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• .NET Database Apps: Your Preferred Setup

  - by mdvaldosta

  I'm struggling to settle into a pattern for developing typical database driven apps in C# and Visual Studio. There are so many ways to set them up, using drag/drop datasets and adapters or writing the queries manually in ADO.NET or Linq to SQL, Linq to Entities, to bind or not to data bind etc etc. Where to store the connection string, in app.config or in a method or both etc etc. So many tutorials and all of them are different. Everytime I write something I start hating the way it looks and works, so I scrap it and start over. It's getting a bit tedious. Maybe it's alittle of the OCD in me. Would any of you professional developers out there share your method of setting up and structuring your database logic and maybe some sample code? It's really how to go about organizing the code and the method(s) of interacting with SQL that I'm trying to get into a routine with, one that works and won't get me laughed at by someone reviewing it.

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• What Belongs to the Aggregate Root

  - by jlembke

  This is a practical Domain Driven Design question: Conceptually, I think I get Aggregate roots until I go to define one. I have an Employee entity, which has surfaced as an Aggregate root. In the Business, some employees can have work-related Violations logged against them: Employee-----*Violations Since not all Employees are subject to this, I would think that Violations would not be a part of the Employee Aggregate, correct? So when I want to work with Employees and their related violations, is this two separate Repository interactions by some Service? Lastly, when I add a Violation, is that method on the Employee Entity? Thanks for the help!

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• How build my own Application Setting

  - by adisembiring

  I want to build a ApplicationSetting for my application. The ApplicationSetting can be stored in a properties file or in a database table. The settings are stored in key-value pairs. E.g. ftp.host = blade ftp.username = dummy ftp.pass = pass content.row_pagination = 20 content.title = How to train your dragon. I have designed it as follows: Application settings reader: interface IApplicationSettingReader { read(); } DatabaseApplicationSettingReader { dao appSettingDao; AppSettings read() { List<AppSettingEntity> listEntity = appSettingsDao.findAll(); Map<String, String> map = new HaspMap<String, String>(); foreach (AppSettingEntity entity : listEntity) { map.put(entity.getConfigName(), entity.getConfigValue()); } return new AppSettings(map); } } DatabaseApplicationSettingReader { dao appSettingDao; AppSettings read() { //read from some properties file return new AppSettings(map); } } Application settings class: AppSettings { private static AppSettings instance; private Map map; Public AppSettings(Map map) { this.map = map; } public static AppSettings getInstance() { if (instance == null) { throw new RuntimeException("Object not configure yet"); } return instance; } public static configure(IApplicationSettingReader reader) { instance = reader.read(); } public String getFtpSetting(String param) { return map.get("ftp." + param); } public String getContentSetting(String param) { return map.get("content." + param); } } Test class: AppSettingsTest { IApplicationSettingReader reader; @Before public void setUp() throws Exception { reader = new DatabaseApplicationSettingReader(); } @Test public void getContentSetting_should_get_content_title() { AppSettings.configure(reader); Instance settings = AppSettings.getInstance(); String title = settings.getContentSetting("title"); assertNotNull(title); Sysout(title); } } My questions are: Can you give your opinion about my code, is there something wrong? I configure my application setting once, while the application start, I configure the application setting with appropriate reader (DbReader or PropertiesReader), I make it singleton. The problem is, when some user edit the database or file directly to database or file, I can't get the changed values. Now, I want to implement something like ApplicationSettingChangeListener. So if the data changes, I will refresh my application settings. Do you have any suggestions how this can be implemented?

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• Hibernate mapping to object that already exists

  - by teehoo

  I have two classes, ServiceType and ServiceRequest. Every ServiceRequest must specify what kind of ServiceType it is. All ServiceType's are predefined in the database, and ServiceRequest is created at runtime by the client. Here are my .hbm files: <hibernate-mapping> <class dynamic-insert="false" dynamic-update="false" mutable="true" name="xxx.model.entity.ServiceRequest" optimistic-lock="version" polymorphism="implicit" select-before-update="false"> <id column="USER_ID" name="id"> <generator class="native"/> </id> <property name="quantity"> <column name="quantity" not-null="true"/> </property> <many-to-one cascade="all" class="xxx.model.entity.ServiceType" column="service_type" name="serviceType" not-null="false" unique="false"/> </class> </hibernate-mapping> and <hibernate-mapping> <class dynamic-insert="false" dynamic-update="false" mutable="true" name="xxx.model.entity.ServiceType" optimistic-lock="version" polymorphism="implicit" select-before-update="false"> <id column="USER_ID" name="id"> <generator class="native"/> </id> <property name="description"> <column name="description" not-null="false"/> </property> <property name="cost"> <column name="cost" not-null="true"/> </property> <property name="enabled"> <column name="enabled" not-null="true"/> </property> </class> </hibernate-mapping> When I run this, I get com.mysql.jdbc.exceptions.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails I think my problem is that when I create a new ServiceRequest object, ServiceType is one of its properties, and therefore when I'm saving ServiceRequest to the database, Hibernate attempts to insert the ServiceType object once again, and finds that it is already exists. If this is the case, how do I make it so that Hibernate points to the exists ServiceType instead of trying to insert it again?

