View source for MyBatis

{{Short description|Java persistence framework}}
{{Infobox Software
| name = MyBatis
| logo = MyBatis logo.png
| logo size = 200px
| screenshot =
| caption =
| developer = The MyBatis team
| latest release version = {{wikidata|property|preferred|references|edit|Q5851860|P348|P548=Q2804309}}
| latest release date = {{wikidata|qualifier|preferred|single|Q5851860|P348|P548=Q2804309|P577}}
| latest preview version =
| latest preview date =
| operating system = [[Cross-platform]]
| programming language = [[Java (programming language)|Java]]
| genre = [[Persistence framework]]
| license = [[Apache License]] 2.0
| website =
}}
'''MyBatis''' is a [[Java (programming language)|Java]] [[persistence framework]] that couples objects with [[stored procedure]]s or [[SQL]] statements using an [[XML]] descriptor or annotations.
MyBatis is [[free software]] that is distributed under the [[Apache License]] 2.0.
MyBatis is a fork of [[iBATIS]] 3.0 and is maintained by a team that includes the original creators of [[iBATIS]].
==Feature summary==
Unlike [[Object-relational mapping|ORM]] frameworks, MyBatis does not map [[Java (programming language)|Java]] objects to [[database]] tables but Java methods to [[SQL]] statements.
MyBatis lets you use all your database functionality like stored procedures, [[View (SQL)|views]], queries of any complexity and vendor proprietary features. It is often a good choice for legacy or de-normalized databases or to obtain full control of SQL execution.
It simplifies coding compared to [[JDBC]]. SQL statements are executed with a single line.
MyBatis provides a mapping engine that maps SQL results to object trees in a declarative way.
SQL statements can be built dynamically by using a built-in language with XML-like syntax or with [[Apache Velocity]] using the Velocity integration plugin.
MyBatis integrates with [[Spring Framework]] and [[Google Guice]]. This feature allows one to build business code free of dependencies.
MyBatis supports declarative data caching. A statement can be marked as cacheable so any data retrieved from the database will be stored in a cache and future executions of that statement will retrieve the cached data instead hitting the database. MyBatis provides a default cache implementation based on a Java HashMap and default connectors for integrating with: [[OSCache]], [[Ehcache]], [[Hazelcast]] and [[Memcached]]. It provides an [[API]] to plug other cache implementations.
==Usage==
SQL statements are stored in [[XML]] files or annotations. Below depicts a MyBatis mapper, that consists of a Java interface with some MyBatis annotations:
<syntaxhighlight lang="java">
package org.mybatis.example;
public interface BlogMapper {
@Select("select * from Blog where id = #{id}")
Blog selectBlog(int id);
}
</syntaxhighlight>
The sentence is executed as follows.
<syntaxhighlight lang="java">
BlogMapper mapper = session.getMapper(BlogMapper.class);
Blog blog = mapper.selectBlog(101);
</syntaxhighlight>
SQL statements and mappings can also be externalized to an XML file as follows.
<syntaxhighlight lang="xml+velocity">
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="org.mybatis.example.BlogMapper">
<select id="selectBlog" parameterType="int" resultType="Blog">
select * from Blog where id = #{id}
</select>
</mapper>
</syntaxhighlight>
Statements can also be executed using the MyBatis API.
<syntaxhighlight lang="java">
Blog blog = session.selectOne("org.mybatis.example.BlogMapper.selectBlog", 101);
</syntaxhighlight>
For details, please refer to the User Guide available at MyBatis site. See external links.
==Spring integration==
MyBatis integrates with [[Spring Framework]]. This module allows MyBatis to participate in Spring transactions. It will also build MyBatis mappers and sessions and inject them into other beans.
The following sample shows a basic XML configuration that sets up a mapper and injects it into a "BlogService" bean.
<syntaxhighlight lang="xml">
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
</bean>
<bean id="blogMapper" class="org.mybatis.spring.mapper.MapperFactoryBean">
<property name="sqlSessionFactory" ref="sqlSessionFactory" />
<property name="mapperInterface" value="org.mybatis.example.BlogMapper" />
</bean>
<bean id="blogService" class="org.mybatis.example.BlogServiceImpl">
<property name="blogMapper" ref="blogMapper" />
</bean>
</syntaxhighlight>
Calling MyBatis is now just calling a bean:
<syntaxhighlight lang="java">
public class BlogServiceImpl implements BlogService {
private BlogMapper blogMapper;
public void setBlogMapper(BlogMapper blogMapper) {
this.blogMapper = blogMapper;
}
public void doSomethingWithABlog(int blogId) {
Blog blog = blogMapper.selectBlog(blogId);
...
}
}
</syntaxhighlight>
==Velocity language==
The Velocity language driver lets you use Apache Velocity to generate your dynamic SQL queries on the fly.
<syntaxhighlight lang="html+velocity">
<select id="findPerson" lang="velocity">
#set( $pattern = $_parameter.name + '%' )
SELECT *
FROM person
WHERE name LIKE @{pattern, jdbcType=VARCHAR}
</select>
</syntaxhighlight>
==MyBatis Generator==
MyBatis provides a code generator. MyBatis Generator will introspect a database table (or many tables) and generate MyBatis artifacts needed to perform [[Create, read, update and delete|CRUD]] operations (Create, Retrieve, Update, Delete).
An [[Eclipse (software)|Eclipse]] plugin is available.
It will preserve any custom code in case of regeneration but only if you use the Eclipse plugin.
==MyBatis Migrations==
MyBatis Migrations is a Java [[Console application|command line tool]] that keeps track of database schema changes managing [[Data definition language|DDL]] files (known as [[Schema migration|migrations]]).
Migrations allows to query the current status of the database, apply schema changes and also undo them. It also helps to detect and solve concurrent database schema changes made by different developers.
==History==
MyBatis project is a subsidiary of [[iBATIS]] 3.0 and maintained by a team which includes the original creators of iBATIS.
The project was created on May 19, 2010 when Apache iBATIS 3.0 was published and the team announced that the development will continue under a new name and a new home at Google Code.<ref>[http://mail-archives.apache.org/mod_mbox/ibatis-user-java/201005.mbox/%3CAANLkTimXoLiHwI-3kbW6It7mH0771xJP4RqT609VKCXC@mail.gmail.com%3E iBATIS Project Team Moving to Google Code]</ref>
<ref>[http://blog.mybatis.org/2013/11/bye-google-code-welcome-github.html Bye Google Code welcome Github]</ref>
==See also==
*[[Hibernate (framework)|Hibernate]]
*[[Speedment]]
*[[Java Database Connectivity]] (JDBC)
*[[Java Persistence API]]
*[[EclipseLink]]
*[[Ebean]]
*[[Java Object Oriented Querying|jOOQ]]
*[[Apache Cayenne]]
*[[IBM PureQuery]]
*[[nHydrate]]
*[[Apache OpenJPA]]
*[[ActiveJPA]]
==References==
{{Reflist}}
==External links==
*{{Official website}}
[[Category:Object–relational mapping]]
[[Category:Persistence frameworks]]
[[Category:Articles with example Java code]]