Spring Boot2 系列教程 (十三) | 整合 MyBatis (XML 版)

前言

如题，今天介绍 SpringBoot 与 Mybatis 的整合以及 Mybatis 的使用，之前介绍过了 SpringBoot 整合MyBatis 注解版的使用，上一篇介绍过 MyBatis 的理论，今天这篇就不介绍 MyBatis 的理论了，有兴趣的跳转阅读：SpringBoot 实战 (十三) | 整合 MyBatis (注解版)

准备工作

• SpringBoot 2.1.3
• IDEA
• JDK 8

创建表

CREATE TABLE `student`  (
  `id` int(32) NOT NULL AUTO_INCREMENT,
  `student_id` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '学号',
  `name` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '姓名',
  `age` int(11) NULL DEFAULT NULL COMMENT '年龄',
  `city` varchar(64) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '所在城市',
  `dormitory` varchar(64) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '宿舍',
  `major` varchar(64) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '专业',
  PRIMARY KEY (`id`) USING BTREE
)ENGINE=INNODB AUTO_INCREMENT=1000 DEFAULT CHARSET=utf8;

引入依赖

<dependencies>
        <!-- jdbc 连接驱动 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <!-- web 启动类 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- mybatis 依赖 -->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.0.0</version>
        </dependency>
        <!-- druid 数据库连接池 -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.14</version>
        </dependency>
        <!-- Mysql 连接类 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
            <scope>runtime</scope>
        </dependency>
        <!-- 分页插件 -->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>1.2.5</version>
        </dependency>
        <!-- test 依赖 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <!-- springboot maven 插件 -->
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <!-- mybatis generator 自动生成代码插件 -->
            <plugin>
                <groupId>org.mybatis.generator</groupId>
                <artifactId>mybatis-generator-maven-plugin</artifactId>
                <version>1.3.2</version>
                <configuration>
                    <configurationFile>${basedir}/src/main/resources/generator/generatorConfig.xml</configurationFile>
                    <overwrite>true</overwrite>
                    <verbose>true</verbose>
                </configuration>
            </plugin>
        </plugins>
    </build>

代码解释很详细了，但这里提一嘴，mybatis generator 插件用于自动生成代码，pagehelper 插件用于物理分页。

项目配置

server:
  port: 8080

spring:
    datasource:
        name: test
        url: jdbc:mysql://127.0.0.1:3306/test
        username: root
        password: 123456
        #druid相关配置
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.jdbc.Driver
        filters: stat
        maxActive: 20
        initialSize: 1
        maxWait: 60000
        minIdle: 1
        timeBetweenEvictionRunsMillis: 60000
        minEvictableIdleTimeMillis: 300000
        validationQuery: select 'x'
        testWhileIdle: true
        testOnBorrow: false
        testOnReturn: false
        poolPreparedStatements: true
        maxOpenPreparedStatements: 20

## 该配置节点为独立的节点，有很多同学容易将这个配置放在spring的节点下，导致配置无法被识别
mybatis:
  mapper-locations: classpath:mapping/*.xml  #注意：一定要对应mapper映射xml文件的所在路径
  type-aliases-package: com.nasus.mybatisxml.model  # 注意：对应实体类的路径

#pagehelper分页插件
pagehelper:
    helperDialect: mysql
    reasonable: true
    supportMethodsArguments: true
    params: count=countSql

mybatis generator 配置文件

这里要注意，配置 pom.xml 中 generator 插件所对应的配置文件时，在 Pom.xml 加入这一句，说明 generator 插件所对应的配置文件所对应的配置文件路径。这里已经在 Pom 中配置了，请见上面的 Pom 配置。

${basedir}/src/main/resources/generator/generatorConfig.xml

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>
    <!-- 数据库驱动:选择你的本地硬盘上面的数据库驱动包-->
    <classPathEntry  location="D:\repository\mysql\mysql-connector-java\5.1.47\mysql-connector-java-5.1.47.jar"/>
    <context id="DB2Tables"  targetRuntime="MyBatis3">
        <commentGenerator>
            <property name="suppressDate" value="true"/>
            <!-- 是否去除自动生成的注释 true：是 ： false:否 -->
            <property name="suppressAllComments" value="true"/>
        </commentGenerator>
        <!--数据库链接URL，用户名、密码 -->
        <jdbcConnection driverClass="com.mysql.jdbc.Driver" connectionURL="jdbc:mysql://127.0.0.1/test" userId="root" password="123456">
        </jdbcConnection>
        <javaTypeResolver>
            <property name="forceBigDecimals" value="false"/>
        </javaTypeResolver>
        <!-- 生成模型的包名和位置-->
        <javaModelGenerator targetPackage="com.nasus.mybatisxml.model" targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
            <property name="trimStrings" value="true"/>
        </javaModelGenerator>
        <!-- 生成映射文件的包名和位置-->
        <sqlMapGenerator targetPackage="mapping" targetProject="src/main/resources">
            <property name="enableSubPackages" value="true"/>
        </sqlMapGenerator>
        <!-- 生成DAO的包名和位置-->
        <javaClientGenerator type="XMLMAPPER" targetPackage="com.nasus.mybatisxml.mapper" targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
        </javaClientGenerator>
        <!-- 要生成的表 tableName是数据库中的表名或视图名 domainObjectName是实体类名-->
        <table tableName="student" domainObjectName="Student" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false"></table>
    </context>
</generatorConfiguration>

