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• Moose and error messages, the sun and the moon [closed]

  - by xxxxxxx

  So again using Moose I write a role like this: package My::Role; use Moose::Role; use Some::Class::Consuming::My::Role; With the note that Some::Class::Consuming::My::Role consumes the role My::Role; And what do I get ? I get an error message like this: A role generator is required to generate roles at /usr/local/share/perl/5.10.0/MooseX/Role/Parameterized/Meta/Role/Parameterizable.pm line 79 MooseX::Role::Parameterized::Meta::Role::Parameterizable::generate_role('MooseX::Role::Parameterized::Meta::Role::Parameterizable=HASH...', 'consumer', 'Moose::Meta::Class=HASH(0x894e540)', 'parameters', 'HASH(0x86fc1e0)') called at /usr/local/share/perl/5.10.0/MooseX/Role/Parameterized/Meta/Role/Parameterizable.pm line 116 MooseX::Role::Parameterized::Meta::Role::Parameterizable::apply('MooseX::Role::Parameterized::Meta::Role::Parameterizable=HASH...', 'Moose::Meta::Class=HASH(0x894e540)', 'element_type', 'Tuple') called at /usr/local/lib/perl/5.10.0/Moose/Util.pm line 132 Moose::Util::_apply_all_roles('Moose::Meta::Class=HASH(0x894e540)', undef, 'Stuff', 'HASH(0x894e1d0)') called at /usr/local/lib/perl/5.10.0/Moose/Util.pm line 86 Moose::Util::apply_all_roles('Moose::Meta::Class=HASH(0x894e540)', 'Stuff', 'HASH(0x894e1d0)') called at /usr/local/lib/perl/5.10.0/Moose.pm line 57 Moose::with('Moose::Meta::Class=HASH(0x894e540)', 'Group', 'HASH(0x894e1d0)') called at /usr/local/lib/perl/5.10.0/Moose/Exporter.pm line 293 Moose::with('Group', 'HASH(0x894e1d0)') called at Some_path_on_disk line 6 require Some_other_path_on_disk called at Some_path_on_disk line 9 Group::BEGIN() called at Yet_another_path_on_disk line 0 eval {...} called at Yet_another_path_on_disk line 0 Compilation failed in require at some_path_on_disk line 9. BEGIN failed--compilation aborted at some_path_on_disk line 9. What am I to make of this ? As Dijkstra would concisely describe, this looks like "just a meaningless concatenation of words"(which is exactly what it is). Would a more appropriate error message be "You cannot use a class consuming the role that you are currently defining " ? What does the error message try to convey ? Can the author make the error message meaningful ? Will he ever make it so ? maybe this can be planned for version 3.14159265358979323846 ? In actuality I get one and a half pages of error which is completely unreadable and devoid of any logic or sense of respect for the user that is using Moose (in terms of intuitive error messages) just like the one above. What's to be done in this case ? I mean I get on my screen these error messages that are sometimes completely unrelated to the problem that I'm having (which I can assess after solving the problems that probably caused them, I say probably becuase I have no idea where these error messages came from because they look like they fell from the sky as they have no relation to the actual situation). Is this: the inexplicable dramatic destiny of the Perl programmer using Moose ? someone being extremely lazy and sloppy at writing error messages ? maybe on heavy drugs ? me not understanding basic english ? Gentlemen, when writing software, please please please, take care of the poor programmer that will use it and respect him by writing relevant error messages. (Except for error messages Moose is a pretty good piece of software)

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• ISQLQuery using AddJoin not loading related instance

  - by Remi Despres-Smyth

  I've got a problem using an ISQLQuery with an AddJoin. The entity I'm trying to return is RegionalFees, which has a composite-id which includes a Province instance. (This is the the instance being improperly loaded.) Here's the mapping: <class name="Project.RegionalFees, Project" table="tblRegionalFees"> <composite-id name="Id" class="Project.RegionalFeesId, project" unsaved-value="any" access="property"> <key-many-to-one class="Project.Province, Project" name="Region" access="property" column="provinceId" not-found="exception" /> <key-property name="StartDate" access="property" column="startDate" type="DateTime" /> </composite-id> <property name="SomeFee" column="someFee" type="Decimal" /> <property name="SomeOtherFee" column="someOtherFee" type="Decimal" /> <!-- Other unrelated stuff --> </class> <class name="Project.Province, Project" table="trefProvince" mutable="false"> <id name="Id" column="provinceId" type="Int64" unsaved-value="0"> <generator class="identity" /> </id> <property name="Code" column="code" access="nosetter.pascalcase-m-underscore" /> <property name="Label" column="label" access="nosetter.pascalcase-m-underscore" /> </class> Here's my query method: public IEnumerable<RegionalFees> GetRegionalFees() { // Using an ISQLQuery cause there doesn't appear to be an equivalent of // the SQL HAVING clause, which would be optimal for loading this set const String qryStr = "SELECT * " + "FROM tblRegionalFees INNER JOIN trefProvince " + "ON tblRegionalFees.provinceId=trefProvince.provinceId " + "WHERE EXISTS ( " + "SELECT provinceId, MAX(startDate) AS MostRecentFeesDate " + "FROM tblRegionalFees InnerRF " + "WHERE tblRegionalFees.provinceId=InnerRF.provinceId " + "AND startDate <= ? " + "GROUP BY provinceId " + "HAVING tblRegionalFees.startDate=MAX(startDate))"; var qry = NHibernateSessionManager.Instance.GetSession().CreateSQLQuery(qryStr); qry.SetDateTime(0, DateTime.Now); qry.AddEntity("RegFees", typeof(RegionalFees)); qry.AddJoin("Region", "RegFees.Id.Region"); return qry.List<RegionalFees>(); } The odd behavior here is that when I call GetRegionalFees (whose goal is to load just the most recent fee instances per region), it all loads fine if the Province instance is a proxy. If, however, Province is not loaded as a transparent proxy, the Province instance which is part of RegionalFees' RegionalFeesId property has null Code and Region values, although the Id value is set correctly. It looks to me like I have a problem in how I'm joining the Province class - since if it's lazy loaded the id is set from tblRegionalFees, and it gets loaded independently afterwards - but I haven't been able to figure out the solution.

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• Implementing EAV pattern with Hibernate for User -> Settings relationship

  - by Trevor

  I'm trying to setup a simple EAV pattern in my web app using Java/Spring MVC and Hibernate. I can't seem to figure out the magic behind the hibernate XML setup for this scenario. My database table "SETUP" has three columns: user_id (FK) setup_item setup_value The database composite key is made up of user_id | setup_item Here's the Setup.java class: public class Setup implements CommonFormElements, Serializable { private Map data = new HashMap(); private String saveAction; private Integer speciesNamingList; private User user; Logger log = LoggerFactory.getLogger(Setup.class); public String getSaveAction() { return saveAction; } public void setSaveAction(String action) { this.saveAction = action; } public User getUser() { return user; } public void setUser(User user) { this.user = user; } public Integer getSpeciesNamingList() { return speciesNamingList; } public void setSpeciesNamingList(Integer speciesNamingList) { this.speciesNamingList = speciesNamingList; } public Map getData() { return data; } public void setData(Map data) { this.data = data; } } My problem with the Hibernate setup, is that I can't seem to figure out how to map out the fact that a foreign key and the key of a map will construct the composite key of the table... this is due to a lack of experience using Hibernate. Here's my initial attempt at getting this to work: <composite-id> <key-many-to-one foreign-key="id" name="user" column="user_id" class="Business.User"> <meta attribute="use-in-equals">true</meta> </key-many-to-one> </composite-id> <map lazy="false" name="data" table="setup"> <key column="user_id" property-ref="user"/> <composite-map-key class="Command.Setup"> <key-property name="data" column="setup_item" type="string"/> </composite-map-key> <element column="setup_value" not-null="true" type="string"/> </map> Any insight into how to properly map this common scenario would be most appreciated!

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• Singleton: How should it be used

  - by Loki Astari

  Edit: From another question I provided an answer that has links to a lot of questions/answers about singeltons: More info about singletons here: So I have read the thread Singletons: good design or a crutch? And the argument still rages. I see Singletons as a Design Pattern (good and bad). The problem with Singleton is not the Pattern but rather the users (sorry everybody). Everybody and their father thinks they can implement one correctly (and from the many interviews I have done, most people can't). Also because everybody thinks they can implement a correct Singleton they abuse the Pattern and use it in situations that are not appropriate (replacing global variables with Singletons!). So the main questions that need to be answered are: When should you use a Singleton How do you implement a Singleton correctly My hope for this article is that we can collect together in a single place (rather than having to google and search multiple sites) an authoritative source of when (and then how) to use a Singleton correctly. Also appropriate would be a list of Anti-Usages and common bad implementations explaining why they fail to work and for good implementations their weaknesses. So get the ball rolling: I will hold my hand up and say this is what I use but probably has problems. I like "Scott Myers" handling of the subject in his books "Effective C++" Good Situations to use Singletons (not many): Logging frameworks Thread recycling pools /* * C++ Singleton * Limitation: Single Threaded Design * See: http://www.aristeia.com/Papers/DDJ_Jul_Aug_2004_revised.pdf * For problems associated with locking in multi threaded applications * * Limitation: * If you use this Singleton (A) within a destructor of another Singleton (B) * This Singleton (A) must be fully constructed before the constructor of (B) * is called. */ class MySingleton { private: // Private Constructor MySingleton(); // Stop the compiler generating methods of copy the object MySingleton(MySingleton const& copy); // Not Implemented MySingleton& operator=(MySingleton const& copy); // Not Implemented public: static MySingleton& getInstance() { // The only instance // Guaranteed to be lazy initialized // Guaranteed that it will be destroyed correctly static MySingleton instance; return instance; } }; OK. Lets get some criticism and other implementations together. :-)

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• Should an event-sourced aggregate root have query access to the event sourcing repository?

  - by JD Courtoy

  I'm working on an event-sourced CQRS implementation, using DDD in the application / domain layer. I have an object model that looks like this: public class Person : AggregateRootBase { private Guid? _bookingId; public Person(Identification identification) { Apply(new PersonCreatedEvent(identification)); } public Booking CreateBooking() { // Enforce Person invariants var booking = new Booking(); Apply(new PersonBookedEvent(booking.Id)); return booking; } public void Release() { // Enforce Person invariants // Should we load the booking here from the aggregate repository? // We need to ensure that booking is released as well. var booking = BookingRepository.Load(_bookingId); booking.Release(); Apply(new PersonReleasedEvent(_bookingId)); } [EventHandler] public void Handle(PersonBookedEvent @event) { _bookingId = @event.BookingId; } [EventHandler] public void Handle(PersonReleasedEvent @event) { _bookingId = null; } } public class Booking : AggregateRootBase { private DateTime _bookingDate; private DateTime? _releaseDate; public Booking() { //Enforce invariants Apply(new BookingCreatedEvent()); } public void Release() { //Enforce invariants Apply(new BookingReleasedEvent()); } [EventHandler] public void Handle(BookingCreatedEvent @event) { _bookingDate = SystemTime.Now(); } [EventHandler] public void Handle(BookingReleasedEvent @event) { _releaseDate = SystemTime.Now(); } // Some other business activities unrelated to a person } With my understanding of DDD so far, both Person and Booking are seperate aggregate roots for two reasons: There are times when business components will pull Booking objects separately from the database. (ie, a person that has been released has a previous booking modified due to incorrect information). There should not be locking contention between Person and Booking whenever a Booking needs to be updated. One other business requirement is that a Booking can never occur for a Person more than once at a time. Due to this, I'm concerned about querying the query database on the read side as there could potentially be some inconsistency there (due to using CQRS and having an eventually consistent read database). Should the aggregate roots be allowed to query the event-sourced backing store for objects (lazy-loading them as needed)? Are there any other avenues of implementation that would make more sense?

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• Silverlight 3 - Creating Custom Objects inside a Merged ResourceDictionary

  - by Tony Heupel

  I have custom classes that I currently instantiate within App.xaml as resources. I want to move these custom objects into a Merged ResourceDictionary, where they are used within styles, and keep them close to where they are used. Here's an example of what I want, arbitrarily using fake converter objects, but they could be any custom object... App.xaml (namespace declarations ommitted): <Application.Resources> <ResourceDictionary> <ResourceDictionary.MergedDictionaries> <ResourceDictionary Source="Merged.xaml" /> </ResourceDictionary.MergedDictionaries> <Style x:Key="SomeStyle" TargetType="SomeControl"> ... </Style> ... </ResourceDictionary> And then in Merged.xaml (namespace declarations omitted): <ResourceDictionary> <cvt:VisibilityToBoolConverter x:Key="BoolToVisibility" Inverted="True"/> <cvt:VisibilityToBoolConverter x:Key="NotBoolToVisibility" Inverted="True" Not="True"/> <Style x:Key="SomethingThatUsesVisibilityToBoolConvertersStyle" TargetType="SomeOtherControl"> .... </Style> </ResourceDictionary> The issue I'm seeing is this: when I create the BoolToVisibility and NotBoolToVisibility objects (as well instantiating other objects that are instances of custom classes I have created) just as part Application.Resources, they are created and all the references work as expected; however, when I move these into a Merged Resource Dictionary (as I have in the sample above), I get a malformed Application exception when the Silverlight application loads. I belive this to be an issue with how objects are instantiated differently in Merged Resource Dictionaries (I belive it is more of a lazy-load approach), but I would expect it to work nonetheless. I am very much able to add Style objects, DataTemplates, ControlTemplates, and the like. But when I want to create instances of custom classes that are named or keyed using Xaml, it works great inside of App.xaml's Application.Resources directly and Application.Resources/ResourceDictionary as well. As soon as they are moved into a merged dictionary, it throws the exception. Is this by design? Any other ideas that work? Thanks in advance...

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• spring jboss ehcache

  - by boyd4715

  I am trying to configure my application to make use of ehCache. I am using Spring 2.5.6, Jboss 5.1.0 GA and its embedded version of Hibernate along with ehCache-core V2.3.1. I have done the following configuration: <property name="hibernateProperties"> <props> <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop> <prop key="hibernate.hbm2ddl.auto">update</prop> <prop key="hibernate.show_sql">true</prop> <prop key="hibernate.jdbc.batch_size">20</prop> <prop key="hibernate.cache.provider_class">net.sf.ehcache.hibernate.SingletonEhCacheProvider</prop> <prop key="net.sf.ehcache.configurationResourceName">ehcache.xml</prop> <prop key="hibernate.cache.use_second_level_cache">true</prop> <prop key="hibernate.cache.use_structured_entries">true</prop> <prop key="hibernate.cache.use_query_cache">true</prop> <prop key="hibernate.generate_statistics">true</prop> <!-- prop key="hibernate.cache.use_second_level_cache">true</prop> <prop key="hibernate.cache.region.factory_class">net.sf.ehcache.hibernate.EhCacheRegionFactory</prop> <prop key="hibernate.cache.provider_class">net.sf.ehcache.hibernate.SingletonEhCacheProvider</prop> <prop key="hibernate.cache.use_second_level_cache">true</prop> <prop key="hibernate.cache.use_query_cache">true</prop--> </props> </property> This is my ehcache.xml <defaultCache eternal="false" overflowToDisk="false" maxElementsInMemory="50000" timeToIdleSeconds="30" timeToLiveSeconds="6000" memoryStoreEvictionPolicy="LRU" /> <cache name="com.model.SystemProperty" maxElementsInMemory="5000" eternal="true" overflowToDisk="false" memoryStoreEvictionPolicy="LFU" /> This file is located in my class path. I have added the following to my domain object: @Cache(usage = CacheConcurrencyStrategy.READ_WRITE, region="vsg.ecotrak.admin.store.domain.Store", include="non-lazy") When I start up the server, it gets stuck. Here is the output: 13:17:09,000 INFO [SettingsFactory] Second-level cache: enabled 13:17:09,000 INFO [SettingsFactory] Query cache: enabled 13:17:09,016 INFO [SettingsFactory] Cache region factory : org.hibernate.cache.impl.bridge.RegionFactoryCacheProviderBridge 13:17:09,017 INFO [RegionFactoryCacheProviderBridge] Cache provider: net.sf.ehcache.hibernate.SingletonEhCacheProvider Any Ideal as to why this is happening? I am running on a Windows 7 64 bit if that matters. I downgraded the ehcache jar to V 1.2.3 and the server now starts.

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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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• Using NHibernate to map a nChar column to an enumerated type

  - by Morrislgn

  Hello Folks, I am trying to map a table frp, a SQL Server 2005 DB to a class which contains an enum: public class MyClass{ private YesNoOptional addressSetting; public YesNoOptional AddressSetting{ {get; set;} } } public enum YesNoOptional { Yes, No, Optional } This will dictate that one of three values is inserted into the corresponding column - 'Y', 'N', 'O'. This column is of type nchar(1). My mapping file is like so (addressSetting is the property which is causing the problem): <class name="IncidentDefinition" table="IR_INCIDENT_DEF" lazy="false" > <id name="Guid" column="INT_GUID" > <generator class="guid"></generator> </id> <property name="Reference" column="INT_REF" ></property> <property name="Description" column="INT_DESCRIPTION" ></property> <property name="AddressSetting" column="INT_ADDRESS_REQ" ></property> <property name="Active" column="INT_ACTIVE" type="YesNo"></property> <property name="PinDocId" column="INT_PIN_DOC_ID"></property> </class> Using the config above I get the following error: NHibernate.ADOException: could not initialize a collection: System.FormatException: Input string was not in a correct format.. If I try to map the enum using a custom type like so: <property name="AddressSetting" column="INT_ADDRESS_REQ" type="ML.Types.YesNoOptional, ML.Types" ></property> Error: System.FormatException: Input string was not in a correct format. Next, if I try using a specific type like so: <property name="AddressSetting" column="INT_ADDRESS_REQ" type="String" ></property> This error is generated: NHibernate.PropertyAccessException: The type System.String can not be assigned to a property of type System.ArgumentException: Object of type 'System.String' cannot be converted to type 'ML.Types.YesNoOptional'.. As a last resort I tried to specify the type as a char like so: <property name="AddressSetting" column="INT_ADDRESS_REQ" type="Char" ></property> This works a bit better, as it in it doesnt throw an error, however instead of returning the character from the table and mapping it to the enumerated type the ASCII value of the character is returned instead - so Y is represented by 89! I am hoping someone can explain what I am doing wrong and\or how why this is happening please? Thanks Morris

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• How to Configure SSL over Database in Spring?

