内容介绍
本文通过一个demo演示Mybatis是如何使用的，不涉及与spring集成相关。本文使用mysql进行演示
本文demo地址：
https://github.com/wheijxiaotbai/HXB_Knowledge.git
分支：hxb_demo_mybatis_01
环境准备
-
依赖包的导入
在demo中使用的是gradle ，直接在gradle配置文件中加入以下依赖即可
// https://mvnrepository.com/artifact/org.mybatis/mybatis compile group: 'org.mybatis', name: 'mybatis', version: '3.5.0' // https://mvnrepository.com/artifact/mysql/mysql-connector-java compile group: 'mysql', name: 'mysql-connector-java', version: '8.0.15' -
mysql环境的准备，表的创建
在具有docker的linux环境下执行
docker run -dit --name demo_mysql -p 3306:3306 -e MYSQL_ROOT_PASSWORD=123456 mysql这样，就能快速启动一个mysql容器，账户为root，密码为123456，当然你可以自己修改MYSQL_ROOT_PASSWORD=123456参数以修改密码
执行下面sql语句创建User表
create table user ( `id` int, `name` VARCHAR(32), `age` int, PRIMARY KEY (`id`) )
原生方式
- 配置mybatis-config.xml
- 配置数据模型对应的sql.xml（比如User模型对应的User.xml）
- 创建model类（User）
mybatis-config.xml
<?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"></transactionManager>
<dataSource type="POOLED">
//数据库驱动
<property name="driver" value="com.mysql.jdbc.Driver"/>
//配置数据库参数
<property name="url" value="jdbc:mysql://192.168.31.150:3306/hxb_demo_mynatis_01" />
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<mappers>
//User.xml文件
<mapper resource="mybatisxml/sqlmap/User.xml"/>
</mappers>
</configuration>
User.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">
<!-- 写Sql语句 -->
//这里将命名空间设置为test
<mapper namespace="test">
<!-- find user by id -->
//parameterType为传入参数类型，resultType为输出数据类型，#{value}即为传入的参数
<select id="findUserById" parameterType="int" resultType="model.User">
select * from user where id = #{value}
</select>
<!-- add user -->
<insert id="addUser" parameterType="model.User">
insert into user (id , name , age)
values (#{id},#{name},#{age})
</insert>
<!-- delete user by id -->
<delete id="deleteUserByID" parameterType="int">
delete from user where id = #{value}
</delete>
<!-- update user by id -->
<update id="updateUserById" parameterType="model.User">
update user
set name = #{name} , age = #{age}
where id = #{id}
</update>
</mapper>
User，user类和你刚刚创建的表一致
public class User {
private int id;
private String name;
private int age;
public User() {}
private User(Builder builder) {
setId(builder.id);
setName(builder.name);
setAge(builder.age);
}
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 static final class Builder {
private int id;
private String name;
private int age;
public Builder() {
}
public Builder id(int val) {
id = val;
return this;
}
public Builder name(String val) {
name = val;
return this;
}
public Builder age(int val) {
age = val;
return this;
}
public User build() {
return new User(this);
}
}
}
接下来进行测试 MybatisTest
import model.User;
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 java.io.InputStream;
public class MybatisTest {
/**
* add user
* @throws Exception
*/
@Test
public void addUserTest() throws Exception {
//加载核心配置文件
String resource = "mybatisxml/mybatis-config.xml";
InputStream in = Resources.getResourceAsStream(resource);
//创建SqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
//创建SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
//执行Sql语句
//通过test.addUser找到user.xml中对于的sql语句，test为user.xml中的命名空间
sqlSession.insert("test.addUser",
new User.Builder()
.id(5)
.name("张三")
.age(67)
.build()
);
sqlSession.commit();
}
/**
* find user by id test
* @throws Exception
*/
@Test
public void findUserByIdTest() throws Exception {
//加载核心配置文件
String resource = "mybatisxml/mybatis-config.xml";
InputStream in = Resources.getResourceAsStream(resource);
//创建SqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
//创建SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
//执行Sql语句
User user = sqlSession.selectOne("test.findUserById", 1);
System.out.println(user.getName());
}
/**
* update user by id
* @throws Exception
*/
@Test
public void updateUserByIdTest() throws Exception {
//加载核心配置文件
String reource = "mybatisxml/mybatis-config.xml";
InputStream in = Resources.getResourceAsStream(reource);
//创建sqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
