本系列都是通过maven构建项目，如果不清楚maven的请先看我的maven系列
本次选用mybatis-3.2.1版本作为演示版本，log4j作为日志的实现，mysql作为数据库。
1.pom.xml配置mybatis包
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.35</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.2.1</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.12</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.6</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
2.引入log4j
maven工程resources文件夹创建log4j.xml文件，配置如下内容（该内容从log4j官方网站下载，未做任何修改）
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration PUBLIC "-//APACHE//DTD LOG4J 1.2//EN" "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
<appender name="A1" class="org.apache.log4j.FileAppender">
<param name="File" value="A1.log" />
<param name="Append" value="false" />
<layout class="org.apache.log4j.xml.XMLLayout" />
</appender>
<appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
<layout class="org.apache.log4j.SimpleLayout" />
</appender>
<category name="org.apache.log4j.xml">
<priority value="debug" />
<appender-ref ref="A1" />
</category>
<root>
<priority value ="debug" />
<appender-ref ref="STDOUT" />
</root>
</log4j:configuration>
3.添加mapper配置文件
新建helloworldmapper.xml，添加如下信息（这里的数据库表mybatis_employee创建就不在演示）
<?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">
<!--
namespace:命名空间-可随便写
id:唯一标识
resultType:返回值类型，想要封装成什么对象
{id}:从传递的参数取得的值
-->
<mapper namespace="org.mybatis.helloworld.EmployeeMapper">
<select id="selectEmployee" resultType="org.mybatis.helloworld.Employee">
select id,last_name lastName,email,gender from mybatis_employee where id ={id}
</select>
</mapper>
4.添加主配置文件
新建mybatis-config.xml文件，添加如下信息
<?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>
<!-- mybatis官方说明，可以不使用该配置文件完成操作，但是通过该配置文件可以简化很多操作 -->
<environments default="development">
<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/td_xkd" />
<property name="username" value="root" />
<property name="password" value="1234" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="helloworldmapper.xml" /><!-- 添加的配置文件 -->
</mappers>
</configuration>
5.创建实体类
新建employee.java
package org.mybatis.helloworld;
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 + "]";
}
}
创建测试类
package org.mybatis.helloworld;
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;
public class MybatisTest {
@Test
public void test1(){
//全局配置文件
String resource = "mybatis-config.xml";
InputStream inputStream = null;
SqlSessionFactory sqlSessionFactory = null;
SqlSession sqlSession = null;
try {
inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
sqlSession = sqlSessionFactory.openSession();
//第一個参数org.mybatis.helloworld.EmployeeMapper为映射文件helloworldmapper.xml中的namespace，selectEmployee为映射文件helloworldmapper.xml中的select标签中的id。在这里拼接为一个字符串，第二個参数为传递的参数对应数据库中的id
Employee employee = sqlSession.selectOne("org.mybatis.helloworld.EmployeeMapper.selectEmployee", 1);
System.out.println(employee);
} catch (IOException e) {
e.printStackTrace();
} finally {
sqlSession.close();
}
}
}
DEBUG - Logging initialized using ‘class org.apache.ibatis.logging.slf4j.Slf4jImpl’ adapter.
DEBUG - PooledDataSource forcefully closed/removed all connections.
DEBUG - PooledDataSource forcefully closed/removed all connections.
DEBUG - PooledDataSource forcefully closed/removed all connections.
DEBUG - PooledDataSource forcefully closed/removed all connections.
DEBUG - Openning JDBC Connection
DEBUG - Created connection 503195940.
DEBUG - ooo Using Connection [com.mysql.jdbc.JDBC4Connection@1dfe2924]
**DEBUG - ==> Preparing: select id,last_name lastName,email,gender from mybatis_employee where id = ?
DEBUG - ==> Parameters: 1(Integer)
Employee [id=1, lastName=zhangsan, email=bestjinyi@163.com, gender=1]**
DEBUG - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@1dfe2924]
DEBUG - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@1dfe2924]
DEBUG - Returned connection 503195940 to pool.
这里lastName使用的是别名：select id,last_name lastName,email,gender from mybatis_employee where id = ?
如果没有别名lastName，那么获取到的数据是null，因为mybatis暂时还没法那么智能的判别数据库使用的到底是什么名。这个会在以后的文章中指出驼峰命名来解决问题。