Springboot+mybatis-plus+dynamic-datasource+继承DynamicRoutingDataSource切换数据源

背景

最近公司要求支持saas，实现动态切换库的操作，默认会加载主租户的数据源，其他租户数据源在使用过程中自动创建加入。

解决问题

1.通过请求中设置租户id 查询对应的库
2.通过设置上下文租户id 查询对应的库
3.测试mybatisplus mapper，service继承后设置上下文能否正常查询对应的库

解决要求

1.改造现有系统尽量少改动,避免过多的耦合代码
2.已有功能正常
3.不影响之前的@DS注解切换数据源的

实现流程

1.代码结构

请添加图片描述

2.引入依赖

 <dependency><groupId>com.alibaba</groupId><artifactId>transmittable-thread-local</artifactId><version>2.14.3</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><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>3.5.3.1</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.47</version></dependency><dependency><groupId>com.baomidou</groupId><artifactId>dynamic-datasource-spring-boot-starter</artifactId><version>4.2.0</version></dependency><dependency><groupId>org.testng</groupId><artifactId>testng</artifactId><version>7.4.0</version></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></dependency>

3.代码

3.1.TenantContextHolder

用于将租户id设置为上下文，获取当前的租户id

package com.liuhm.context;import com.alibaba.ttl.TransmittableThreadLocal;/*** saas 上下文 Holder*/
public class TenantContextHolder {/*** 当前租户编号*/private static final ThreadLocal<String> TENANT_ID = new TransmittableThreadLocal<>();/*** 获得租户编号。** @return 租户编号*/public static String getTenantId() {return TENANT_ID.get();}/*** 获得租户编号。如果不存在，则抛出 NullPointerException 异常** @return 租户编号*/public static String getRequiredTenantId() {String tenantId = getTenantId();if (tenantId == null) {throw new NullPointerException("TenantContextHolder 不存在租户编号！");}return tenantId;}public static void setTenantId(String tenantId) {TENANT_ID.set(tenantId);}public static void clear() {TENANT_ID.remove();}}

3.2.TenantWebFilter

拦截所有的请求获取header或者url中租户id的值，然后设置到上下文中。

(获取租户id可以改成获取token，并将租户id存入token值中，方便获取租户id)

package com.liuhm.config;import com.liuhm.context.TenantContextHolder;
import org.springframework.util.StringUtils;
import org.springframework.web.filter.OncePerRequestFilter;import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Objects;public class TenantWebFilter extends OncePerRequestFilter {public static final String HEADER_TENANT_ID = "X-Tenant-Id";public static String getTenantId(HttpServletRequest request){String tenantId = StringUtils.hasLength(request.getHeader(HEADER_TENANT_ID)) ?request.getHeader(HEADER_TENANT_ID) :request.getHeader(HEADER_TENANT_ID.toLowerCase());if (StringUtils.isEmpty(tenantId)) {tenantId = getQueryParam(request.getQueryString(),HEADER_TENANT_ID);}return StringUtils.hasText(tenantId) ? tenantId : null;}public static String getQueryParam(String query,String key){if(Objects.isNull(query)){return null;}String[] params = query.split("&");for (String param : params) {String[] keyValue = param.split("=");if(Objects.equals(key.toLowerCase(),keyValue[0].toLowerCase()) && keyValue.length > 1){return keyValue[1];}}return null;}@Overrideprotected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain chain) throws ServletException, IOException{if (request.getRequestURI().equalsIgnoreCase("/harbor/clear")) {chain.doFilter(request, response);} else {String tenantId = getTenantId(request);if (tenantId != null) {TenantContextHolder.setTenantId(tenantId);}try {chain.doFilter(request, response);} finally {// 清理TenantContextHolder.clear();}}}
}

3.3 MyDynamicRoutingDataSource

MyDynamicRoutingDataSource继承DynamicRoutingDataSource 重新修改选择数据源的逻辑。
DynamicDataSourceContextHolder.peek()为空时，表示原功能默认的@DS没有设置，就通过tenantId去获取数据源
getDataSourceProperty 通过tenantId 获取数据源的配置信息
createDatasourceIfAbsent 通过配置信息去创建数据源并加入到dataSourceMap中
通过对应的key去获取对应的数据源

