基於mybatis-plus實現數據源動態切換、加載

簡介

基於springboot，mybatis plus集成了一套多數據源的解決方案，在使用時引入相應的插件dynamic-datasource-spring-boot-starter，可以實現數據源的動態添加、刪除等功能，對於多租戶或者分庫等操作可以根據AOP切面代理到不同的數據源、實現單一系統數據隔離的目的。

代碼示例

mavne依賴

<!--mybatis-plus-->
<dependency>
	<groupId>com.baomidou</groupId>
	<artifactId>mybatis-plus-boot-starter</artifactId>
	<version>3.4.3.4</version>
</dependency>

<!--dynamic-datasource-->
<dependency>
	<groupId>com.baomidou</groupId>
	<artifactId>dynamic-datasource-spring-boot-starter</artifactId>
	<version>3.4.1</version>
</dependency>

數據源增加、移除

@RestController
@RequestMapping("/datasources")
public class DataSourceController {

    @Resource
    private DataSource dataSource;
    @Resource
    private DefaultDataSourceCreator dataSourceCreator;
    

    @GetMapping("list")
    public Set<String> list() {
        DynamicRoutingDataSource ds = (DynamicRoutingDataSource) dataSource;
        return ds.getDataSources().keySet();
    }

    @PostMapping("add")
    public Set<String> 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);
    }
}

默認的數據源連接池加載順序為: druid>hikaricp>beecp>dbcp>spring basic

數據源切換

基於AOP切換

添加注解,排除不做切換的接口

package com.starsray.dynamic.datasource.annotation;

import java.lang.annotation.*;

/**
 * <p>
 * 用戶標識僅可以使用默認數據源
 * </p>
 *
 * @author starsray
 * @since 2021-11-10
 */
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DefaultDs {
}

切面具體實現

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;

/**
 * <p>
 * 數據源選擇器切面
 * </p>
 *
 * @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，攔截具體請求，獲取header里的數據源id，設置線程變量里，用於后續切換數據源
     */
    @Before("datasourcePointcut()")
    public void doBefore(JoinPoint joinPoint) {
        Signature signature = joinPoint.getSignature();
        MethodSignature methodSignature = (MethodSignature) signature;
        Method method = methodSignature.getMethod();

        // 排除不可切換數據源的方法
        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，設置回默認的數據源id
     */
    @AfterReturning("datasourcePointcut()")
    public void doAfter() {
        DynamicDataSourceContextHolder.push("master");
    }

}

基於重寫處理器

mybatis plus提供了默認處理器來決定使用的數據源，可以重寫處理器實現自定義參數，比如從請求header里面獲取參數切換數據源。

@DS("#header.tenantId")

自定義處理器

public class HeaderProcessor extends DsProcessor {

    private static final String HEADER = "#header";

    @Override
    public boolean matches(String key) {
        return key.startsWith(HEADER);
    }

    @Override
    public String doDetermineDatasource(MethodInvocation invocation, String key) {
        HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest();
        return request.getHeader(key.substring(8));
    }
}

注冊自定義處理器

@Configuration
public class CustomerDynamicDataSourceConfig{

   @Bean
   public DsProcessor dsProcessor() {
        DsHeaderProcessor headerProcessor = new DsHeaderProcessor();
        DsSessionProcessor sessionProcessor = new DsSessionProcessor();
        DsSpelExpressionProcessor spelExpressionProcessor = new DsSpelExpressionProcessor();
        headerProcessor.setNextProcessor(sessionProcessor);
        sessionProcessor.setNextProcessor(spelExpressionProcessor);
        return headerProcessor;
   }
}

如果有場景需要手動切換數據源，可以使用組件提供的工具來實現。

DynamicDataSourceContextHolder.push("master");

自定義數據源

mybatis plus提供了一個接口來加載數據源信息。

public interface DynamicDataSourceProvider {
    Map<String, DataSource> loadDataSources();
}

這個接口有一個抽象實現類AbstractDataSourceProvider,通過模板方法定義了加載數據源來源的方式，mybatis plus通過YmlDynamicDataSourceProvider實現了讀取yml文件配置來初始化數據源的方式。

public abstract class AbstractDataSourceProvider implements DynamicDataSourceProvider {
    private static final Logger log = LoggerFactory.getLogger(AbstractDataSourceProvider.class);
    @Autowired
    private DefaultDataSourceCreator defaultDataSourceCreator;

    public AbstractDataSourceProvider() {
    }

    protected Map<String, DataSource> createDataSourceMap(Map<String, DataSourceProperty> dataSourcePropertiesMap) {
        Map<String, DataSource> dataSourceMap = new HashMap(dataSourcePropertiesMap.size() * 2);
        Iterator var3 = dataSourcePropertiesMap.entrySet().iterator();

        while(var3.hasNext()) {
            Entry<String, DataSourceProperty> 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;
    }
}

如果有需要從數據庫加載數據源信息，可以重寫AbstractJdbcDataSourceProvider中的executeStmt方法來加載數據庫配置信息。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
@Configuration
public class DsProvider {

    @Resource
    private DefaultDsConfig defaultDsConfig;

    @Bean
    public DynamicDataSourceProvider jdbcDynamicDataSourceProvider() {
        return new AbstractJdbcDataSourceProvider(defaultDsConfig.getDriverClassName(), defaultDsConfig.getUrl(), defaultDsConfig.getUsername(), defaultDsConfig.getPassword()) {
            @Override
            protected Map<String, DataSourceProperty> executeStmt(Statement statement) {
                Map<String, DataSourceProperty> 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;
            }
        };
    }
}

通過讀取源碼可以發現，如果還有其他需要自定義加載數據源的方式，只需要繼承AbstractDataSourceProvider抽象類，實現DynamicDataSourceProvider接口，重寫loadDataSources方法就可以實現自定義數據源。

完整代碼示例:https://gitee.com/starsray/dynamic-datasource