" table="Recruits"> <id name="ID"> <generator class="native"/> </id> <property name="Lastname" column="lastname"/> <property name="Name" column="name"/> <property name="MedicalReport" column="medicalReport"/> <property name="DateOfBirth" column ="dateOfBirth" type="Date"/> <many-to-one name="AssignedOnRecruitmentOffice" column="assignedOnRecruitmentOffice" class="RecruitmentOffice"/> which is many-to-one connected to RecruitmentOffices: <class name="RecruitmentOffice" table="RecruitmentOffices"> <id name="ID" column="ID"> <generator class="native"/> </id> <property name="Chief" column="chief"/> <property name="Name" column="name"/> <property name ="Address" column="address"/> <set name="Recruits" cascade="save-update" inverse="true" lazy="true"> <key> <column name="AssignedOnRecruitmentOffice"/> </key> <one-to-many class="Recruit"/> </set> And create Repository class with method Insert: public void Insert(Recruit recruit) { using (ITransaction transaction = session.BeginTransaction()) { session.Save(recruit); transaction.Commit(); } } then I try to save new recrui to base: Recruit test = new Recruit(); RecruitmentOffice office = new RecruitmentOffice(); ofice.Name = "test"; office.Chief = "test"; test.AssignedOnRecruitmentOffice = office; test.Name = "test"; test.DateOfBirth = DateTime.Now; RecruitRepository testing = new RecruitRepository(); testing.Insert(test); And have this error GenericADOException could not insert: [OSiUBD.Models.DAO.Recruit][SQL: INSERT INTO Recruits (lastname, name, medicalReport, dateOfBirth, assignedOnRecruitmentOffice) VALUES (?, ?, ?, ?, ?); select SCOPE_IDENTITY()] on session.Save

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• Fixing up an entity framework query

  - by vdh_ant

  My table structure is as follows: Person 1-M PesonAddress Person 1-M PesonPhone Person 1-M PesonEmail Person 1-M Contract Contract M-M Program Contract M-1 Organization At the end of this query I need a populated object graph where each person has their: PesonAddress's PesonPhone's PesonEmail's PesonPhone's Contract's - and this has its respective Program's Now I had the following query and I thought that it was working great, but it has a couple of problems: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") where people.Contract.Any( contract => (param.OrganizationId == contract.OrganizationId) && contract.Program.Any( contractProgram => (param.ProgramId == contractProgram.ProgramId))) select people; The problem is that it filters the person to the criteria but not the Contracts or the Contract's Programs. It brings back all Contracts that each person has not just the ones that have an OrganizationId of x and the same goes for each of those Contract's Programs respectively. What I want is only the people that have at least one contract with an OrgId of x with and where that contract has a Program with the Id of y... and for the object graph that is returned to have only the contracts that match and programs within that contract that match. I kinda understand why its not working, but I don't know how to change it so it is working... This is my attempt thus far: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") let currentContracts = from contract in people.Contract where (param.OrganizationId == contract.OrganizationId) select contract let currentContractPrograms = from contractProgram in currentContracts let temp = from x in contractProgram.Program where (param.ProgramId == contractProgram.ProgramId) select x where temp.Any() select temp where currentContracts.Any() && currentContractPrograms.Any() select new Person { PersonId = people.PersonId, FirstName = people.FirstName, ..., ...., MiddleName = people.MiddleName, Surname = people.Surname, ..., ...., Gender = people.Gender, DateOfBirth = people.DateOfBirth, ..., ...., Contract = currentContracts, ... }; //This doesn't work But this has several problems (where the Person type is an EF object): I am left to do the mapping by myself, which in this case there is quite a lot to map When ever I try to map a list to a property (i.e. Scholarship = currentScholarships) it says I can't because IEnumerable is trying to be cast to EntityCollection Include doesn't work Hence how do I get this to work. Keeping in mind that I am trying to do this as a compiled query so I think that means anonymous types are out.

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• Complex Entity Framework linked-graphs issue: how to limit change set / break the graph?