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• Unidirectional OneToMany in Doctrine 2

  - by darja

  I have two Doctrine entities looking like that: /** * @Entity * @Table(name = "Locales") */ class Locale { /** * @Id @Column(type="integer") * @GeneratedValue(strategy="IDENTITY") */ private $id; /** @Column(length=2, name="Name", type="string") */ private $code; } /** * @Entity * @Table(name = "localized") */ class LocalizedStrings { /** * @Id @Column(type="integer") * @GeneratedValue(strategy="IDENTITY") */ private $id; /** @Column(name="Locale", type="integer") */ private $locale; /** @Column(name="SomeText", type="string", length=300) */ private $someText; } I'd like to create reference between these entities. LocalizedStrings needs reference to Locale but Locale doesn't need reference to LocalizedStrings. How to write such mapping via Doctrine 2?

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• What is the motivation behind "Use Extension Methods Sparingly?"

  - by Robert Harvey

  I find them a very natural way to extend existing classes, especially when you just need to "spot-weld" some functionality onto an existing class. Microsoft says, "In general, we recommend that you implement extension methods sparingly and only when you have to." And yet extension methods form the foundation of Linq; in fact, Linq was the reason extension methods were created. Are there specific design criteria where using extension methods are perferred over inheritance or composition? Under what criteria are they discouraged?

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• Ignore Hibernate @Where annotation

  - by Zecrates

  I have an Entity which has an association to another Entity annotated with @Where, like so public class EntityA { @OneToMany @Where(...) private List<EntityB> entityBList; } Recently the inevitable has happened, I need to load EntityB's that don't conform to the @Where clause. I could remove the @Where annotation, but it is used a lot, so ideally I don't want to do that. Apart from loading the list of EntityB's manually, with another query, what are my options? Can I tell Hibernate to ignore the @Where annotation?

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• Default Accessor Needed: Custom ConfigurationSection

  - by Mark

  I am totally confused by a simple Microsoft error message. When I run XSD.exe against an assembly that contains a custom ConfigurationSection (which in turn utilizes a custom ConfigurationElement and a custom ConfigurationElementCollection, as well as several ConfigurationProperties), I get the following error message: Error: There was an error processing 'Olbert.Entity.Utils.dll'. There was an error reflecting type 'Olbert.Entity.DatabaseConnection'. You must implement a default accessor on System.Configuration.ConfigurationLockCollection because it inherits from ICollection. Yet the class in question has a default accessor: public object this[int idx] { get { return null; } set { } } I realize the above doesn't do anything, but I don't need to access the element's properties by index. I'm just trying to work around the error message. So what's going on?

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• What is the "owning side" in an ORM mapping?

  - by Yousui

  Hi guys, I'm new to JPA. Now I have a question that what exactly is the owning side mean? I only have a rough idea of it. Can someone give me an explanation with some mapping examples(one to many, one to one, many to one) please? Great thanks. ps, the following text is excerpt from the decription of @OneToOne in java EE 6 documentation. You can see the concept owning side in it. Defines a single-valued association to another entity that has one-to-one multiplicity. It is not normally necessary to specify the associated target entity explicitly since it can usually be inferred from the type of the object being referenced. If the relationship is bidirectional, the non-owning side must use the mappedBy element of the OneToOne annotation to specify the relationship field or property of the owning side.

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• Accessing Textboxes in Repeater Control

  - by CccTrash

  All the ways I can think to do this seem very hackish. What is the right way to do this, or at least most common? I am retrieving a set of images from a LINQ-to-SQL query and databinding it and some other data to a repeater. I need to add a textbox to each item in the repeater that will let the user change the title of each image, very similar to Flickr. How do I access the textboxes in the repeater control and know which image that textbox belongs to? Here is what the repeater control would look like, with a submit button which would update all the image rows in Linq-to-SQL:

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• Combine Hibernate class with @Bindable for SwingBuilder without Griffon?

