# 从零开始创建SpringBoot项目

SpringBoot2 MyBatis MySQL 从零开始搭建增删改查的Web项目，结构如下图

# 准备工作

MySQL 新建一个tb_user表

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for tb_user
-- ----------------------------
DROP TABLE IF EXISTS `tb_user`;
CREATE TABLE `tb_user`  (
  `user_id` int(0) NOT NULL DEFAULT 0 COMMENT '主键ID',
  `name` varchar(25) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NULL DEFAULT NULL COMMENT '名称',
  `nickname` varchar(25) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NULL DEFAULT NULL COMMENT '名称',
  `age` int(0) NULL DEFAULT NULL COMMENT '年龄',
  `avatar` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NULL DEFAULT NULL COMMENT '头像',
  `phone` varchar(15) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NULL DEFAULT NULL COMMENT '电话',
  `address` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NULL DEFAULT NULL COMMENT '地址',
  `remark` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NULL DEFAULT NULL COMMENT '备注',
  `created_time` datetime(0) NULL DEFAULT NULL COMMENT '创建时间',
  `updated_time` datetime(0) NULL DEFAULT NULL COMMENT '更新时间'
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_520_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of tb_user
-- ----------------------------
INSERT INTO `tb_user` VALUES (10002, '马云01', '风清扬', 18, '', '15566886688', '浙江省杭州市', '1964年9月10日生于浙江省杭州市，祖籍浙江省嵊州市谷来镇， 阿里巴巴集团主要创始人', '2021-07-28 22:38:49', NULL);
INSERT INTO `tb_user` VALUES (10003, '马化腾01', 'pony', 16, '', '13900889988', '广东省汕头市潮南区', '1993年获深圳大学理学学士学位。腾讯公司主要创办人之一。现任腾讯公司董事会主席兼首席执行官；', '2021-07-28 22:38:49', NULL);

SET FOREIGN_KEY_CHECKS = 1;

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UserEntity 实体

@Data
public class UserEntity implements Serializable {

    private static final long serialVersionUID = 1L;

    /**
     * 主键id
     */
    private Integer userId;

    /**
     * 名称
     */
    private String name;

    /**
     * 名称
     */
    private String nickname;

    /**
     * 年龄
     */
    private Integer age;

    /**
     * 头像
     */
    private String avatar;

    /**
     * 电话
     */
    private String phone;

    /**
     * 地址
     */
    private String address;

    /**
     * 备注
     */
    private String remark;

    /**
     * 创建时间
     */
    private Date createdTime;

    /**
     * 更新时间
     */
    private Date updatedTime;

}

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UserMapper

public interface UserMapper {

    /**
     * 新增
     *
     * @author biubiu
     * @date 2021/08/08
     **/
    int insert(UserEntity userEntity);

    /**
     * 刪除
     *
     * @author biubiu
     * @date 2021/08/08
     **/
    int delete(int id);

    /**
     * 更新
     *
     * @author biubiu
     * @date 2021/08/08
     **/
    int update(UserEntity userEntity);

    /**
     * 查询 根据主键 id 查询
     *
     * @author biubiu
     * @date 2021/08/08
     **/
    UserEntity load(int id);

    /**
     * 查询 分页查询
     *
     * @author biubiu
     * @date 2021/08/08
     **/
    List<UserEntity> pageList(int pageNum, int pageSize);

    /**
     * 查询 分页查询 count
     *
     * @author biubiu
     * @date 2021/08/08
     **/
    int pageListCount(int pageNum, int pageSize);
}

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UserMapper.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.biubiu.multidatabase.mapper.UserMapper">

    <resultMap id="BaseResultMap" type="com.biubiu.multidatabase.entity.UserEntity" >
        <result column="user_id" property="userId" />
        <result column="name" property="name" />
        <result column="nickname" property="nickname" />
        <result column="age" property="age" />
        <result column="avatar" property="avatar" />
        <result column="phone" property="phone" />
        <result column="address" property="address" />
        <result column="remark" property="remark" />
        <result column="created_time" property="createdTime" />
        <result column="updated_time" property="updatedTime" />
    </resultMap>

    <sql id="Base_Column_List">
        user_id,
        name,
        nickname,
        age,
        avatar,
        phone,
        address,
        remark,
        created_time,
        updated_time
    </sql>