  - by Hightechrider

  I have an EDMX containing Sentences, and Words, say and a Sentence contains three Words, say. Appropriate FK relationships exist between the tables. I create some words: Word word1 = new Word(); Word word2 = ... I build a Sentence: Sentence x = new Sentence (word1, word2, word3); I build another Sentence: Sentence y = new Sentence (word1, word4, word5); I try to save x to the database, but EF builds a change set that includes everything, including y, word4 and word5 that aren't ready to save to the database. When SaveChanges() happens it throws an exception: Unable to determine the principal end of the ... relationship. Multiple added entities may have the same primary key. I think it does this because Word has an EntityCollection<Sentence> on it from the FK relationship between the two tables, and thus Sentence y is inextricably linked to Sentence x through word1. So I remove the Navigation Property Sentences from Word and try again. It still tries to put the entire graph into the change set. What suggestions do the Entity Framework experts have for ways to break this connection. Essentially what I want is a one-way mapping from Sentence to Word; I don't want an EntityCollection<Sentence> on Word and I don't want the object graph to get intertwined like this. Code sample: This puts two sentences into the database because Verb1 links them and EF explores the entire graph of existing objects and added objects when you do Add/SaveChanges. Word subject1 = new Word(){ Text = "Subject1"}; Word subject2 = new Word(){ Text = "Subject2"}; Word verb1 = new Word(){ Text = "Verb11"}; Word object1 = new Word(){ Text = "Object1"}; Word object2 = new Word(){ Text = "Object2"}; Sentence s1 = new Sentence(){Subject = subject1, Verb=verb1, Object=object1}; Sentence s2 = new Sentence(){Subject=subject2, Verb=verb1, Object=object2}; context.AddToSentences(s1); context.SaveChanges(); foreach (var s in context.Sentences) { Console.WriteLine(s.Subject + " " + s.Verb + " " + s.Object); }

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• Dependency Injection and Unit of Work pattern

  - by sunwukung

  I have a dilemma. I've used DI (read: factory) to provide core components for a homebrew ORM. The container provides database connections, DAO's,Mappers and their resultant Domain Objects on request. Here's a basic outline of the Mappers and Domain Object classes class Mapper{ public function __constructor($DAO){ $this->DAO = $DAO; } public function load($id){ if(isset(Monitor::members[$id]){ return Monitor::members[$id]; $values = $this->DAO->selectStmt($id); //field mapping process omitted for brevity $Object = new Object($values); return $Object; } } class User(){ public function setName($string){ $this->name = $string; //mark modified by means fair or foul } } The ORM also contains a class (Monitor) based on the Unit of Work pattern i.e. class Monitor(){ private static array modified; private static array dirty; public function markClean($class); public function markModified($class); } The ORM class itself simply co-ordinates resources extracted from the DI container. So, to instantiate a new User object: $Container = new DI_Container; $ORM = new ORM($Container); $User = $ORM->load('user',1); //at this point the container instantiates a mapper class //and passes a database connection to it via the constructor //the mapper then takes the second argument and loads the user with that id $User->setName('Rumpelstiltskin');//at this point, User must mark itself as "modified" My question is this. At the point when a user sets values on a Domain Object class, I need to mark the class as "dirty" in the Monitor class. I have one of three options as I can see it 1: Pass an instance of the Monitor class to the Domain Object. I noticed this gets marked as recursive in FirePHP - i.e. $this-Monitor-markModified($this) 2: Instantiate the Monitor directly in the Domain Object - does this break DI? 3: Make the Monitor methods static, and call them from inside the Domain Object - this breaks DI too doesn't it? What would be your recommended course of action (other than use an existing ORM, I'm doing this for fun...)

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• How do I destruct data associated with an object after the object no longer exists?

  - by Phineas

  I'm creating a class (say, C) that associates data (say, D) with an object (say, O). When O is destructed, O will notify C that it soon will no longer exist :( ... Later, when C feels it is the right time, C will let go of what belonged to O, namely D. If D can be any type of object, what's the best way for C to be able to execute "delete D;"? And what if D is an array of objects? My solution is to have D derive from a base class that C has knowledge of. When the time comes, C calls delete on a pointer to the base class. I've also considered storing void pointers and calling delete, but I found out that's undefined behavior and doesn't call D's destructor. I considered that templates could be a novel solution, but I couldn't work that idea out. Here's what I have so far for C, minus some details: // This class is C in the above description. There may be many instances of C. class Context { public: // D will inherit from this class class Data { public: virtual ~Data() {} }; Context(); ~Context(); // Associates an owner (O) with its data (D) void add(const void* owner, Data* data); // O calls this when he knows its the end (O's destructor). // All instances of C are now aware that O is gone and its time to get rid // of all associated instances of D. static void purge (const void* owner); // This is called periodically in the application. It checks whether // O has called purge, and calls "delete D;" void refresh(); // Side note: sometimes O needs access to D Data *get (const void *owner); private: // Used for mapping owners (O) to data (D) std::map _data; }; // Here's an example of O class Mesh { public: ~Mesh() { Context::purge(this); } void init(Context& c) const { Data* data = new Data; // GL initialization here c.add(this, new Data); } void render(Context& c) const { Data* data = c.get(this); } private: // And here's an example of D struct Data : public Context::Data { ~Data() { glDeleteBuffers(1, &vbo); glDeleteTextures(1, &texture); } GLint vbo; GLint texture; }; }; P.S. If you're familiar with computer graphics and VR, I'm creating a class that separates an object's per-context data (e.g. OpenGL VBO IDs) from its per-application data (e.g. an array of vertices) and frees the per-context data at the appropriate time (when the matching rendering context is current).