代码注释很详细，不多说。

生成代码过程

第一步：选择编辑配置

第二步：选择添加 Maven 配置

第三步：添加命令 mybatis-generator:generate -e 点击确定

第四步：运行该配置，生成代码

特别注意！！！同一张表一定不要运行多次，因为 mapper 的映射文件中会生成多次的代码，导致报错，切记。如要运行多次，请把上次生成的 mapper 映射文件代码删除再运行。

第五步：检查生成结果

遇到的问题

请参照别人写好的遇到问题的解决方法，其中我就遇到数据库时区不对以及只生成 Insert 方法这两个问题。都是看以下这篇文章解决的：

Mybatis Generator自动生成代码以及可能出现的问题

生成的代码

1、实体类：Student.java

package com.nasus.mybatisxml.model;

public class Student {

    private Long id;

    private Integer age;

    private String city;

    private String dormitory;

    private String major;

    private String name;

    private Long studentId;

   // 省略 get 和 set 方法
}

2、mapper 接口：StudentMapper.java

package com.nasus.mybatisxml.mapper;

import com.nasus.mybatisxml.model.Student;
import java.util.List;
import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface StudentMapper {
    int deleteByPrimaryKey(Long id);

    int insert(Student record);

    int insertSelective(Student record);

    Student selectByPrimaryKey(Long id);

    // 我添加的方法，相应的要在映射文件中添加此方法
    List<Student> selectStudents();

    int updateByPrimaryKeySelective(Student record);

    int updateByPrimaryKey(Student record);
}

3、映射文件：StudentMapper.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" >
<mapper namespace="com.nasus.mybatisxml.mapper.StudentMapper" >
  <resultMap id="BaseResultMap" type="com.nasus.mybatisxml.model.Student" >
    <id column="id" property="id" jdbcType="BIGINT" />
    <result column="age" property="age" jdbcType="INTEGER" />
    <result column="city" property="city" jdbcType="VARCHAR" />
    <result column="dormitory" property="dormitory" jdbcType="VARCHAR" />
    <result column="major" property="major" jdbcType="VARCHAR" />
    <result column="name" property="name" jdbcType="VARCHAR" />
    <result column="student_id" property="studentId" jdbcType="BIGINT" />
  </resultMap>

  <sql id="Base_Column_List" >
    id, age, city, dormitory, major, name, student_id
  </sql>

  <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Long" >
    select
    <include refid="Base_Column_List" />
    from student
    where id = #{id,jdbcType=BIGINT}
  </select>

  <delete id="deleteByPrimaryKey" parameterType="java.lang.Long" >
    delete from student
    where id = #{id,jdbcType=BIGINT}
  </delete>

  <insert id="insert" parameterType="com.nasus.mybatisxml.model.Student" >
    insert into student (id, age, city,
      dormitory, major, name,
      student_id)
    values (#{id,jdbcType=BIGINT}, #{age,jdbcType=INTEGER}, #{city,jdbcType=VARCHAR},
      #{dormitory,jdbcType=VARCHAR}, #{major,jdbcType=VARCHAR}, #{name,jdbcType=VARCHAR},
      #{studentId,jdbcType=BIGINT})
  </insert>

  <insert id="insertSelective" parameterType="com.nasus.mybatisxml.model.Student" >
    insert into student
    <trim prefix="(" suffix=")" suffixOverrides="," >
      <if test="id != null" >
        id,
      </if>
      <if test="age != null" >
        age,
      </if>
      <if test="city != null" >
        city,
      </if>
      <if test="dormitory != null" >
        dormitory,
      </if>
      <if test="major != null" >
        major,
      </if>
      <if test="name != null" >
        name,
      </if>
      <if test="studentId != null" >
        student_id,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides="," >
      <if test="id != null" >
        #{id,jdbcType=BIGINT},
      </if>
      <if test="age != null" >
        #{age,jdbcType=INTEGER},
      </if>
      <if test="city != null" >
        #{city,jdbcType=VARCHAR},
      </if>
      <if test="dormitory != null" >
        #{dormitory,jdbcType=VARCHAR},
      </if>
      <if test="major != null" >
        #{major,jdbcType=VARCHAR},
      </if>
      <if test="name != null" >
        #{name,jdbcType=VARCHAR},
      </if>
      <if test="studentId != null" >
        #{studentId,jdbcType=BIGINT},
      </if>
    </trim>
  </insert>

