【超详细】MyBatis详解

- 日理万妓 2024-03-29 15:26 57阅读 0赞

**目录**

一、什么是MyBatis？

二、MyBatis快速入门

三、Mapper代理开发

四、MyBatis核心配置文件

五、配置文件完成增删改查

5.1 环境准备

5.2 功能清单列表

5.2.1 查询

5.2.2 添加

5.2.3 修改

5.2.4 删除

六、MyBatis参数传递

七、注解完成增删改查

八、MyBatis的逆向工程

九、分页插件

--------------------

## 一、什么是MyBatis？ ##

*  MyBatis是一款优秀的持久层框架，用于简化JDBC开发。
 *  MyBatis本来是Apache的一个开源项目iBatis，2010年这个项目由apache software foundation迁移到了google code，并且改名为MyBatis。2013年11月迁移到Github
 *  官网：http://mybatis.org/mybatis-3/zh/index.html

**持久层**：负责将数据保存到数据库的安那一层代码。

**JavaEE三层架构**：表现层、业务层、持久层

**框架：**框架就是一个半成品软件，是一套可重用的、通用的。软件基础代码模型。

在框架的基础上构建软件编写更加高效、规范、通用、可扩展。

![94cdd80696bf4c2dab3a40d393897426.png][]

## 二、MyBatis快速入门 ##

![c2a79577978242abb21ebd05e3941dfd.png][] mybatis-config.xml的基础配置：

![5d683b18eded4043958787efec5183e4.png][]

userMapper：

![11c96ac93b334e9c9bacd896af8c4f77.png][] Java代码：

public class MyBatisDemo {
        public static void main(String[] args) throws IOException {
            //加载mybatis的核心配置文件，获取SqlSessionFactory
            String resource = "mybatis-config.xml";
            //返回一个字节输入流
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    
    
            //2.获取SqlSession对象，用它来执行sql
            SqlSession sqlSession = sqlSessionFactory.openSession();
    
            //3.执行sql
            List<User> users = sqlSession.selectList("test.selectAll");
    
            System.out.println(users);
    
            //4.释放资源
            sqlSession.close();
    
        }
    
    }

![95456520e52548f2b7e5c31f6c7256cd.png][]

## 三、Mapper代理开发 ##

> 目的：
> 
> 1. 解决原生方式中的硬编码。
> 
> 2.简化后期执行SQL

![a91f620c5f414f17870614c06908f664.png][]

步骤：使用Mapper代理方式完成入门案例

1.  定义与sql映射文件（.xml文件）**同名**的Mapper接口，并且将Mapper接口和sql映射文件放置在**同一目录**下
2.  设置sql映射文件的namesapce**属性**为Mapper**全限定名**
3.  在Mapper接口中定义方法，**方法名**就是sql映射文件中sql语句中的**id**，并保持参数类型和返回值类型一致
4.  编码![137159bd55f04b65a973877084e7c56c.png][]

![bc368b7a1a8346b881f4d8fe5709adae.png][]

/**
     * MyBatis 代理开发
     */
    public class MyBatisDemo2 {
        public static void main(String[] args) throws IOException {
            //加载mybatis的核心配置文件，获取SqlSessionFactory
            String resource = "mybatis-config.xml";
            //返回一个字节输入流
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    
    
            //2.获取SqlSession对象，用它来执行sql
            SqlSession sqlSession = sqlSessionFactory.openSession();
    
            //3.执行sql
            //List<User> users = sqlSession.selectList("test.selectAll");
    
            //3.1获取UserMapper接口的代理对象
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            List<User> users = userMapper.selectAll();
    
            System.out.println(users);
    
    
            //4.释放资源
            sqlSession.close();
    
        }
    
    }

## 四、MyBatis核心配置文件 ##

![18004c5873344d04aa541cdcaf3e451b.png][]

## 五、配置文件完成增删改查 ##

### ![7071bcc17f244b19b0bef7d6acf3610f.png][] ###

### 5.1 环境准备 ###

1.  数据库表tb\_brand
2.  实体类Brand
3.  测试用例
4.  安装MyBatisX插件

![61b436b53dde4f20b0a62a71a449e5ff.png][]

