MyBatis简单配置及简单查询

1.把所需jar（mysql-connector-java-5.1.18-bin.jar和mybatis-3.3.0.jar）拷贝到lib目录下

2.编写与数据库对应的实体类UserInfo

3.创建mybatis-config.xml配置文件：

<!-- 	配置数据库连接   	-->
<environments default="developments">
<environment id="mysql">
<transactionManager type="JDBC">
<property name="" value=""/>
</transactionManager>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=utf8"/>
<property name="username" value="root"/>
<property name="password" value="wc654321"/>
</dataSource>
</environment>
</environments>

<!-- 对应的sql映射文件userinfo.xml -->
<mappers>
<mapper resource="com/wc/config/userinfo.xml"/>
</mappers>

4.创建DBFactory类获取SqlSessionFactory

/**
* 访问数据库类
*/
public class DBFactory {
public static SqlSessionFactory sqlSessionFactory = null;
static {
try {
String resource = "com/wc/config/mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream,"mysql");//第二个参数：指定需要连接的数据库配置

} catch (IOException e) {

e.printStackTrace();
}
}
public static SqlSessionFactory getFactory(){
return sqlSessionFactory;
}

或者

/**
* 访问数据库类
*/
public class DBAccess {

public SqlSession getSqlSession() throws IOException{

//（1）通过配置文件获取数据库连接相关信息<br>
Reader reader = Resources.getResourceAsReader("com/wc/config/Configuration.xml");
//（2）通过配置信息构建SqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader,"mysql");
//（3）通过SqlSessionFactory打开数据库回话
SqlSession sqlSession = sqlSessionFactory.openSession();
return sqlSession;
}
}

5.创建mybatis的sql映射文件userinfo.xml
<mapper namespace="com.wc.Interface.IuserInfo"> :对应接口，统一命名空间，重要！
resultMap： property对应实体类属性，column 对应着数据库字段
sql语句:
id="selectUserByInterface" 唯一标识
parameterType="java.lang.Integer" 参数的类型
resultMap="userResult" 返回类型
select <include refid="columns"/> from user_info order by user_id
<sql id="columns">user_id,user_name,user_sex</sql>

<?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="com.wc.Interface.IUserInfo">

<resultMap type="com.wc.po.UserInfo" id="UserResult">
<id column="user_id" jdbcType="INTEGER" property="userId"/>
<result column="user_name" jdbcType="VARCHAR" property="userName"/>
<result column="user_sex" jdbcType="VARCHAR" property="userSex"/>
</resultMap>

<select id="selectUserByInterface" parameterType="com.wc.po.UserInfo" resultMap="UserResult">
select <include refid="columns"/> from user_info
order by user_id
</select>

<select id="selectOneUserByInterface" parameterType="java.lang.Integer" resultMap="UserResult">
select <include refid="columns"/> from user_info where user_id=#{userID}
</select>

</mapper>

6.通过接口的方式调用XML的查询语句（面向接口式编程）

public interface IUserInfo {

/**
* 根据user_id查询单个信息
*/
public UserInfo selectOneUserByInterface(int i);

/**
* 查询全部信息
*/
public List<UserInfo> selectUserByInterface();

}

7.从SqlSessionFactory里面获取SqlSession：DBFactory.getFactory().openSession();
在从SqlSession拿到增删修查一系列方法

/**
* 使用接口的方式进行全部查询
*/
@Test
public void selectUserByInterface() {
List<UserInfo>  userInfo = new ArrayList<UserInfo>();
// 获取sqlSession
SqlSession session = null;
try {
// 从SqlSessionFactory里获取SqlSession
session = DBFactory.getFactory().openSession();
//接口
IUserInfo iUserInfo = session.getMapper(IUserInfo.class);
userInfo = iUserInfo.selectUserByInterface();
if (userInfo != null && userInfo.size() > 0) {
for (UserInfo user : userInfo) {
System.out.println(user);
}
}
} catch (Exception e) {

} finally {
if (session != null) {
session.close();
}
}
}

/**
* 使用接口的方式进行单条查询
*/
@Test
public void selectOneUserByInterface() {
// 获取sqlSession
SqlSession session = null;
try {
// 从SqlSessionFactory里获取SqlSession
session = DBFactory.getFactory().openSession();
//UserInfo userInfo = session.selectOne("userinfo.selectOneUser",3);userinfo是以前的命名空间
IUserInfo iUserInfo = session.getMapper(IUserInfo.class);
UserInfo userInfo = iUserInfo.selectOneUserByInterface(3);
System.out.println(userInfo);

} catch (Exception e) {

} finally {
if (session != null) {
session.close();
}
}
}

最后关闭SqlSession