MyBatis入门实例

cencenhai

关于MyBatis，不作太多介绍，在google一搜索，有很多资料，我也是参考别人的例子，MyBatis入门非常容易，希望我现在发的代码对大家有用。
实体类：

package bean;
public class User {
private String name;
private Integer age;
public User() {
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public User(String name, Integer age) {
super();
this.name = name;
this.age = age;
}
}


映射器，这是一个接口，这个接口不需要实现类

package mapper;
import org.apache.ibatis.annotations.Select;
import bean.User;
/**
* 映射器
*
*/
public interface UserMapper {
public void insertUser(User user);
//可以使用Java注解来替换XML
@Select("select * from user where name=#{name}")
public User getUser(String name);
}


SQL映射的XML文件

<?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="mapper.UserMapper">
<!-- 这里namespace必须是UserMapper接口的路径，不然要运行的时候要报错 “is not known to the MapperRegistry”-->
<insert id="insertUser" parameterType="User">
insert into user(name,age) values(#{name},#{age})
<!-- 这里sql结尾不能加分号，否则报“ORA-00911”的错误 -->
</insert>
<!-- 这里的id必须和UserMapper接口中的接口方法名相同，不然运行的时候也要报错 -->
<!--    <select id="getUser" resultType="User" parameterType="java.lang.String"> -->
<!--        select * from user where name=#{name} -->
<!--    </select> -->
</mapper>

XML映射配置文件

<?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>
<settings>
<!-- changes from the defaults for testing -->
<setting name="cacheEnabled" value="false" />
<setting name="useGeneratedKeys" value="true" />
<setting name="defaultExecutorType" value="REUSE" />
</settings>
<typeAliases>
<typeAlias alias="User" type="bean.User"/>
</typeAliases>
<environments default="development">
<!-- environment元素体中包含对事务管理和连接池的环境配置 -->
<!-- 你可以配置多种环境，但你只能为每个SqlSessionFactory实例选择一个。 -->
<environment id="development">
<transactionManager type="jdbc"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/test"/>
<property name="username" value="root"/>
<property name="password" value="123"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="resource/UserMapper.xml" />
</mappers>
</configuration>


创建SqlSessionFactory的工具类

package utils;
import java.io.IOException;
import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
public class MyBatisUtil {
//每一个MyBatis的应用程序都以一个SqlSessionFactory对象的实例为核心
//使用SqlSessionFactory的最佳实践是在应用运行期间不要重复创建多次,最佳范围是应用范围
private  final static SqlSessionFactory sqlSessionFactory;
static {
String resource = "resource/configuration.xml";
Reader reader = null;
try {
reader = Resources.getResourceAsReader(resource);
} catch (IOException e) {
System.out.println(e.getMessage());
}
//SqlSessionFactory对象的实例可以通过SqlSessionFactoryBuilder对象来获得
//SqlSessionFactoryBuilder实例的最佳范围是方法范围（也就是本地方法变量）。
sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
}
public static SqlSessionFactory getSqlSessionFactory() {
return sqlSessionFactory;
}
}


测试类

package testMapper;
import mapper.UserMapper;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.junit.Test;
import utils.MyBatisUtil;
import bean.User;
public class TestMapper {
static SqlSessionFactory sqlSessionFactory = null;
static {
sqlSessionFactory = MyBatisUtil.getSqlSessionFactory();
}
@Test
public void addUser() {
//获得SqlSession的实例
//每个线程都应该有它自己的SqlSession实例。SqlSession的实例不能被共享，也是线程不安全的。因此最佳的范围是请求或方法范围。
SqlSession sqlSession = sqlSessionFactory.openSession();
try {
//映射器实例的最佳范围是方法范围。
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
User user = new User("neng",new Integer(5));
userMapper.insertUser(user);
sqlSession.commit();//这里一定要提交，不然数据进不去数据库中
} finally {
//确保SqlSession关闭
sqlSession.close();
}
}
@Test
public void getUser() {
SqlSession sqlSession = sqlSessionFactory.openSession();
try {
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
User user = userMapper.getUser("neng");
System.out.println("name: "+user.getName()+"|age: "+user.getAge());
} finally {
sqlSession.close();
}
}
}