建议安装1.4X版本，该版本下的resultType实体类对象别名不爆红

### 5.2 功能清单列表 ###

#### 5.2.1 查询 ####

1.  查询所有数据
2.  查看详情
3.  条件查询

>  **1. 查询所有数据**
> 
> ①编写接口的方法：Mapper接口
> 
>  *  参数：无
>  *  结果：List<Brand>
> 
> ②Map接口
> 
>     List<Brand> selectAll();
> 
> 编写SQL语句：编写SQL映射文件
> 
>     <select id="selectById" resultType="brand">
>             select * from tb_brand;
>      </select>
> 
> ③执行方法，测试
> 
>     @Test
>         public void testSelectAll() throws IOException {
>             //1.获取SqlSessionFactory
>             //加载mybatis的核心配置文件，获取SqlSessionFactory
>             String resource = "mybatis-config.xml";
>             //返回一个字节输入流
>             InputStream inputStream = Resources.getResourceAsStream(resource);
>             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
>     
>     
>             //2. 获取sqlSession对象
>             SqlSession sqlSession = sqlSessionFactory.openSession();
>     
>             //3. 获取Mapper接口的代理对象
>             BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
>     
>             //4. 执行方法
>             List<Brand> brands = brandMapper.selectAll();
>             System.out.println(brands);
>     
>             //5. 释放资源
>             sqlSession.close();
>         }

**解决数据库表的列名(brand\_name)与实体类(brandName)的属性名不匹配方案：**

数据库表的字段名称和实体类属性名称不一样，则不能自动封装数据  
**方案一：起别名**：对不一样的列名起别名，让别名和实体类的属性名也一样  
缺点：每次查询都要定义一次别名

<select id="selectAll" resultType="brand">
         select id, brand_name as brandName, company_name as companyName,
                ordered,description, status
         from tb_brand;
     </select>

**改进：**  
采用 sql片段

<sql id="brand_column">
        id, brand_name as brandName, company_name as companyName, 
        ordered, description, status 
    </sql>
    <select id="selectAll" resultType="brand">
        select
        <include refid="brand_column"></include>
        from tb_brand;
    </select>

缺点：不灵活

**改进：**

**使用resultMap**

> resultMap:id为唯一标识  
> 1.定义<resultMap>标签  
> 2.<select>标签中使用resultMap属性来替换resultType属性

*  id：完成主键字段的映射
 *  column：数据库表的列名
 *  property：对应的实体类属性名

<resultMap id="brandResultMap" type="brand">
         <result column="brand_name" property="brandName"/>
         <result column="compnamy_name" property="companyName"/>
     </resultMap>
    
     <select id="selectAll" resultMap="brandResultMap">
         select *
         from tb_brand;
     </select>

**方案二**：在mybatis-config.xml中设置<configuration>中的<setting>标签的value值为true

*  是否开启驼峰命名自动映射，即从经典数据库列名 A\_COLUMN 映射到经典 Java 属性名 aColumn。

<mapper namespace="com.itheima.mapper.BrandMapper">
    
    
        
        <resultMap id="brandResultMap" type="brand">
            <result column="brand_name" property="brandName"/>
            
            <result column="compnamy_name" property="companyName"/>       
        </resultMap>
        
        <select id="selectAll" resultMap="brandResultMap">
            select *
            from tb_brand;
        </select>
    
       
    
    </mapper>

**2. 查看详情**

> ①编写接口的方法：Mapper接口
> 
>  *  参数：id
>  *  结果：Brand对象
> 
> ②Map接口
> 
>     Brand selectById(int id);
> 
> 编写SQL语句：编写SQL映射文件
> 
>     <select id="selectAllById" resultMap="brandResultMap">
>             select *
>             from tb_brand where id = #{id};
>      </select>
> 
>     *参数占位符
>         1. #{}:将其替换为 ? ,为了防止SQL注入
>         2. ${}:拼SQL，会存在SQl注入
>         3. 使用时机:
>             *参数传递时，用#{}
>             *表名或者列名不固定的情况下，${}一定会存在SQL注入问题
>     
>      * 参数类型:parameterType:用于设置参数类型，可以省略
>      * 特殊字符处理:
>           1.转义字符(eg:'<'转义为'<')
>           2.CDATA区(CD+enter，CD提示,将符号写在括号内)
>             <![CDATA[
>     
>             ]]>
> 
> ③执行方法，测试
> 
>     <resultMap id="brandResultMap" type="brand">
>             <result column="brand_name" property="brandName"/>
>             
>             <result column="company_name" property="companyName"/>
>         </resultMap>
>     
>     
>         
>         <select id="selectAllById" resultMap="brandResultMap">
>             select *
>             from tb_brand where id = #{id};
>         </select>

