SpringBoot使用Mybatis

Orm 框架的本质是简化编程中操作数据库的编码，发展到现在基本上就剩两家了，一个是宣称可以不用写一句

Sql 的 Hibernate，一个是可以灵活调试动态 Sql 的 Mybatis ,两者各有特点，在企业级系统开发中可以根据需求灵

活使用。发现一个有趣的现象：传统企业大都喜欢使用 Hibernate ,互联网行业通常使用 Mybatis 。

Hibernate 特点就是所有的 Sql 都用 Java 代码来生成，不用跳出程序去写（看） Sql ，有着编程的完整性，发展

到最顶端就是 Spring Data Jpa 这种模式了，基本上根据方法名就可以生成对应的 Sql 了。

Mybatis 初期使用比较麻烦，需要各种配置文件、实体类、Dao 层映射关联、还有一大推其它配置。当然 Mybatis

也发现了这种弊端，初期开发了generator https://github.com/mybatis/generator 可以根据表结果自动生

产实体类、配置文件和 Dao 层代码，可以减轻一部分开发量；后期也进行了大量的优化可以使用注解了，自动管

理 Dao 层和配置文件等，发展到最顶端就是今天要讲的这种模式了，mybatis-spring-boot-starter 就是

Spring Boot+ Mybatis 可以完全注解不用配置文件，也可以简单配置轻松上手。

现在想想 Spring Boot 就是牛逼呀，任何东西只要关联到 Spring Boot 都是化繁为简。

1、mybatis-spring-boot-starter

官方说明：MyBatis Spring-Boot-Starter will help you use MyBatis with Spring Boot

其实就是 Mybatis 看 Spring Boot 这么火热也开发出一套解决方案来凑凑热闹，但这一凑确实解决了很多问题，

使用起来确实顺畅了许多。mybatis-spring-boot-starter主要有两种解决方案，一种是使用注解解决一切问

题，一种是简化后的老传统。

当然任何模式都需要首先引入mybatis-spring-boot-starter的 Pom 文件：

<dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId><version>2.0.0</version>
</dependency>

好了下来分别介绍两种开发模式。

2、无配置文件注解版

就是一切使用注解搞定。

2.1 pom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 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.1.0.RELEASE</version><relativePath/></parent><groupId>com.example</groupId><artifactId>spring-boot-mybatis-annotation</artifactId><version>0.0.1-SNAPSHOT</version><name>spring-boot-mybatis-annotation</name><description>spring-boot-mybatis-annotation</description><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><java.version>1.8</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId><version>2.0.0</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

2.2 application.properties

mybatis.type-aliases-package=com.example.modelspring.datasource.url=jdbc:mysql://localhost:3306/test_user?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8&useSSL=true
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

Spring Boot 会自动加载 spring.datasource.* 相关配置，数据源就会自动注入到 sqlSessionFactory 中，

sqlSessionFactory 会自动注入到 Mapper 中，对了，你一切都不用管了，直接拿起来使用就行了。

在启动类中添加对 mapper 包扫描@MapperScan

package com.example;import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplication
@MapperScan("com.example.mapper")
public class SpringBootMybatisAnnotationApplication {public static void main(String[] args) {SpringApplication.run(SpringBootMybatisAnnotationApplication.class, args);}}

或者直接在 Mapper 类上面添加注解@Mapper，建议使用上面那种，不然每个 mapper 加个注解也挺麻烦的。

2.3 开发 Mapper

第三步是最关键的一块， Sql 生产都在这里

package com.example.mapper;import com.example.enums.UserSexEnum;
import com.example.model.User;
import org.apache.ibatis.annotations.*;
import org.springframework.stereotype.Component;import java.util.List;@Component
public interface UserMapper {@Select("SELECT * FROM users")@Results({@Result(property = "userSex", column = "user_sex", javaType = UserSexEnum.class),@Result(property = "nickName", column = "nick_name")})List<User> getAll();@Select("SELECT * FROM users WHERE id = #{id}")@Results({@Result(property = "userSex", column = "user_sex", javaType = UserSexEnum.class),@Result(property = "nickName", column = "nick_name")})User getOne(Long id);@Insert("INSERT INTO users(userName,passWord,user_sex) VALUES(#{userName}, #{passWord}, #{userSex})")void insert(User user);@Update("UPDATE users SET userName=#{userName},nick_name=#{nickName} WHERE id =#{id}")void update(User user);@Delete("DELETE FROM users WHERE id =#{id}")void delete(Long id);}

