基于mybatis|基于mybatis plus实现数据源动态添加、删除、切换，自定义数据源的示例代码基于mybatisplus实现数据源动态添

简介
代码示例

mavne依赖
数据源增加、移除
数据源切换

基于AOP切换
基于重写处理器

自定义数据源

简介基于springboot，mybatis plus集成了一套多数据源的解决方案，在使用时引入相应的插件dynamic-datasource-spring-boot-starter，可以实现数据源的动态添加、删除等功能，对于多租户或者分库等操作可以根据AOP切面代理到不同的数据源、实现单一系统数据隔离的目的。

代码示例
mavne依赖

com.baomidou mybatis-plus-boot-starter 3.4.3.4 com.baomidou dynamic-datasource-spring-boot-starter 3.4.1

数据源增加、移除

@RestController@RequestMapping("/datasources")public class DataSourceController { @Resourceprivate DataSource dataSource; @Resourceprivate DefaultDataSourceCreator dataSourceCreator; @GetMapping("list")public Set list() {DynamicRoutingDataSource ds = (DynamicRoutingDataSource) dataSource; return ds.getDataSources().keySet(); } @PostMapping("add")public Set add(@Validated @RequestBody DataSourceDTO dto) {DataSourceProperty dataSourceProperty = new DataSourceProperty(); BeanUtils.copyProperties(dto, dataSourceProperty); DynamicRoutingDataSource ds = (DynamicRoutingDataSource) dataSource; DataSource dataSource = dataSourceCreator.createDataSource(dataSourceProperty); ds.addDataSource(dto.getPollName(), dataSource); return ds.getDataSources().keySet(); } @DeleteMapping("remove")public void remove(String name) {DynamicRoutingDataSource ds = (DynamicRoutingDataSource) dataSource; ds.removeDataSource(name); }}

默认的数据源连接池加载顺序为: druid>hikaricp>beecp>dbcp>spring basic

数据源切换

基于AOP切换添加注解,排除不做切换的接口

package com.starsray.dynamic.datasource.annotation; import java.lang.annotation.*; /** * * 用户标识仅可以使用默认数据源 *
* * @author starsray * @since 2021-11-10 */@Target({ElementType.METHOD})@Retention(RetentionPolicy.RUNTIME)@Documentedpublic @interface DefaultDs {}

切面具体实现

package com.starsray.dynamic.datasource.interceptor; import com.baomidou.dynamic.datasource.toolkit.DynamicDataSourceContextHolder; import com.starsray.dynamic.datasource.annotation.DefaultDs; import com.starsray.dynamic.datasource.exception.ExceptionEnum; import com.starsray.dynamic.datasource.exception.GlobalException; import lombok.RequiredArgsConstructor; import org.apache.commons.lang3.StringUtils; import org.aspectj.lang.JoinPoint; import org.aspectj.lang.Signature; import org.aspectj.lang.annotation.AfterReturning; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Before; import org.aspectj.lang.annotation.Pointcut; import org.aspectj.lang.reflect.MethodSignature; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Component; import org.springframework.web.context.request.RequestAttributes; import org.springframework.web.context.request.RequestContextHolder; import org.springframework.web.context.request.ServletRequestAttributes; import org.springframework.web.servlet.HandlerInterceptor; import javax.servlet.http.HttpServletRequest; import java.lang.reflect.Method; /** * * 数据源选择器切面 *
* * @author starsray * @since 2021-11-10 */@Aspect@Component@RequiredArgsConstructor(onConstructor_ = @Autowired)public class DsInterceptor implements HandlerInterceptor { @Pointcut("execution(public * com.starsray.dynamic.datasource.controller.*.*(..))")public void datasourcePointcut() {} /*** 前置操作，拦截具体请求，获取header里的数据源id，设置线程变量里，用于后续切换数据源*/@Before("datasourcePointcut()")public void doBefore(JoinPoint joinPoint) {Signature signature = joinPoint.getSignature(); MethodSignature methodSignature = (MethodSignature) signature; Method method = methodSignature.getMethod(); // 排除不可切换数据源的方法DefaultDs annotation = method.getAnnotation(DefaultDs.class); if (null != annotation) {DynamicDataSourceContextHolder.push("master"); } else {RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes(); ServletRequestAttributes attributes = (ServletRequestAttributes) requestAttributes; assert attributes != null; HttpServletRequest request = attributes.getRequest(); String header = request.getHeader("tenantName"); if (StringUtils.isNotBlank(header)) {DynamicDataSourceContextHolder.push(header); } else {throw new GlobalException(ExceptionEnum.NOT_TENANT); }}} /*** 后置操作，设置回默认的数据源id*/@AfterReturning("datasourcePointcut()")public void doAfter() {DynamicDataSourceContextHolder.push("master"); } }

基于重写处理器 mybatis plus提供了默认处理器来决定使用的数据源，可以重写处理器实现自定义参数，比如从请求header里面获取参数切换数据源。

@DS("#header.tenantId")

