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在 SpringBoot 中实现多数据源访问的最佳实践

2020-08-05    
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1 概述

在实际业务开发中通常会在单个应用中通过 分库分表 或者 读写分离的方式来提供应用的读写性能。

在具体的开发中有很多方式：

  1. 通过不同的 mApper，映射到不同的 mybatis 源的方式
  2. 通过继承 Spring 的 AbstractRoutingDataSource 抽象类并重写 determineCurrentLookupKey 方法来管理多个数据源的方式

本文将详细介绍在 SpringBoot 应用中如何通过 自定义注解 和 aop 的方式实现多数据源的访问，采用了第二种的方式。

2 关键点

3 使用场景

  1. 分库分表，根据业务来划分不同的库，比如与用户相关的表在 db_user 库，与订单相关的表在 db_order 库。
  2. 读写分离，master 和 slave 模式，master 库只用来写入数据，slave 库只用来读取数据。

这里根据场景 1 来实现具体的例子。

4 具体的例子

4.1 开发环境

4.2 数据库和表

CREATE TABLE `t_user` (
  `id` int(18) NOT NULL AUTO_INCREMENT COMMENT '流水号',
  `name` varchar(25) COLLATE utf8_bin DEFAULT NULL COMMENT '名称',
  `age` int(10) DEFAULT NULL COMMENT '年龄',
  `sex` char(1) COLLATE utf8_bin DEFAULT NULL COMMENT '性别',
  `remarks` varchar(255) COLLATE utf8_bin DEFAULT NULL COMMENT '备注',
  `create_date` datetime DEFAULT NULL COMMENT '创建时间',
  `create_user` varchar(64) COLLATE utf8_bin DEFAULT NULL COMMENT '创建人',
  `update_date` datetime DEFAULT NULL COMMENT '更新时间',
  `update_user` varchar(64) COLLATE utf8_bin DEFAULT NULL COMMENT '更新人',
  `del_flag` char(1) COLLATE utf8_bin DEFAULT NULL COMMENT '删除标记（0：正常；1：删除）',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8 COLLATE=utf8_bin COMMENT='用户信息表'

CREATE TABLE `t_order` (
  `id` int(18) NOT NULL AUTO_INCREMENT COMMENT '流水号',
  `user_id` int(18) DEFAULT NULL COMMENT '用户id',
  `order_date` datetime DEFAULT NULL COMMENT '订单时间',
  `order_amount` decimal(10,0) DEFAULT NULL COMMENT '订单金额',
  `remarks` varchar(255) COLLATE utf8mb4_bin DEFAULT NULL COMMENT '备注',
  `create_date` datetime DEFAULT NULL COMMENT '创建时间',
  `create_user` varchar(64) COLLATE utf8mb4_bin DEFAULT NULL COMMENT '创建人',
  `update_date` datetime DEFAULT NULL COMMENT '更新时间',
  `update_user` varchar(64) COLLATE utf8mb4_bin DEFAULT NULL COMMENT '更新人',
  `del_flag` char(1) COLLATE utf8mb4_bin DEFAULT NULL COMMENT '删除标记（0：正常；1：删除）',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin COMMENT='订单表'

4.3 代码结构如下

在 SpringBoot 中实现多数据源访问的最佳实践

 

4.4 自定义注解和 AOP 实现

  1. MultiDataSource
import com.ckJAVA.entity.DbEnum;
import java.lang.annotation.*;

/**
 * 数据库切换的注解，只作用在方法上
 */
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface MultiDataSource {

    // 用于指定数据库名称的
    DbEnum value() default DbEnum.user;
}
  1. 通过 aop 来读取注解的配置，并在方法前后进行数据库的切换
import com.ckjava.aop.annotation.MultiDataSource;
import com.ckjava.config.MultiDataSourceHolder;
import com.ckjava.entity.DbEnum;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
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.core.annotation.Order;
import org.springframework.stereotype.Component;

import java.lang.reflect.Method;

/**
 * 通过 aop 来读取注解的配置，并在方法前后进行数据库的切换
 */
@Aspect
@Component
@Order(1)
public class MultiDataSourceAspect {

    @Pointcut("@annotation(com.ckjava.aop.annotation.MultiDataSource)")
    public void dataSourcePointCut() {
    }

    /**
     * 在方法执行前设置数据库 key
     *
     * @param point
     */
    @Before("dataSourcePointCut()")
    public void before(JoinPoint point) {
        MethodSignature signature = (MethodSignature) point.getSignature();
        Method method = signature.getMethod();