    <insert id="insert" useGeneratedKeys="true" keyColumn="id" keyProperty="id"
            parameterType="com.biubiu.multidatabase.entity.UserEntity">
        INSERT INTO tb_user
        <trim prefix="(" suffix=")" suffixOverrides=",">
            <if test="null != userId and '' != userId">
                user_id,
            </if>
            <if test="null != name and '' != name">
                name,
            </if>
            <if test="null != nickname and '' != nickname">
                nickname,
            </if>
            <if test="null != age and '' != age">
                age,
            </if>
            <if test="null != avatar and '' != avatar">
                avatar,
            </if>
            <if test="null != phone and '' != phone">
                phone,
            </if>
            <if test="null != address and '' != address">
                address,
            </if>
            <if test="null != remark and '' != remark">
                remark,
            </if>
            <if test="null != createdTime and '' != createdTime">
                created_time,
            </if>
            <if test="null != updatedTime and '' != updatedTime">
                updated_time
            </if>
        </trim>
        <trim prefix="values (" suffix=")" suffixOverrides=",">
            <if test="null != userId and '' != userId">
                #{userId},
            </if>
            <if test="null != name and '' != name">
                #{name},
            </if>
            <if test="null != nickname and '' != nickname">
                #{nickname},
            </if>
            <if test="null != age and '' != age">
                #{age},
            </if>
            <if test="null != avatar and '' != avatar">
                #{avatar},
            </if>
            <if test="null != phone and '' != phone">
                #{phone},
            </if>
            <if test="null != address and '' != address">
                #{address},
            </if>
            <if test="null != remark and '' != remark">
                #{remark},
            </if>
            <if test="null != createdTime and '' != createdTime">
                #{createdTime},
            </if>
            <if test="null != updatedTime and '' != updatedTime">
                #{updatedTime}
            </if>
        </trim>
    </insert>

    <delete id="delete" >
        DELETE FROM tb_user
        WHERE user_id = #{id}
    </delete>

    <update id="update" parameterType="com.biubiu.multidatabase.entity.UserEntity">
        UPDATE tb_user
        <set>
            <if test="null != userId and '' != userId">user_user_id = #{userId},</if>
            <if test="null != name and '' != name">name = #{name},</if>
            <if test="null != nickname and '' != nickname">nickname = #{nickname},</if>
            <if test="null != age and '' != age">age = #{age},</if>
            <if test="null != avatar and '' != avatar">avatar = #{avatar},</if>
            <if test="null != phone and '' != phone">phone = #{phone},</if>
            <if test="null != address and '' != address">address = #{address},</if>
            <if test="null != remark and '' != remark">remark = #{remark},</if>
            <if test="null != createdTime and '' != createdTime">created_time = #{createdTime},</if>
            <if test="null != updatedTime and '' != updatedTime">updated_time = #{updatedTime}</if>
        </set>
        WHERE user_id = #{id}
    </update>


    <select id="load" resultMap="BaseResultMap">
        SELECT <include refid="Base_Column_List" />
        FROM tb_user
        WHERE user_id = #{id}
    </select>

    <select id="pageList" resultMap="BaseResultMap">
        SELECT <include refid="Base_Column_List" />
        FROM tb_user
        LIMIT #{pageNum}, #{pageSize}
    </select>

    <select id="pageListCount" resultType="java.lang.Integer">
        SELECT count(1)
        FROM tb_user
    </select>

</mapper>

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service层

UserService

public interface UserService {
    /**
     * 新增
     */
    public Object insert(UserEntity tbUserEntity);

    /**
     * 删除
     */
    public ReturnT<String> delete(int id);

    /**
     * 更新
     */
    public ReturnT<String> update(UserEntity tbUserEntity);

    /**
     * 根据主键 id 查询
     */
    public UserEntity load(int id);

    /**
     * 分页查询
     */
    public Map<String, Object> pageList(int offset, int pagesize);
}

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UserServiceImpl

@Service
public class UserServiceImpl implements UserService {

    @Resource
    private UserMapper userMapper;


    @Override
    public Object insert(UserEntity tbUserEntity) {

        // valid
        if (tbUserEntity == null) {
            return ReturnT.error("必要参数缺失");
        }

        userMapper.insert(tbUserEntity);
        return ReturnT.success();
    }


    @Override
    public ReturnT<String> delete(int id) {
        int ret = userMapper.delete(id);
        return ret > 0 ? ReturnT.success() : ReturnT.error();
    }


    @Override
    public ReturnT<String> update(UserEntity tbUserEntity) {
        int ret = userMapper.update(tbUserEntity);
        return ret > 0 ? ReturnT.success() : ReturnT.error();
    }


