docs/basics/java-basic/h2-db.md
H2是一个开源的嵌入式（非嵌入式设备）数据库引擎，它是一个用Java开发的类库，可直接嵌入到应用程序中，与应用程序一起打包发布，不受平台限制。
H2与Derby、HSQLDB、MySQL、PostgreSQL等开源数据库相比，H2的优势为：
接下来介绍Spring+Mybatis+H2的数据库访问实践，参考：https://blog.csdn.net/xktxoo/article/details/78014739
添加H2数据库依赖：
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<version>1.4.190</version>
</dependency>
H2数据库属性文件配置如下，本文采用内存模式访问H2数据库：
driver=org.h2.Driver
# 内存模式
url=jdbc:h2:mem:testdb;MODE=MYSQL;DB_CLOSE_DELAY=-1
# 持久化模式
#url= jdbc:h2:tcp://localhost/~/test1;MODE=MYSQL;DB_CLOSE_DELAY=-1
H2数据库访问的Spring配置文件为：
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://www.springframework.org/schema/beans"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:jdbc="http://www.springframework.org/schema/jdbc"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
http://www.springframework.org/schema/jdbc
http://www.springframework.org/schema/jdbc/spring-jdbc-3.0.xsd">
<!-- 引入属性文件 -->
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>classpath:config.properties</value>
</list>
</property>
</bean>
<!-- 自动扫描DAO -->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.xiaofan.test" />
</bean>
<!-- 配置Mybatis sqlSessionFactory -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
<property name="configLocation" value="classpath:mybatis_config.xml"/>
<property name="mapperLocations" value="classpath:user_mapper.xml"/>
</bean>
<!-- 配置数据源 -->
<bean id="dataSource"
class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="${driver}" />
<property name="url" value="${url}" />
<!--<property name="username" value="sa" />-->
<!--<property name="password" value="123" />-->
</bean>
<!-- 初始化数据库 -->
<jdbc:initialize-database data-source="dataSource" ignore-failures="DROPS">
<jdbc:script location="classpath:sql/ddl.sql" />
<jdbc:script location="classpath:sql/dml.sql" />
</jdbc:initialize-database>
<!-- 配置事务管理 -->
<tx:annotation-driven transaction-manager="transactionManager" proxy-target-class="true"/>
<bean id="transactionManager"
class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"/>
</bean>
</beans>
初始化数据库的DDL语句文件为：
CREATE TABLE `user` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(100) NOT NULL,
`age` int(11) NOT NULL,
PRIMARY KEY (`id`)
);
初始化数据库的DML语句文件为：
insert into `user` (`id`,`name`,`age`) values (1, 'Jerry', 27);
insert into `user` (`id`,`name`,`age`) values (2, 'Angel', 25);
编写测试文件，如下：
/**
* Created by Jerry on 17/7/30.
*/
@ContextConfiguration(locations = {"classpath:config.xml"})
@RunWith(SpringJUnit4ClassRunner.class)
public class Test extends AbstractJUnit4SpringContextTests{
@Resource
UserDAO userDAO;
@org.junit.Test
public void testInsert() {
int result = userDAO.insert(new User(null, "LiLei", 27));
Assert.assertTrue(result > 0);
}
@org.junit.Test
public void testUpdate() {
int result = userDAO.update(new User(2L, "Jerry update", 28));
Assert.assertTrue(result > 0);
}
@org.junit.Test
public void testSelect() {
User result = userDAO.findByName(new User(null, "Jerry", null));
Assert.assertTrue(result.getAge() != null);
}
@org.junit.Test
public void testDelete() {
int result = userDAO.delete("Jerry");
Assert.assertTrue(result > 0);
}
}