package com.liuhm.config;import com.baomidou.dynamic.datasource.DynamicRoutingDataSource;
import com.baomidou.dynamic.datasource.creator.DataSourceProperty;
import com.baomidou.dynamic.datasource.creator.DefaultDataSourceCreator;
import com.baomidou.dynamic.datasource.provider.DynamicDataSourceProvider;
import com.baomidou.dynamic.datasource.spring.boot.autoconfigure.DynamicDataSourceProperties;
import com.baomidou.dynamic.datasource.toolkit.DynamicDataSourceContextHolder;
import com.liuhm.context.TenantContextHolder;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Lazy;import javax.annotation.Resource;
import javax.sql.DataSource;
import java.util.List;
import java.util.Set;/*** @ClassName：MyDynamicRoutingDataSource* @Description: TODO* @Author: liuhaomin* @Date: 2024/5/9 8:44*/
@Slf4j
public class MyDynamicRoutingDataSource extends DynamicRoutingDataSource {@Overridepublic DataSource determineDataSource() {if(DynamicDataSourceContextHolder.peek() == null){String tenantId = TenantContextHolder.getTenantId();if(tenantId == null){throw new RuntimeException("租户id不能为空");}DataSourceProperty dataSourceProperty = getDataSourceProperty(tenantId);createDatasourceIfAbsent(dataSourceProperty);return getDataSource(tenantId);}else {DataSourceProperty dataSourceProperty = getDataSourceProperty(DynamicDataSourceContextHolder.peek());createDatasourceIfAbsent(dataSourceProperty);return super.determineDataSource();}}public MyDynamicRoutingDataSource(List<DynamicDataSourceProvider> providers) {super(providers);}/*** 用于创建租户数据源的 Creator*/@Resource@Lazyprivate DefaultDataSourceCreator dataSourceCreator;@Resource@Lazyprivate DynamicDataSourceProperties dynamicDataSourceProperties;@Value("${spring.datasource.dynamic.primaryDatabase}")private String primaryDatabase;public DataSourceProperty getDataSourceProperty(String tenantId){DataSourceProperty dataSourceProperty = new DataSourceProperty();DataSourceProperty primaryDataSourceProperty = dynamicDataSourceProperties.getDatasource().get(dynamicDataSourceProperties.getPrimary());BeanUtils.copyProperties(primaryDataSourceProperty,dataSourceProperty);dataSourceProperty.setUrl(dataSourceProperty.getUrl().replace(primaryDatabase,tenantId));dataSourceProperty.setPoolName(tenantId);return dataSourceProperty;}private String createDatasourceIfAbsent(DataSourceProperty dataSourceProperty){// 1. 重点：如果数据源不存在，则进行创建if (isDataSourceNotExist(dataSourceProperty)) {// 问题一：为什么要加锁？因为，如果多个线程同时执行到这里，会导致多次创建数据源// 问题二：为什么要使用 poolName 加锁？保证多个不同的 poolName 可以并发创建数据源// 问题三：为什么要使用 intern 方法？因为，intern 方法，会返回一个字符串的常量池中的引用// intern 的说明，可见 https://www.cnblogs.com/xrq730/p/6662232.html 文章synchronized(dataSourceProperty.getPoolName().intern()){if (isDataSourceNotExist(dataSourceProperty)) {log.debug("创建数据源：{}", dataSourceProperty.getPoolName());DataSource dataSource = null;try {dataSource = dataSourceCreator.createDataSource(dataSourceProperty);}catch (Exception e){log.error("e {}",e);if(e.getMessage().contains("Unknown database")){throw new RuntimeException("租户不存在");}throw e;}addDataSource(dataSourceProperty.getPoolName(), dataSource);}}} else {log.debug("数据源已存在,无需创建：{}", dataSourceProperty.getPoolName());}// 2. 返回数据源的名字return dataSourceProperty.getPoolName();}private boolean isDataSourceNotExist(DataSourceProperty dataSourceProperty){return !getDataSources().containsKey(dataSourceProperty.getPoolName());}
}

3.4.TenantAutoConfiguration

TenantWebFilter加入FilterRegistrationBean
创建 MyDynamicRoutingDataSource Bean

package com.liuhm.config;import com.baomidou.dynamic.datasource.provider.DynamicDataSourceProvider;
import com.baomidou.dynamic.datasource.spring.boot.autoconfigure.DynamicDataSourceProperties;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;import javax.sql.DataSource;
import java.util.List;@Configuration
public class TenantAutoConfiguration {@Beanpublic FilterRegistrationBean<TenantWebFilter> tenantContextWebFilter() {FilterRegistrationBean<TenantWebFilter> registrationBean = new FilterRegistrationBean<>();registrationBean.setFilter(new TenantWebFilter());registrationBean.setOrder(-104);return registrationBean;}@Autowiredprivate DynamicDataSourceProperties properties;@Beanpublic DataSource dataSource(List<DynamicDataSourceProvider> providers) {MyDynamicRoutingDataSource dataSource = new MyDynamicRoutingDataSource(providers);dataSource.setPrimary(properties.getPrimary());dataSource.setStrict(properties.getStrict());dataSource.setStrategy(properties.getStrategy());dataSource.setP6spy(properties.getP6spy());dataSource.setSeata(properties.getSeata());dataSource.setGraceDestroy(properties.getGraceDestroy());return dataSource;}
}

4.总结

4.1.多租户切换的方法

dynamic-datasource 跨库进行切换数据源可以用DynamicDataSourceContextHolder.push()

在过滤器[filter]里切换
拦截器里切换数据源
方法内部硬编码切换
通过service，mapper加注解进行切换@DS （不推荐，有切面没有切成功的，如本类调用自己的方法）

重写DynamicRoutingDataSource选择器，自定义上下文获取租户id获取对应的DataSource

4.2.上诉方法中都可以实现

过滤器和拦截器切换数据源的时候，线程执行的方法不容切换，需要手动切换，或者在设置租户id的时候进行切换数据源。（耦合性过大，代码不够单一，如果在设置租户id的时候去切换数据源）
重写DynamicRoutingDataSource选择器，只是在执行sql前进行数据源获取的切换，耦合性小，代码单一性好，且不影响之前的功能。