**3. 条件查询**

*  **多条件查询：**![d49aed046ae241f393c499fddc23a7f5.png][]

> ①编写接口的方法：
> 
>  *  参数：所有查询条件
>  *  结果：List<Brand>
> 
>  ②编写SQL语句
> 
> **散装参数（**Mapper接口**）：**
> 
>     List<Brand> selectByCondition(@Param("status") int status, @Param("companyName") String companyName, @Param("brandName") String brandName);
> 
>  **对象参数（**Mapper接口**）：**
> 
>     List<Brand> selectByCondition(Brand brand);
> 
>  **map集合（**Mapper接口**）：** 
> 
>     List<Brand> selectByCondition(Map map);
> 
> SQL语句：编写SQL映射文件
> 
>     <select id="selectByCondition" resultMap="brandResultMap">
>             select *
>             from tb_brand
>             where status = #{status}
>             and company_name like #{companyName}
>             and brand_name like #{brandName}
>     </select>
> 
> ③执行方法，测试
> 
>     **参数接收：
>     *  1.散装参数（如果方法中有多个参数，需要使用@Param（“SQL参数占位符名称”）
> 
>     @Test
>         public void testSelectByCondition() throws IOException {
>     
>             //接收参数：
>             int status = 1;
>             String companyName = "华为";
>             String brandName = "华为";
>     
>             //处理参数
>             companyName = "%" + companyName + "%";
>             brandName = "%" + brandName + "%";
>     
>     
>             //1.获取SqlSessionFactory
>             //加载mybatis的核心配置文件，获取SqlSessionFactory
>             String resource = "mybatis-config.xml";
>             //返回一个字节输入流
>             InputStream inputStream = Resources.getResourceAsStream(resource);
>             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
>     
>     
>             //2. 获取sqlSession对象
>             SqlSession sqlSession = sqlSessionFactory.openSession();
>     
>             //3. 获取Mapper接口的代理对象
>             BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
>     
>             //4. 执行方法
>             List<Brand> brands = brandMapper.selectByCondition(status, companyName, brandName);
>          
>             System.out.println(brands);
>     
>             //5. 释放资源
>             sqlSession.close();
>         }
> 
>     *  2.对象参数
> 
>     
>       @Test
>         public void testSelectByCondition() throws IOException {
>     
>             //接收参数：
>             int status = 1;
>             String companyName = "华为";
>             String brandName = "华为";
>     
>             //处理参数
>             companyName = "%" + companyName + "%";
>             brandName = "%" + brandName + "%";
>     
>     
>             //1.获取SqlSessionFactory
>             //加载mybatis的核心配置文件，获取SqlSessionFactory
>             String resource = "mybatis-config.xml";
>             //返回一个字节输入流
>             InputStream inputStream = Resources.getResourceAsStream(resource);
>             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
>     
>     
>             //2. 获取sqlSession对象
>             SqlSession sqlSession = sqlSessionFactory.openSession();
>     
>             //3. 获取Mapper接口的代理对象
>             BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
>     
>             //4. 执行方法
>             List<Brand> brands = brandMapper.selectByCondition(status, companyName, brandName);
>          
>             System.out.println(brands);
>     
>             //5. 释放资源
>             sqlSession.close();
>         }
>     
>     
> 
>     *  3.map集合参数
> 
>     @Test
>         public void testSelectByCondition() throws IOException {
>     
>             //接收参数：
>             int status = 1;
>             String companyName = "华为";
>             String brandName = "华为";
>     
>             //处理参数
>             companyName = "%" + companyName + "%";
>             brandName = "%" + brandName + "%";
>     
>             //封装对象
>     
>             Map map = new HashMap();
>             map.put("status",status);
>             map.put("companyName",companyName);
>             map.put("brandName",brandName);
>     
>             //1.获取SqlSessionFactory
>             //加载mybatis的核心配置文件，获取SqlSessionFactory
>             String resource = "mybatis-config.xml";
>             //返回一个字节输入流
>             InputStream inputStream = Resources.getResourceAsStream(resource);
>             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
>     
>     
>             //2. 获取sqlSession对象
>             SqlSession sqlSession = sqlSessionFactory.openSession();
>     
>             //3. 获取Mapper接口的代理对象
>             BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
>     
>             //4. 执行方法
>             List<Brand> brands = brandMapper.selectByCondition(map);
>             System.out.println(brands);
>     
>             //5. 释放资源
>             sqlSession.close();
>         }
> 
> ![6953b39af3bc469e8a86f9d83a5169e1.png][]