  - by Misha Koshelev

  Dear All: I have implemented a back-end for my application in Groovy/Gradle, and am now trying to implement a GUI. I am using Hibernate for my data storage (with HSQLDB) per http://groovy.codehaus.org/Using+Hibernate+with+Groovy (with Jasypt for encryption) and it is working quite well. I was wondering if there are any good tips for using @Bindable with, e.g., an @Entity class such as @Entity class Book { @Id @GeneratedValue(strategy = GenerationType.AUTO) public Long id @OneToMany(cascade=CascadeType.ALL) public Set<Author> authors public String title String toString() { "$title by ${authors.name.join(', ')}" } } or if I am: (i) asking for Griffon (ii) completely on the wrong track? Thank you! Misha

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• sending binary data via POST on android

  - by wo_shi_ni_ba_ba

  Android supports a limited version of apache's http client(v4). typically if I want to send binary data using content type= application/octet-stream via POST, I do the following: HttpClient client = getHttpClient(); HttpPost method=new HttpPost("http://192.168.0.1:8080/xxx"); System.err.println("send to server "+s); if(compression){ byte[]compressed =compress(s); RequestEntity entity = new ByteArrayRequestEntity(compressed); method.setEntity(entity); } HttpResponse resp=client.execute(method); however ByteArrayRequestEntity is not supported on android. what can I do?

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• Groupby in relationtable

  - by Dofs

  I am creating some tag functionality for a forum using linq2sql, and I have two tables [Tag] TagId TagName [ForumTagRelation] TagId ForumId I would like to retrieve, like SO, the most popular tags. I have tried to do this by: List<Tag> popularTags = db.Tags.Select(x => x.ForumTagRelations.GroupBy(y => y.TagId).OrderByDescending(z => z.Count())).Take(count).ToList(); But this just returns the following error: Error 1 Cannot implicitly convert type 'System.Collections.Generic.List<System.Linq.IOrderedEnumerable<System.Linq.IGrouping<System.Guid?,SampleWebsite.ForumTagRelation>>>' to 'System.Collections.Generic.IEnumerable<SampleWebsite.Tag>'. An explicit conversion exists (are you missing a cast?) The question is how I easily can return a list of tags which has the most counts in the ForumTagRelation table?

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• Reading chunked data from HttpEntity

  - by Gagan

  I have the following code: HttpClient FETCHER HttpResponse response = FETCHER.execute(host, httpMethod); Im trying to read its contents to a string like this: HttpEntity entity = response.getEntity(); InputStream st = entity.getContent(); StringWriter writer = new StringWriter(); IOUtils.copy(st, writer); String content = writer.toString(); The problem is, when i fetch http://www.google.co.in/ page, the transfer encoding is chunked, and i get only the first chunk. It fetches till first "". How do i get all the chunks at once so i can dump the complete output and do some processing on it ?

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• Setting a property value on each of the results in a FetchedResults set

  - by RickiG

  Hi On my Core Data Entity "Book" i have a boolean property, 'wasViewed' (NSNumber numberWithBool) that tells me if the Book was "viewed". I would like to implement a sort of "reset" this property for all my NSManagedObjects "Book". So that I can set them all to NO between sessions. I use an NSPredicate to retrieve all the Books like this: NSPredicate *predicate = [NSPredicate predicateWithFormat:@"wasViewed == %@", [NSNumber numberWithBool:YES]]; // code for setting entity, request etc... NSMutableArray *mutableFetchResults = [[[managedObjectContext executeFetchRequest:request error:&error] mutableCopy] autorelease]; This is working just fine, however, now I need to set up a loop, go through each Book object, something like this: for(Book *b in mutableFetchResults) { [b setWasViewed:NO] } Is there a way to perform an action on each element that fits the predicate instead of retrieving it? So instead of executeFetchRequest on a managedObjectContext it could be executeOperationOnFetchRequestResults or something along those lines. Thanks for any input given:)

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• How sophisticated should be DAL?

  - by Andrew Florko

  Basically, DAL (Data Access Layer) should provide simple CRUD (Create/Read/Update/Delete) methods but I always have a temptation to create more sophisticated methods in order to minimize database access roundtrips from Business Logic Layer. What do you think about following extensions to CRUD (most of them are OK I suppose): Read: GetById, GetByName, GetPaged, GetByFilter... e.t.c. methods Create: GetOrCreate methods (model entity is returned from DB or created if not found and returned), Create(lots-of-relations) instead of Create and multiple AssignTo methods calls Update: Merge methods (entities list are updated, created and deleted in one call) Delete: Delete(bool children) - optional children delete, Cleanup methods Where do you usually implement Entity Cache capabilities? DAL or BLL? (My choice is BLL, but I have seen DAL implementations also) Where is the boundary when you decide: this operation is too specific so I should implement it in Business Logic Layer as DAL multiple calls? I often found insufficient BLL operations that were implemented in dozen database roundtrips because developer was afraid to create a bit more sophisticated DAL. Thank you in advance!

