Mybatis入门案例

一、准备开发环境

1、创建测试项目，普通java project项目或者是Dynamic Web project项目均可，如下图所示：



2、导入需要的jar包

Mybatis的核心包、Mybatis的lib文件夹下的所有jar包以及连接数据的驱动包，如下图所示：



3、创建数据库和表，针对MySQL数据库

CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(30) DEFAULT NULL,
`age` int(11) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8

二、使用MyBatis查询表中的数据

1、在src目录下建一个名为log4j.properties的文件，文件内容为：

log4j.rootLogger=debug, stdout
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

2、根据数据库表的信息创建pojo实体类

package com.guigu.pojo;

public class Student {
private int id;
private String name;
private int age;
private String address;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + ", age=" + age + ", address=" + address + "]";
}

}

3、创建一个对应的Mapper.xml,内容为：

<?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="test">
<!-- 根据id查询数据 -->
<select id="findById" parameterType="int" resultType="com.guigu.pojo.Student">
SELECT * FROM student WHERE id=#{id}
</select>
</mapper>

4、编写核心配置文件

<?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>
<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/mybatis?characterEncoding=UTF-8" />
<property name="username" value="root" />
<property name="password" value="root" />
</dataSource>
</environment>

</environments>
<!--引入映射文件  -->
<mappers>
<mapper resource="com/guigu/pojo/StudentMapper.xml"/>
</mappers>

</configuration>

5、编写测试类

package com.guigu.test;

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 com.guigu.pojo.Student;

public class TestMybatis {
public static void main(String[] args) throws Exception {

SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
InputStream  inputStream = Resources.getResourceAsStream("mybatis-config.xml");
//创建Session工厂
SqlSessionFactory  factory = builder.build(inputStream);
//获得session会话
SqlSession  sqlSession = factory.openSession();
//查询id为1的student信息
Student student= sqlSession.selectOne("test.findById", 1);

sqlSession.close();

System.out.println(student);

}

执行结果如下：



可以看到数据库中的信息已经被查询出来了。