*  **动态条件查询：**![9dbb98e5d9f048938147bb9390cda213.png][]

>  **多条件-动态条件查询**
> 
> ①编写接口的方法：Mapper接口
> 
> 参数：所有查询条件
> 
> 结果：List<Brand>
> 
> ②Map接口
> 
>     List<Brand> selectByCondition(@Param("status") int status, @Param("companyName") String companyName, @Param("brandName") String brandName);
> 
> 编写SQL语句：编写SQL映射文件
> 
>     <select id="selectByCondition" resultMap="brandResultMap">
>             select *
>             from tb_brand
>             <where>
>                 <if test="status != null">
>                     status = #{status}
>                 </if>
>                 <if test="companyName != null and companyName!= ''">
>                     and company_name like #{companyName}
>                 </if>
>     
>                 <if test="brandName != null and brandName!= ''">
>                     and brand_name like #{brandName}
>                 </if>
>             </where>
>      </select>
> 
> ③执行方法，测试
> 
>     多条件-动态条件查询
>         if:条件判断
>             test：逻辑表达式
>         问题：只有没有第一个条件时会出现SQL语法错误
>             *恒等式：添加"1=1"并将后续语句改为条件一致，构造SQL
> 
>     select *
>     from tb_brand
>     where 1 = 1
>         <if test="status != null">
>             and  status = #{status}
>         </if>
>         <if test="companyName != null and companyName!= ''">
>             and company_name like #{companyName}
>         </if>
>         <if test="brandName != null and brandName!= ''">
>             and brand_name like #{brandName}
>         </if>
> 
>     *用标签<where> 替换 where 关键字
> 
>     select *
>     from tb_brand
>     <where>
>         <if test="status != null">
>             status = #{status}
>         </if>
>         <if test="companyName != null and companyName!= ''">
>             and company_name like #{companyName}
>          </if>
>          <if test="brandName != null and brandName!= ''">
>              and brand_name like #{brandName}
>          </if>
>     </where>
> 
>     @Test
>         public void testSelectByCondition() throws IOException {
>     
>             //接收参数：
>             int status = 1;
>             String companyName = "华为";
>             String brandName = "华为";
>     
>             //处理参数
>             companyName = "%" + companyName + "%";
>             brandName = "%" + brandName + "%";
>     
>             //封装对象
>            /* Brand brand = new Brand();
>             brand.setStatus(status);
>             brand.setCompanyName(companyName);
>             brand.setBrandName(brandName);*/
>     
>             Map map = new HashMap();
>             map.put("status",status);
>             map.put("companyName",companyName);
>             map.put("brandName",brandName);
>     
>             //1.获取SqlSessionFactory
>             //加载mybatis的核心配置文件，获取SqlSessionFactory
>             String resource = "mybatis-config.xml";
>             //返回一个字节输入流
>             InputStream inputStream = Resources.getResourceAsStream(resource);
>             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
>     
>     
>             //2. 获取sqlSession对象
>             SqlSession sqlSession = sqlSessionFactory.openSession();
>     
>             //3. 获取Mapper接口的代理对象
>             BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
>     
>             //4. 执行方法
>     //      List<Brand> brands = brandMapper.selectByCondition(status, companyName, brandName);
>     //      List<Brand> brands = brandMapper.selectByCondition(brand);
>             List<Brand> brands = brandMapper.selectByCondition(map);
>             System.out.println(brands);
>     
>             //5. 释放资源
>             sqlSession.close();
>         }
>

> ![7673c65c60204a4eb82f4aa398c4c154.png][]