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• FluentNHibernate Many-To-One References where Foreign Key is not to Primary Key and column names are

  - by Todd Langdon

  I've been sitting here for an hour trying to figure this out... I've got 2 tables (abbreviated): CREATE TABLE TRUST ( TRUSTID NUMBER NOT NULL, ACCTNBR VARCHAR(25) NOT NULL ) CONSTRAINT TRUST_PK PRIMARY KEY (TRUSTID) CREATE TABLE ACCOUNTHISTORY ( ID NUMBER NOT NULL, ACCOUNTNUMBER VARCHAR(25) NOT NULL, TRANSAMT NUMBER(38,2) NOT NULL POSTINGDATE DATE NOT NULL ) CONSTRAINT ACCOUNTHISTORY_PK PRIMARY KEY (ID) I have 2 classes that essentially mirror these: public class Trust { public virtual int Id {get; set;} public virtual string AccountNumber { get; set; } } public class AccountHistory { public virtual int Id { get; set; } public virtual Trust Trust {get; set;} public virtual DateTime PostingDate { get; set; } public virtual decimal IncomeAmount { get; set; } } How do I do the many-to-one mapping in FluentNHibernate to get the AccountHistory to have a Trust? Specifically, since it is related on a different column than the Trust primary key of TRUSTID and the column it is referencing is also named differently (ACCTNBR vs. ACCOUNTNUMBER)???? Here's what I have so far - how do I do the References on the AccountHistoryMap to Trust??? public class TrustMap : ClassMap<Trust> { public TrustMap() { Table("TRUST"); Id(x => x.Id).Column("TRUSTID"); Map(x => x.AccountNumber).Column("ACCTNBR"); } } public class AccountHistoryMap : ClassMap<AccountHistory> { public AccountHistoryMap() { Table("TRUSTACCTGHISTORY"); Id (x=>x.Id).Column("ID"); References<Trust>(x => x.Trust).Column("ACCOUNTNUMBER").ForeignKey("ACCTNBR").Fetch.Join(); Map(x => x.PostingDate).Column("POSTINGDATE"); ); I've tried a few different variations of the above line but can't get anything to work - it pulls back AccountHistory data and a proxy for the Trust; however it says no Trust row with given identifier. This has to be something simple. Anyone? Thanks in advance.

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• Closure Tables - Is this enough data to display a tree view?

  - by James Pitt

  Here is the table I have created by testing the closure table method. | id | parentId | childId | hops | | | | | 270 | 6 | 6 | 0 | 271 | 7 | 7 | 0 | 272 | 8 | 8 | 0 | 273 | 9 | 9 | 0 | 276 | 10 | 10 | 0 | 281 | 9 | 10 | 1 | 282 | 7 | 9 | 1 | 283 | 7 | 10 | 2 | 285 | 7 | 8 | 1 | 286 | 6 | 7 | 1 | 287 | 6 | 9 | 2 | 288 | 6 | 10 | 3 | 289 | 6 | 8 | 2 | 293 | 6 | 9 | 1 | 294 | 6 | 10 | 2 I am trying to create a simple tree of this using PHP. There does not seem to be enough data to create the table. For example, when I look purely at parentId = 6: -Part 6 -Part 7 - ? - ? -Part 9 - ? - ? We know that parts 8 and 10 exists below Part 7 or 9, but not which. We know that part 10 exists at both 3 and 4 nodes deep but where? If I look at other data in the table it is possible to tell it should be: - Part 6 - Part 7 - Part 9 - Part 10 - Part 9 - Part 10 I thought one of the benefits of closure tables was there was no need for recursive queries? Could you help explain what I am doing wrong? EDIT: For clarification, this is a mapping table. There is another table called "parts" which has a column called part_id that correlates to both the parentId and childId columns in the "closure" table. The "id" column in the table above (closure) is just for the purposes of maintaining a primary key. It is not really necessary. The methods I have used to create this closure table is described in the following article: http://dirtsimple.org/2010/11/simplest-way-to-do-tree-based-queries.html EDIT2: It can have two and three hops. I will explain easier by assigning names to the items. Part 6 = Bicycle Part 7 = Gears Part 8 = Chain Part 9 = Bolt Part 10 = Nut Nut is part of Bolt. The Bolt and Nut combo exists directly within Bicycle and within Gears which is part of Bicycle. In relation to what method to use I have looked at Adjacency, Edges, Enum Paths, Closures, DAGS(networks) and the Nested Set Model. I am still trying to work out what is what, but this is an extremely complex component database where there are multiple parents and any modification to a sub-tree must propogate through the other trees. More importantly there will be insertions, deletions and tree views that I wish to avoid recursion during general use, even at the cost of database space and query time during entry.