  - by Sameer Malhotra

  Hi, I want to add SSL security in the Database layer. I am using Struts2.1.6, Spring 2.5, JBOSS 5.0 and Informix 11.5. Any idea how to do this? I have researched through a lot on the internet but could not find any solution. Please suggest! Here is my datasource and entity manager beans which is working perfect without SSL: <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> <property name="dataSource" ref="dataSource" /> <property name="jpaVendorAdapter"> <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"> <property name="database" value="INFORMIX" /> <property name="showSql" value="true" /> </bean> </property> </bean> <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close"> <property name="driverClassName" value="com.informix.jdbc.IfxDriver" /> <property name="url" value="jdbc:informix-sqli://SERVER_NAME:9088/DB_NAME:INFORMIXSERVER=SERVER_NAME;DELIMIDENT=y;" /> <property name="username" value="username" /> <property name="password" value="password" /> <property name="minIdle" value="2" /> </bean> <bean class="org.springframework.beans.factory.config.MethodInvokingFactoryBean" lazy-init="false"> <property name="targetObject" ref="dataSource" /> <property name="targetMethod" value="addConnectionProperty" /> <property name="arguments"> <list> <value>characterEncoding</value> <value>UTF-8</value> </list> </property> </bean> <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate" scope="prototype"> <property name="dataSource" ref="dataSource" /> </bean> <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager"> <property name="entityManagerFactory" ref="entityManagerFactory" /> </bean> <tx:annotation-driven transaction-manager="transactionManager" />

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• Insertions into Zipper trees on XML files in Clojure

  - by ivar

  I'm confused as how to idiomatically change a xml tree accessed through clojure.contrib's zip-filter.xml. Should be trying to do this at all, or is there a better way? Say that I have some dummy xml file "itemdb.xml" like this: <itemlist> <item id="1"> <name>John</name> <desc>Works near here.</desc> </item> <item id="2"> <name>Sally</name> <desc>Owner of pet store.</desc> </item> </itemlist> And I have some code: (require '[clojure.zip :as zip] '[clojure.contrib.duck-streams :as ds] '[clojure.contrib.lazy-xml :as lxml] '[clojure.contrib.zip-filter.xml :as zf]) (def db (ref (zip/xml-zip (lxml/parse-trim (java.io.File. "itemdb.xml"))))) ;; Test that we can traverse and parse. (doall (map #(print (format "%10s: %s\n" (apply str (zf/xml-> % :name zf/text)) (apply str (zf/xml-> % :desc zf/text)))) (zf/xml-> @db :item))) ;; I assume something like this is needed to make the xml tags (defn create-item [name desc] {:tag :item :attrs {:id "3"} :contents (list {:tag :name :attrs {} :contents (list name)} {:tag :desc :attrs {} :contents (list desc)})}) (def fred-item (create-item "Fred" "Green-haired astrophysicist.")) ;; This disturbs the structure somehow (defn append-item [xmldb item] (zip/insert-right (-> xmldb zip/down zip/rightmost) item)) ;; I want to do something more like this (defn append-item2 [xmldb item] (zip/insert-right (zip/rightmost (zf/xml-> xmldb :item)) item)) (dosync (alter db append-item2 fred-item)) ;; Save this simple xml file with some added stuff. (ds/spit "appended-itemdb.xml" (with-out-str (lxml/emit (zip/root @db) :pad true))) I am unclear about how to use the clojure.zip functions appropriately in this case, and how that interacts with zip-filter. If you spot anything particularly weird in this small example, please point it out.

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• Sending multiline message via sockets without closing the connection

  - by Yasir Arsanukaev

  Hello folks. Currently I have this code of my client-side Haskell application: import Network.Socket import Network.BSD import System.IO hiding (hPutStr, hPutStrLn, hGetLine, hGetContents) import System.IO.UTF8 connectserver :: HostName -- ^ Remote hostname, or localhost -> String -- ^ Port number or name -> IO Handle connectserver hostname port = withSocketsDo $ do -- withSocketsDo is required on Windows -- Look up the hostname and port. Either raises an exception -- or returns a nonempty list. First element in that list -- is supposed to be the best option. addrinfos <- getAddrInfo Nothing (Just hostname) (Just port) let serveraddr = head addrinfos -- Establish a socket for communication sock <- socket (addrFamily serveraddr) Stream defaultProtocol -- Mark the socket for keep-alive handling since it may be idle -- for long periods of time setSocketOption sock KeepAlive 1 -- Connect to server connect sock (addrAddress serveraddr) -- Make a Handle out of it for convenience h <- socketToHandle sock ReadWriteMode -- Were going to set buffering to LineBuffering and then -- explicitly call hFlush after each message, below, so that -- messages get logged immediately hSetBuffering h LineBuffering return h sendid :: Handle -> String -> IO String sendid h id = do hPutStr h id -- Make sure that we send data immediately hFlush h -- Retrieve results hGetLine h The code portions in connectserver are from this chapter of Real World Haskell book where they say: When dealing with TCP data, it's often convenient to convert a socket into a Haskell Handle. We do so here, and explicitly set the buffering – an important point for TCP communication. Next, we set up lazy reading from the socket's Handle. For each incoming line, we pass it to handle. After there is no more data – because the remote end has closed the socket – we output a message about that. Since hGetContents blocks until the server closes the socket on the other side, I used hGetLine instead. It satisfied me before I decided to implement multiline output to client. I wouldn't like the server to close a socket every time it finishes sending multiline text. The only simple idea I have at the moment is to count the number of linefeeds and stop reading lines after two subsequent linefeeds. Do you have any better suggestions? Thanks.

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• How do you stop a user-instance of Sql Server? (Sql Express user instance database files locked, eve

  - by Bittercoder

  When using SQL Server Express 2005's User Instance feature with a connection string like this: <add name="Default" connectionString="Data Source=.\SQLExpress; AttachDbFilename=C:\My App\Data\MyApp.mdf; Initial Catalog=MyApp; User Instance=True; MultipleActiveResultSets=true; Trusted_Connection=Yes;" /> We find that we can't copy the database files MyApp.mdf and MyApp_Log.ldf (because they're locked) even after stopping the SqlExpress service, and have to resort to setting the SqlExpress service from automatic to manual startup mode, and then restarting the machine, before we can then copy the files. It was my understanding that stopping the SqlExpress service should stop all the user instances as well, which should release the locks on those files. But this does not seem to be the case - could anyone shed some light on how to stop a user instance, such that it's database files are no longer locked? Update OK, I stopped being lazy and fired up Process Explorer. Lock was held by sqlserver.exe - but there are two instances of sql server: sqlserver.exe PID: 4680 User Name: DefaultAppPool sqlserver.exe PID: 4644 User Name: NETWORK SERVICE The file is open by the sqlserver.exe instance with the PID: 4680 Stopping the "SQL Server (SQLEXPRESS)" service, killed off the process with PID: 4644, but left PID: 4680 alone. Seeing as the owner of the remaining process was DefaultAppPool, next thing I tried was stopping IIS (this database is being used from an ASP.Net application). Unfortunately this didn't kill the process off either. Manually killing off the remaining sql server process does remove the open file handle on the database files, allowing them to be copied/moved. Unfortunately I wish to copy/restore those files in some pre/post install tasks of a WiX installer - as such I was hoping there might be a way to achieve this by stopping a windows service, rather then having to shell out to kill all instances of sqlserver.exe as that poses some problems: Killing all the sqlserver.exe instances may have undesirable consequencies for users with other Sql Server instances on their machines. I can't restart those instances easily. Introduces additional complexities into the installer. Does anyone have any further thoughts on how to shutdown instances of sql server associated with a specific user instance?