package com.example.enums;public enum UserSexEnum {MAN, WOMAN
}

package com.example.model;import com.example.enums.UserSexEnum;import java.io.Serializable;public class User implements Serializable {private static final long serialVersionUID = 1L;private Long id;private String userName;private String passWord;private UserSexEnum userSex;private String nickName;public User() {super();}public User(String userName, String passWord, UserSexEnum userSex) {super();this.passWord = passWord;this.userName = userName;this.userSex = userSex;}public Long getId() {return id;}public void setId(Long id) {this.id = id;}public String getUserName() {return userName;}public void setUserName(String userName) {this.userName = userName;}public String getPassWord() {return passWord;}public void setPassWord(String passWord) {this.passWord = passWord;}public UserSexEnum getUserSex() {return userSex;}public void setUserSex(UserSexEnum userSex) {this.userSex = userSex;}public String getNickName() {return nickName;}public void setNickName(String nickName) {this.nickName = nickName;}@Overridepublic String toString() {// TODO Auto-generated method stubreturn "userName " + this.userName + ", pasword " + this.passWord + ", sex " + userSex.name();}}

为了更接近生产我特地将 user_sex、nick_name 两个属性在数据库加了下划线和实体类属性名不一致，另外

user_sex 使用了枚举。

DROP TABLE IF EXISTS `users`;
CREATE TABLE `users` (`id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键id',`userName` varchar(32) DEFAULT NULL COMMENT '用户名',`passWord` varchar(32) DEFAULT NULL COMMENT '密码',`user_sex` varchar(32) DEFAULT NULL,`nick_name` varchar(32) DEFAULT NULL,PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

• @Select 是查询类的注解，所有的查询均使用这个

• @Result 修饰返回的结果集，关联实体类属性和数据库字段一一对应，如果实体类属性和数据库属性名保持

  一致，就不需要这个属性来修饰。

• @Insert 插入数据库使用，直接传入实体类会自动解析属性到对应的值

• @Update 负责修改，也可以直接传入对象

• @delete 负责删除

了解更多属性参考这里：http://www.mybatis.org/mybatis-3/zh/java-api.html

注意，使用#符号和$符号的不同：

// This example creates a prepared statement, something like select * from teacher where name = ?;
@Select("Select * from teacher where name = #{name}")
Teacher selectTeachForGivenName(@Param("name") String name);// This example creates n inlined statement, something like select * from teacher where name = 'someName';
@Select("Select * from teacher where name = '${name}'")
Teacher selectTeachForGivenName(@Param("name") String name);

2.4 控制器

package com.example.web;import com.example.mapper.UserMapper;
import com.example.model.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.List;@RestController
public class UserController {@Autowiredprivate UserMapper userMapper;@RequestMapping("/getUsers")public List<User> getUsers() {List<User> users = userMapper.getAll();return users;}@RequestMapping("/getUser")public User getUser(Long id) {User user = userMapper.getOne(id);return user;}@RequestMapping("/add")public void save(User user) {userMapper.insert(user);}@RequestMapping(value = "update")public void update(User user) {userMapper.update(user);}@RequestMapping(value = "/delete/{id}")public void delete(@PathVariable("id") Long id) {userMapper.delete(id);}}

2.5 测试

上面三步就基本完成了相关 Mapper 层开发，使用的时候当作普通的类注入进入就可以了。

package com.example.mapper;import com.example.enums.UserSexEnum;
import com.example.model.User;
import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;import java.util.List;@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {@Autowiredprivate UserMapper userMapper;@Testpublic void testInsert() throws Exception {userMapper.insert(new User("aa1", "a123456", UserSexEnum.MAN));userMapper.insert(new User("bb1", "b123456", UserSexEnum.WOMAN));userMapper.insert(new User("cc1", "b123456", UserSexEnum.WOMAN));Assert.assertEquals(3, userMapper.getAll().size());}@Testpublic void testQuery() throws Exception {List<User> users = userMapper.getAll();System.out.println(users.toString());}@Testpublic void testUpdate() throws Exception {User user = userMapper.getOne(1l);System.out.println(user.toString());user.setNickName("neo");userMapper.update(user);Assert.assertTrue(("neo".equals(userMapper.getOne(1l).getNickName())));}}

