准备:驱动和jar包,我用idea所以maven工程添加依赖,mysql里根据实体类来建表,最好存点数据
注意:驱动版本别太新也别太旧,容易出bug……
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.yiki.mybatis</groupId>
<artifactId>test_mybatis</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.6</version>
</dependency>
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.27</version>
</dependency>
</dependencies>
</project>
目录结构
新建需要映射的实体类
package com.yiki.Entity;
public class Person {
private Integer pId;
private String pName;//当和表里的列名不一致的时候,查询语句应该起别名
//p_Name(原表里的列名) pname别名
private String email;
public Integer getpId() {
return pId;
}
public void setpId(Integer pId) {
this.pId = pId;
}
public String getpName() {
return pName;
}
public void setpName(String pName) {
this.pName = pName;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
@Override
public String toString() {
return "Person{" +
"pId=" + pId +
", pName='" + pName + '\'' +
", email='" + email + '\'' +
'}';
}
}
在resources下新建mybatis.xml配置文件
环境配置是对数据库的连接,mapper写映射的配置文件(必须添加)
<?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"/>
<property name="username" value="root"/>
<property name="password" value="*********"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="PersonMapper.xml"/>
</mappers>
</configuration>
依然是在resources下新建PersonMapper.xml,其作用是对Person写sql语句
<?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">
<!--名称空间:随便起名(还是要规范下)
id:唯一标识
resultype:返回值类型(写全类名)
-->
<mapper namespace="com.yiki.Entity.PersonMapper">
<select id="selectPerson" resultType="com.yiki.Entity.Person">
<!-- select * from Person where pid = #{id}-->
select pid,p_name pname,email from Person where pid = #{id}
</select>
</mapper>
新建测试类
select语句里最好写名称空间+id
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package com.yiki.Test;
import com.yiki.Entity.Person;
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 Tests{
public static void main(String[] args) throws IOException {
String resource = "mybatis.xml";//根据全局配置文件
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
//第一个参数:写唯一标识,最好是namespace+id
//第二个参数:写sql要传入的参数
Person person = sqlSession.selectOne("com.yiki.Entity.PersonMapper.selectPerson",1);
System.out.println(person);
sqlSession.close();
}
}