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• rails named_scope ignores eager loading

  - by Craig

  Two models (Rails 2.3.8): User; username & disabled properties; User has_one :profile Profile; full_name & hidden properties I am trying to create a named_scope that eliminate the disabled=1 and hidden=1 User-Profiles. The User model is usually used in conjunction with the Profile model, so I attempt to eager-load the Profile model (:include = :profile). I created a named_scope on the User model called 'visible': named_scope :visible, { :joins => "INNER JOIN profiles ON users.id=profiles.user_id", :conditions => ["users.disabled = ? AND profiles.hidden = ?", false, false] } I've noticed that when I use the named_scope in a query, the eager-loading instruction is ignored. Variation 1 - User model only: # UserController @users = User.find(:all) # User's Index view <% for user in @users %> <p><%= user.username %></p> <% end %> # generates a single query: SELECT * FROM `users` Variation 2 - use Profile model in view; lazy load Profile model # UserController @users = User.find(:all) # User's Index view <% for user in @users %> <p><%= user.username %></p> <p><%= user.profile.full_name %></p> <% end %> # generates multiple queries: SELECT * FROM `profiles` WHERE (`profiles`.user_id = 1) ORDER BY full_name ASC LIMIT 1 SHOW FIELDS FROM `profiles` SELECT * FROM `profiles` WHERE (`profiles`.user_id = 2) ORDER BY full_name ASC LIMIT 1 SELECT * FROM `profiles` WHERE (`profiles`.user_id = 3) ORDER BY full_name ASC LIMIT 1 SELECT * FROM `profiles` WHERE (`profiles`.user_id = 4) ORDER BY full_name ASC LIMIT 1 SELECT * FROM `profiles` WHERE (`profiles`.user_id = 5) ORDER BY full_name ASC LIMIT 1 SELECT * FROM `profiles` WHERE (`profiles`.user_id = 6) ORDER BY full_name ASC LIMIT 1 Variation 3 - eager load Profile model # UserController @users = User.find(:all, :include => :profile) #view; no changes # two queries SELECT * FROM `users` SELECT `profiles`.* FROM `profiles` WHERE (`profiles`.user_id IN (1,2,3,4,5,6)) Variation 4 - use name_scope, including eager-loading instruction #UserConroller @users = User.visible(:include => :profile) #view; no changes # generates multiple queries SELECT `users`.* FROM `users` INNER JOIN profiles ON users.id=profiles.user_id WHERE (users.disabled = 0 AND profiles.hidden = 0) SELECT * FROM `profiles` WHERE (`profiles`.user_id = 1) ORDER BY full_name ASC LIMIT 1 SELECT * FROM `profiles` WHERE (`profiles`.user_id = 2) ORDER BY full_name ASC LIMIT 1 SELECT * FROM `profiles` WHERE (`profiles`.user_id = 3) ORDER BY full_name ASC LIMIT 1 SELECT * FROM `profiles` WHERE (`profiles`.user_id = 4) ORDER BY full_name ASC LIMIT 1 Variation 4 does return the correct number of records, but also appears to be ignoring the eager-loading instruction. Is this an issue with cross-model named scopes? Perhaps I'm not using it correctly. Is this sort of situation handled better by Rails 3?

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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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• Is this scatter-brained workflow realizable in Git?

  - by Luke Maurer

  This is what I'd like my workflow to look like at a conceptual level: I hack on my new feature for a while I notice a typo in a comment I change it Since the typo is completely unrelated to anything else, I put that change in a pile of comment fixes I keep working on the code I realize I need to flesh out a few utility functions I do so I put that change in its own pile Steps 2, 3, and 4 each repeat throughout the day I finish the new feature and put the changes for that feature in a pile I push nice patches upstream: One with the new feature, a few for the other tweaks, and one with a bunch of comment fixes if enough have accumulated Since I'm both lazy and a perfectionist, I want to be able to do some things out of order: I might correct a typo but forget to put it in the comment fix pile; when I prepare the upstream patches (I'm using git-svn, so I need to be pretty deliberate about these), I'll then pull out the comment fixes at that point. I might forget to separate things altogether until the very end. But I might /also/ have committed some of the piles along the way (sorry, the metaphor is breaking down …). This is all rather like just using Eclipse changesets with SVN, only I can have different changes to the same file in different piles (having to disentangle changes into different commits is what motivated me to move to git-svn, in fact …), and with Git I can have my full discombobulated change history, experimental branches and all, but still make a nice, neat patch. I've just recently started with Git after having wanted to for a good while, and I'm quite happy so far. The biggest way in which the above workflow doesn't really map into Git, though, is that a “bin” can't really be just a local branch, since the working tree only ever reflects the state of a single branch. Or maybe the Git index is a “pile,” and what I want is to have more than one somehow (effectively). I can think of a few ways to approximate what I want (maybe creative use of stash? Intricate stash-checkout-merge dances?), but my grasp on Git isn't solid enough to be sure of how best to put all the pieces together. It's said that Git is more a toolkit than a VCS, so I guess the question comes down to: How do I build this thing with these tools?