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• With NHibernate, how can I create an INHibernateProxy?

  - by Eric

  After lots of reading about serialization, I've decided to try to create DTOs. After more reading, I decided to use AutoMapper. What I would like to do is transform the parent (easy enough) and transform the entity properties if they've been initialized, which I've done with ValueResolvers like below (I may try to make it generic once I get it fully working). This part works. public class OrderItemResolver : ValueResolver<Order, OrderItem> { protected override OrderItem ResolveCore(Order source) { // could also use NHibernateUtil.IsInitialized(source.OrderItem) if (source.OrderItem is NHibernate.Proxy.INHibernateProxy) return null; else return source.OrderItem; } } } When I transform the DTO back to an entity, for the entities that weren't initialized, I want to create a proxy so that if the entity wants to access it, it can. However, I can't figure out how to create a proxy. I'm using Castle if that's relevant. I've tried a bunch of things with no luck. The below code is a mess, mainly because I've been trying things at random without knowing what I should be doing. Anybody have any suggestions? public class OrderItemDTOResolver : ValueResolver<OrderDTO, OrderItem> { protected override OrderItem ResolveCore(OrderDTO source) { if (source.OrderItem == null) { //OrderItem OrderItem = new ProxyGenerator().CreateClassProxy<OrderItem>(); // Castle.Core.Interceptor. //OrderItem OrderItem = new ProxyGenerator().CreateClassProxy<OrderItem>(); //OrderItem.Id = source.OrderItemId; //OrderItem OrderItem = new OrderItem(); //var proxy = new OrderItem() as INHibernateProxy; //var proxy = OrderItem as INHibernateProxy; //return (OrderItem)proxy.HibernateLazyInitializer //ILazyInitializer proxy = new LazyInitializer("OrderItem", OrderItem, source.OrderItemId, null, null, null, null); //return (OrderItem)proxy; //return (OrderItem)proxy.HibernateLazyInitializer.GetImplementation(); //return OrderItem; IProxyTargetAccessor proxy = new Castle.Core.Interceptor. var initializer = new LazyInitializer("OrderItem", typeof(OrderItem), source.OrderItemId, null, null, null, null); //var proxyFactory = new SerializableProxyFactory{Interfaces = Interfaces, TargetSource = initializer, ProxyTargetType = IsClassProxy}; //proxyFactory.AddAdvice(initializer); //object proxyInstance = proxyFactory.GetProxy(); //return (INHibernateProxy) proxyInstance; return null; //OrderItem.Id = source.OrderItemId; //return OrderItem; } else return OrderItemDTO.Unmap(source.OrderItem); } } Thanks, Eric

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• Catching constraint violations in JPA 2.0.

  - by Dennetik

  Consider the following entity class, used with, for example, EclipseLink 2.0.2 - where the link attribute is not the primary key, but unique nontheless. @Entity public class Profile { @Id private Long id; @Column(unique = true) private String link; // Some more attributes and getter and setter methods } When I insert records with a duplicate value for the link attribute, EclipseLink does not throw a EntityExistsException, but throws a DatabaseException, with the message explaining that the unique constraint was violated. This doesn't seem very usefull, as there would not be a simple, database independent, way to catch this exception. What would be the advised way to deal with this? A few things that I have considered are: Checking the error code on the DatabaseException - I fear that this error code, though, is the native error code for the database; Checking the existence of a Profile with the specific value for link beforehand - this obviously would result in an enormous amount of superfluous queries.

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• Best architecture for accessing secondary database

  - by fearofawhackplanet

  I'm currently developing an app which will use a Linq to SQL (or possibly EF) data access layer. We already have a database which holds all our Contacts information, but there is currently no API around this. I need to interact with this DB from the new app to retrieve contact details. I can think of two ways I could do this - 1) Develop a suite of web services against the contacts database 2) Write a Linq to SQL (or EF) DAL and API against the contacts database I will probably be developing several further apps in the future which will also need access to the Contacts data. Which would generally be the prefered method? What are the points I need to consider? Am I even asking a sensible question, or am I missing something obvious?