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• ASP.NET MVC 2 AJAX dilemma: Lose Models concept or create unmanageable JavaScript

  - by Slightly Frustrated

  Hi, Ok, let's assume we are working with ASP.NET MVC 2 (latest and greatest preview) and we want to create AJAX user interface with jQuery. So what are our real options here? Option 1 - Pass Json from the Controller to the view, and then the view submits Json back to the controller. This means (in the order given): User opens some View (let's say - /Invoices/January) which has to visualize a list of data (e.g. <IEnumerable<X.Y.Z.Models.Invoice>>) Controller retrieves the Model from the repository (assuming we are using repository pattern). Controller creates a new instance of a class which we will serialize to Json. The reasaon we do this, is because the model may not be serializable (circular reference ftl) Controller populates the soon-to-be-serialized class with data Controller serializes the class to Json and passes it the view. User does some change and submits the 'form' The View submits back Json to the controller The Controller now must 'manually' validate the input, because the Json passed does not bind to a Model See, if our View is communicating to the controller via Json, we lose the Model validation, which IMHO is incredible disadvantage. In this case, forget about data annotations and stuff. Option 2 - Ok, the alternative of the first approach is to pass the Models to the Views, which is the default behavior in the template when you start a new project. We pass a strong typed model to the view The view renders the appropriate html and javascript, sticking to the model property names. This is important! The user submits the form. If we stick to the model names, when we .serialize() the form and submit it to the controller it will map to a model. There is no Json mapping. The submitted form directly binds to a strongly typed model, hence, we can use the model validation. E.g. we keep the business logic where it should be. Problem with this approach is, if we refactor some of the Models (change property names, types, etc), the javascript we wrote would become invalid. We will have to manually refactor the scripting and hope we don't miss something. There is no way you can test it either. Ok, the question is - how to write an AJAX front end, which keeps the business logic validation in the model (e.g. controller passes and receives a Model type), but in the same time doesn't screw up the javascript and html when we refactor the model?

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• LINQ Query Returning Multiple Copies Of First Result

  - by Mike G

  I'm trying to figure out why a simple query in LINQ is returning odd results. I have a view defined in the database. It basically brings together several other tables and does some data munging. It really isn't anything special except for the fact that it deals with a large data set and can be a bit slow. I want to query this view based on a long. Two sample queries below show different queries to this view. var la = Runtime.OmsEntityContext.Positions.Where(p => p.AccountNumber == 12345678).ToList(); var deDa = Runtime.OmsEntityContext.Positions.Where(p => p.AccountNumber == 12345678).Select(p => new { p.AccountNumber, p.SecurityNumber, p.CUSIP }).ToList(); The first one should hand back a List. The second one will be a list of anonymous objects. When I do these queries in entities framework the first one will hand me back a list of results where they're all exactly the same. The second query will hand me back data where the account number is the one that I queried and the other values differ. This seems to do this on a per account number basis, ie if I were to query for one account number or another all the Position objects for one account would have the same value (the first one in the list of Positions for that account) and the second account would have a set of Position objects that all had the same value (again, the first one in it's list of Position objects). I can write SQL that is in effect the same as either of the two EF queries. They both come back with results (say four) that show the correct data, one account number with different securities numbers. Why does this happen??? Is there something that I could be doing wrong so that if I had four results for the first query above that the first record's data also appears in the 2-4th's objects??? I cannot fathom what would/could be causing this. I've searched Google for all kinds of keywords and haven't seen anyone with this issue. We partial class out the Positions class for added functionality (smart object) and some smart properties. There are even some constructors that provide some view model type support. None of this is invoked in the request (I'm 99% sure of this). However, we do this same pattern all over the app. The only thing I can think of is that the mapping in the EDMX is screwy. Is there a way that this would happen if the "primary keys" in the EDMX were not in fact unique given the way the view is constructed? I'm thinking that the dev who imported this model into the EDMX let the designer auto select what would be unique. Any help would give a haggered dev some hope!

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• Many-To-Many Query with Linq-To-NHibernate

