使用Mybatis-Plus实现动态多数据源切换

摘要： 本文将介绍如何使用Mybatis-Plus配合Spring Boot来实现动态多数据源的切换。我们将讨论依赖引入、配置修改、自定义数据源提供者、配置类编写、数据源工具类实现以及AOP切面编程的应用。

一、引言

在现代的企业级应用中，常常需要根据不同的业务场景动态地切换数据源。Mybatis-Plus提供了一个基于Spring Boot的快速集成多数据源的启动器，dynamic-datasource-spring-boot-starter，以简化这一过程。

二、依赖引入

首先，在项目的pom.xml文件中引入所需的依赖：

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>dynamic-datasource-spring-boot-starter</artifactId>
    <version>3.5.1</version>
</dependency>

三、修改yml配置

接下来，在application.yml件中配置数据源：

spring:
  datasource:
    type: com.zaxxer.hikari.HikariDataSource
    dynamic:
      primary: master
      strict: false
      datasource:
        master:
          driver-class-name: com.mysql.cj.jdbc.Driver
          url: jdbc:mysql://localhost:3306/master_db
          username: root
          password: pass

四、实现自定义数据源提供者

我们可以通过继承AbstractJdbcDataSourceProvider类来实现自定义的数据源提供者：

public class CustomDynamicDataSourceProvider extends AbstractJdbcDataSourceProvider {
	
	    public CustomDynamicDataSourceProvider(String driverClassName, String url, String username, String password) {
	        super(driverClassName, url, username, password);
	    }
	
	    @Override
	    protected Map<String, DataSourceProperty> executeStmt(Statement statement) throws SQLException {
	        Map<String, DataSourceProperty> map = new HashMap<>();
	        ResultSet rs = statement.executeQuery(GlobalConstant.DB_QUERY);
	        /**
	         * 获取信息
	         */
	        while (rs.next()) {
	            String dbName = rs.getString("db_name");
	            String dbIp = rs.getString("db_ip");
	            String dbIpPort = rs.getString("db_ip_port");
	            String jdbcUrl = GlobalConstant.DB_URL
	                    .replace("{dbIp}", dbIp)
	                    .replace("{dbPort}", dbIpPort)
	                    .replace("{dbName}", dbName);
	            String dbUser = rs.getString("db_user");
	            String dbPwd = rs.getString("db_pwd");
	            String key = rs.getString("id");
	            String name = rs.getString("name");
	            DataSourceProperty dataSourceProperty = new DataSourceProperty();
	            dataSourceProperty
	                    .setDriverClassName(GlobalConstant.DB_DRIVER)
	                    .setUrl(jdbcUrl)
	                    .setUsername(dbUser)
	                    .setPassword(dbPwd)
	                    .setPoolName(name);
	            map.put(key, dataSourceProperty);
	        }
	        return map;
	  }
}

五、添加DataSourceConfiguration配置类

@Primary
@Configuration
public class DataSourceConfiguration {

    @Autowired
    private DynamicDataSourceProperties properties;

    @Value("${spring.datasource.dynamic.primary}")
    private String masterName;

    @Bean
    public DynamicDataSourceProvider customDynamicDataSourceProvider() {
        Map<String, DataSourceProperty> datasource = properties.getDatasource();
        DataSourceProperty property = datasource.get(masterName);
        return new CustomDynamicDataSourceProvider(property.getDriverClassName(), property.getUrl(), property.getUsername(), property.getPassword());
    }
}

六、实现数据源工具类DataSourceService

@Service
public class DataSourceService {

    @Autowired
    private DynamicRoutingDataSource dataSource;

    @Autowired
    private HikariDataSourceCreator dataSourceCreator;

    public DataSource get(String key){
        return dataSource.getDataSource(key);
    }

    public Set<String> getList(){
        return dataSource.getDataSources().keySet();
    }

    public Set<String> add(DataSourceProperty dsp, String key) {
        dsp.setDriverClassName(GlobalConstant.DB_DRIVER);
        DataSource creatorDataSource = dataSourceCreator.createDataSource(dsp);
        dataSource.addDataSource(key, creatorDataSource);
        return dataSource.getDataSources().keySet();
    }

    public Boolean remove(String name) {
        dataSource.removeDataSource(name);
        return Boolean.TRUE;
    }
}

七、通过AOP动态切换数据源

最后，我们使用AOP来实现数据源的动态切换：

@Slf4j
@Aspect
@Component
public class DataSourceAspect {

    @Autowired
    private DataSourceService sourceService;

    @Pointcut("within(com.baomidou.mybatisplus.extension.service.IService+)")
    public void dataSourcePointcut() {}

    @Before("dataSourcePointcut()")
    public void doBefore(JoinPoint joinPoint) {
        String org = ThreadLocalContext.getOrg();
        String master = "master";
        if (StringUtils.isEmpty(org) || "null".equals(org) || NumberConstant.STRING_ZERO.equals(org) || master.equals(org)) {
            String peek = DynamicDataSourceContextHolder.peek();
            if (master.equals(peek)) {
                return;
            }
            DynamicDataSourceContextHolder.push(master);
        } else {
            Set<String> set = sourceService.getList();
            if (!set.contains(org)) {
                throw new BusinessException("当前机构未配置数据源，请联系管理员！");
            }
            try {
                DynamicDataSourceContextHolder.push(org);
            } catch (Exception e) {
                throw new BusinessException("当前机构未配置数据源，请联系管理员！");
            }
        }
        Class<?> clazz = joinPoint.getTarget().getClass();
        String methodName = joinPoint.getSignature().getName();
        log.info(clazz + "类-" + methodName + "方法-" + org + "数据源");
    }

    @AfterReturning("dataSourcePointcut()")
    public void doAfter(JoinPoint joinPoint) {
        DynamicDataSourceContextHolder.poll();
    }
}

自定义的当前线程请求上线文ThreadLocalContext

public class ThreadLocalContext {

	private static ThreadLocal<String> threadLocalOrg = new ThreadLocal<String>();
	
	public static String getOrg() {
		return threadLocalOrg.get();
	}

	public static void setOrg(String org) {
		threadLocalOrg.set(org);
	}

	public static void remove() {
		threadLocalOrg.remove();
	}
}

在请求拦截器里面添加线程请求的机构

@Component
public class ManageInterceptorHandler extends HandlerInterceptorAdapter {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
    	// ...
		ThreadLocalContext.setOrg(authToken.getOrgId());
		return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
                           ModelAndView modelAndView) {
        // ...
    }
}

八、总结

通过上述步骤，我们已经成功地实现了Mybatis-Plus配合Spring Boot的动态多数据源切换。这种配置方式既灵活又强大，非常适合需要处理多个数据库的现代应用程序。