自定义处理器

public class HeaderProcessor extends DsProcessor { private static final String HEADER = "#header"; @Overridepublic boolean matches(String key) {return key.startsWith(HEADER); } @Overridepublic String doDetermineDatasource(MethodInvocation invocation, String key) {HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest(); return request.getHeader(key.substring(8)); }}

注册自定义处理器

@Configurationpublic class CustomerDynamicDataSourceConfig{ @Beanpublic DsProcessor dsProcessor() {DsHeaderProcessor headerProcessor = new DsHeaderProcessor(); DsSessionProcessor sessionProcessor = new DsSessionProcessor(); DsSpelExpressionProcessor spelExpressionProcessor = new DsSpelExpressionProcessor(); headerProcessor.setNextProcessor(sessionProcessor); sessionProcessor.setNextProcessor(spelExpressionProcessor); return headerProcessor; }}

如果有场景需要手动切换数据源，可以使用组件提供的工具来实现。

DynamicDataSourceContextHolder.push("master");

自定义数据源
mybatis plus提供了一个接口来加载数据源信息。

public interface DynamicDataSourceProvider {Map loadDataSources(); }

这个接口有一个抽象实现类AbstractDataSourceProvider,通过模板方法定义了加载数据源来源的方式，mybatis plus通过YmlDynamicDataSourceProvider实现了读取yml文件配置来初始化数据源的方式。

public abstract class AbstractDataSourceProvider implements DynamicDataSourceProvider {private static final Logger log = LoggerFactory.getLogger(AbstractDataSourceProvider.class); @Autowiredprivate DefaultDataSourceCreator defaultDataSourceCreator; public AbstractDataSourceProvider() {} protected Map createDataSourceMap(Map dataSourcePropertiesMap) {Map dataSourceMap = new HashMap(dataSourcePropertiesMap.size() * 2); Iterator var3 = dataSourcePropertiesMap.entrySet().iterator(); while(var3.hasNext()) {Entry item = (Entry)var3.next(); String dsName = (String)item.getKey(); DataSourceProperty dataSourceProperty = (DataSourceProperty)item.getValue(); String poolName = dataSourceProperty.getPoolName(); if (poolName == null || "".equals(poolName)) {poolName = dsName; } dataSourceProperty.setPoolName(poolName); dataSourceMap.put(dsName, this.defaultDataSourceCreator.createDataSource(dataSourceProperty)); }return dataSourceMap; }}

如果有需要从数据库加载数据源信息，可以重写AbstractJdbcDataSourceProvider中的executeStmt方法来加载数据库配置信息。示例：

package com.digital.cnzz.dynamic.ds.provider; import com.baomidou.dynamic.datasource.provider.AbstractJdbcDataSourceProvider; import com.baomidou.dynamic.datasource.provider.DynamicDataSourceProvider; import com.baomidou.dynamic.datasource.spring.boot.autoconfigure.DataSourceProperty; import com.digital.cnzz.dynamic.ds.config.DefaultDsConfig; import com.digital.cnzz.dynamic.ds.constant.DsDriverEnum; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.context.annotation.Primary; import javax.annotation.Resource; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.HashMap; import java.util.Map; @Primary@Configurationpublic class DsProvider { @Resourceprivate DefaultDsConfig defaultDsConfig; @Beanpublic DynamicDataSourceProvider jdbcDynamicDataSourceProvider() {return new AbstractJdbcDataSourceProvider(defaultDsConfig.getDriverClassName(), defaultDsConfig.getUrl(), defaultDsConfig.getUsername(), defaultDsConfig.getPassword()) {@Overrideprotected Map executeStmt(Statement statement) {Map dataSourcePropertiesMap = null; ResultSet rs = null; try {dataSourcePropertiesMap = new HashMap<>(); rs = statement.executeQuery("SELECT * FROM DYNAMIC_DATASOURCE_INSTANCE"); while (rs.next()) {String name = rs.getString("name"); DataSourceProperty property = new DataSourceProperty(); property.setDriverClassName(rs.getString("driver")); property.setUrl(rs.getString("url")); property.setUsername(rs.getString("username")); property.setPassword(rs.getString("password")); dataSourcePropertiesMap.put(name, property); }} catch (SQLException e) {e.printStackTrace(); } finally {try {if (rs != null) {rs.close(); }} catch (SQLException e) {e.printStackTrace(); }try {statement.close(); } catch (SQLException e) {e.printStackTrace(); }}return dataSourcePropertiesMap; }}; }}

通过读取源码可以发现，如果还有其他需要自定义加载数据源的方式，只需要继承AbstractDataSourceProvider抽象类，实现DynamicDataSourceProvider接口，重写loadDataSources方法就可以实现自定义数据源。
完整代码示例:https://gitee.com/starsray/dynamic-datasource
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