  - by rjygraham

  Ok guys (and gals), this one has been driving me nuts all night and I'm turning to your collective wisdom for help. I'm using Fluent Nhibernate and Linq-To-NHibernate as my data access story and I have the following simplified DB structure: CREATE TABLE [dbo].[Classes]( [Id] [bigint] IDENTITY(1,1) NOT NULL, [Name] [nvarchar](100) NOT NULL, [StartDate] [datetime2](7) NOT NULL, [EndDate] [datetime2](7) NOT NULL, CONSTRAINT [PK_Classes] PRIMARY KEY CLUSTERED ( [Id] ASC ) CREATE TABLE [dbo].[Sections]( [Id] [bigint] IDENTITY(1,1) NOT NULL, [ClassId] [bigint] NOT NULL, [InternalCode] [varchar](10) NOT NULL, CONSTRAINT [PK_Sections] PRIMARY KEY CLUSTERED ( [Id] ASC ) CREATE TABLE [dbo].[SectionStudents]( [SectionId] [bigint] NOT NULL, [UserId] [uniqueidentifier] NOT NULL, CONSTRAINT [PK_SectionStudents] PRIMARY KEY CLUSTERED ( [SectionId] ASC, [UserId] ASC ) CREATE TABLE [dbo].[aspnet_Users]( [ApplicationId] [uniqueidentifier] NOT NULL, [UserId] [uniqueidentifier] NOT NULL, [UserName] [nvarchar](256) NOT NULL, [LoweredUserName] [nvarchar](256) NOT NULL, [MobileAlias] [nvarchar](16) NULL, [IsAnonymous] [bit] NOT NULL, [LastActivityDate] [datetime] NOT NULL, PRIMARY KEY NONCLUSTERED ( [UserId] ASC ) I omitted the foreign keys for brevity, but essentially this boils down to: A Class can have many Sections. A Section can belong to only 1 Class but can have many Students. A Student (aspnet_Users) can belong to many Sections. I've setup the corresponding Model classes and Fluent NHibernate Mapping classes, all that is working fine. Here's where I'm getting stuck. I need to write a query which will return the sections a student is enrolled in based on the student's UserId and the dates of the class. Here's what I've tried so far: 1. var sections = (from s in this.Session.Linq<Sections>() where s.Class.StartDate <= DateTime.UtcNow && s.Class.EndDate > DateTime.UtcNow && s.Students.First(f => f.UserId == userId) != null select s); 2. var sections = (from s in this.Session.Linq<Sections>() where s.Class.StartDate <= DateTime.UtcNow && s.Class.EndDate > DateTime.UtcNow && s.Students.Where(w => w.UserId == userId).FirstOrDefault().Id == userId select s); Obviously, 2 above will fail miserably if there are no students matching userId for classes the current date between it's start and end dates...but I just wanted to try. The filters for the Class StartDate and EndDate work fine, but the many-to-many relation with Students is proving to be difficult. Everytime I try running the query I get an ArgumentNullException with the message: Value cannot be null. Parameter name: session I've considered going down the path of making the SectionStudents relation a Model class with a reference to Section and a reference to Student instead of a many-to-many. I'd like to avoid that if I can, and I'm not even sure it would work that way. Thanks in advance to anyone who can help. Ryan

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• Deterministic key serialization

  - by Mike Boers

  I'm writing a mapping class which uses SQLite as the storage backend. I am currently allowing only basestring keys but it would be nice if I could use a couple more types hopefully up to anything that is hashable (ie. same requirements as the builtin dict). To that end I would like to derive a deterministic serialization scheme. Ideally, I would like to know if any implementation/protocol combination of pickle is deterministic for hashable objects (e.g. can only use cPickle with protocol 0). I noticed that pickle and cPickle do not match: >>> import pickle >>> import cPickle >>> def dumps(x): ... print repr(pickle.dumps(x)) ... print repr(cPickle.dumps(x)) ... >>> dumps(1) 'I1\n.' 'I1\n.' >>> dumps('hello') "S'hello'\np0\n." "S'hello'\np1\n." >>> dumps((1, 2, 'hello')) "(I1\nI2\nS'hello'\np0\ntp1\n." "(I1\nI2\nS'hello'\np1\ntp2\n." Another option is to use repr to dump and ast.literal_eval to load. This would only be valid for builtin hashable types. I have written a function to determine if a given key would survive this process (it is rather conservative on the types it allows): def is_reprable_key(key): return type(key) in (int, str, unicode) or (type(key) == tuple and all( is_reprable_key(x) for x in key)) The question for this method is if repr itself is deterministic for the types that I have allowed here. I believe this would not survive the 2/3 version barrier due to the change in str/unicode literals. This also would not work for integers where 2**32 - 1 < x < 2**64 jumping between 32 and 64 bit platforms. Are there any other conditions (ie. do strings serialize differently under different conditions)? (If this all fails miserably then I can store the hash of the key along with the pickle of both the key and value, then iterate across rows that have a matching hash looking for one that unpickles to the expected key, but that really does complicate a few other things and I would rather not do it.) Any insights?

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• How to store date into Mysql database with play framework in scala?