> **单条件-动态条件查询**
> 
>  *  **从多个条件中选择一个**
>  *  **choose（when，otherwise）：选择，类似于Java中的switch语句**
> 
> ①编写接口的方法：Mapper接口
> 
>  *  参数：所有查询条件
>  *  结果：List<Brand>
> 
> ②Mapper接口
> 
>     List<Brand> selectByConditionSingle(Brand brand);
> 
> 编写SQL语句：编写SQL映射文件
> 
>     <select id="selectByConditionSingle" resultMap="brandResultMap">
>     
>     
>     
>     
>     
>     
>     
>     
>     
>     
>     
>     
>     
>     
>     
>     
>     
>     
>             select *
>             from tb_brand
>             <where>
>                 <choose>
>                 <when test="status != null">
>                     status = #{status}
>                 </when>
>                 <when test="companyName != null and companyName!= ''">
>                     company_name like #{companyName}
>                 </when>
>                 <when test="brandName != null and brandName!= ''">
>                     brand_name like #{brandName}
>                 </when>
>                 </choose>
>             </where>
>     </select>
> 
> ③执行方法，测试
> 
>     单条件-动态条件查询
>         choose(when,otherwise):选择，类似于Java中的switch语句
>             test：逻辑表达式
>         问题：只有没有条件时会出现SQL语法错误
>             *恒等式：添加"1=1"构造SQL使之符合语法。
> 
>     <select id="selectByConditionSingle" resultMap="brandResultMap">
>             select *
>             from tb_brand
>             where
>                 <choose>
>                     <when test="status != null">
>                         status = #{status}
>                     </when>
>                     <when test="companyName != null and companyName!= ''">
>                         company_name like #{companyName}
>                     </when>
>                     <when test="brandName != null and brandName!= ''">
>                         brand_name like #{brandName}
>                     </when>
>                     <otherwise>
>                         1 = 1
>                     </otherwise>
>                 </choose>
>      </select>
> 
>     *用标签<where> 替换 where 关键字
> 
>     <select id="selectByConditionSingle" resultMap="brandResultMap">
>             select *
>             from tb_brand
>             <where>
>                 <choose>
>                 <when test="status != null">
>                     status = #{status}
>                 </when>
>                 <when test="companyName != null and companyName!= ''">
>                     company_name like #{companyName}
>                 </when>
>                 <when test="brandName != null and brandName!= ''">
>                     brand_name like #{brandName}
>                 </when>
>                 </choose>
>             </where>
>      </select>
> 
>     @Test
>         public void testSelectByCondition() throws IOException {
>     
>             //接收参数：
>             int status = 1;
>             String companyName = "华为";
>             String brandName = "华为";
>     
>             //处理参数
>             companyName = "%" + companyName + "%";
>             brandName = "%" + brandName + "%";
>     
>             //封装对象
>             Brand brand = new Brand();
>             //brand.setStatus(status);
>             brand.setCompanyName(companyName);
>             //brand.setBrandName(brandName);
>     
>             //1.获取SqlSessionFactory
>             //加载mybatis的核心配置文件，获取SqlSessionFactory
>             String resource = "mybatis-config.xml";
>             //返回一个字节输入流
>             InputStream inputStream = Resources.getResourceAsStream(resource);
>             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
>     
>     
>             //2. 获取sqlSession对象
>             SqlSession sqlSession = sqlSessionFactory.openSession();
>     
>             //3. 获取Mapper接口的代理对象
>             BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
>     
>             //4. 执行方法
>     //      List<Brand> brands = brandMapper.selectByCondition(status, companyName, brandName);
>     //      List<Brand> brands = brandMapper.selectByCondition(brand);
>             List<Brand> brands = brandMapper.selectByCondition(map);
>             System.out.println(brands);
>     
>             //5. 释放资源
>             sqlSession.close();
>         }
>

#### 5.2.2 添加 ####

①编写接口的方法：Mapper接口

void add(Brand brand);

*  参数：除id之外的所有数据
 *  结果：void

②编写SQL语句、编写SQL映射文件

<insert id="add">
            insert into tb_brand (brand_name, company_name, ordered, description, status)
            values (#{brandName},#{companyName},#{ordered},#{description},#{status});
    </insert>

③执行方法，测试

@Test
        public void testadd() throws IOException {
    
            //接收参数：
            int status = 1;
            String companyName = "波导手机";
            String brandName = "波导";
            String description = "手机中的战斗机";
            int ordered = 100;
    
    
            //封装对象
            Brand brand = new Brand();
            brand.setStatus(status);
            brand.setCompanyName(companyName);
            brand.setBrandName(brandName);
            brand.setDescription(description);
            brand.setOrdered(ordered);
    
            //1.获取SqlSessionFactory
            //加载mybatis的核心配置文件，获取SqlSessionFactory
            String resource = "mybatis-config.xml";
            //返回一个字节输入流
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    
    
            //2. 获取sqlSession对象
    //        SqlSession sqlSession = sqlSessionFactory.openSession();
            SqlSession sqlSession = sqlSessionFactory.openSession(true);
            //3. 获取Mapper接口的代理对象
            BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
    
            //4. 执行方法
            brandMapper.add(brand);
    
            //提交事务
    //        sqlSession.commit();
    