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• JSF: how to update the list after delete an item of that list

  - by Harry Pham

  It will take a moment for me to explain this, so please stay with me. I have table COMMENT that has OneToMany relationship with itself. @Entity public class Comment(){ ... @ManyToOne(optional=true, fetch=FetchType.LAZY) @JoinColumn(name="REPLYTO_ID") private Comment replyTo; @OneToMany(mappedBy="replyTo", cascade=CascadeType.ALL) private List<Comment> replies = new ArrayList<Comment>(); public void addReply(NewsFeed reply){ replies.add(reply); reply.setReplyTo(this); } public void removeReply(NewsFeed reply){ replies.remove(reply); } } So you can think like this. Each comment can have a List of replies which are also type Comment. Now it is very easy for me to delete the original comment and get the updated list back. All I need to do after delete is this. allComments = myEJB.getAllComments(); //This will query the db and return updated list But I am having problem when trying to delete replies and getting the updated list back. So here is how I delete the replies. Inside my managed bean I have //Before invoke this method, I have the value of originalFeed, and deletedFeed set. //These original comments are display inside a p:dataTable X, and the replies are //displayed inside p:dataTable Y which is inside X. So when I click the delete button //I know which comment I want to delete, and if it is the replies, I will know //which one is its original post public void deleteFeed(){ if(this.deletedFeed != null){ scholarEJB.deleteFeeds(this.deletedFeed); if(this.originalFeed != null){ //Since the originalFeed is not null, this is the `replies` //that I want to delete scholarEJB.removeReply(this.originalFeed, this.deletedFeed); } feeds = scholarEJB.findAllFeed(); } } Then inside my EJB scholarEJB, I have public void removeReply(NewsFeed comment, NewsFeed reply){ comment = em.merge(comment); comment.removeReply(reply); em.persist(comment); } public void deleteFeeds(NewsFeed e){ e = em.find(NewsFeed.class, e.getId()); em.remove(e); } When I get out, the entity (the reply) get correctly removed from the database, but inside the feeds List, reference of that reply still there. It only until I log out and log back in that the reply disappear. Please help

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• JavaScript Resource Management Design Pattern

  - by Adam

  As a web developer, a common problem I find myself tackling is waiting for something to load before doing something else. In particular, I often hide (using either display: none; or visibility: hidden; depending on the situation) elements while waiting for a background image or a CSS file to load. Consider this example from Last.FM. They overlay a semi-transparant PNG over each album art image so that it looks like it's inside a jewel-case. They let it load when it loads, so depending on your internet speed, you may see the art image by itself (without the overlay) temporarily. In this case, the album art looks fine without the jewel-case effect. But in similar situations, I have found that I don't want the user to see the site's design mangled as resources incrementally load. So, in rare cases I have hidden everything from the user until the whole kit and kaboodle has loaded. But this is often a pain to write out, and may force the user to wait for a pretty long time to see anything (besides "loading..." text). I can think of (and have used on occasion) some obvious solutions/compromises: Use some inline CSS so that as certain parts of the DOM load and render, they will immediately have the correct size/position/etc. Immediately render the navigation part of the site, so that if the user wanted to use the current page purely to get somewhere else, they don't have to wait for the rest to load. Load pixelated images first as placeholders for layout while lazy-loading higher quality images as replacements. Something quirky like using a cute animated gif to distract the user during a "loading..." phase. Show useful information as a reference while loading the full UI. (Something akin to Gmail Inbox Preview, etc.) (Sorry if my question was basically just asked and answered...) Despite all of these ideas, I still find myself hoping there are better ways of doing some of these things. So I guess what I'm looking for is some inspiration and/or any creative ways of dealing with this problem that you guys may have seen out in the wild.

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• Passing a comparator syntax help in Java

  - by Crystal

  I've tried this a couple ways, the first is have a class that implements comparator at the bottom of the following code. When I try to pass the comparat in sortListByLastName, I get a constructor not found error and I am not sure why import java.util.*; public class OrganizeThis implements WhoDoneIt { /** Add a person to the organizer @param p A person object */ public void add(Person p) { staff.put(p.getEmail(), p); //System.out.println("Person " + p + "added"); } /** * Remove a Person from the organizer. * * @param email The email of the person to be removed. */ public void remove(String email) { staff.remove(email); } /** * Remove all contacts from the organizer. * */ public void empty() { staff.clear(); } /** * Find the person stored in the organizer with the email address. * Note, each person will have a unique email address. * * @param email The person email address you are looking for. * */ public Person findByEmail(String email) { Person aPerson = staff.get(email); return aPerson; } /** * Find all persons stored in the organizer with the same last name. * Note, there can be multiple persons with the same last name. * * @param lastName The last name of the persons your are looking for. * */ public Person[] find(String lastName) { ArrayList<Person> names = new ArrayList<Person>(); for (Person s : staff.values()) { if (s.getLastName() == lastName) { names.add(s); } } // Convert ArrayList back to Array Person nameArray[] = new Person[names.size()]; names.toArray(nameArray); return nameArray; } /** * Return all the contact from the orgnizer in * an array sorted by last name. * * @return An array of Person objects. * */ public Person[] getSortedListByLastName() { PersonLastNameComparator comp = new PersonLastNameComparator(); Map<String, Person> sorted = new TreeMap<String, Person>(comp); ArrayList<Person> sortedArrayList = new ArrayList<Person>(); for (Person s: sorted.values()) { sortedArrayList.add(s); } Person sortedArray[] = new Person[sortedArrayList.size()]; sortedArrayList.toArray(sortedArray); return sortedArray; } private Map<String, Person> staff = new HashMap<String, Person>(); public static void main(String[] args) { OrganizeThis testObj = new OrganizeThis(); Person person1 = new Person("J", "W", "111-222-3333", "[email protected]"); Person person2 = new Person("K", "W", "345-678-9999", "[email protected]"); Person person3 = new Person("Phoebe", "Wang", "322-111-3333", "[email protected]"); Person person4 = new Person("Nermal", "Johnson", "322-342-5555", "[email protected]"); Person person5 = new Person("Apple", "Banana", "123-456-1111", "[email protected]"); testObj.add(person1); testObj.add(person2); testObj.add(person3); testObj.add(person4); testObj.add(person5); System.out.println(testObj.findByEmail("[email protected]")); System.out.println("------------" + '\n'); Person a[] = testObj.find("W"); for (Person p : a) System.out.println(p); System.out.println("------------" + '\n'); a = testObj.find("W"); for (Person p : a) System.out.println(p); System.out.println("SORTED" + '\n'); a = testObj.getSortedListByLastName(); for (Person b : a) { System.out.println(b); } System.out.println(testObj.getAuthor()); } } class PersonLastNameComparator implements Comparator<Person> { public int compare(Person a, Person b) { return a.getLastName().compareTo(b.getLastName()); } } And then when I tried doing it by creating an anonymous inner class, I also get a constructor TreeMap cannot find symbol error. Any thoughts? inner class method: public Person[] getSortedListByLastName() { //PersonLastNameComparator comp = new PersonLastNameComparator(); Map<String, Person> sorted = new TreeMap<String, Person>(new Comparator<Person>() { public int compare(Person a, Person b) { return a.getLastName().compareTo(b.getLastName()); } }); ArrayList<Person> sortedArrayList = new ArrayList<Person>(); for (Person s: sorted.values()) { sortedArrayList.add(s); } Person sortedArray[] = new Person[sortedArrayList.size()]; sortedArrayList.toArray(sortedArray); return sortedArray; }

