浮生若梦，就当它是梦，尽兴地梦它一场；世事如云，就当它是云，从容地观它千变万化。

Mybatis-Plus中提供了各种插件，乐观锁、多租户、动态表名。。。。今天来研究一下基于动态表名插件实现分表的案例

数据库建三张表测试

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for user_0
-- ----------------------------
DROP TABLE IF EXISTS `user_0`;
CREATE TABLE `user_0`  (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `age` int(2) NULL DEFAULT NULL,
  `email` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Table structure for user_1
-- ----------------------------
DROP TABLE IF EXISTS `user_1`;
CREATE TABLE `user_1`  (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `age` int(2) NULL DEFAULT NULL,
  `email` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Table structure for user_2
-- ----------------------------
DROP TABLE IF EXISTS `user_2`;
CREATE TABLE `user_2`  (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `age` int(2) NULL DEFAULT NULL,
  `email` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

SET FOREIGN_KEY_CHECKS = 1;

pom依赖

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.5.2</version>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
    </dependency>
</dependencies>

server:
  port: 8099

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/my_user?useUnicode=true&characterEncoding=utf8&useSSL=false&allowMultiQueries=true&serverTimezone=Asia/Shanghai
    username: root
    password: root
    #取模分表 格式 表名&表总数量（多个,分隔）。这里随便怎么定义和解析规则对应即可
    modTables: user&3
# Logger Config
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

请求参数传递辅助类，就是根据什么去分表，这里是根据id

public class RequestDataHelper {
    /**
     * 请求参数存取
     */
    private static final ThreadLocal<Long> REQUEST_DATA = new ThreadLocal<>();

    /**
     * 设置请求参数
     *
     * @param requestData 请求参数 Long
     */
    public static void setRequestData(Long requestData) {
        REQUEST_DATA.set(requestData);
    }

    /**
     * 获取请求参数
     *
     * @param param 请求参数
     * @return 请求参数 MAP 对象
     */
    public static <T> T getRequestData(String param) {
        Long id = getRequestData();
        if (null != id) {
            return (T) id;
        }
        return null;
    }

    /**
     * 获取请求参数
     *
     * @return 请求参数 MAP 对象
     */
    public static Long getRequestData() {
        return REQUEST_DATA.get();
    }
}

注入插件，并且程序初始化时解析分表配置

@Configuration
@MapperScan("com.sample.mapper") //和你包名一致，别问我你的怎么报错了
public class MybatisPlusConfig {

    private static String modTables;
    private static Map<String, Integer> tableMap = new HashMap<>(16);


    @Value("${spring.datasource.modTables:null}")
    public void setModTables(String modTables) {
        MybatisPlusConfig.modTables = modTables;
    }
    @PostConstruct
    public void init() throws Exception {
        String[] split = modTables.split(",");
        for (String s : split) {
            String[] split1 = s.split("&");
            if (split1.length < 2) {
                throw new RuntimeException("分表配置错误");
            }
            MybatisPlusConfig.tableMap.put(split1[0], Integer.valueOf(split1[1]));
        }
    }


    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        DynamicTableNameInnerInterceptor dynamicTableNameInnerInterceptor = new DynamicTableNameInnerInterceptor();
        dynamicTableNameInnerInterceptor.setTableNameHandler((sql, tableName) -> {


            Integer integer = tableMap.get(tableName);
            if (integer != null) {
                // 获取参数方法
                Long id = RequestDataHelper.getRequestData();
                if(id == null){
                    throw new RuntimeException("未设置分表配置");
                }
                long l = Math.floorMod(id, Long.parseLong(integer.toString()));
                return tableName + "_" + l;
            }

            return tableName;
        });
        interceptor.addInnerInterceptor(dynamicTableNameInnerInterceptor);
        // 3.4.3.2 作废该方式
        // dynamicTableNameInnerInterceptor.setTableNameHandlerMap(map);
        return interceptor;
    }
}

@Data
@Accessors(chain = true)
@TableName(value = "user")
public class User {
    private Long id;
    private String name;
    private Integer age;
    private String email;
}

mapper

/**
 * @author: yh
 * @Description: 支持不需要 UserMapper.xml 这个模块演示内置 CRUD 咱们就不要 XML 部分了
 * @date: 2022/6/6 12:24
 */

public interface UserMapper extends BaseMapper<User> {
}

现在就可以测试啦，编写一个测试方法

@Resource
    private UserMapper userMapper;

    /**
     * 分表测试
     * 执行后观察打印sql
     * @author yh
     * @date 2022/6/6
     */
    @Test
    public void test1() {
        RequestDataHelper.setRequestData(1L);
        userMapper.selectList(null);

        RequestDataHelper.setRequestData(2L);
        userMapper.selectList(null);

        RequestDataHelper.setRequestData(3L);
         userMapper.selectList(null);

        RequestDataHelper.setRequestData(4L);
        userMapper.selectList(null);
    }

不同的业务id按照​ ​user_​ ​​ 加 ​ ​id取模​ ​，组成表名查询。这里的分表规则随便怎么定义 时间、id、字符串hash都可以。

完整代码已上传​​Gitee Spring整合常用组件​​

到此，本章内容就介绍完啦