one-to-one

问题 I have a basic one to one mapping. When i try to extract information with the foreign key the first time i run the program i get an error message:ERROR: Connection leak detected: there are 1 unclosed connections upon shutting down pool jdbc:mysql://localhost:3306/novabaza?useSSL=false&serverTimezone=UTC Exception in thread "main" java.lang.NullPointerException at oto_otm_mtm.Blogic.main(Blogic.java:46). Second time i run the progam it always goes smoothly. Tried to close the session then

问题 I am having some trouble doing a one to one relationship with user_info table and userImage table. When I try to upload my image, it didn't save into my database and it user_id is 0. I managed to successfully do a one to many and one to one relationship in the past but not with CRUD together. Can anyone help me? Best to give me some example for me to refer or advice on what should I do. Thanks in advance Here are my current codes: createController: public function create1(){ return view(

问题 I have questions about What are the benefits of using a one-to-one association on foreign key or a one-to-one association on the primary key ? I've read the documentation of Hibernate available at: http://docs.jboss.org/hibernate/orm/3.3/reference/en/html/associations.html#assoc-unidirectional-121 Can someone tell me with details the plus of using the first or the second implementation? Another question, I have a one-to-one unidirectional relationship between User and Perimeter. (User ---->

问题 I'm trying to learn NHibernate 3.2 built-in mapping by code api ( NOT Fluent NHibernate ). Can you help me to map a one-to-one(or zero) relationship between these entities please? NOTE: I googled the question, also I search the SOF, all examples are using Fluent API or xml; I'm trying to use built-in mapping api in NHibernate 3.2 public class Person { public virtual int Id { get; set; } public virtual string FirstName { get; set; } public virtual string LastName { get; set; } // can be null

问题 I'd like to have a principal entity ( Person ) with optional dependent entity ( Car ) mapped using the default conventions in Entity Framework code-first model. One solution is described in this answer, which uses the fluent API on modelBuilder to map to the key. Is it possible to do this using only the default EF conventions? The following code will throw a Unable to determine the principal end of an association between the types Person and Car. invalid operation exception. public

问题 I have two base abstract classes and there are multiple additional classes derived from these two, adding additional attributes etc. There exist relations between those specific derived types. A simple illustrating example: Role and Group classes are abstract , but they are not marked as @MappedSuperclass . InheritanceType.JOINED strategy is being used, so both tables Role (for abstract class) and AdminRole (for derived class) should exist (they both will have the same RoleID ).

问题 I have a form responsible of creating and updating users. A user can (or not) have an address (OneToOne unidirectional relation from user). When I create a user, no problem. When I update a user, usually no problem. Problems come up when i update a user which already has an address and try to unset all the address fields. There is then a validation error. The wanted behavior would be to have the user->address relation set to null (and delete the previously set address on the DB). There is a

问题 I use EF4.3 to create 1 to 1...0 relationship, but it throw an exception of "The operation failed because an index or statistics with name 'IX_id' already exists on table 'TestAs'" The code as below namespace ConsoleApplication1 { class Program { static void Main(string[] args) { using (myContext context = new myContext()) { TestA tA = new TestA(); TestB tB = new TestB(); TestC tC = new TestC(); context.testA.Add(tA); context.testB.Add(tB); context.testC.Add(tC); context.SaveChanges(); } } }

问题 I am creating a photo sharing app for the iPhone using Parse.com and so far everything has been pretty easy and I just finished writing the code for uploading photos to the Parse server. So far, I have been using the default "_User" class. Here are some of the key types of data that are being stored for each user: objectId, username, email, and an array object called "friends" that contains the usernames of other users in the database that the user has added to their friends list. Now, I need

问题 this is my ApplicationUser class.I have added only one new property ---- public class ApplicationUser : IdentityUser { //public ApplicationUser() //{ // UserProfileInfo = new UserProfileInfo { ImageSize = 0, FileName = null, ImageData = 0 }; //} public string HomeTown { get; set; } public virtual UserProfileInfo UserProfileInfo { get; set; } and this is my userProfileInfo class where i want to save every user's profile pic after they have completed the registration---- public class