Mybatis实例及配置（一）

创建实体类：package com.test.mybatis.bean;public class Employee {
private Integer id;
private String lastName;
private String email;
private String gender;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
@Override
public String toString() {
return "Employee [id=" + id + ", lastName=" + lastName + ", email="
+ email + ", gender=" + gender + "]";
}}

<?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>
<!--
1、mybatis可以使用properties来引入外部配置文件的内容
resource:引入类路径下的资源
url:引入网络路径或者磁盘路径下的资源
-->
<properties resource="jdbcconf.properties">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</properties>
<!--
2、settings包含很多的设置项
setting：用来设置每一个设置项
name：设置项名
value：设置项取值
-->
<settings>
<!--
驼峰命名规则：当数据库名与实体类名发生不一致时，驼峰命名则会发挥作用
如：
数据库字段：id stuname
实体类属性：id stuName
-->
<setting name="mapUnderscoreToCamelCase" value="true"/>
</settings>
<!--
3、typeAliases:别名处理器,可以为Java类型起别名
别名不区分大小写
-->
<typeAliases>
<!--
type:指定要起别名的类型全类名；默认别名就是类名小写：
alias：指定新的别名
-->
<!-- <typeAlias type="com.test.mybatis.Employee" alias="emp"/> -->
<!--
package:为某个包下的所有类批量起别名
也可在具体的实体类中使用@Alias注解为某个类型指定新的别名
-->
<package name="com.test.mybatis.bean"/>
</typeAliases>
<!-- 配置环境 -->
<environments default="development">
<environment id="development">
<!-- 事务类型 -->
<transactionManager type="JDBC"/>
<!-- 数据源 -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<!-- 将我们写好的sql映射文件（EmployeeMapper.xml）一定要注册到 mybatis-config.xml中-->
<mappers>
<mapper resource="EmployeeMapper.xml"/>
</mappers> </configuration>

package com.test.mybatis.dao;import com.test.mybatis.bean.Employee;public interface EmployeeMapper { public Employee getEmpById(Integer id);

}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mtbatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.test.mybatis.dao.EmployeeMapper">
<!--
namespace:名称空间 指定为接口的全类名
id:唯一标识
resultType:返回值类型
#{id}:从传递过来的参数中去吃id值
-->
<select id="getEmpById" resultType="employee">
select * from tbl_employee where id=#{id}
</select>
</mapper>

package com.test.mybatis.test;import java.io.IOException;
import java.io.InputStream;import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;import com.test.mybatis.bean.Employee;
import com.test.mybatis.dao.EmployeeMapper;public class MyBatisTest {
//读取配置文件，得到SQLSessionFactory
public SqlSessionFactory getSqlSessionFactory() throws IOException{
String resource="mybatis-config.xml";
InputStream is=Resources.getResourceAsStream(resource);
return new SqlSessionFactoryBuilder().build(is);
}
@Test
public void test() throws IOException{
//获取sqlSessionFactory对象
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
//获取sqlSession
//代表和数据库的一次对话，用完必须关闭，相当于connection，都是非线程安全。每次使用都应该获取新的对象
SqlSession openSession = sqlSessionFactory.openSession();
try{
//获取接口的实现类对象
//会为接口自动的创建一个代理对象，代理对象去执行增删查改方法
//mapper接口没有实现类，但是mybatis会为这个接口生成一个代理对象
//（将接口和xml进行绑定）
EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
Employee emp = mapper.getEmpById(1);
System.out.println(emp);
}finally{
openSession.close();
}
}}