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• RenderTargetBitmap + Resource'd VisualBrush = incomplete image

  - by Will

  I've found a new twist on the "Visual to RenderTargetBitmap" question! I'm rendering previews of WPF stuff for a designer. That means I need to take a WPF visual and render it to a bitmap without that visual ever being displayed. Got a nice little method to do it like to see it here it goes private static BitmapSource CreateBitmapSource(FrameworkElement visual) { Border b = new Border { Width = visual.Width, Height = visual.Height }; b.BorderBrush = Brushes.Black; b.BorderThickness = new Thickness(1); b.Background = Brushes.White; b.Child = visual; b.Measure(new Size(b.Width, b.Height)); b.Arrange(new Rect(b.DesiredSize)); RenderTargetBitmap rtb = new RenderTargetBitmap( (int)b.ActualWidth, (int)b.ActualHeight, 96, 96, PixelFormats.Pbgra32); // intermediate step here to ensure any VisualBrushes are rendered properly DrawingVisual dv = new DrawingVisual(); using (var dc = dv.RenderOpen()) { var vb = new VisualBrush(b); dc.DrawRectangle(vb, null, new Rect(new Point(), b.DesiredSize)); } rtb.Render(dv); return rtb; } Works fine, except for one leeetle thing... if my FrameworkElement has a VisualBrush, that brush doesn't end up in the final rendered bitmap. Something like this: <UserControl.Resources> <VisualBrush x:Key="LOLgo"> <VisualBrush.Visual> <!-- blah blah --> <Grid Background="{StaticResource LOLgo}"> <!-- yadda yadda --> Everything else renders to the bitmap, but that VisualBrush just won't show. The obvious google solutions have been attempted and have failed. Even the ones that specifically mention VisualBrushes missing from RTB'd bitmaps. I have a sneaky suspicion this might be caused by the fact that its a Resource, and that lazy resource isn't being inlined. So a possible fix would be to, somehow(???), force resolution of all static resource references before rendering. But I have absolutely no idea how to do that. Anybody have a fix for this?

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• JavaFX - question regarding binding button's disabled state

  - by jamiebarrow

  I'm trying to create a dummy application that maintains a list of tasks. For now, all I'm trying to do is add to the list. I enter a task name in a text box, click on the add task button, and expect the list to be updated with the new item and the task name input to be cleared. I only want to be able to add tasks if the task name is not empty. The below code is my implementation, but I have a question regarding the binding. I'm binding the textbox's text variable to a string in my view model, and the button's disable variable to a boolean in my view model. I have a trigger to update the disabled state when the task name changes. When the binding of the task name happens the boolean is updated accordingly, but the button still appears disabled. But then when I mouse over the button, it becomes enabled. I believe this is due to JavaFX 1.3's binding being lazy - only updates the bound variable when it is read. Also, when I've added the task, I clear the task name in the model, but the textbox's text doesn't change - even though I'm using bind with inverse. Is there a way to make the textbox's text and the button's disabled state update automatically via the binding as I was expecting? Thanks, James AddTaskViewModel.fx: package jamiebarrow; import java.lang.System; public class AddTaskViewModel { function logChange(prop:String,oldValue,newValue):Void { println("{System.currentTimeMillis()} : {prop} [{oldValue}] to [{newValue}] "); } public var newTaskName: String on replace old { logChange("newTaskName",old,newTaskName); isAddTaskDisabled = (newTaskName == null or newTaskName.trim().length() == 0); }; public var isAddTaskDisabled: Boolean on replace old { logChange("isAddTaskDisabled",old,isAddTaskDisabled); }; public var taskItems = [] on replace old { logChange("taskItems",old,taskItems); }; public function addTask() { insert newTaskName into taskItems; newTaskName = ""; } } Main.fx: package jamiebarrow; import javafx.scene.control.Button; import javafx.scene.control.TextBox; import javafx.scene.control.ListView; import javafx.scene.Scene; import javafx.scene.layout.VBox; import javafx.stage.Stage; import javafx.scene.layout.HBox; def viewModel = AddTaskViewModel{}; var txtName: TextBox = TextBox { text: bind viewModel.newTaskName with inverse onKeyTyped: onKeyTyped }; function onKeyTyped(event): Void { txtName.commit(); // ensures model is updated cmdAddTask.disable = viewModel.isAddTaskDisabled;// the binding only occurs lazily, so this is needed } var cmdAddTask = Button { text: "Add" disable: bind viewModel.isAddTaskDisabled with inverse action: onAddTask }; function onAddTask(): Void { viewModel.addTask(); } var lstTasks = ListView { items: bind viewModel.taskItems with inverse }; Stage { scene: Scene { content: [ VBox { content: [ HBox { content: [ txtName, cmdAddTask ] }, lstTasks ] } ] } }

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• Should an event-sourced aggregate root have access to the event sourcing repository?

  - by JD Courtoy

  I'm working on an event-sourced CQRS implementation, using DDD in the application / domain layer. I have an object model that looks like this: public class Person : AggregateRootBase { private Guid? _bookingId; public Person(Identification identification) { Apply(new PersonCreatedEvent(identification)); } public Booking CreateBooking() { // Enforce Person invariants var booking = new Booking(); Apply(new PersonBookedEvent(booking.Id)); return booking; } public void Release() { // Enforce Person invariants // Should we load the booking here from the aggregate repository? // We need to ensure that booking is released as well. var booking = BookingRepository.Load(_bookingId); booking.Release(); Apply(new PersonReleasedEvent(_bookingId)); } [EventHandler] public void Handle(PersonBookedEvent @event) { _bookingId = @event.BookingId; } [EventHandler] public void Handle(PersonReleasedEvent @event) { _bookingId = null; } } public class Booking : AggregateRootBase { private DateTime _bookingDate; private DateTime? _releaseDate; public Booking() { //Enforce invariants Apply(new BookingCreatedEvent()); } public void Release() { //Enforce invariants Apply(new BookingReleasedEvent()); } [EventHandler] public void Handle(BookingCreatedEvent @event) { _bookingDate = SystemTime.Now(); } [EventHandler] public void Handle(BookingReleasedEvent @event) { _releaseDate = SystemTime.Now(); } // Some other business activities unrelated to a person } With my understanding of DDD so far, both Person and Booking are seperate aggregate roots for two reasons: There are times when business components will pull Booking objects separately from the database. (ie, a person that has been released has a previous booking modified due to incorrect information). There should not be locking contention between Person and Booking whenever a Booking needs to be updated. One other business requirement is that a Booking can never occur for a Person more than once at a time. Due to this, I'm concerned about querying the query database on the read side as there could potentially be some inconsistency there (due to using CQRS and having an eventually consistent read database). Should the aggregate roots be allowed to query the event-sourced backing store by id for objects (lazy-loading them as needed)? Are there any other avenues of implementation that would make more sense?