    @Override
    public UserEntity load(int id) {
        return userMapper.load(id);
    }


    @Override
    public Map<String, Object> pageList(int pageNum, int pageSize) {

        List<UserEntity> pageList = userMapper.pageList(pageNum, pageSize);
        int totalCount = userMapper.pageListCount(pageNum, pageSize);

        // result
        Map<String, Object> result = new HashMap<String, Object>();
        result.put("pageList", pageList);
        result.put("totalCount", totalCount);

        return result;
    }
}

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controller

@RestController
@RequestMapping("/user")
public class UserController {
    @Resource
    private UserService userService;

    /**
     * 新增
     *
     * @author biubiu
     * @date 2021/08/08
     **/
    @RequestMapping("/insert")
    public Object insert(UserEntity tbUser) {
        return userService.insert(tbUser);
    }

    /**
     * 刪除
     *
     * @author biubiu
     * @date 2021/08/08
     **/
    @RequestMapping("/delete")
    public ReturnT<String> delete(int id) {
        return userService.delete(id);
    }

    /**
     * 更新
     *
     * @author biubiu
     * @date 2021/08/08
     **/
    @RequestMapping("/update")
    public ReturnT<String> update(UserEntity tbUser) {
        return userService.update(tbUser);
    }

    /**
     * 查询 根据主键 id 查询
     *
     * @author biubiu
     * @date 2021/08/08
     **/
    @RequestMapping("/load")
    public Object load(int id) {
        return userService.load(id);
    }

    /**
     * 查询 分页查询
     *
     * @author biubiu
     * @date 2021/08/08
     **/
    @RequestMapping("/pageList")
    public Map<String, Object> pageList(@RequestParam(required = false, defaultValue = "0") int pageNum,
                                        @RequestParam(required = false, defaultValue = "10") int pageSize) {
        return userService.pageList(pageNum, pageSize);
    }
}

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统一返回实体 common ReturnT

public class ReturnT<T> implements Serializable {

    private static final long serialVersionUID = 1L;

    private int code;
    private String message;
    private T data;

    private ReturnT(int code, String message, T data) {
        this.code = code;
        this.message = message;
        this.data = data;
    }


    public static <T> ReturnT<T> success(T data) {
        return new ReturnT<>(0, "success", data);
    }

    public static <T> ReturnT<T> success() {
        return success(null);
    }

    public static <T> ReturnT<T> error(int code, String message) {
        return new ReturnT<>(code, message, null);
    }

    public static <T> ReturnT<T> error(String message) {
        return error(-1, message);
    }

    public static <T> ReturnT<T> error() {
        return error("error");
    }

}

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配置

Mapper接口扫描

@MapperScan("com.biubiu.multidatabase.mapper")
@Configuration
public class MyBatisConfig {
}

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数据源配置

spring:
  datasource:
    url: jdbc:mysql://127.0.0.1:3306/biubiu?useUnicode=true&characterEncoding=UTF-8&useSSL=true
    driver-class-name: com.mysql.cj.jdbc.Driver
    username: root
    password: root
    type: com.alibaba.druid.pool.DruidDataSource

mybatis:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  mapper-locations: classpath:mapper/*.xml

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pom.xml

<?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">
  <parent>
    <artifactId>springboot-demo</artifactId>
    <groupId>com.biubiu</groupId>
    <version>0.0.1-SNAPSHOT</version>
  </parent>
  <modelVersion>4.0.0</modelVersion>

  <artifactId>springboot-multidatabase-demo</artifactId>


  <properties>
    <java.version>1.8</java.version>
    <mybatis.version>2.2.0</mybatis.version>
    <fastjson.version>1.2.76</fastjson.version>
    <druid.version>1.2.6</druid.version>
  </properties>


  <dependencies>
    <!--web启动器-->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <!-- 添加AOP坐标 -->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-aop</artifactId>
    </dependency>
    <!--MyBatis框架-->
    <dependency>
      <groupId>org.mybatis.spring.boot</groupId>
      <artifactId>mybatis-spring-boot-starter</artifactId>
      <version>${mybatis.version}</version>
    </dependency>
    <!--MySQL驱动-->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <scope>runtime</scope>
    </dependency>
    <!--Druid数据源-->
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid-spring-boot-starter</artifactId>
      <version>${druid.version}</version>
    </dependency>
    <!--lombok工具-->
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
    </dependency>
    <!--fastjson-->
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>fastjson</artifactId>
      <version>${fastjson.version}</version>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
    </plugins>
  </build>

</project>

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测试没问题