Questions tagged [jpa]

The Java Persistence API (JPA) is a Java specification for accessing, persisting, and managing data between Java objects/classes and a relational database. It is part of the EJB 3.0 specification and is the industry standard approach for Object to Relational Mapping (ORM).

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spring boot jpa repositories vs hql queries vs native queries

I'm currently working on a Spring Boot project. I have a big dilemma between the usage of JPA repositories, HQL queries, and SQL native queries. Converting all query logic to a native query is a ...
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How to define API notations for multiple tables data in the response

The question is specific to the API notation shown in the screen under the heading Table Name with the comment Joins Multiple Tables. I am using Spring Boot with JPA (Database: RDBMS) I have defined ...
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Implementing transactional entity lockouts with Spring and JPA

Spring Boot/Java 8/MySQL here. I have a widgets table in my MySQL DB that is modeled by a JPA entity like so: @Entity @Table(name = "widgets") @Data public class Widget { @Column(name = ...
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How best to structure my Service/Repository layers when persisting a Many to One object?

I'm working on a project where I need to do CRUD operations on Book and Library objects. Naturally the relationship between Book and Library is Many to One, like so: @Entity @Getter @Setter @...
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3 answers
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Best practices for retrieving data scattered over multiple tables

In the company I work with, we have a 3-layer architecture in our micro-services and the flow is like this: Repository/DAO (entity) => Service (entity) => Controller (dto) At the Controller ...
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Entity objects with data external to the database

I'm looking for design patterns to model (java) objects that are partially stored in a database and partially stored some other external source. In my case the external data is a whole lot of files ...
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2 votes
1 answer
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Best way to handle lazy models with mapstruct and spring transnational scope

In a typical Java Spring Web APP: we have the following layers: Model [DB Models] Repositories [where you have queries to DB] Services [Business service where you have the @Transactional annotation] ...
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3 answers
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Pattern for syncing databases with undo option

I work on a large and old application consisting of a server and a fat client. Part of what the application does is handle a large-ish (a few 100MBs) database of frequently changing data (~a dozen ...
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Normalize timestamp values or have multiple SQL queries

I have a Spring Boot application to implement a RESTful API. One of the GET requests have two query parameters: from and until (of type date). Those parameters are optional, so user-agents can send ...
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What's a valid use case of JPA annotation @Transient?

I'm new to JPA and Hibernate. I just saw an annotation called @Transient, which can mark a field to be non-persistent in the database. However, for the sake of "separation of concerns" ...
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Implementing a user ID system like Discords for a web app using Java Spring, JPA, Hibernate and MySQL

I’m trying to create a web application with a forum and user profile along with other functions. However I’m thinking about how I might implement an ID for each user. The best way I’ve seen other ...
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How to share entity classes (JPA) among projects, where not all have DB access?

So, I have project in which several WebServices will be created (REST). For the sake of simplicity, Lets name them A, B, and C. A and B handle different tasks, but both of them consume C, which is the ...
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Best practice for references in DTOs and entities in Spring

Given the following architecture and frameworks: Spring Boot Application with Spring Data JPA (Hibernate is used as OR mapper); layered architecture as followed. REST layer Service layer Persistence ...
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In a Spring Boot Project, would you use interfaces for entities or not?

I am currently on the decision, whether to use interfaces throughout my whole spring project or not. I scouted some open source projects and saw, that many big projects are handling that quite ...
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Jpa Repository save inside a for loop

I have this requirement: Csv Upload (using opencsv) Should display if the record is inserted (if it doesn't exist in the db) or updated (if it exists). Eg.: 5 records inserted 2 records updated. ...
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2 votes
2 answers
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Query with a lot of fields and joins

I have to map a legacy database with tables that have a lot of fields and relations. For example (simplified code), @Entity @Table(name = "VISIT") public class VisitEntity { @Id private ...
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performance suggestions on Aggregate root containing thousands of child entities

I understand that DDD is a design concept and implementation through ORMs are tricky but help me understand how would you solve this problem? So here is my confusion on changing on aggregates only ...
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Performance impact of JPARepository save() on a large database table with index

We have a few tables with a large amount of data and with indexes on those tables to help in faster retrieval. We are also using Spring Data JPA JpaRepository for adding data to those tables using the ...
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In new project where you have ability to define DB and write app code, what is seen as best practice?

Good day When starting a new project and you have access to the db as well as writing the code. In this specific case it is PostgreSQL and Java EE with JPA and Hibernate. Should one: Aim to ...
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2 votes
2 answers
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Returning JPA Entities in Rest Api's?

Recently Ive seen so many devs working with the stack Spring/JPA and returning all these JPA entities on their rest controllers. In my opinion it's a BAD PRACTICE for several reason such: ...
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3 votes
2 answers
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Using Map to pass query parameters in DAO

It's very common see a generic's DAO implementation like this: public List<E> getResultList(String namedQuery, Map<String, Object> parameters) { Query query = entityManager....
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2 votes
1 answer
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How to represent and validate website URLs for a JPA entity

I have an application that will allow the user to enter and store (in a DB) a website URL for a company. The only requirement (as of now) beyond entry of the website URL is to validate that the URL is ...
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Reserving database independence using Spring JPA

We are planning to use Spring Boot with JPA for our next project and I am wondering how much flexibility JPA gives in reality. If we start developing using a self-hosted PostgreSQL server and later ...
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Correct way to separate JPA with Service layer

I have two tables: area ( id int PK autoincrement code varchar ) products ( id int PK autoincrement name varchar area_id int PK to AREA ... ) The classes are persisted using eclipselink ...
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Class Design for JPA Entities with Multiple Tables Referring to Same Business Object

I have an application that works with products from various external data sources (in DataSourceProduct) and it also maintains its own version of the product (in MasterProduct). Here's the DB schema: ...
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Problem related to optimistic locking performance

I'm designing a system that like the majority of social related application has posts, people can like the posts and comment on them. And also like the majority of the applications the users can see ...
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3 votes
1 answer
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Calling repository inside a mapper

Is it bad practice to autowire and call a repository from within a mapper class? I have a mapper class that maps a model to an entity for JPA. In order to keep repository calls within my service, it ...
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3 votes
2 answers
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Allowing users to add their own custom fields in a Spring MVC Hibernate application - What's an ideal approach?

