[MyBatis]idea+maven最简单入门示例

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

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();
 }
}