shardingJDBC整合mybatisplus

### Sharding-JDBC 整合 MyBatis-Plus 示例教程 #### 项目准备 为了使Sharding-JDBC与MyBatis-Plus顺利协作，需先创建一个基础的Spring Boot工程并引入必要的依赖项。这包括但不限于`spring-boot-starter-web`, `mybatis-plus-boot-starter`, 和`sharding-jdbc-spring-boot-starter`等。 ```xml <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <!-- mybatis plus --> <dependency> <groupId>com.baomidou</groupId> <artifactId>mybatis-plus-boot-starter</artifactId> <version>${mybatis.plus.version}</version> </dependency> <!-- sharding jdbc --> <dependency> <groupId>io.shardingsphere</groupId> <artifactId>sharding-jdbc-spring-boot-starter</artifactId> <version>${sharding.jdbc.version}</version> </dependency> ``` #### 数据源配置 在application.yml文件中定义多个数据源以及分片策略的相关参数设置。这里假设存在两个真实的物理数据库实例db0和db1用于水平拆分表结构[^2]。 ```yaml spring: shardingsphere: datasource: names: ds_0,ds_1 ds_0: type: com.zaxxer.hikari.HikariDataSource driver-class-name: com.mysql.cj.jdbc.Driver jdbc-url: jdbc:mysql://localhost:3306/db0?useSSL=false&serverTimezone=UTC username: root password: 123456 ds_1: type: com.zaxxer.hikari.HikariDataSource driver-class-name: com.mysql.cj.jdbc.Driver jdbc-url: jdbc:mysql://localhost:3306/db1?useSSL=false&serverTimezone=UTC username: root password: 123456 rules: sharding: tables: book: actual-data-nodes: ds_${0..1}.book_$->{0..1} table-strategy: standard: sharding-column: id precise-algorithm-class-name: com.example.demo.algorithm.ModuloTableShardingAlgorithm key-generate-strategy: column: id key-generator-class-name: io.shardingsphere.core.keygen.DefaultKeyGenerator ``` #### Mapper接口编写 通过继承`BaseMapper<T>`来快速构建CRUD操作的基础方法，如下所示： ```java package com.macky.springbootshardingjdbc.mapper; import com.baomidou.mybatisplus.core.mapper.BaseMapper; import com.macky.springbootshardingjdbc.entity.Book; /** * @author Macky */ public interface BookMapper extends BaseMapper<Book> { } ``` 此部分展示了如何利用MyBatis-Plus简化持久化层开发工作的同时享受Sharding-JDBC带来的分布式能力[^4]。 #### 自定义分片算法实现 针对具体业务场景设计合理的分片逻辑至关重要。可以通过自定义类实现`StandardShardingAlgorithm`接口完成这一目标。例如按照ID取模决定记录存储位置的方法可以这样写： ```java package com.example.demo.algorithm; import org.apache.shardingsphere.api.sharding.standard.PreciseShardingAlgorithm; import org.apache.shardingsphere.api.sharding.standard.PreciseShardingValue; import java.util.Collection; import java.util.Properties; public class ModuloTableShardingAlgorithm implements PreciseShardingAlgorithm<Long> { private final Properties properties = new Properties(); public String doSharding(final Collection<String> availableTargetNames, final PreciseShardingValue<Long> shardingValue) { Long value = shardingValue.getValue(); int targetIndex = (int)(value % 2); return "book_" + targetIndex; } } ``` 上述代码片段实现了基于ID字段值对两张子表(`book_0`,`book_1`)进行轮询分配的功能。