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• JSON or YAML encoding in GWT/Java on both client and server

  - by KennethJ

  I'm looking for a super simple JSON or YAML library (not particularly bothered which one) written in Java, and can be used in both GWT on the client, and in its original Java form on the server. What I'm trying to do is this: I have my models, which are shared between the client and the server, and these are the primary source of data interchange. I want to design the web service in between to be as simple as possible, and decided to take the RESTful approach. My problem is that I know our application will grow substantially in the future, and writing all the getters, setters, serialization, factories, etc. by hand fills me with absolute dread. So in order to avoid it, I decided to implement annotations to keep track of attributes on the models. The reason I can't just serialize everything directly, using GWT's own one, or one which works through reflection, is because we need a certain amount of logic going on in the serialization process. I.e. whether references to other models get serialized during the serialization of the original model, or whether an ID is just passed, and general simple things like that. I've then written an annotation processor to preprocess my shared models and generate an implementing class with all the getters, setters, serialization, lazy-loading, etc. To make a long story short, I need some type of simple YAML or JSON library, which allows me to encode and decode manually, so I can generate this code through my annotation processor. I have had a look around the interwebs, but every single one I ran into supported some reflection which, while all fine and dandy, make it pretty much useless for GWT. And in the case of GWT's own JSON library, it uses JSNI for speed purposes, making it useless server side. One solution I did think about involved writing writing two sets of serialization methods on the models, one for the client and one for the server, but I'd rather not do that. Also, I'm pretty new to GWT, and even though I have done a lot of Java, it was back in the 1.2 days, so it's a bit rusty. So if you think I'm going about this problem completely the wrong way, I'm open to suggestions.

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• XmlHttpRequest bug?

  - by valdo

  Hello all. I'm writing a program that among other things needs to download a file given its URL. I'm too lazy to implement the Http/Https protocols manually, so that I needed some library/object/function that'll do the job. Critical requirement: The download must be asynchronous. That is, the thread that issued the download must be able to do something else "while" downloading the file, plus the download must be able to be aborted anytime without any barbaric side effects (such as internal call to TerminateThread). Nice-to-have requirements: Should be able to download the file "into memory". Means - read the contents of the file as they arrive, not necessarily save it into some "file system" file. It'd be nice to have some convenient Win32 progress notification mechanism (waitable event, semahpore, completion port, etc.), rather than just periodically polling the download status. I've chosen the XmlHttpRequest COM object to do the work. It seemed to work fine enough, plus it supported asynchronous mode. However I noticed that after some period it just stops working. That is, after several successful file downloads it stops downloading anything. I periodically poll it to get its status, it reports "in-progress", but nothing actually happens, and there's no network activity. Moreover, when the same process creates another instance of XmlHttpRequest object to perform new downloads - the effect is the same. The object reports "in progress", whereas it doesn't even try to connect to the server (according to network sniffers and system TCP state). The only way to make this object work back is to restart the process. This makes me suspect that there's a sort of a bug (sorry, I meant undocumented feature) in the object. Also it's not a bug at the level of an individual object, since the problem persists when the object is destroyed and another one is created. It's probably some global state of the DLL that implements this object. Does anyone know something about this? Is this a known bug? I'm pretty sure there's no chance that I have another bug in my code, because of which it seems to me to be the bug is in the XmlHttpRequest. I've done enoughtests and spent time with the debugger to conclude without reasonable doubt that it's just the object stops working. BTW, while the object should work, I do all the waiting via MsgWaitXXXX API calls. So that if this object needs the message loop to work properly (for instance, it may create a hidden notification window and bind it to a socket via WSAAsyncSelect) - I give it the opportunity.

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• Why does Scala apply thunks automatically, sometimes?

  - by Anonymouse

  At just after 2:40 in ShadowofCatron's Scala Tutorial 3 video, it's pointed out that the parentheses following the name of a thunk are optional. "Buh?" said my functional programming brain, since the value of a function and the value it evaluates to when applied are completely different things. So I wrote the following to try this out. My thought process is described in the comments. object Main { var counter: Int = 10 def f(): Int = { counter = counter + 1; counter } def runThunk(t: () => Int): Int = { t() } def main(args: Array[String]): Unit = { val a = f() // I expect this to mean "apply f to no args" println(a) // and apparently it does val b = f // I expect this to mean "the value f", a function value println(b) // but it's the value it evaluates to when applied to no args println(b) // and the evaluation happens immediately, not in the call runThunk(b) // This is an error: it's not println doing something funny runThunk(f) // Not an error: seems to be val doing something funny } }   To be clear about the problem, this Scheme program (and the console dump which follows) shows what I expected the Scala program to do. (define counter (list 10)) (define f (lambda () (set-car! counter (+ (car counter) 1)) (car counter))) (define runThunk (lambda (t) (t))) (define main (lambda args (let ((a (f)) (b f)) (display a) (newline) (display b) (newline) (display b) (newline) (runThunk b) (runThunk f)))) > (main) 11 #<procedure:f> #<procedure:f> 13   After coming to this site to ask about this, I came across this answer which told me how to fix the above Scala program: val b = f _ // Hey Scala, I mean f, not f() But the underscore 'hint' is only needed sometimes. When I call runThunk(f), no hint is required. But when I 'alias' f to b with a val then apply it, it doesn't work: the evaluation happens in the val; and even lazy val works this way, so it's not the point of evaluation causing this behaviour.   That all leaves me with the question: Why does Scala sometimes automatically apply thunks when evaluating them? Is it, as I suspect, type inference? And if so, shouldn't a type system stay out of the language's semantics? Is this a good idea? Do Scala programmers apply thunks rather than refer to their values so much more often that making the parens optional is better overall? Examples written using Scala 2.8.0RC3, DrScheme 4.0.1 in R5RS.

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