//创建SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
//执行Sql语句
sqlSession.update("test.updateUserById" ,
new User.Builder()
.id(5)
.name("李四")
.age(8)
.build()
);
sqlSession.commit();
}
@Test
public void deleteUserByID() throws Exception {
//加载核心配置文件
String reource = "mybatisxml/mybatis-config.xml";
InputStream in = Resources.getResourceAsStream(reource);
//创建sqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
//创建SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
//执行sql语句
sqlSession.delete("test.deleteUserByID" , 5);
sqlSession.commit();
}
}
mapper动态代理方式
- 配置mybatis-config.xml
- 配置数据模型对应的sql.xml（比如User模型对应的User.xml）
- 创建model类（User）
- mapper映射接口
mapper动态代理方式的mybatis-config.xml，User文件与上一种一致user.xml略有区别
User.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">
<!-- 写Sql语句 -->
//这里的命名空间改为user的mapper映射接口
<mapper namespace="mapper.UserMapper">
<!-- find user by id -->
<select id="findUserById" parameterType="int" resultType="model.User">
select * from user where id = #{value}
</select>
<!-- add user -->
<insert id="addUser" parameterType="model.User">
insert into user (id , name , age)
values (#{id},#{name},#{age})
</insert>
<!-- delete user by id -->
<delete id="deleteUserByID" parameterType="int">
delete from user where id = #{value}
</delete>
<!-- update user by id -->
<update id="updateUserById" parameterType="model.User">
update user
set name = #{name} , age = #{age}
where id = #{id}
</update>
</mapper>
UserMapper
public interface UserMapper {
//遵循四个原则
//接口 方法名 == User.xml 中 id 名
//返回值类型 与 Mapper.xml文件中返回值类型要一致
//方法的入参类型 与Mapper.xml中入参的类型要一致
//命名空间 绑定此接口
public User findUserById(int id);
public void addUser(User user);
public void updateUserById(User user);
public void deleteUserByID(int id);
}
接下来进行测试
MybatisMapperTest
import mapper.UserMapper;
import model.User;
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 java.io.InputStream;
public class MybatisMapperTest {
/**
* add user
* @throws Exception
*/
@Test
public void addUserTest() throws Exception {
//加载核心配置文件
String resource = "mybatisxml/mybatis-config.xml";
InputStream in = Resources.getResourceAsStream(resource);
//创建SqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
//创建SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
//sqlSession生成实现类
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
//调用方法
userMapper.addUser(
new User.Builder()
.id(5)
.name("张三")
.age(67)
.build()
);
sqlSession.commit();
}
/**
* find user by id test
* @throws Exception
*/
@Test
public void findUserByIdTest() throws Exception {
//加载核心配置文件
String resource = "mybatisxml/mybatis-config.xml";
InputStream in = Resources.getResourceAsStream(resource);
//创建SqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
//创建SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
//sqlSession生成实现类
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
//调用方法
User user = userMapper.findUserById(1);
System.out.println(user.getName());
}
/**
* update user by id
* @throws Exception
*/
@Test
public void updateUserByIdTest() throws Exception {
//加载核心配置文件
String reource = "mybatisxml/mybatis-config.xml";
InputStream in = Resources.getResourceAsStream(reource);
//创建sqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
//创建SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
//sqlSession生成实现类
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
//调用方法
userMapper.updateUserById(
new User.Builder()
.id(5)
.name("李四")
.age(8)
.build()
);
sqlSession.commit();
}
@Test
public void deleteUserByID() throws Exception {
//加载核心配置文件
String reource = "mybatisxml/mybatis-config.xml";
InputStream in = Resources.getResourceAsStream(reource);
//创建sqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
//创建SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
//sqlSession生成实现类
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
//调用方法
userMapper.deleteUserByID(5);
sqlSession.commit();
}
}
可能会出现的问题
-
can not found xxx.xml
这种一般是你的xml文件放的位置不对，或者你写的路径不正确
在mybatis-config.xml中<property name="driver" value="com.mysql.jdbc.Driver"/>导入失败或者错误，会导致在test的时候空指针异常，应为没有连接上数据库
