You’ve already had a few good answers here on how to do exactly as you ask.. For reference let me just mention the recommended way to do this in Hibernate instead, which is to use a surrogate key as primary key, and to mark business keys as NaturalId’s: Although we recommend the use of surrogate … Read more
Although answer given by Subhendu Mahanta is correct. But @CollectionOfElements is deprecated. You can use @ElementCollection instead: @ElementCollection @JoinTable(name=”ATTRIBUTE_VALUE_RANGE”, joinColumns=@JoinColumn(name=”ID”)) @MapKeyColumn (name=”RANGE_ID”) @Column(name=”VALUE”) private Map<String, String> attributeValueRange = new HashMap<String, String>(); There is no need to create a separate Entity class for the Map field. It will be done automatically.
If it’s really dictionary like arbitrary data you’re looking for you can probably use a two-level setup with one model that’s a container and another model that’s key-value pairs. You’d create an instance of the container, create each of the key-value instances, and associate the set of key-value instances with the container instance. Something like: … Read more
According to the JDO Documentation you create one PersistenceManagerFactory per datastore. If you are using JDO to access databases via SQL and you have more than one database, then you will need one PersistenceManagerFactory per database (since you need to specify the JDBC URL, user name and password when you create the PersistenceManagerFactory). For simple … Read more
You can use the persist() method rather than save(). https://forum.hibernate.org/viewtopic.php?f=1&t=1011405 However, unlike save(), persist() does not guarantee that the identifier value will be set immediately on the persisted instance. https://forum.hibernate.org/viewtopic.php?f=1&t=951275 (and you can jump to christian’s last post in the thread)
Well, this works: using System; using System.Configuration; using System.IO; using System.Linq; using System.Xml.Linq; using System.Xml.XPath; public static class SettingsIO { internal static void Import(string settingsFilePath) { if (!File.Exists(settingsFilePath)) { throw new FileNotFoundException(); } var appSettings = Properties.Settings.Default; try { var config = ConfigurationManager.OpenExeConfiguration( ConfigurationUserLevel.PerUserRoamingAndLocal); string appSettingsXmlName = Properties.Settings.Default.Context[“GroupName”].ToString(); // returns “MyApplication.Properties.Settings”; // Open settings file … Read more
Let’s say you want to save score and level, which are both properties of an object called dataHolder. DataHolder can be created as a singleton, so you don’t have to worry too much about from where you access it (its sharedInstance actually): It’s code would look a bit like this: DataHolder.h #import <Foundation/Foundation.h> @interface DataHolder … Read more
The typical table for one T1 to many T2 is to have a foreign key on T2 pointing toward T1. The T1_T2 table is usually not needed. The JPA structure would then be a One-To-Many, possibly two-way. There could be some arrangements, to make the structure you describe work. You could change T1_T2: add a … Read more
I have never tried it, but what about redis ? Its homepage says (quoting) : Redis is a key-value database. It is similar to memcached but the dataset is not volatile, and values can be strings, exactly like in memcached, but also lists and sets with atomic operations to push/pop elements. In order to be … Read more
These 2 links help me understand the inheritance concept the most: http://docs.oracle.com/javaee/6/tutorial/doc/bnbqn.html http://www.javaworld.com/javaworld/jw-01-2008/jw-01-jpa1.html?page=6 To understand discriminator, first you must understand the inheritance strategies: SINGLE_TABLE, JOINED, TABLE_PER_CLASS. Discriminator is commonly used in SINGLE_TABLE inheritance because you need a column to identify the type of the record. Example: You have a class Student and 2 sub-classes: GoodStudent … Read more