            //5. 释放资源
            sqlSession.close();
        }

>  Mybatis事务：
> 
> openSession（）：默认开启事务，进行增删改后需要使用sqlSession.commit();手动提交事务
> 
> openSession（true）：可以设置为自动提交事务（默认为false:手动提交事务）

**\*\*\*\*添加---主键返回 \*\*\*\***

在数据添加成功后，需要获取插入数据库数据的主键的值

![c3e38e80ca7d45fdb75a33534e364204.png][]

比如：添加订单和订单项

1.添加订单

2.添加订单项，订单项中需要设置所属订单的id

<insert id="add" useGeneratedKeys="true" keyProperty="id">
            insert into tb_brand (brand_name, company_name, ordered, description, status)
            values (#{brandName},#{companyName},#{ordered},#{description},#{status});
    </insert>

#### 5.2.3 修改 ####

1.  修改所有字段
2.  修改动态字段

**1.修改所有字段**

①编写接口的方法：Mapper接口

void update(Brand brand);

*  参数：所有数据
 *  结果：void

②编写SQL语句：编写SQL映射文件

<update id="update">
            update tb_brand
            set brand_name = #{brandName},
                company_name = #{companyName},
                ordered = #{ordered},
                description = #{description},
                status = #{status}
            where id = #{id};
        </update>

③执行方法，测试

/**
         * 修改
         * @throws IOException
         */
        @Test
        public void testUpdate() throws IOException {
    
            //接收参数：
            int status = 1;
            String companyName = "波导手机";
            String brandName = "波导";
            String description = "波导手机，手机中的战斗机";
            int ordered = 200;
    
            int id = 5;
    
            //封装对象
            Brand brand = new Brand();
            brand.setStatus(status);
            brand.setCompanyName(companyName);
            brand.setBrandName(brandName);
            brand.setDescription(description);
            brand.setOrdered(ordered);
            brand.setId(id);
    
            //1.获取SqlSessionFactory
            //加载mybatis的核心配置文件，获取SqlSessionFactory
            String resource = "mybatis-config.xml";
            //返回一个字节输入流
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    
    
            //2. 获取sqlSession对象
            SqlSession sqlSession = sqlSessionFactory.openSession(true);
            //3. 获取Mapper接口的代理对象
            BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
    
            //4. 执行方法
            int count = brandMapper.update(brand);
    
            System.out.println(count);
    
            //5. 释放资源
            sqlSession.close();
        }

**2. 修改动态字段**

①编写接口的方法：Mapper接口

void update(Brand brand);

*  参数：所有数据
 *  结果：void

②编写SQL语句：编写SQL映射文件

<update id="update">
            update tb_brand
            <set>
                <if test="brandName != null and brandName!= ''">
                    brand_name = #{brandName},
                </if>
                <if test="companyName != null and brandName!= ''">
                    company_name = #{companyName},
                </if>
                <if test="ordered != null">
                    ordered = #{ordered},
                </if>
                <if test="description != null and brandName!= ''">
                    description = #{description},
                </if>
                <if test="status != null">
                    status = #{status}
                </if>
            </set>
            where id = #{id};
        </update>

③执行方法，测试

/**
         * 修改动态字段
         * @throws IOException
         */
        @Test
        public void testUpdate() throws IOException {
    
            //接收参数：
            int status = 0;
            String companyName = "波导手机";
            String brandName = "波导";
            String description = "波导手机，手机中的战斗机";
            int ordered = 200;
    
            int id = 7;
    
            //封装对象
            Brand brand = new Brand();
            brand.setStatus(status);
    //        brand.setCompanyName(companyName);
    //        brand.setBrandName(brandName);
    //        brand.setDescription(description);
    //        brand.setOrdered(ordered);
            brand.setId(id);
    
            //1.获取SqlSessionFactory
            //加载mybatis的核心配置文件，获取SqlSessionFactory
            String resource = "mybatis-config.xml";
            //返回一个字节输入流
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    
    
            //2. 获取sqlSession对象
            SqlSession sqlSession = sqlSessionFactory.openSession(true);
            //3. 获取Mapper接口的代理对象
            BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
    
            //4. 执行方法
            int count = brandMapper.update(brand);
    
            System.out.println(count);
    
