SivaLabs

Hurray… My first book, Java Persistence with MyBatis3, is published. I would like to thank Packt Publishers for giving me this opportunity to write about my favorite framework, MyBatis.

For most software applications, data persistence is a key and important aspect. In the Java world, we have many ways of implementing the persistence layer, starting from low-level JDBC to fancy ORM frameworks. JDBC is too low-level an API and requires writing a lot of boilerplate code. On the other hand, we have full-fledged ORM frameworks like JPA (Hibernate, EclipseLink, etc.) which hide the complexity of working with SQL directly by letting developers work with objects and generate SQL based on the RDBMS (Dialect) being used. But each approach has its own set of pros and cons; there is no one-size-fits-all solution. Many large applications are using Hibernate successfully, and many other applications got screwed up by using Hibernate/JPA incorrectly. It is not a problem with JPA/Hibernate; it is simply because JPA/Hibernate may not be the best fit for those applications, or developers don’t understand them properly.

MyBatis Tutorial: Part1 – CRUD Operations

MyBatis Tutorial: Part-2: CRUD operations Using Annotations

MyBatis Tutorial: Part 3 – Mapping Relationships

MyBatis Tutorial : Part4 – Spring Integration

MyBatis-Spring is a sub-project of MyBatis that provides Spring integration support, which drastically simplifies MyBatis usage. For those who are familiar with Spring’s Dependency Injection process, using MyBatis-Spring is very simple.

First, let us see the process of using MyBatis without Spring.

1. Create SqlSessionFactory using SqlSessionFactoryBuilder by passing mybatis-config.xml, which contains DataSource properties, a list of Mapper XMLs, TypeAliases, etc.
2. Create an SqlSession object from SqlSessionFactory.
3. Get a Mapper instance from SqlSession and execute queries.
4. Commit or roll back the transaction using the SqlSession object.

With MyBatis-Spring, most of the above steps can be configured in the Spring ApplicationContext, and SqlSession or Mapper instances can be injected into Spring Beans. Then we can use Spring’s TransactionManagement features without writing transaction commit/rollback code all over the place.

In this post, let us see how to use MyBatis ResultMap configuration to map relationships.

MyBatis Tutorial: Part1 – CRUD Operations

MyBatis Tutorial: Part-2: CRUD operations Using Annotations

MyBatis Tutorial: Part 3 – Mapping Relationships

MyBatis Tutorial : Part4 – Spring Integration

To illustrate, we are considering the following sample domain model:

There will be Users and each User may have a Blog and each Blog can contain zero or more posts.

In this post, I will explain how to perform CRUD operations using MyBatis’s annotation support without needing to configure queries in XML mapper files.

MyBatis Tutorial: Part1 – CRUD Operations

MyBatis Tutorial: Part-2: CRUD operations Using Annotations

MyBatis Tutorial: Part 3 – Mapping Relationships

MyBatis Tutorial : Part4 – Spring Integration

Step#1: Create a table BLOG and a java domain Object Blog.

CREATE TABLE  blog 
(
      blog_id int(10) unsigned NOT NULL auto_increment,
      blog_name varchar(45) NOT NULL,
      created_on datetime NOT NULL,
      PRIMARY KEY  (blog_id)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

package com.sivalabs.mybatisdemo.domain;

import java.util.Date;

public class Blog 
{
     private Integer blogId;
     private String blogName;
     private Date createdOn;
     
     //Setters and getters
     
     @Override
     public String toString() {
      return "Blog [blogId=" + blogId + ", blogName=" + blogName
        + ", createdOn=" + createdOn + "]";
     }
}

Step#2: Create UserMapper.java interface with SQL queries in Annotations.

MyBatis is an SQL Mapper tool which greatly simplifies database programming when compared to using JDBC directly.

MyBatis Tutorial: Part1 – CRUD Operations

MyBatis Tutorial: Part-2: CRUD operations Using Annotations

MyBatis Tutorial: Part 3 – Mapping Relationships

MyBatis Tutorial : Part4 – Spring Integration

Step1: Create a Maven project and configure MyBatis dependencies.

<project xmlns="http://maven.apache.org/POM/4.0.0" 
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 <modelVersion>4.0.0</modelVersion>

 <groupId>com.sivalabs</groupId>
 <artifactId>mybatis-demo</artifactId>
 <version>0.0.1-SNAPSHOT</version>
 <packaging>jar</packaging>

 <name>mybatis-demo</name>
 <url>http://maven.apache.org</url>

 <properties>
  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 </properties>

 <build>
  <plugins>
   <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>2.3.2</version>
    <configuration>
     <source>1.6</source>
     <target>1.6</target>
     <encoding>${project.build.sourceEncoding}</encoding>
    </configuration>
   </plugin>
  </plugins>
 </build>

 <dependencies>
  <dependency>
   <groupId>junit</groupId>
   <artifactId>junit</artifactId>
   <version>4.10</version>
   <scope>test</scope>
  </dependency>
  <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.1.1</version>
  </dependency>
  <dependency>
     <groupId>mysql</groupId>
     <artifactId>mysql-connector-java</artifactId>
     <version>5.1.21</version>
     <scope>runtime</scope>
  </dependency>
 </dependencies>
</project>

Step#2: Create the table USER and a Java domain Object User as follows: