前言
https://mybatis.org/mybatis-3/zh/getting-started.html
1.每个基于MyBatis的应用都是以一个SqlSessionFactory的实例为核心。
2.SqlSessionFactory 的实例可以通过 SqlSessionFactoryBuilder 获得。
3.SqlSessionFactoryBuilder 则可以从 XML 配置文件或一个预先配置的 Configuration 实例来构建出 SqlSessionFactory 实例。
4.从 XML 文件中构建 SqlSessionFactory 的实例非常简单，建议使用类路径下的资源文件进行配置。 但也可以使用任意的输入流（InputStream）实例，比如用文件路径字符串或 file:// URL 构造的输入流。MyBatis 包含一个名叫 Resources 的工具类，它包含一些实用方法，使得从类路径或其它位置加载资源文件更加容易。
String resource = "org/mybatis/example/mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
5.既然有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例。
SqlSession session = sqlSessionFactory.openSession()；
一、创建一个Maven项目，在pom文件中导入相关依赖jar包。
<dependencies>
<!--mysql-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.19</version>
</dependency>
<!--mybatis-->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.3</version>
</dependency>
<!--junit-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
</dependencies>
二、在resources文件夹下编写mabatis和数据源配置文件。
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>
<!--引入db.properties-->
<properties resource="db.properties"/>
<!--配置数据源-->
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</dataSource>
</environment>
</environments>
<!--配置mapper.xml路径-->
<mappers>
<mapper resource="com/zhy/dao/UserMapper.xml"/>
</mappers>
</configuration>
db.properties:
driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/test?useSSL=false&useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC
username=root
password=123456
补充：解决Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration.Cause: java.io.IOException: Could not find resource com/zhy/dao/UserMapper.xml异常。
<build>
<!--扫描到resources下的xml等资源文件-->
<!--解决Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration.
Cause: java.io.IOException: Could not find resource com/zhy/dao/UserMapper.xml-->
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
</resources>
</build>
三、创建mybatis工具类，获取sqlSession。
/**
* mybatis工具类，获取sqlSession
*/
public class MybatisUtils {
private static SqlSessionFactory sqlSessionFactory;
static {
try {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (Exception e) {
e.printStackTrace();
}
}
public static SqlSession getSqlSession() {
return sqlSessionFactory.openSession();
}
}
四、编写实体类。
public class User {
private Integer id;
private String name;
private String password;
private String telephone;
private String gender;
public User() {
}
public User(Integer id, String name, String password, String telephone, String gender) {
this.id = id;
this.name = name;
this.password = password;
this.telephone = telephone;
this.gender = gender;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getTelephone() {
return telephone;
}
public void setTelephone(String telephone) {
this.telephone = telephone;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
@Override
public String toString() {
return "User{" + "id=" + id + ", name='" + name + '\'' + ", password='" + password + '\'' + ", telephone='" + telephone + '\'' + ", gender='" + gender + '\'' + '}';
}
}
五、编写接口，编写抽象方法。
public interface UserMapper {
List<User> getUserList();
}
六、编写Mapper.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">
<mapper namespace="com.zhy.dao.UserMapper">
<select id="getUserList" resultType="com.zhy.entity.User">
SELECT id,name,telephone,gender FROM user
</select>
</mapper>
七、编写测试类
@Test
public void test(){
//1.获取sqlSession
SqlSession sqlSession = MybatisUtils.getSqlSession();
//2.执行SQL
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
//3.获取数据并遍历
List<User> userList = mapper.getUserList();
for (User user : userList){
System.out.println(user);
}
//4.关闭sqlSession
sqlSession.close();
}