You go to the bank to deposit 2 checks, and withdraw a small sum. So you stand in line until a teller opens. You make your first deposit. Then your second. Then you make your withdrawal. Now you’re done, you leave the teller line. Getting to the teller is like creating your session, now you’re … Read more
You could use this as a rough “ruleset”: YES, use persistent connections, if: There are only few applications/users accessing the database, i.e. you will not result in 200 open (but probably idle) connections, because there are 200 different users shared on the same host. The database is running on another server that you are accessing … Read more
PersistenceUnit injects an EntityManagerFactory, and PersistenceContext injects an EntityManager. It’s generally better to use PersistenceContext unless you really need to manage the EntityManager lifecycle manually.
I ran into this same issue and realized that, since I am using spring boot, all I needed to do to resolve the issue was to add the following dependency: <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency>
The problem with this approach is that you can have the N+1 effect. Imagine that you have the following entity: public class Person{ @OneToMany // default to lazy private List<Order> orderList; } If you have a report that returns 10K of persons, and if in this report you execute the code person.getOrderList() the JPA/Hibernate will … Read more
Many applications may provide a way to capture user preferences on the settings of a specific application or an activity. For supporting this, Android provides a simple set of APIs. Preferences are typically name value pairs. They can be stored as “Shared Preferences” across various activities in an application (note currently it cannot be shared … Read more
You can detach an entity by calling Session.evict(). Other options are create a defensive copy of your entity before translation of values, or use a DTO instead of the entity in that code. I think these options are more elegant since they don’t couple conversion to JSON and persistence layer.
Yeah, if you want the data to persist across reloads, your options are going to be storing that info server-side (via an api call) or in browser storage (local storage, session storage, cookies). The option you’ll want to use depends on what level of persistence you’re looking to achieve. Regardless of storage choice, it would … Read more
You can’t do it from python, but some clever bash tricks can do something similar. The basic reasoning is this: environment variables exist in a per-process memory space. When a new process is created with fork() it inherits its parent’s environment variables. When you set an environment variable in your shell (e.g. bash) like this: … Read more
Instead of defining EntityManager in each of your resource, you can define it once by creating a Custom JpaRepository. Reference Then use the refresh of your EntityManager in each of your repository directly. Refer the below example: CustomRepository Interface import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.data.repository.NoRepositoryBean; import java.io.Serializable; @NoRepositoryBean public interface CustomRepository<T, ID extends Serializable> extends JpaRepository<T, ID> … Read more