We all may have seen applications like JIRA, or many CRM or other applications that allow its users to define their own custom fields to an entity, and do a variety of stuff with it, like making them ...
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2 answers
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Any drawbacks to having very descriptive table and column names in DB tables for Java web app?

I would like to know if there are any drawbacks to having descriptive names for database tables and columns. This would be for a Java based web application, and most of the times I have seen database ...
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Decoupled architecture between business and data layers in Spring JPA / Hibernate

I'm using Spring Boot with JPA / Hibernate and I'm trying to decouple the business layer from the data layer. I would like to be able to (relatively easily) switch from a relational database to a rdf ...
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3 votes
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Are Remote EJBs the right way to go?

I am planning to remodel my current application and I am not sure if this is the right approach. Currently I have a Java Enterprise server application with 3 web-applications and an ejb-application ...
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1 vote
1 answer
733 views

auto generated web CMS for pre-existing SQL db?

What I'm looking for is a way to auto-generate a simple web-based CMS for a simple pre-existing SQL database. To be used by 'app administrators', not the general public. Something that: allows basic ...
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Approach for querying an arbitrary set of user submitted fields and values in Spring application? Like a shopping site sidebar search?

I am working on a Spring Boot and Angular application which has a requirement to search based on any number of the available filters being applied to a list. For example, a user searches on 'Title' ...
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Handle publishing data across environments

I am rewriting a website that has a back-end database for containing meta-data that is displayed to the user when they enter a text code. Background: The old/existing system stored this data in XML ...
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How to avoid LazyInitializationException using Hibernate and Jersey

I am working with Spring Boot + Jersey + JPA/Hibernate to build a RESTful API. The issue I am encountering right now is when I have a relationship in my JPA Entity that is lazy loaded I get a lazy ...
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8 votes
1 answer
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ORM: runtime proxies vs bytecode instrumentation

What are the benefits of using runtime proxies with an ORM provider like Hibernate or EclipseLink compared to bytecode instrumentation/enhancement? I know that bytecode instrumentation helps to ...
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1 vote
1 answer
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DTO and JPA Version

I have DB tables representing Employees and Departments. The server side(JavaEE) contains JPA entities representing the same. The client is a standalone client and communicates with the server using ...
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4 votes
2 answers
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What's the correct approach to DAO layer in presence of ORM framework

I'm using JPA/Hibernate but probably it doesn't limit question. Currently I'm writing my data access code in my web controller classes. Thanks to JPA, in most cases this code is very simple, ...
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Can I ditch the persistence.xml file on JBoss?

I have a Spring based app where another programmer is using JPA's persistence.xml file to define the setup of hibernate and to define the entities that are being persisted. The app is using Spring's ...
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1 vote
3 answers
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Limiting complexity in JPA programs Java/Hibernate

I've been working on a new application for some months now. It's my first big JPA program, and is still in the early stages. However, the complexity of my JPA object tree is becoming a growing problem....
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6 votes
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Is this database design good? What JPA Entities should I create for this design?

I am trying my hands on JPA. For this I am thinking of using the example of a student admission process as shown in the diagram below. Is this design good ? Any suggestions for improvement are more ...
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Producing JSON objects from JPA entities in REST API

I have a REST service producing JSON and consuming JSON. A lot of this are simple CRUD operations. My initial idea was to simply use the DAOs directly in the controller: @ResponseBody() @...
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22 votes
5 answers
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Is staying implementation agnostic really worth it?

I have a project that I'm working on currently using Tomcat, Spring 4, Spring Security, MySQL, and JPA w/ Hibernate. I picked JPA from the standpoint that it's suppose to make swapping out the ...
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8 votes
1 answer
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Where to put JPA annotations? Field, or getter?

version in field: @Column(name = "SAMPLE_STRING") private String sampleString; public String getSampleString(){ return sampleString; } version in getter: private String sampleString; @...
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21 votes
4 answers
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How can I use unit tests and TDD to test an app that relies mostly on database CRUD operations?

At work, one of my projects is mostly about taking data passed in from an external client and persisting it in a database. It's a Java enterprise app using JPA and most of our logic revolves around ...
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1 vote
1 answer
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Is Java's ElementCollection Considered a Bad Practice?

From my understanding, an ElementCollection has no primary key, is embedded with the class, and cannot be queried. This sounds pretty hefty, but it allows me the comfort of writing an enum class which ...
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3 votes
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ORM: Design of the service layer

I'm currently writing a medium sized web-application and find myself asking this question many times. For example, let's say there are users, which have files (one-to-many). How should the UI access ...
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1 vote
1 answer
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Creating a separate project for JPA entities

Where I work it is a common practice to create a separate for JPA entities and a project for the web application (the WAR). So basically you have (at least) two project for each application - appJPA ...
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16 votes
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Entity to DTO Usage

Been trying to come up with a flow for a basic tiered web application, and have been reading conflicting information online. What I'm trying to figure out is if there is an advantage to still using ...
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6 votes
3 answers
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When Business Object fields should not exactly reflect database columns

Main advantage with Hibernate annotations is the fact that a simple POJO (also called a Business Object the most of time) can become persistent through Hibernate annotations (or actually JPA) . In ...
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