# SpringBoot_MyBatis

**Repository Path**: CYSpringBoot/SpringBoot_MyBatis

## Basic Information

- **Project Name**: SpringBoot_MyBatis
- **Description**:  使用MyBatis框架访问数据库
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2019-07-05
- **Last Updated**: 2020-12-19

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# SpringBoot_MyBatis

#### 介绍
> [SpringBoot_Jpa](https://gitee.com/CYSpringBoot/springboot_jpa.git) 中已经介绍了通过Jpa访问数据库，<br>
本篇将通过MyBatis来访问mysql数据，
```
两者之间的区别:
Jpa优势:
    Hibernate的DAO层开发比MyBatis简单，Mybatis需要维护SQL和结果映射。 
    Hibernate对对象的维护和缓存要比MyBatis好，对增删改查的对象的维护要方便。 
    Hibernate数据库移植性很好，MyBatis的数据库移植性不好，不同的数据库需要写不同SQL。
    Hibernate有更好的二级缓存机制，可以使用第三方缓存。MyBatis本身提供的缓存机制不佳。
MyBatis: 
    MyBatis可以进行更为细致的SQL优化，可以减少查询字段。
    MyBatis容易掌握，而Hibernate门槛较高。
    
但是hibernate的sql很多都是自动生成的，无法直接维护sql，一些复杂的sql语句, 
需要编写sql时的灵活度上hibernate不及mybatis
    
```

#### MyBatis配置

- 配置MyBatis依赖以及mysql依赖
```xml
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>1.3.1</version>
</dependency>
```

- 数据库配置 application.properties
```properties
# 服务器端口
server.port=8888

# 链接mysql jdbc驱动
spring.datasource.driver-class-name = com.mysql.jdbc.Driver

# mysql地址
spring.datasource.url = jdbc:mysql://127.0.0.1:3306/springboot?useUnicode=true\
        &characterEncoding=utf-8&useSSL=false

# 数据库用户名
spring.datasource.username = root

# 数据库密码
spring.datasource.password = 123456
```

#### 编写代码使用MyBatis访问数据库

- 使用[SpringBoot_Jpa](https://gitee.com/CYSpringBoot/springboot_jpa.git)访问数据库中的实体类
```java
package com.lcy.springboot_mybatis.Entity;

public class User {

    private Integer userId;

    // 用户名
    private String userName;

    // 用户密码
    private String userPassword;

    // 用户年龄
    private String userAge;

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getUserAge() {
        return userAge;
    }

    public void setUserAge(String userAge) {
        this.userAge = userAge;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserPassword() {
        return userPassword;
    }

    public void setUserPassword(String userPassword) {
        this.userPassword = userPassword;
    }
}
```

- 编写MyBatis需要的mapper文件
```java
package com.lcy.springboot_mybatis.mapper;

import com.lcy.springboot_mybatis.Entity.User;

import java.util.List;

@Mapper
public interface UserMapper {

    // 增加用户
    public void insertUser(User user);

    // 查找所有用户
    public List<User> findAllUsers();

    // 通过ID查询用户
    public User findUserById(Integer id);

    // 更新用户信息
    public void updateUser(User user);

    // 删除用户
    public void deleteUser(Integer id);
}
```

- 增加mapper的XML文件
> [src] -> [main] -> [resources] 创建usermapper.xml文件

``` 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" >
<resultMap id="BaseResultMap" type="com.lcy.springboot_mybatis.Entity.User" >
        <id column="user_id" property="userId" />
        <result column="user_name" property="userName" />
        <result column="user_password" property="userPassword" />
        <result column="user_age" property="userAge" />
    </resultMap>

    <insert id="insertUser" parameterType="com.lcy.springboot_mybatis.Entity.User">
        insert into user (user_name, user_password, user_age)
        values
        (#{userName}, #{userPassword}, #{userAge})
    </insert>

    <select id="findAllUsers" resultMap="BaseResultMap" 
            resultType="com.lcy.springboot_mybatis.Entity.User">
        select * from user
    </select>

    <select id="findUserById" resultMap="BaseResultMap" 
            resultType="com.lcy.springboot_mybatis.Entity.User">
        select * from user where user_id = #{userId}
    </select>

    <update id="updateUser" parameterType="com.lcy.springboot_mybatis.Entity.User">
        update user
        set user_name = #{userName},
        user_password = #{userPassword},
        user_age = #{userAge}
        where user_id = #{userId}
    </update>

    <delete id="deleteUser" parameterType="java.lang.Integer">
        delete from user
        where user_id = #{userId}
    </delete>
```

- 配置xml扫描路径 application.properties
```properties
mybatis.type-aliases-package= com.lcy.springboot_mybatis.Entity
mybatis.mapper-locations= classpath:mapping/*.xml
```

#### 接口实现
- Service
```java
import com.lcy.springboot_mybatis.Entity.User;

import java.util.List;

public interface UserService {

    // 增加用户
    public void insertUser(User user);

    // 查找所有用户
    public List<User> findAllUsers();

    // 通过ID查询用户
    public User findUserById(Integer id);

    // 更新用户信息
    public void updateUser(User user);

    // 删除用户
    public void deleteUser(Integer id);
}
```

````java
import com.lcy.springboot_mybatis.Entity.User;
import com.lcy.springboot_mybatis.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import java.util.List;

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserMapper userMapper;

    @Override
    public void insertUser(User user) {
        userMapper.insertUser(user);
    }

    @Override
    public List<User> findAllUsers() {
        return userMapper.findAllUsers();
    }

    @Override
    public User findUserById(Integer id) {
        return userMapper.findUserById(id);
    }

    @Override
    public void updateUser(User user) {
        userMapper.updateUser(user);
    }

    @Override
    public void deleteUser(Integer id) {
        userMapper.deleteUser(id);
    }
}
````

- Controller 
```java
import com.lcy.springboot_mybatis.Entity.User;
import com.lcy.springboot_mybatis.Service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
public class UserController {

    @Autowired
    private UserService userService;

    @PostMapping(value = "insertUser")
    public String insertUser(@RequestBody User user) {
        userService.insertUser(user);
        return "插入成功";
    }

    @PostMapping(value = "updateUser")
    public String updateUser(@RequestBody User user) {
        userService.updateUser(user);
        return "更新成功";
    }

    @GetMapping(value = "findAllUsers")
    public List<User> findAllUsers() {
        return userService.findAllUsers();
    }

    @GetMapping(value = "findUserById")
    public User findUserById(Integer userId) {
        return userService.findUserById(userId);
    }

    @PostMapping(value = "deleteUserById")
    public String deleteUserById(Integer userId) {
        userService.deleteUser(userId);
        return "删除成功";
    }
}
```

> 测试接口和 [SpringBoot_Jpa](https://gitee.com/CYSpringBoot/springboot_jpa.git) 测试完全一致，不再赘述。

#### 完成
> 待续...