一共涉及3个文件夹8个文件,心累…
注意config文件夹和lib文件夹需要设置为资源文件夹,不然找不到文件
放入lib文件夹
mybatis: https://github.com/mybatis/mybatis-3/releases
mysql-connector: https://dev.mysql.com/downloads/connector/j/
demo的数据库下有一个names
的数据表,字段类型和数据如下
mysql> desc names;
+-------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+----------------+
| id | int(10) | NO | PRI | NULL | auto_increment |
| name | varchar(255) | YES | UNI | NULL | |
| age | int(10) | YES | | NULL | |
+-------+--------------+------+-----+---------+----------------+
mysql> select * from names;
+----+--------+------+
| id | name | age |
+----+--------+------+
| 2 | 大红 | 27 |
| 3 | 大壮 | 24 |
| 4 | 秀英 | 25 |
+----+--------+------+
4、Person类编写
其实就是一个普通的java类
Person.class
public class Person {
private Integer id;
private String name;
private Integer age;
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String toString(){
return "[Person] id: "+ id + " name: " + name + " age :"+ age;
}
}
5、配置映射器
方式一 文件配置映射器:
映射接口 PersonMapper.class
public interface PersonMapper {
public Person getPersonById(Integer id);
}
映射文件 PersonMapper.xml
<?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">
<!--
1.PersonMapper为命名空间,为映射接口的全类名
2.id为唯一标识,与PersonMapper接口中的对应方法名相同
3.resultType为查询后的返回类型
4.#{id}指从传递过来的参数中取出id值
-->
<mapper namespace="PersonMapper">
<select id="getPersonById" resultType="Person">
select id,name, age from names where id = #{id}
</select>
</mapper>
方式二 注解配置映射器:
PersonMapperAnnoation.class
import org.apache.ibatis.annotations.Select;
public interface PersonMapperAnnoation {
@Select("select id, name, age from names where id = #{id}")
public Person getPersonById(Integer id);
}
这样看来,方式2更为简洁和清晰
6、数据库配置填入数据库的地址,账号,密码
配置映射器,可以使用两种方式resource
和 class
<?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">
<!-- 配置事务管理器,采用的是JDBC的管理器方式 -->
<transactionManager type="JDBC"/>
<!-- POOLED代表采用MyBatis内部提供的连接池方式 -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/demo"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<!-- 引入映射器 包名+文件名-->
<mappers>
<mapper resource="PersonMapper.xml"/>
<mapper class="PersonMapperAnnoation"/>
</mappers>
</configuration>
7、代码测试
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 java.io.IOException;
import java.io.InputStream;
public class mybatisDemo {
public static void main(String[] args) throws IOException{
//1.根据MyBatis的配置文件,即mybatis-config.xml创建SqlSessionFactory
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
//2.获取session实例开启会话,其能直接执行*已经映射的SQL语句*
SqlSession session = sqlSessionFactory.openSession();
try {
// 方式1 查询
//3.获取接口的实现类对象
PersonMapper personMapper = session.getMapper(PersonMapper.class);
//4.执行查询操作
Person person = personMapper.getPersonById(2);
System.out.println(person);
// 方式2 查询
//3.获取接口的实现类对象
PersonMapperAnnoation personMapperAnnoation = session.getMapper(PersonMapperAnnoation.class);
//4.执行查询操作
Person person1 = personMapperAnnoation.getPersonById(2);
System.out.println(person1);
} finally {
//4.关闭会话session
session.close();
}
}
//根据MyBatis的配置文件,即mybatis-config.xml创建SqlSessionFactory
public static SqlSessionFactory getSqlSessionFactory() throws IOException {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
return sqlSessionFactory;
}
}
/*
两种方式都能查到数据
[Person] id: 2 name: 大红 age :27
[Person] id: 2 name: 大红 age :27
*/