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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86 views

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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153 views

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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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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Two JPA read/write Entities vs SpringJdbcTemplate for implementing CQRS without event sourcing?

So we are trying to implement DDD and CQRS (without event sourcing). I am need of clarity about the implementation details (Spring + JPA). DDD with multiple small aggregate roots require @Entity ...
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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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1answer
404 views

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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2answers
418 views

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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2answers
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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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1answer
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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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2answers
639 views

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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2answers
478 views

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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1answer
3k views

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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2answers
122 views

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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1answer
474 views

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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848 views

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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2answers
85 views

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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1answer
961 views

Decoupled architecure 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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97 views

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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1answer
463 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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1answer
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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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1answer
1k views

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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1answer
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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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1answer
1k views

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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2answers
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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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1answer
758 views

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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3answers
663 views

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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1answer
1k views

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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1answer
2k views

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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5answers
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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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1answer
9k views

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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4answers
3k views

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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1answer
3k views

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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1answer
411 views

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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1answer
2k views

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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2answers
24k views

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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3answers
2k views

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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4answers
537 views

Should OO design, or database design, drive the coding of my @Entity classes?

I have two classes that I want related to each other in an JEE application using JPA2. In an OO world, I would say that a Chatroom has an attribute List messages. In the relational world composition ...
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1answer
11k views

IntelliJ with Maven compilation

I have a project that needs Hibernate jars. I added them as dependencies in the pom.xml and Maven compiles my project well. However, in the IDE, all annotations and calls to Hibernate API are marked ...
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2answers
3k views

Designing complex query builders in java/jpa/hibernate

I need to build complex sql queries programatically, based on large filter conditions. For example, below are few sample/hypothitical filter conditions, based on which i need to fetch users Country: ...
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1answer
2k views

When using Java Persistence API (JPA), which layer owns the entities?

When working with annotations on entities in JPA, do these entities belong to the model layer or the persistence layer? Does there have to be some kind of clone of the entities (simple JavaBeans) in ...
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3answers
311 views

in doubt of using code generators

I am now entering the world of java ee 6. And I am supposed to used different technologies like jsf, jpa, different kinds of beans and all that stuff. I am learning using the netbeans IDE, which is, ...
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1answer
2k views

Has JPA replaced CMP?

No question too stupid right :) Came across this on wikipedia The Java Persistence API replaces the persistence solution of EJB 2.0 CMP (Container Managed Persistence). My understanding was the ...
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2answers
392 views

When designing data models for JPA, what's the best way to make use of polymorphism?

I've been asked to support a Java EE application. The data model was poorly-designed and will not support several necessary use cases; so I'm developing a new data model using EclipseLink (the old one ...
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2answers
2k views

Is JSF and JPA worth learning? [closed]

I'm attending a company sponsored training event for JSF and JPA that crams 10 days of training into 5 days. I plan on getting all that I can out of the class, but there is no "final exam".