运行testInsert()：

运行testQuery()：

[userName aa1, pasword a123456, sex MAN, userName bb1, pasword b123456, sex WOMAN, userName cc1, pasword b123456, sex WOMAN]

运行testUpdate()：

3、极简xml版本

极简 xml 版本保持映射文件的老传统，接口层只需要定义空方法，系统会自动根据方法名在映射文件中找对应的

Sql。

3.1 pom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 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.1.0.RELEASE</version><relativePath/></parent><groupId>com.example</groupId><artifactId>spring-boot-mybatis-xml</artifactId><version>0.0.1-SNAPSHOT</version><name>spring-boot-mybatis-xml</name><description>spring-boot-mybatis-xml</description><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><java.version>1.8</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId><version>2.0.0</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

3.2 配置文件

pom 文件和上个版本一样，只是application.properties新增以下配置

mybatis.config-location=classpath:mybatis/mybatis-config.xml
mybatis.mapper-locations=classpath:mybatis/mapper/*.xml
mybatis.type-aliases-package=com.example.model
spring.datasource.url=jdbc:mysql://localhost:3306/test_user?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8&useSSL=true
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

指定了 Mybatis 基础配置文件和实体类映射文件的地址。

mybatis-config.xml 配置

<?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><typeAliases><typeAlias alias="Integer" type="java.lang.Integer" /><typeAlias alias="Long" type="java.lang.Long" /><typeAlias alias="HashMap" type="java.util.HashMap" /><typeAlias alias="LinkedHashMap" type="java.util.LinkedHashMap" /><typeAlias alias="ArrayList" type="java.util.ArrayList" /><typeAlias alias="LinkedList" type="java.util.LinkedList" /></typeAliases>
</configuration>

这里也可以添加一些 Mybatis 基础的配置。

3.3 添加 User 的映射文件

UserMapper.xml文件

<?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" >
<mapper namespace="com.example.mapper.UserMapper" ><resultMap id="BaseResultMap" type="com.example.model.User" ><id column="id" property="id" jdbcType="BIGINT" /><result column="userName" property="userName" jdbcType="VARCHAR" /><result column="passWord" property="passWord" jdbcType="VARCHAR" /><result column="user_sex" property="userSex" javaType="com.example.enums.UserSexEnum"/><result column="nick_name" property="nickName" jdbcType="VARCHAR" /></resultMap><sql id="Base_Column_List" >id, userName, passWord, user_sex, nick_name</sql><select id="getAll" resultMap="BaseResultMap"  >SELECT <include refid="Base_Column_List" />FROM users</select><select id="getOne" parameterType="java.lang.Long" resultMap="BaseResultMap" >SELECT <include refid="Base_Column_List" />FROM usersWHERE id = #{id}</select><insert id="insert" parameterType="com.example.model.User" >INSERT INTO users(userName,passWord,user_sex) VALUES(#{userName}, #{passWord}, #{userSex})</insert><update id="update" parameterType="com.example.model.User" >UPDATE users SET <if test="userName != null">userName = #{userName},</if><if test="passWord != null">passWord = #{passWord},</if>nick_name = #{nickName}WHERE id = #{id}</update><delete id="delete" parameterType="java.lang.Long" >DELETE FROMusers WHERE id =#{id}</delete></mapper>

其实就是把上个版本中 Mapper 的 Sql 搬到了这里的 xml 中了

3.4 编写 Mapper 层的代码

package com.example.mapper;import com.example.model.User;
import org.springframework.stereotype.Component;import java.util.List;@Component
public interface UserMapper {List<User> getAll();User getOne(Long id);void insert(User user);void update(User user);void delete(Long id);}