  <update id="updateByPrimaryKeySelective" parameterType="com.nasus.mybatisxml.model.Student" >
    update student
    <set >
      <if test="age != null" >
        age = #{age,jdbcType=INTEGER},
      </if>
      <if test="city != null" >
        city = #{city,jdbcType=VARCHAR},
      </if>
      <if test="dormitory != null" >
        dormitory = #{dormitory,jdbcType=VARCHAR},
      </if>
      <if test="major != null" >
        major = #{major,jdbcType=VARCHAR},
      </if>
      <if test="name != null" >
        name = #{name,jdbcType=VARCHAR},
      </if>
      <if test="studentId != null" >
        student_id = #{studentId,jdbcType=BIGINT},
      </if>
    </set>
    where id = #{id,jdbcType=BIGINT}
  </update>

  <update id="updateByPrimaryKey" parameterType="com.nasus.mybatisxml.model.Student" >
    update student
    set age = #{age,jdbcType=INTEGER},
      city = #{city,jdbcType=VARCHAR},
      dormitory = #{dormitory,jdbcType=VARCHAR},
      major = #{major,jdbcType=VARCHAR},
      name = #{name,jdbcType=VARCHAR},
      student_id = #{studentId,jdbcType=BIGINT}
    where id = #{id,jdbcType=BIGINT}
  </update>

  <!-- 我添加的方法 -->
  <select id="selectStudents" resultMap="BaseResultMap">
    SELECT
    <include refid="Base_Column_List" />
    from student
  </select>
</mapper>

serviec 层

1、接口：

public interface StudentService {

    int addStudent(Student student);

    Student findStudentById(Long id);

    PageInfo<Student> findAllStudent(int pageNum, int pageSize);

}

2、实现类

@Service
public class StudentServiceImpl implements StudentService{

    //会报错，不影响
    @Resource
    private StudentMapper studentMapper;

    /**
     * 添加学生信息
     * @param student
     * @return
     */
    @Override
    public int addStudent(Student student) {
        return studentMapper.insert(student);
    }

    /**
     * 根据 id 查询学生信息
     * @param id
     * @return
     */
    @Override
    public Student findStudentById(Long id) {
        return studentMapper.selectByPrimaryKey(id);
    }

    /**
     * 查询所有学生信息并分页
     * @param pageNum
     * @param pageSize
     * @return
     */
    @Override
    public PageInfo<Student> findAllStudent(int pageNum, int pageSize) {
        //将参数传给这个方法就可以实现物理分页了，非常简单。
        PageHelper.startPage(pageNum, pageSize);
        List<Student> studentList = studentMapper.selectStudents();
        PageInfo result = new PageInfo(studentList);
        return result;
    }
}

controller 层

@RestController
@RequestMapping("/student")
public class StudentController {

    @Autowired
    private StudentService studentService;

    @GetMapping("/{id}")
    public Student findStidentById(@PathVariable("id") Long id){
        return studentService.findStudentById(id);
    }

    @PostMapping("/add")
    public int insertStudent(@RequestBody Student student){
        return studentService.addStudent(student);
    }

    @GetMapping("/list")
    public PageInfo<Student> findStudentList(@RequestParam(name = "pageNum", required = false, defaultValue = "1") int pageNum,
            @RequestParam(name = "pageSize", required = false, defaultValue = "10") int pageSize){
        return studentService.findAllStudent(pageNum,pageSize);
    }
}

启动类

@SpringBootApplication
@MapperScan("com.nasus.mybatisxml.mapper") // 扫描 mapper 接口，必须加上
public class MybatisxmlApplication {

    public static void main(String[] args) {
        SpringApplication.run(MybatisxmlApplication.class, args);
    }
}

提一嘴，@MapperScan("com.nasus.mybatisxml.mappe") 这个注解非常的关键，这个对应了项目中 mapper(dao) 所对应的包路径，必须加上，否则会导致异常。

Postman 测试

1、插入方法：

2、根据 id 查询方法：

3、分页查询方法：

源码下载

https://github.com/turoDog/Demo/tree/master/springboot_mybatisxml_demo

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