edwin

According to Wikipedia, transaction comprises a unit of work performed within a database management system (or similar system) against a database, and treated in a coherent and reliable way independent of other transactions.

Transactions in a database environment have two main purposes:
1. To provide reliable units of work that allow correct recovery from failures and keep a database consistent even in cases of system failure, when execution stops (completely or partially) and many operations upon a database remain uncompleted, with unclear status.
2. To provide isolation between programs accessing a database concurrently. If this isolation is not provided the programs outcome are possibly erroneous.

So basically, the concept of transaction is all-or-nothing. Whether all the query on transaction succesfully executed, or none of them executed.
On this example im trying to insert 5 datas, but on the 5th data i will throw an exception. If the database transaction is running well, none of the datas is on the database.
And dont forget, if you are using MySQL, please make sure that your table engine is InnoDB.

First, as always, i’ll start with a simple MySQL table,

CREATE TABLE `testing` (
  `Id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(30) NOT NULL,
  `address` varchar(255) NOT NULL,
  PRIMARY KEY (`Id`),
  UNIQUE KEY `ix` (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

Next is a java bean,

package com.edw.bean;

public class Testing {

    private Integer id;
    private String name;
    private String address;
	
	// other setter and getter
	
    @Override
    public String toString() {
        return "testing{" + "id=" + id + ", name=" + name + ", address=" + address + '}';
    }
}

Next is creating xml file for database configuration,

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
       <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="UNPOOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost/test"/>
                <property name="username" value="root"/>
                <property name="password" value=""/>
            </dataSource>
        </environment>          
    </environments>
    <mappers />        		
</configuration>

A java class to load my database configuration

package com.edw.config;

import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

public class MyBatisSqlSessionFactory {

    private static final SqlSessionFactory FACTORY;

    static {
        try {
            Reader reader = Resources.getResourceAsReader("com/edw/sqlmap/Configuration.xml");
            FACTORY = new SqlSessionFactoryBuilder().build(reader);
        } catch (Exception e){
            throw new RuntimeException("Fatal Error.  Cause: " + e, e);
        }
    }

    public static SqlSessionFactory getSqlSessionFactory() {
        return FACTORY;
    }
}

And a java interface for insert queries,

package com.edw.mapper;

import com.edw.bean.Testing;
import org.apache.ibatis.annotations.Insert;

public interface TestingMapper {
    
    @Insert("INSERT INTO testing values(null, #{name},#{address})")
    public void insert(Testing testing);
    
}

This is the main class for my application

package com.edw.main;

import com.edw.bean.Testing;
import com.edw.config.MyBatisSqlSessionFactory;
import com.edw.mapper.TestingMapper;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.log4j.Logger;

public class Main {

    private Logger logger = Logger.getLogger(Main.class);
    
    public Main(){        
    }

    private void start(){
        logger.debug("==== BEGIN ====");
        SqlSessionFactory sqlSessionFactory = MyBatisSqlSessionFactory.getSqlSessionFactory();
        sqlSessionFactory.getConfiguration().addMapper(TestingMapper.class);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        TestingMapper testingMapper = sqlSession.getMapper(TestingMapper.class);
        
        try {
            Testing testing = new Testing();
            testing.setName("Edwin");
            testing.setAddress("Ciledug");
            testingMapper.insert(testing);
            
            testing = new Testing();
            testing.setName("Kamplenk");
            testing.setAddress("Karawaci");
            testingMapper.insert(testing);
            
            testing = new Testing();
            testing.setName("Jeklit");
            testing.setAddress("Cibinong");
            testingMapper.insert(testing);
            
            testing = new Testing();
            testing.setName("Nugie");
            testing.setAddress("Pamulang");
            testingMapper.insert(testing);
            
            testing = new Testing();
            testing.setName("Tebek");
            testing.setAddress("Isvil");
            testingMapper.insert(testing);
            
            // try to create an exception
            if(testing.getName().equals("Tebek"))
                throw new Exception("No Tebek allowed");
            
            sqlSession.commit();
            logger.debug("=== END =====");
        } catch (Exception e) {
            logger.error(e,e);
            sqlSession.rollback();
        } finally{
            sqlSession.close();
        }                
    }
    
    public static void main(String[] args) {
        new Main().start();
    }    
}

It supposed to show exception on your Netbeans console, and your data wont be on your database.

and last but not least, my log4j properties

log4j.rootLogger=DEBUG, stdout

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d %c:%L - %m%n

This is the screenshot for my netbeans project structure,

Cheers (D)