用Idea搭建一个Mybatis项目

什么是 MyBatis?

MyBatis 是一款优秀的持久层框架,它支持自定义 SQL、存储过程以及高级映射。MyBatis 免除了几乎所有的 JDBC 代码以及设置参数和获取结果集的工作。MyBatis 可以通过简单的 XML 或注解来配置和映射原始类型、接口和 Java POJO(Plain Old Java Objects,普通老式 Java 对象)为数据库中的记录。

官方文档

https://mybatis.org/mybatis-3/zh/index.html
最好的官方文档之一,一篇文档读懂,根本不用看其他任何教程

环境

window10
IntelliJ Idea(2020.2)
JDK 8
MySql server

新建项目

打开idea,file -> new -> Project -> maven

用Idea搭建一个Mybatis项目_第1张图片

点击next,下一步设置项目名和组织名

用Idea搭建一个Mybatis项目_第2张图片
项目名(name)随意,GroupId一般是域名的倒写,一般和你的包结构一致
其实随便填就行

点击Finish,项目新建成功

用Idea搭建一个Mybatis项目_第3张图片
图片仅供参考,我是在项目中创建了子Module,不必模仿,用你们新建的项目就够了

数据库中创建测试用的表

DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(32) NOT NULL COMMENT '用户名称',,
  `pwd` varchar(256) DEFAULT NULL COMMENT '地址',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=35 DEFAULT CHARSET=utf8;
 
-- ----------------------------
-- Records of user
-- ----------------------------
INSERT INTO `user` VALUES ('1', '王五',123);
INSERT INTO `user` VALUES ('10', '张三', '123');
INSERT INTO `user` VALUES ('16', '张小明',123);
INSERT INTO `user` VALUES ('22', '陈小明',123);
INSERT INTO `user` VALUES ('24', '张三丰',123);
INSERT INTO `user` VALUES ('25', '陈小明',123);
INSERT INTO `user` VALUES ('26', '王五',123);

项目中创建表对应的实体类

新建package名叫model
新建class User

package com.term.model;

import java.io.Serializable;

public class User implements Serializable {
    private int id;
    private String name;
    private String pwd;

    public User() {
    }

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    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 String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

创建mapper接口

新建package名叫dao
新建interface名叫UserDao

package com.term.dao;

import com.term.model.User;

import java.util.List;
import java.util.Map;

public interface UserDao {
    List<User> getAllUsers();
    int updateUser(User user);
    int addUser(User user);
    int deleteUser(int id);
    User getOneUser(Map<String, Object> map);
    List<User> getUsersByNameLike(String name);

}

以上内容和普通的JDBC一致
接下来引入Mybatis
打开项目的pom文件,导入Mybatis依赖

<?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.term</groupId>
    <artifactId>MybatisStudy</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties
                    **/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties
                    **/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>
</project>

如上所示,我导入了mybatis 3.5.2 jar包,和mybatis所依赖的Junit、mysql
中的内容时配置文件扫描,以免编译器不加载配置文件

创建Mybatis核心配置文件

在项目的resources文件夹中创建mybatis-config.xml
别问我为什么叫这个名字,其实想叫什么叫什么,只是因为官方文档叫这个名字,所有大家都喜欢用这个名字,显得比较专业

<?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?useUnicode=true&characterEncoding=utf8&autoReconnect=true"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/term/dao/UserMapper.xml"/>
    </mappers>
</configuration>

简单解释一下,这是mybatis最简单的配置,
environments便签是环境配置,如上主要是dataSource连接数据库的参数,以及transactionManager决定数据库事务处理方式
mappers标签用来指定mapper.xml,如上
意思就是我待会会在com/term/dao中创建一个Mapper.xml实现数据库具体操作
如果不配置这各标签,那么mapper将不生效
就这些

MybatisUtils

写一个全局的工具类,静态返回初始化好的SqlSession对象:

package com.term.utils;

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;

/**
 * 初始化sqlSessionFactory,并返回sqlSession
 */
public class MybatisUtils {
	//SqlSessionFactory 对象最好是全局的单例变量
    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
	//每个请求初始化一个SqlSession,调用这个方法
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }
    //得到支持自动提交的SqlSession对象
    public static SqlSession getAutoCommitSqlSession(){
        return sqlSessionFactory.openSession(true);
    }
}

创建mapper.xml

刚才我们写了一个UserDao接口,并定义了一些数据库操作方法,mybatis要求我们使用xml文件的方式去实现这个接口

<?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">
<!-- namespace指定你要实现的mapper接口全名 -->
<mapper namespace="com.term.dao.UserDao">
    <!--标签名是操作方式,id与接口中方法名一致 resultType指定返回值类型的全名-->
    <select id="getAllUsers" resultType="com.term.model.User">
        <!--标签内写sql语句-->
        select * from user
    </select>
    <update id="updateUser" parameterType="com.term.model.User">
        <!--用#{}传入参数,实体类的属性可以直接用属性名调用,方法参数可以直接用参数名-->
        update user set name=#{name},pwd=#{pwd} where id=#{id}
    </update>
    <insert id="addUser" parameterType="com.term.model.User">
        insert into user (id,name,pwd) values (#{id},#{name},#{pwd})
    </insert>
    <delete id="deleteUser" parameterType="int">
        delete from user where id=#{id}
    </delete>

    <select id="getOneUser" parameterType="map" resultType="com.term.model.User">
        select * from user where id=#{id}
    </select>
    <select id="getUsersByNameLike" parameterType="String" resultType="com.term.model.User">
        select * from user where name like #{name}
    </select>
</mapper>

好了,写完了

使用JUNIT测试

package com.term.dao;

import com.term.model.User;
import com.term.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Mybatis 增删改查Junit
 */
public class UserDaoTest {
    @Test
    public void testGetAllUser() {
        final SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        List<User> users = userDao.getAllUsers();
        for (User user : users) {
            System.out.println(user);
        }


        sqlSession.close();
    }

    @Test
    public void testAddUser() {
        final SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        userDao.addUser(new User(1, "li", "zhang3"));

        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void testUpdateUser() {
        final SqlSession sqlSession = MybatisUtils.getSqlSession();
        final UserDao userDao = sqlSession.getMapper(UserDao.class);
        userDao.updateUser(new User(2, "lisi", "lisq"));

        //增删改需要提交事务
        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void testDelUser(){
        final SqlSession sqlSession = MybatisUtils.getSqlSession();
        final UserDao userDao = sqlSession.getMapper(UserDao.class);
        userDao.deleteUser(1);

        //增删改需要提交事务
        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void testGetOneUser(){
        final SqlSession sqlSession = MybatisUtils.getSqlSession();
        final UserDao userDao = sqlSession.getMapper(UserDao.class);
        Map<String, Object> map = new HashMap<>();
        map.put("id", 2);

        System.out.println(userDao.getOneUser(map));
        sqlSession.close();
    }

    @Test
    public void testGetUsersByNameLike(){
        final SqlSession sqlSession = MybatisUtils.getSqlSession();
        final UserDao userDao = sqlSession.getMapper(UserDao.class);
        List<User> users = userDao.getUsersByNameLike("%l%");
        for (User user : users)
            System.out.println(user);
        sqlSession.close();
    }
}

感谢大家收看

你可能感兴趣的:(Java菜鸡笔记,mybatis,java)