  - by Rahul Kulhari

  I am working with play framework with scala and what am i doing : login page to login into web app sign up page to register into web app after login i want to store all databases values to user what i want to do: when user register for web app then i want to store user values into database with current time and date but my form is giving error. error: List(FormError(dates,error.required,List())),None) controllers/Application.scala object Application extends Controller { val ta:Form[Keyword] = Form( mapping( "id" -> ignored(NotAssigned:Pk[Long]), "word" -> nonEmptyText, "blog" -> nonEmptyText, "cat" -> nonEmptyText, "score"-> of[Long], "summaryId"-> nonEmptyText, "dates" -> date("yyyy-MM-dd HH:mm:ss") )(Keyword.apply)(Keyword.unapply) ) def index = Action { Ok(html.index(ta)); } def newTask= Action { implicit request => ta.bindFromRequest.fold( errors => {println(errors) BadRequest(html.index(errors))}, keywo => { Keyword.create(keywo) Ok(views.html.data(Keyword.all())) } ) } models/keyword.scala case class Keyword(id: Pk[Long],word: String,blog: String,cat: String,score: Long, summaryId: String,dates: Date ) object Keyword { val keyw = { get[Pk[Long]]("keyword.id") ~ get[String]("keyword.word")~ get[String]("keyword.blog")~ get[String]("keyword.cat")~ get[Long]("keyword.score") ~ get[String]("keyword.summaryId")~ get[Date]("keyword.dates") map { case id~blog~cat~word~score~summaryId~dates => Keyword(id,word,blog,cat,score, summaryId,dates) } } def all(): List[Keyword] = DB.withConnection { implicit c => SQL("select * from keyword").as(Keyword.keyw *) } def create(key: Keyword){DB.withConnection{implicit c=> SQL("insert into keyword values({word},{blog}, {cat}, {score},{summaryId},{dates})").on('word-> key.word,'blog->key.blog, 'cat -> key.cat, 'score-> key.score, 'summaryId -> key.summaryId, 'dates->new Date()).executeUpdate } } views/index.scala.html @(taskForm: Form[Keyword]) @import helper._ @main("Todo list") { @form(routes.Application.newTask) { @inputText(taskForm("word")) @inputText(taskForm("blog")) @inputText(taskForm("cat")) @inputText(taskForm("score")) @inputText(taskForm("summaryId")) <input type="submit"> <a href="">Go Back</a> } } please give me some idea to store date into mysql databse and date is not a field of form

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• Entity Framework 4 CTP 5 POCO - Many-to-many configuration, insertion, and update?

  - by Saxman

  I really need someone to help me to fully understand how to do many-to-many relationship with Entity Framework 4 CTP 5, POCO. I need to understand 3 concepts: How to config my model to indicates some tables are many-to-many. How to properly do insert. How to properly do update. Here are my current models: public class MusicSheet { [Key] public int ID { get; set; } public string Title { get; set; } public string Key { get; set; } public virtual ICollection<Author> Authors { get; set; } public virtual ICollection<Tag> Tags { get; set; } } public class Author { [Key] public int ID { get; set; } public string Name { get; set; } public string Bio { get; set; } public virtual ICollection<MusicSheet> MusicSheets { get; set; } } public class Tag { [Key] public int ID { get; set; } public string TagName { get; set; } public virtual ICollection<MusicSheet> MusicSheets { get; set; } } As you can see, the MusicSheet can have many Authors or Tags, and an Author or Tag can have multiple MusicSheets. Again, my questions are: What to do on the EntityTypeConfiguration to set the relationship between them as well as mapping to an table/object that associates with the many-to-many relationship. How to insert a new music sheets (where it might have multiple authors or multiple tags). How to update a music sheet. For example, I might set TagA, TagB to MusicSheet1, but later I need to change the tags to TagA and TagC. It seems like I need to first check to see if the tags already exists, if not, insert the new tag and then associate it with the music sheet (so that I doesn't re-insert TagA?). Or this is something already handled by the framework? Thank you very much. I really hope to fully understand it rather than just doing it without fully understand what's going on. Especially on #3.

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• How to fine tune FluentNHibernate's auto mapper?

  - by Venemo

  Okay, so yesterday I managed to get the latest trunk builds of NHibernate and FluentNHibernate to work with my latest little project. (I'm working on a bug tracking application.) I created a nice data access layer using the Repository pattern. I decided that my entities are nothing special, and also that with the current maturity of ORMs, I don't want to hand-craft the database. So, I chose to use FluentNHibernate's auto mapping feature with NHibernate's "hbm2ddl.auto" property set to "create". It really works like a charm. I put the NHibernate configuration in my app domain's config file, set it up, and started playing with it. (For the time being, I created some unit tests only.) It created all tables in the database, and everything I need for it. It even mapped my many-to-many relationships correctly. However, there are a few small glitches: All of the columns created in the DB allow null. I understand that it can't predict which properties should allow null and which shouldn't, but at least I'd like to tell it that it should allow null only for those types for which null makes sense in .NET (eg. non-nullable value types shouldn't allow null). All of the nvarchar and varbinary columns it created, have a default length of 255. I would prefer to have them on max instead of that. Is there a way to tell the auto mapper about the two simple rules above? If the answer is no, will it work correctly if I modify the tables it created? (So, if I set some columns not to allow null, and change the allowed length for some other, will it correctly work with them?) EDIT: I managed to achieve the above by using Fluent NHibernate's convention API. Thanks to everyone who helped! However, there is one more thing: after checking out the convention API, I really would like my IDs to be calld "ID", not "Id", but it seems to me that the PrimaryKey.Name.Is(x => "ID") is not working at all. If I add it to the conventions collection and rewrite my entities' properties to "ID" instead of "Id", it throws an exception that there is no primary key mapped. Any thoughts on this?