对比上一步，这里只需要定义接口方法。

package com.example.enums;public enum UserSexEnum {MAN, WOMAN
}

package com.example.model;import com.example.enums.UserSexEnum;import java.io.Serializable;public class User implements Serializable {private static final long serialVersionUID = 1L;private Long id;private String userName;private String passWord;private UserSexEnum userSex;private String nickName;public User() {super();}public User(String userName, String passWord, UserSexEnum userSex) {super();this.passWord = passWord;this.userName = userName;this.userSex = userSex;}public Long getId() {return id;}public void setId(Long id) {this.id = id;}public String getUserName() {return userName;}public void setUserName(String userName) {this.userName = userName;}public String getPassWord() {return passWord;}public void setPassWord(String passWord) {this.passWord = passWord;}public UserSexEnum getUserSex() {return userSex;}public void setUserSex(UserSexEnum userSex) {this.userSex = userSex;}public String getNickName() {return nickName;}public void setNickName(String nickName) {this.nickName = nickName;}@Overridepublic String toString() {return "userName " + this.userName + ", pasword " + this.passWord + "sex " + userSex.name();}}

3.5 控制器

package com.example.web;import com.example.mapper.UserMapper;
import com.example.model.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.List;@RestController
public class UserController {@Autowiredprivate UserMapper userMapper;@RequestMapping("/getUsers")public List<User> getUsers() {List<User> users = userMapper.getAll();return users;}@RequestMapping("/getUser")public User getUser(Long id) {User user = userMapper.getOne(id);return user;}@RequestMapping("/add")public void save(User user) {userMapper.insert(user);}@RequestMapping(value = "update")public void update(User user) {userMapper.update(user);}@RequestMapping(value = "/delete/{id}")public void delete(@PathVariable("id") Long id) {userMapper.delete(id);}}

3.6 启动类

package com.example;import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplication
@MapperScan("com.example.mapper")
public class SpringBootMybatisXmlApplication {public static void main(String[] args) {SpringApplication.run(SpringBootMybatisXmlApplication.class, args);}
}

3.7 测试

package com.example.mapper;import com.example.enums.UserSexEnum;
import com.example.model.User;
import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;import java.util.List;@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {@Autowiredprivate UserMapper userMapper;@Testpublic void testInsert() throws Exception {userMapper.insert(new User("aa1", "a123456", UserSexEnum.MAN));userMapper.insert(new User("bb1", "b123456", UserSexEnum.WOMAN));userMapper.insert(new User("cc1", "b123456", UserSexEnum.WOMAN));Assert.assertEquals(3, userMapper.getAll().size());}@Testpublic void testQuery() throws Exception {List<User> users = userMapper.getAll();System.out.println(users.toString());}@Testpublic void testUpdate() throws Exception {User user = userMapper.getOne(1l);System.out.println(user.toString());user.setNickName("neo");userMapper.update(user);Assert.assertTrue(("neo".equals(userMapper.getOne(1l).getNickName())));}}

package com.example.web;import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.http.MediaType;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
import org.springframework.test.web.servlet.setup.MockMvcBuilders;
import org.springframework.web.context.WebApplicationContext;import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print;@RunWith(SpringRunner.class)
@SpringBootTest
public class UserControllerTest {@Autowiredprivate WebApplicationContext wac;private MockMvc mockMvc;@Beforepublic void setUp() throws Exception {mockMvc = MockMvcBuilders.webAppContextSetup(wac).build(); //初始化MockMvc对象}@Testpublic void getUsers() throws Exception {mockMvc.perform(MockMvcRequestBuilders.post("/getUsers").accept(MediaType.APPLICATION_JSON_UTF8)).andDo(print());}}

运行getUsers()：

             Body = [{"id":1,"userName":"aa1","passWord":"a123456","userSex":"MAN","nickName":"neo"},{"id":2,"userName":"bb1","passWord":"b123456","userSex":"WOMAN","nickName":null},{"id":3,"userName":"cc1","passWord":"b123456","userSex":"WOMAN","nickName":null}]

4、如何选择

两种模式各有特点，注解版适合简单快速的模式，其实像现在流行的这种微服务模式，一个微服务就会对应一个自

已的数据库，多表连接查询的需求会大大的降低，会越来越适合这种模式。

老传统模式比适合大型项目，可以灵活的动态生成 Sql ，方便调整 Sql ，也有痛痛快快，洋洋洒洒的写 Sql 的感

觉。