            //5. 释放资源
            sqlSession.close();
        }

#### 5.2.4 删除 ####

1.  删除一个
2.  批量删除

> **1. 删除一个** 
> 
> ①编写接口的方法：Mapper接口
> 
>     void update(Brand brand);
> 
>  *  参数：id
>  *  结果：void
> 
> ②编写SQL语句：编写SQL映射文件
> 
>     <select id="deleteById">
>         delete from tb_brand where id = #{id};
>     </select>
> 
> ③执行方法，测试
> 
>     /**
>          * 根据Id删除一个
>          * @throws IOException
>          */
>         @Test
>         public void testDeleteById() throws IOException {
>     
>             //接收参数：
>             int id = 9;
>     
>             //1.获取SqlSessionFactory
>             //加载mybatis的核心配置文件，获取SqlSessionFactory
>             String resource = "mybatis-config.xml";
>             //返回一个字节输入流
>             InputStream inputStream = Resources.getResourceAsStream(resource);
>             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
>     
>     
>             //2. 获取sqlSession对象
>             SqlSession sqlSession = sqlSessionFactory.openSession(true);
>             //3. 获取Mapper接口的代理对象
>             BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
>     
>             //4. 执行方法
>             brandMapper.deleteById(id);
>     
>     
>             //5. 释放资源
>             sqlSession.close();
>         }

>  **2. 批量删除** 
> 
> ①编写接口的方法：Mapper接口
> 
>     void update(Brand brand);
> 
>  *  参数：id数组
>  *  结果：void
> 
> ②编写SQL语句：编写SQL映射文件
> 
>     
>        
>     <delete id="deleteByIds">
>             delete from tb_brand where id
>             in
>             /*
>             **separator:分隔符
>             **open:循环开始前的字符
>             **close：循环结束后的字符
>             */
>             <foreach collection="array" item="id" separator="," open="(" close=")">
>                 #{id}
>             </foreach>;
>     </delete>
> 
> ③执行方法，测试
> 
>     /**
>          * 根据Id删除一个
>          * @throws IOException
>          */
>         @Test
>         public void testDeleteById() throws IOException {
>     
>             //接收参数：
>             int id = 9;
>     
>             //1.获取SqlSessionFactory
>             //加载mybatis的核心配置文件，获取SqlSessionFactory
>             String resource = "mybatis-config.xml";
>             //返回一个字节输入流
>             InputStream inputStream = Resources.getResourceAsStream(resource);
>             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
>     
>     
>             //2. 获取sqlSession对象
>             SqlSession sqlSession = sqlSessionFactory.openSession(true);
>             //3. 获取Mapper接口的代理对象
>             BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
>     
>             //4. 执行方法
>             brandMapper.deleteById(id);
>     
>             //5. 释放资源
>             sqlSession.close();
>         }
> 
> 注意：
> 
>     Mybatis会将数组参数封装为一个Map集合。
>         *默认：array = 数组
>         *可以使用@Param注解改变map集合的默认key名称
> 
>     delete from tb_brand where id
>      in
>     /*
>     **separator:分隔符
>     **open:循环开始前的字符
>     **close：循环结束后的字符
>     */
>          <foreach collection="ids" item="id" separator="," open="(" close=")">
>              #{id}
>          </foreach>;

## 六、MyBatis参数传递 ##

![1136eb2aa6e24166bab586faca73ff9d.png][]

![9447471c21ba4fe6b59818c54958dabe.png][]

## 七、注解完成增删改查 ##

![a17a7ece83ad4223a8e631745265945e.png][]

使用注解来映射简单语句会使代码显得更加简洁，但对于稍微**复杂一点**的语句，Java 注解不仅力不从心，还会让本就复杂的 SQL 语句更加混乱不堪。 因此，如果你需要做一些很复杂的操作，最好用 **XML** 来映射语句。

选择何种方式来配置映射，以及是否应该要统一映射语句定义的形式，完全取决于你和你的团队。 换句话说，永远不要拘泥于一种方式，你可以很轻松地在基于注解和 XML 的语句映射方式间自由移植和切换。

## 八、MyBatis的逆向工程 ##

自动生成Mapper接口和对应的实体类以及映射文件

generatorConfig.xml：

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE generatorConfiguration
            PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN" "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
    <generatorConfiguration>
        
        <context id="DB2Tables" targetRuntime="MyBatis3">
            
            <jdbcConnection driverClass="com.mysql.cj.jdbc.Driver" connectionURL="jdbc:mysql://localhost:3306/ssm?serverTimezone=UTC"
                            userId="root" password="4">
            </jdbcConnection>
            
            <javaModelGenerator targetPackage="com.itguigu.mybatis.pojo" targetProject=".\src\main\java">
                <property name="enableSubPackages" value="true" />
                <property name="trimStrings" value="true" />
            </javaModelGenerator>
            
