Best object-relational mapping software

Apache Cayenne. Apache OpenJPA. Read our complete collection of recommended free and open source software. The collection covers all categories of software. The software collection forms part of our series of informative articles for Linux enthusiasts. There are essentially three different ways to map inheritance hierarchies to database tables. Some frameworks offer further variations and mixtures of these three basic methods. Table per inheritance hierarchy: In this procedure, all attributes of the base class and all classes derived from it are stored in a common table.

In addition, restrictions on the number of allowed columns per table can thwart this approach for large classes or class hierarchies. Table per subclass: In this procedure, a table is created for the base class and another table is created for each subclass derived from it.

A discriminator is not needed because the class of an object is defined by a 1-to-1 relationship between the entry in the base class table and an entry in one of the tables of the derived classes.

Table per specific class: Here, the attributes of the abstract base class are included in the tables for the concrete subclasses. The table for the base class is omitted. The disadvantage of this approach is that it is not possible to use a query to discover instances of different classes.

Another method is the mapping of structures relationships, inheritance and data in general tables. The entire database contains exactly 5 tables: one for classes, one for relationships including inheritance relationships , one for attributes, one for instances of the classes , and one for values of the attributes. However, this procedure has little significance in practice. You can read more about it in the GitHub Dapper project. Like in the previous cases, an example below.

Java has been out there for a while, and you have many options, but probably the best way to go is Hibernate. Check out more in the official documentation. Also there, you have to define classes and properties in them. Like any ORM, you will use that to represent your database structure. In short, ORM is a programming technique where you write code, and that code gets translated into SQL queries for you. With ORM, you are free from thinking about the database so that you can focus on your business logic.

A great step up in productivity! What is ORM? Object-Relational Mapping Explained. Alessandro Maggio May 28, Share This Post. Share on linkedin. Share on facebook.

Share on twitter. Share on email. In ORM, your code defines your database. An example of using ORM Examples make everything clearer. Database migrations Unlike what you might expect, database migrations are not necessarily the transition from a database to another.

Python ORM Django Django is a great python project that helps you to build a fully-fledged web application. IntegerField As you can see from the example, you directly define fields and relationships when defining the classes.

Never Stop Learning Programmers maintain a lot of control over their data interface with SQL. It requires a lot of work, but it is more flexible and detailed than an ORM abstraction. Using raw SQL also has its drawbacks. For instance, the developer is responsible for the safety and security of the database code. SQL injection is a problem where user input can affect the data state causing issues with the application and data integrity. ORMs sanitizes the code, making it easier to avoid these problems.

Query builders add a layer of abstraction over the raw SQL without masking all of the underlying details. The builders formalize querying patterns and add methods to or functions that add escape items for easier application integration. They add a templating layer to help developers understand the database structure within the same coding application. Template builders still require developers to understand the database structure, requiring them to know SQL.

There are four significant benefits of using object-related mappers to manage the interface between applications and databases. Using a tool like an ORM that automatically generates the data-access code saves tremendous development time that does not add value to the application. In some cases, the ORM can write percent of the data-access code for the application.

The ORM can also help you keep track of database changes making it easier to debug and change the application in the future. A well-written ORM will implement design patterns to force you to use best practices for application design. If you use an ORM to manage the data interface, you do not need to create the perfect database schema in advance. You will be able to change the existing interface easily. Separating the database table from the programming code also allows you to switch out data for different applications.

One way to reuse data is to create a class library to generate a separate dynamic-link library DLL. You can create a new application without needing to duplicate the data-access code.

Since the code generated by the ORM is well-tested, you do not need to spend as much time testing the data-access code. Instead, you can focus on testing the business logic and code. ORMs are an excellent tool for many applications, but some developers found several drawbacks in using ORMs for data-access applications.