persistence

问题 I'm trying to build a flattened array that preserves metadata from a pretty tricky array coming from a view in my CodeIgniter project. That metadata is things like an identifier, depth, and parent node. The data is from a query builder JavaScript library that allows a user to generate rules that will be used in business logic. I need to persist this data, and the model I've gone with to represent the tree-like nature of these rules is an adjacency list. Here's what I have, and it does work

问题 I have an entity of type A with a referenced member entity of type B. I want to insert a relationship between an instance of A to an existing instance of B without having to fetch B. Is there a way to do it simply by ID? Something like: B mockB = new B(); mockB.id = "id_persisted_b"; instanceA.setB(mockB); Thanks. 回答1: If you are using JPA you can use EntityManager.getReference() to obatin a proxy of the object without fetching all the fields, e.g.: B mockB = entityManager.getReference(B

问题 I have a full Java EE web application with a presentation layer and a database. I'm using derby with glassfish 3.1 and JPA to handle persistence. I've created a Read ok but now I'm having troulbe doing a Create and persisting to the database. I think I'm close but something is not right with the way I'm trying to do the create. Here is my EAO code: /** * Session Bean implementation class XRSSeao */ @Stateless @LocalBean public class XRSSeao { @PersistenceContext EntityManager em; public

问题 Hello guys i am new to hibernate. while i was surfing stack overflow for hibernate related topics i found this Need clarification about mapping objects to database, annotations, and one to many relationships after reading the solution i was a bit confused and started building the exact scenario to understand the actual mechanism behind many to one, where i used oracle 11g database. When i am running my project hibernate is generating the tables and FK relations automatically but in the time

问题 I am learning to use Hibernate in my Java web app. I have the following sessionFactory started with a configuration for the location of my hibernate.cfg.xml file, but it still complains: resources/hibernate.cfg.xml not found The "resources" folder is a subdirectory of my "src" folder in the java project. public class HibernateUtil { private static final SessionFactory sessionFactory = new Configuration().configure("resources/hibernate.cfg.xml").buildSessionFactory(); public static void main

问题 If my object has a protected List<String> fileNote; What is the right way to define that relationship in an orm.xml? (note: I do not want to use annotations.) 回答1: Most simple, if you are satisfied with defaults is: <element-collection name="fileNote"/> If more customization is needed, you can go further: <element-collection name="fileNote" fetch="EAGER" access="FIELD/> <column name="some_name_for_column_that_holds_note" /> <collection-table name="descriptive_name_for_table"> <join-column

问题 I'm trying to implement a few tests with JBPM 6. I'm currently working a a simple hello world bpmn2 file, which is loaded correctly. My understading of the documentation ( Click ) is that persistence should be disabled by default. "By default, if you do not configure the process engine otherwise, process instances are not made persistent." However, when I try to implement it, and without doing anything special to enable persistence, I hit persistence related problems every time I try to do

问题 Say you had: a database a bunch of .NET Windows GUI programs a bunch of Java web applications you could use Hibernate for the Java stuff and NHibernate for the .NET stuff - but would the two actually interoperate or would they be entirely different stacks? If not then is there a persistence framework out there that lets Java and .NET share business logic? 回答1: I can't talk for the Java people, but from the .NET side of things I believe the mapping files could be shared (xml files describing

问题 According to MSDN, one can add customized settings files to ones project for convenient management of groups of settings. So I created a custom settings by visual designer, set all properties as a User Scoped to be able to save them.I bind some control properties to this customized settings. And change some values mannually through Properties.CustomSettings.MyValue = x; But when I do Properties.CustomSettings.Default.Save() - nothing happens. The changes are not persisted between application

问题 Is there an existing (Python) implementation of a hash-like data structure that exists partially on disk? Or, can persist specific keys to some secondary storage, based on some criteria (like last-accessed-time)? ex: "data at key K has not been accessed in M milliseconds; serialize it to persistent storage (disk?), and delete it". I was referred to this, but I'm not sure I can digest it. EDIT: I've recd two excellent answers (sqlite; gdb)m; in order to determine a winner, I'll have to wait