            <sqlMapGenerator targetPackage="com.itguigu.mybatis.mapper" targetProject=".\src\main\resources">
                <property name="enableSubPackages" value="true" />
            </sqlMapGenerator>
            
            <javaClientGenerator type="XMLMAPPER" targetPackage="com.atguigu.mybatis.mapper"	targetProject=".\src\main\java">
                <property name="enableSubPackages" value="true" />
            </javaClientGenerator>
            
            
            
            <table tableName="t_emp" domainObjectName="Emp"/>
            <table tableName="t_dept" domainObjectName="Dept"/>
        </context>
    </generatorConfiguration>

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>
    
        <properties resource="jdbc.properties"></properties>
        <settings>
            <setting name="mapUnderscoreToCamelCase" value="true"/>
        </settings>
        <typeAliases>
            <package name="com.itguigu.mybatis.pojo"/>
        </typeAliases>
        <environments default="development">
            <environment id="development">
                <transactionManager type="JDBC"/>
                <dataSource type="POOLED">
                    <property name="driver" value="${jdbc.driver}"/>
                    <property name="url" value="${jdbc.url}"/>
                    <property name="username" value="${jdbc.username}"/>
                    <property name="password" value="${jdbc.password}"/>
                </dataSource>
            </environment>
        </environments>
    
        
        <mappers>
            <package name="com.itguigu.mybatis.mapper"/>
        </mappers>
        
    </configuration>

pom文件中引入的依赖：

<packaging>jar</packaging>
        
        <dependencies>
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.5.7</version>
            </dependency>
            
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.12</version>
                <scope>test</scope>
            </dependency>
    
            
            <dependency>
                <groupId>log4j</groupId>
                <artifactId>log4j</artifactId>
                <version>1.2.17</version>
            </dependency>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>8.0.16</version>
            </dependency>
        </dependencies>
    
        
        <build>
    
            
            <plugins>
    
                
                <plugin>
                    <groupId>org.mybatis.generator</groupId>
                    <artifactId>mybatis-generator-maven-plugin</artifactId>
                    <version>1.3.0</version>
    
                    
                    <dependencies>
    
                        
                        <dependency>
                            <groupId>org.mybatis.generator</groupId>
                            <artifactId>mybatis-generator-core</artifactId>
                            <version>1.3.2</version>
                        </dependency>
    
                        
                        <dependency>
                            <groupId>mysql</groupId>
                            <artifactId>mysql-connector-java</artifactId>
                            <version>8.0.16</version>
                        </dependency>
                    </dependencies>
                </plugin>
            </plugins>
        </build>

然后点击Idea中右侧Maven中的mybatis-generator插件即可自动生成。

## 九、分页插件 ##

limit index，pageSize

index：当前页的起始索引，index=（pageNum-1）\*pageSize

pageSize：每页显示条数

pageNum：当前页的页码

count：总记录数

totalPage：总页数

if（count%pageSize !=0）\{

totalPage+=1；

导入依赖：

<dependency>
                <groupId>com.github.pagehelper</groupId>
                <artifactId>pagehelper</artifactId>
                <version>5.2.0</version>
            </dependency>

同时还需要在核心配置文件中配置：

查询功能开启前要开启分页功能：

Page<Object> page = PageHelper.startPage(1, 4);

分页数据：

PageInfo<Emp> pageInfo = new PageInfo<>(emps, 5);

> 分页相关数据：
> 
> PageInfo\{  
> pageNum=8, pageSize=4, size=2, startRow=29, endRow=30, total=30, pages=8,  
> list=Page\{count=true, pageNum=8, pageSize=4, startRow=28, endRow=32, total=30,  
> pages=8, reasonable=false, pageSizeZero=false\},  
> prePage=7, nextPage=0, isFirstPage=false, isLastPage=true, hasPreviousPage=true,  
> hasNextPage=false, navigatePages=5, navigateFirstPage4, navigateLastPage8,  
> navigatepageNums=\[4, 5, 6, 7, 8\]  
> \}  
> pageNum：当前页的页码  
> pageSize：每页显示的条数  
> size：当前页显示的真实条数  
> total：总记录数  
> pages：总页数  
> prePage：上一页的页码  
> nextPage：下一页的页码  
> isFirstPage/isLastPage：是否为第一页/最后一页  
> hasPreviousPage/hasNextPage：是否存在上一页/下一页  
> navigatePages：导航分页的页码数  
> navigatepageNums：导航分页的页码，\[1,2,3,4,5\]

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