{{Short description|Concept in software engineering}} In [[software engineering]], the '''active record pattern''' is an [[Architectural pattern (computer science)|architectural pattern]]. It is found in software that stores in-memory object data in [[relational database]]s. It was named by [[Martin Fowler (software engineer)|Martin Fowler]] in his 2003 book ''Patterns of Enterprise Application Architecture''.<ref>[https://martinfowler.com/eaaCatalog/activeRecord.html P of EAA Catalog - Active Record]</ref><ref>{{cite book |last=Fowler |first=Martin |title=Patterns of enterprise application architecture |publisher=Addison-Wesley |year=2003 |isbn=978-0-321-12742-6 |url=https://books.google.com/books?id=FyWZt5DdvFkC&q=active+record&pg=PT187 }}</ref> The interface of an object conforming to this pattern would include functions such as Insert, Update, and Delete, plus properties that correspond more or less directly to the columns in the underlying database table.
The Active Record pattern is a [[Data access layer|Data Access Layer]] that performs bidirectional transfer of data between a persistent data store (often a [[relational database]]) and an in-memory data representation (the domain layer). A [[database table]] or [[View (database)|view]] is wrapped into a [[class (computer science)|class]]. Thus, an [[object (computer science)|object]] instance is tied to a single row in the table. After creation of an object, a new row is added to the table upon save. Any object loaded gets its information from the database. When an object is updated, the corresponding row in the table is also updated. The wrapper class implements [[accessor]] [[Method (computer programming)|methods]] or properties for each column in the table or view.
This pattern is commonly used by object persistence tools and in [[object–relational mapping]] (ORM). Typically, [[foreign key]] relationships will be exposed as an object instance of the appropriate type via a property.
== Implementations == Implementations of the concept can be found in various [[Software framework|framework]]s for many programming environments. For example, if there is a table <code>parts</code> in a database with columns <code>name</code> (string type) and <code>price</code> (number type), and the Active Record pattern is implemented in the class <code>Part</code>, the pseudo-code <syntaxhighlight lang="java"> Part part = new Part("Sample part", 123.45); </syntaxhighlight> will create a new row in the <code>parts</code> table with the given values, and is roughly equivalent to the [[SQL]] command <syntaxhighlight lang="sql"> INSERT INTO parts (name, price) VALUES ('Sample part', 123.45); </syntaxhighlight>
Conversely, the class can be used to query the database: <syntaxhighlight lang="java"> Part b = parts.stream() .filter(p -> "gearbox".equals(p.getName())) .findFirst() .orElse(null); </syntaxhighlight>
This will find a new <code>Part</code> object based on the first matching row from the <code>parts</code> table whose <code>name</code> column has the value "gearbox". The SQL command used might be similar to the following, depending on the SQL implementation details of the database:
<syntaxhighlight lang="sql"> SELECT * FROM parts WHERE name = 'gearbox' LIMIT 1; -- MySQL or PostgreSQL </syntaxhighlight>
Various libraries implement an active record pattern framework, such as [[POCO C++ Libraries]] in library <code>Poco::ActiveRecord</code>.<ref>{{Cite web|title=Namespace Poco::ActiveRecord|url=https://docs.pocoproject.org/current/Poco.ActiveRecord.html|access-date=18 October 2025|website=docs.pocoproject.org|publisher=POCO Project}}</ref>
== Example == This is a simple example of an active record object <code>User</code>, in [[Java (programming language)|Java]]. Here the <code>User</code> class is both the model and [[data access object]] and provides <code>save()</code>, <code>find()</code>, and <code>delete()</code> methods. <syntaxhighlight lang="java"> package org.wikipedia.examples;
import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement;
public class User { private int id; private String name; private String email;
public User(String name, String email) { this.name = name; this.email = email; }
public int getId() { return id; }
public void setId(int id) { this.id = id; }
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public String getEmail() { return email; }
public void setEmail(String email) { this.email = email; }
public void save() { try (Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "user", "password")) { if (this.id == 0) { String sql = "INSERT INTO users (name, email) VALUES (?, ?)"; try (PreparedStatement stmt = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS)) { stmt.setString(1, this.name); stmt.setString(2, this.email); stmt.executeUpdate(); ResultSet rs = stmt.getGeneratedKeys(); if (rs.next()) { this.id = rs.getInt(1); } } } else { String sql = "UPDATE users SET name = ?, email = ? WHERE id = ?"; try (PreparedStatement stmt = conn.prepareStatement(sql)) { stmt.setString(1, this.name); stmt.setString(2, this.email); stmt.setInt(3, this.id); stmt.executeUpdate(); } } } catch (SQLException e) { System.err.printf("A SQLException occurred: %s%n", e.getMessage()); e.printStackTrace(); } }
public static User find(int id) { try (Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "user", "password")) { String sql = "SELECT * FROM users WHERE id = ?"; try (PreparedStatement stmt = conn.prepareStatement(sql)) { stmt.setInt(1, id); ResultSet rs = stmt.executeQuery(); if (rs.next()) { User user = new User(rs.getString("name"), rs.getString("email")); user.setId(rs.getInt("id")); return user; } } } catch (SQLException e) { System.err.printf("A SQLException occurred: %s%n", e.getMessage()); e.printStackTrace(); } return null; }
public void delete() { try (Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "user", "password")) { String sql = "DELETE FROM users WHERE id = ?"; try (PreparedStatement stmt = conn.prepareStatement(sql)) { stmt.setInt(1, this.id); stmt.executeUpdate(); } } catch (SQLException e) { System.err.printf("A SQLException occurred: %s%n", e.getMessage()); e.printStackTrace(); } } } </syntaxhighlight>
== Criticism ==
=== Single responsibility principle and separation of concerns === Another critique of the active record pattern is that, due to the strong coupling of database interaction and application logic, an active record object does not follow the [[single responsibility principle]] and [[separation of concerns]]. This is opposed to [[multitier architecture]], which properly addresses these practices.{{citation needed |date=November 2019}}{{Clarify|date=August 2018}} Because of this, the active record pattern is best and most often employed in simple applications that are all forms-over-data with [[Create, read, update and delete|CRUD]] functionality, or only as one part of an architecture.{{citation needed |date=November 2019}} Typically that part is data access and why several ORMs implement the active record pattern.
== See also ==
* {{Annotated link |Business object}} * {{Annotated link |Create, read, update and delete|CRUD}} * {{Annotated link |Data mapper pattern}} * {{Annotated link |Object–relational mapping}}
== References == {{Reflist}}
{{Design Patterns Patterns}}
{{DEFAULTSORT:Active Record Pattern}} [[Category:Architectural pattern (computer science)]] [[Category:Software design patterns]]