ShardingSphere 是一个开源的分布式数据库中间件，支持在运行时动态添加数据源。以下为你详细介绍在 Spring Boot 项目里动态添加数据库的步骤和示例代码：

1. 添加依赖

在 pom.xml 里添加 ShardingSphere JDBC 的依赖：

xml

<dependency>
    <groupId>org.apache.shardingsphere</groupId>
    <artifactId>shardingsphere-jdbc-core-spring-boot-starter</artifactId>
    <version>5.4.1</version>
</dependency>

2. 配置 ShardingSphere

在 application.yml 中进行 ShardingSphere 的基本配置：

yaml

spring:
  shardingsphere:
    mode:
      type: Memory
    datasource:
      names: ds0
      ds0:
        type: com.zaxxer.hikari.HikariDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        jdbc-url: jdbc:mysql://localhost:3306/db0
        username: root
        password: root
    rules:
      - !SHARDING
        tables:
          your_table_name:
            actual-data-nodes: ds0.your_table_name
            table-strategy:
              standard:
                sharding-column: id
                sharding-algorithm-name: inline
        sharding-algorithms:
          inline:
            type: INLINE
            props:
              algorithm-expression: your_table_name_$->{id % 2}

3. 动态添加数据源的代码示例

以下是在运行时动态添加数据源的示例代码：

shardingsphere-dynamic-add-db
ShardingSphere 动态添加数据库的 Java 代码

import org.apache.shardingsphere.infra.config.RuleConfiguration;
import org.apache.shardingsphere.infra.config.datasource.DataSourceConfiguration;
import org.apache.shardingsphere.infra.config.datasource.DataSourceConverter;
import org.apache.shardingsphere.infra.config.mode.ModeConfiguration;
import org.apache.shardingsphere.infra.yaml.config.pojo.YamlRootConfiguration;
import org.apache.shardingsphere.infra.yaml.config.swapper.YamlDataSourceConfigurationSwapper;
import org.apache.shardingsphere.infra.yaml.config.swapper.resource.YamlDataSourceConfigurationSwappers;
import org.apache.shardingsphere.sharding.api.config.ShardingRuleConfiguration;
import org.apache.shardingsphere.sharding.api.config.rule.ShardingTableRuleConfiguration;
import org.apache.shardingsphere.sharding.api.config.strategy.sharding.StandardShardingStrategyConfiguration;
import org.apache.shardingsphere.spring.boot.SpringBootConfiguration;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import javax.sql.DataSource;
import java.util.*;

@Service
public class DynamicDataSourceAddition {

    @Autowired
    private SpringBootConfiguration springBootConfiguration;

    public void addDataSource(String dataSourceName, String jdbcUrl, String username, String password) {
        YamlRootConfiguration rootConfig = springBootConfiguration.getYamlRootConfig();
        // 创建新的数据源配置
        DataSourceConfiguration dataSourceConfig = createDataSourceConfig(jdbcUrl, username, password);
        // 添加新的数据源配置
        rootConfig.getDataSources().put(dataSourceName, dataSourceConfig);
        // 更新规则配置（根据需要）
        updateShardingRuleConfiguration(rootConfig.getRules(), dataSourceName);
        // 重新初始化数据源
        reInitializeDataSource(rootConfig);
    }

    private DataSourceConfiguration createDataSourceConfig(String jdbcUrl, String username, String password) {
        Map<String, Object> props = new HashMap<>();
        props.put("jdbcUrl", jdbcUrl);
        props.put("driverClassName", "com.mysql.cj.jdbc.Driver");
        props.put("username", username);
        props.put("password", password);
        return new DataSourceConfiguration("com.zaxxer.hikari.HikariDataSource", props);
    }

    private void updateShardingRuleConfiguration(Collection<RuleConfiguration> rules, String dataSourceName) {
        for (RuleConfiguration rule : rules) {
            if (rule instanceof ShardingRuleConfiguration) {
                ShardingRuleConfiguration shardingRuleConfig = (ShardingRuleConfiguration) rule;
                // 假设这里添加一个新的表规则
                ShardingTableRuleConfiguration tableRule = new ShardingTableRuleConfiguration("new_table", dataSourceName + ".new_table");
                tableRule.setTableShardingStrategy(new StandardShardingStrategyConfiguration("id", "inline"));
                shardingRuleConfig.getTables().add(tableRule);
            }
        }
    }

    private void reInitializeDataSource(YamlRootConfiguration rootConfig) {
        YamlDataSourceConfigurationSwapper dataSourceSwapper = new YamlDataSourceConfigurationSwapper();
        Map<String, DataSource> dataSources = DataSourceConverter.getDataSourceMap(dataSourceSwapper.swapToDataSources(rootConfig.getDataSources()));
        // 这里需要根据实际情况更新数据源到 ShardingSphere 中
        // 例如，重新初始化 ShardingSphereDataSource
        // 以下代码仅为示例，实际实现可能需要根据具体情况调整
        // ShardingSphereDataSource shardingSphereDataSource = new ShardingSphereDataSource(dataSources, rootConfig.getRules(), new ModeConfiguration("Memory", null));
    }
}    

4. 使用示例

在需要动态添加数据源的地方调用 addDataSource 方法：

java

@Autowired
private DynamicDataSourceAddition dynamicDataSourceAddition;

public void addNewDataSource() {
    dynamicDataSourceAddition.addDataSource("ds1", "jdbc:mysql://localhost:3306/db1", "root", "root");
}

说明

上述代码展示了如何在运行时动态添加数据源。首先创建新的数据源配置，然后将其添加到现有的配置中，接着更新规则配置，最后重新初始化数据源。
实际使用时，要依据具体的业务需求和 ShardingSphere 版本对代码进行调整。

按照以上步骤操作，你就能在 ShardingSphere 里动态添加数据库了。