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• Intermittent "Specified cast is invalid" with StructureMap injected data context

  - by FreshCode

  I am intermittently getting an System.InvalidCastException: Specified cast is not valid. error in my repository layer when performing an abstracted SELECT query mapped with LINQ. The error can't be caused by a mismatched database schema since it works intermittently and it's on my local dev machine. Could it be because StructureMap is caching the data context between page requests? If so, how do I tell StructureMap v2.6.1 to inject a new data context argument into my repository for each request? Update: I found this question which correlates my hunch that something was being re-used. Looks like I need to call Dispose on my injected data context. Not sure how I'm going to do this to all my repositories without copypasting a lot of code. Edit: These errors are popping up all over the place whenever I refresh my local machine too quickly. Doesn't look like it's happening on my remote deployment box, but I can't be sure. I changed all my repositories' StructureMap life cycles to HttpContextScoped() and the error persists. Code: public ActionResult Index() { // error happens here, which queries my page repository var page = _branchService.GetPage("welcome"); if (page != null) ViewData["Welcome"] = page.Body; ... } Repository: GetPage boils down to a filtered query mapping in my page repository. public IQueryable<Page> GetPages() { var pages = from p in _db.Pages let categories = GetPageCategories(p.PageId) let revisions = GetRevisions(p.PageId) select new Page { ID = p.PageId, UserID = p.UserId, Slug = p.Slug, Title = p.Title, Description = p.Description, Body = p.Text, Date = p.Date, IsPublished = p.IsPublished, Categories = new LazyList<Category>(categories), Revisions = new LazyList<PageRevision>(revisions) }; return pages; } where _db is an injected data context as an argument, stored in a private variable which I reuse for SELECT queries. Error: Specified cast is not valid. Exception Details: System.InvalidCastException: Specified cast is not valid. Stack Trace: [InvalidCastException: Specified cast is not valid.] System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult) +4539 System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries) +207 System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) +500 System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute(Expression expression) +50 System.Linq.Queryable.FirstOrDefault(IQueryable`1 source) +383 Manager.Controllers.SiteController.Index() in C:\Projects\Manager\Manager\Controllers\SiteController.cs:68 lambda_method(Closure , ControllerBase , Object[] ) +79 System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +258 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +39 System.Web.Mvc.<>c__DisplayClassd.<InvokeActionMethodWithFilters>b__a() +125 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation) +640 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList`1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +312 System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +709 System.Web.Mvc.Controller.ExecuteCore() +162 System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__4() +58 System.Web.Mvc.Async.<>c__DisplayClass1.<MakeVoidDelegate>b__0() +20 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +453 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +371

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• How to add new object to an IList mapped as a one-to-many with NHibernate?

  - by Jørn Schou-Rode

  My model contains a class Section which has an ordered list of Statics that are part of this section. Leaving all the other properties out, the implementation of the model looks like this: public class Section { public virtual int Id { get; private set; } public virtual IList<Static> Statics { get; private set; } } public class Static { public virtual int Id { get; private set; } } In the database, the relationship is implemented as a one-to-many, where the table Static has a foreign key pointing to Section and an integer column Position to store its index position in the list it is part of. The mapping is done in Fluent NHibernate like this: public SectionMap() { Id(x => x.Id); HasMany(x => x.Statics).Cascade.All().LazyLoad() .AsList(x => x.WithColumn("Position")); } public StaticMap() { Id(x => x.Id); References(x => x.Section); } Now I am able to load existing Statics, and I am also able to update the details of those. However, I cannot seem to find a way to add new Statics to a Section, and have this change persisted to the database. I have tried several combinations of: mySection.Statics.Add(myStatic) session.Update(mySection) session.Save(myStatic) but the closest I have gotten (using the first two statements), is to an SQL exception reading: "Cannot insert the value NULL into column 'Position'". Clearly an INSERT is attempted here, but NHibernate does not seem to automatically append the index position to the SQL statement. What am I doing wrong? Am I missing something in my mappings? Do I need to expose the Position column as a property and assign a value to it myself? EDIT: Apparently everything works as expected, if I remove the NOT NULL constraint on the Static.Position column in the database. I guess NHibernate makes the insert and immediatly after updates the row with a Position value. While this is an anwers to the question, I am not sure if it is the best one. I would prefer the Position column to be not nullable, so I still hope there is some way to make NHibernate provide a value for that column directly in the INSERT statement. Thus, the question is still open. Any other solutions?