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• nested repeaters - how to sort

  - by Cristian Boariu

  Hi guys, I have a table: Category with some sort of categories category1 category2 category3 I have another table Subcategory which has a fk to Category. So, each category1 can have subcategoryB, subcategoryA, subcategoryZ. Well... i've made two repeaters. The first one is binded to a linq data source which takes the categories from the parent table. The children repeater is binded to that foreign key like: DataSource='<%# Eval("Subcategories_1s") %' So the result is: category1 subcategoryB subcategoryA subcategoryZ category2 etc. Well, the strange question is: how can i order the subcategories alphabetically? If i'd have binded the children repeater to a linq it would be easy. But in this case...?

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• SelfReferenceProperty vs. ListProperty Google App Engine

  - by John

  Hi All, I am experimenting with the Google App Engine and have a question. For the sake of simplicity, let's say my app is modeling a computer network (a fairly large corporate network with 10,000 nodes). I am trying to model my Node class as follows: class Node(db.Model): name = db.StringProperty() neighbors = db.SelfReferenceProperty() Let's suppose, for a minute, that I cannot use a ListProperty(). Based on my experiments to date, I can assign only a single entity to 'neighbors' - and I cannot use the "virtual" collection (node_set) to access the list of Node neighbors. So... my questions are: Does SelfReferenceProperty limit you to a single entity that you can reference? If I instead use a ListProperty, I believe I am limited to 5,000 keys, which I need to exceed. Thoughts? Thanks, John

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• Solr dataimport skips entities in my data-config.xml

  - by lerhaupt

  My data-config.xml defines 3 different entities under the document tag (lets call them foo, bar and baz). When I issue a basic full import localhost:8983/solr/dataimport?command=full-import, only 2 of the 3 entities get indexed (foo and bar are in my index but baz never makes it). However, if I then issue a command to just import baz via localhost:8983/solr/dataimport?command=full-import&entity=baz&clean=false it adds baz documents just fine and the index then has all 3 types. Does anyone have any thoughts on why one entity gets skipped in the general data import but then still works okay if I specifically call it out? Is there an error/warning log I can check? Nothing bad shows up in /solr/logs/ but those just appear to be request logs.

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• Silverlight datagrid don't show any data with anonymous query RIA services

  - by user289082

  Hi all! I have an anonymous linq query that I bind to a datagrid, when I debug it brings alright the data but it doesn't show in the datagrid, I suspect that the request to RIA services isn't completed before I bound it to the datagrid. I could use the LoadOperation<() Completed event. But it only works with Defined Entities so how can I do that? For reference here is the last post: http://stackoverflow.com/questions/2403903/linq-query-null-reference-exception Here is the query: var bPermisos = from b in ruc.Permisos where b.IdUsuario == SelCu.Id select new { Id=b.Id, IdUsuario=b.IdUsuario, IdPerfil=b.IdPerfil, Estatus=b.Estatus, Perfil=b.Cat_Perfil.Nombre, Sis=b.Cat_Perfil.Cat_Sistema.Nombre }; I'm a totally newbie sorry if is a very simple question. Thanks!!

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• Is it valid for Hibernate list() to return duplicates?

  - by skaffman

  Is anyone aware of the validity of Hibernate's Criteria.list() and Query.list() methods returning multiple occurrences of the same entity? Occasionally I find when using the Criteria API, that changing the default fetch strategy in my class mapping definition (from "select" to "join") can sometimes affect how many references to the same entity can appear in the resulting output of list(), and I'm unsure whether to treat this as a bug or not. The javadoc does not define it, it simply says "The list of matched query results." (thanks guys). If this is expected and normal behaviour, then I can de-dup the list myself, that's not a problem, but if it's a bug, then I would prefer to avoid it, rather than de-dup the results and try to ignore it. Anyone got any experience of this?

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• How to handle JPA annotations for a pointer to a generic interface

  - by HDave

  I have a generic class that is also a mapped super class that has a private field that holds a pointer to another object of the same type: @MappedSuperclass public abstract class MyClass<T extends MyIfc<T>> implements MyIfc<T> { @OneToOne() @JoinColumn(name = "previous", nullable = true) private T previous; ... } My problem is that Eclipse is showing an error in the file at the OneToOne "Target Entity "T" for previous is not an Entity." All of the implementations of MyIfc are, in fact, Entities. I should also add that each concrete implementation that inherit from MyClass uses a different value for T (because T is itself) so I can't use the "targetEntity" attribute. I guess if there is no answer then I'll have to move this JPA annotation to all the concrete subclasses of MyClass. It just seems like JPA/Hibernate should be smart enough to know it'll all work out at run-time. Makes me wonder if I should just ignore this error somehow.

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