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• JPA entity design / cannot delete entity

  - by timaschew

  I though its simple what I want, but I cannot find any solution for my problem. I'm using playframework 1.2.3 and it's using Hibernate as JPA. So I think playframework has nothing to do with the problem. I have some classes (I omit the nonrelevant fields) public class User { ... } public class Task { public DataContainer dataContainer; } public class DataContainer { public Session session; public User user; } public class Session { ... } So I have association from Task to DataContainer and from DataContainer to Sesssion and the DataContainer belongs to a User. The DataContainers can have always the same User, but the Session have to be different for each instance. And the DataContainer of a Task have also to be different in each instance. A DataContainer can have a Sesesion or not (it's optinal). I use only unidirectional assoc. It should be sufficient. In other words: Every Task must has one DataContainer. Every DataContainer must has one/the same User and can have one Session. To create a DB schema I use JPA annotations: @Entity public class User extends Model { ... } @Entity public class Task extends Model { @OneToOne(optional = false, cascade = CascadeType.ALL) public DataContainer dataContainer; } @Entity public class DataContainer extends Model { @OneToOne(optional = true, cascade = CascadeType.ALL) public Session session; @ManyToOne(optional = false, cascade = CascadeType.ALL) public User user; } @Entity public class Session extends Model { ... } BTW: Model is a play class and provides the primary id as long type. When I create some for each entity a object and 'connect them', I mean the associations, it works fine. But when I try to delete a Session, I get a constraint violation exception, because a DataContainer still refers to the Session I want to delete. I want that the Session (field) of the DataContainer will be set to null respectively the foreign key (session_id) should be unset in the database. This will be okay, because its optional. I don't know, I think I have multiple problems. Am I using the right annotation @OneToOne ? I found on the internet some additional annotation and attributes: @JoinColumn and a mappedBy attribute for the inverse relationship. But I don't have it, because its not bidirectional. Or is a bidirectional assoc. essentially? Another try was to use @OnDelete(action = OnDeleteAction.CASCADE) the the contraint changed from NO ACTIONs when update or delete to: ADD CONSTRAINT fk4745c17e6a46a56 FOREIGN KEY (session_id) REFERENCES annotation_session (id) MATCH SIMPLE ON UPDATE NO ACTION ON DELETE CASCADE; But in this case, when I delete a session, the DataContainer and User is deleted. That's wrong for me. EDIT: I'm using postgresql 9, the jdbc stuff is included in play, my only db config is db=postgres://app:app@localhost:5432/app

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• Linq query challenge - can this be done?

  - by vdh_ant

  My table structure is as follows: Person 1-M PesonAddress Person 1-M PesonPhone Person 1-M PesonEmail Person 1-M Contract Contract M-M Program Contract M-1 Organization At the end of this query I need a populated object graph where each person has their: PesonAddress's PesonPhone's PesonEmail's PesonPhone's Contract's - and this has its respective Program's Now I had the following query and I thought that it was working great, but it has a couple of problems: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") where people.Contract.Any( contract => (param.OrganizationId == contract.OrganizationId) && contract.Program.Any( contractProgram => (param.ProgramId == contractProgram.ProgramId))) select people; The problem is that it filters the person to the criteria but not the Contracts or the Contract's Programs. It brings back all Contracts that each person has not just the ones that have an OrganizationId of x and the same goes for each of those Contract's Programs respectively. What I want is only the people that have at least one contract with an OrgId of x with and where that contract has a Program with the Id of y... and for the object graph that is returned to have only the contracts that match and programs within that contract that match. I kinda understand why its not working, but I don't know how to change it so it is working... This is my attempt thus far: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") let currentContracts = from contract in people.Contract where (param.OrganizationId == contract.OrganizationId) select contract let currentContractPrograms = from contractProgram in currentContracts let temp = from x in contractProgram.Program where (param.ProgramId == contractProgram.ProgramId) select x where temp.Any() select temp where currentContracts.Any() && currentContractPrograms.Any() select new Person { PersonId = people.PersonId, FirstName = people.FirstName, ..., ...., MiddleName = people.MiddleName, Surname = people.Surname, ..., ...., Gender = people.Gender, DateOfBirth = people.DateOfBirth, ..., ...., Contract = currentContracts, ... }; //This doesn't work But this has several problems (where the Person type is an EF object): I am left to do the mapping by myself, which in this case there is quite a lot to map When ever I try to map a list to a property (i.e. Scholarship = currentScholarships) it says I can't because IEnumerable is trying to be cast to EntityCollection Include doesn't work Hence how do I get this to work. Keeping in mind that I am trying to do this as a compiled query so I think that means anonymous types are out.

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