        // 在含有 MultiDataSource 注解的方法执行前，设置线程的数据库源变量
        MultiDataSource dataSource = method.getAnnotation(MultiDataSource.class);
        if (dataSource == null) {
            MultiDataSourceHolder.setDataSource(DbEnum.user);
        } else {
            MultiDataSourceHolder.setDataSource(dataSource.value());
        }
    }

    /**
     * 在方法执行后移除 数据库 key
     */
    @After("dataSourcePointCut()")
    public void after() {
        // 移除线程本地数据库源变量
        MultiDataSourceHolder.clearDataSource();
    }
}

4.5 继承 AbstractRoutingDataSource 抽象类，重写 determineCurrentLookupKey 方法

具体如下

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

/**
 * AbstractRoutingDataSource 在获取 Connection 前会通过 determineTargetDataSource 来从多个数据源中根据 key 来
 *
 * 获取一个 DataSource 对象，这里 determineCurrentLookupKey 由子类来实现
 */
public class MultiRoutingDataSource extends AbstractRoutingDataSource {

    @Override
    protected Object determineCurrentLookupKey() {
        return MultiDataSourceHolder.getDataSource();
    }

}

4.6 多数据源配置以及 mybatis 配置

import com.ckjava.entity.DbEnum;
import com.ckjava.properties.OrderDataSourceProperties;
import com.ckjava.properties.UserDataSourceProperties;
import com.zaxxer.hikari.HikariDataSource;
import org.Apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;

import javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;

@Configuration
@EnableTransactionManagement
@MapperScan(basePackages = {"com.ckjava.dao"}, sqlSessionFactoryRef = "sqlSessionFactory") // 扫描 Mapper 接口并容器管理
public class MultiDataSourceConfig {

    // 精确到 master 目录，以便跟其他数据源隔离
    public static final String MAPPER_LOCATION = "classpath:mapper/data/*Mapper.xml";
    public static final String CONFIG_LOCATION = "classpath:mapper/data/config.xml";

    @Autowired
    private UserDataSourceProperties userSourceProperties;
    @Autowired
    private OrderDataSourceProperties orderDataSourceProperties;

    @Bean("userDataSource")
    public DataSource userDataSource() {
        HikariDataSource dataSource = DataSourceBuilder
                .create()
                .driverClassName(userSourceProperties.getDriverClassName())
                .url(userSourceProperties.getUrl())
                .username(userSourceProperties.getUsername())
                .password(userSourceProperties.getPassword())
                .type(HikariDataSource.class)
                .build();
        dataSource.setMaximumPoolSize(userSourceProperties.getMaxPoolSize());
        dataSource.setAutoCommit(true);
        return dataSource;
    }

    @Bean("orderDataSource")
    public DataSource orderDataSource() {
        HikariDataSource dataSource = DataSourceBuilder
                .create()
                .driverClassName(orderDataSourceProperties.getDriverClassName())
                .url(orderDataSourceProperties.getUrl())
                .username(orderDataSourceProperties.getUsername())
                .password(orderDataSourceProperties.getPassword())
                .type(HikariDataSource.class)
                .build();
        dataSource.setMaximumPoolSize(orderDataSourceProperties.getMaxPoolSize());
        dataSource.setAutoCommit(true);
        return dataSource;
    }

    @Bean
    @Primary
    public DataSource multiRoutingDataSource(@Qualifier("userDataSource") DataSource userDataSource,
                                             @Qualifier("orderDataSource") DataSource orderDataSource) {
        Map<Object, Object> targetDataSources = new HashMap<>();
        targetDataSources.put(DbEnum.user, userDataSource);
        targetDataSources.put(DbEnum.order, orderDataSource);

        MultiRoutingDataSource myRoutingDataSource = new MultiRoutingDataSource();
        myRoutingDataSource.setDefaultTargetDataSource(userDataSource);
        myRoutingDataSource.setTargetDataSources(targetDataSources);
        return myRoutingDataSource;
    }

    @Bean(name = "transactionManager")
    @Primary
    public PlatformTransactionManager transactionManager(@Qualifier("userDataSource") DataSource userDataSource,
                                                         @Qualifier("orderDataSource") DataSource orderDataSource) throws Exception {
        return new DataSourceTransactionManager(multiRoutingDataSource(userDataSource, orderDataSource));
    }

    @Bean(name = "sqlSessionFactory")
    @Primary
    public SqlSessionFactory sqlSessionFactory(@Qualifier("userDataSource") DataSource userDataSource,
                                               @Qualifier("orderDataSource") DataSource orderDataSource) throws Exception {
        final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
        sessionFactory.setDataSource(multiRoutingDataSource(userDataSource, orderDataSource));
        sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver().getResources(MultiDataSourceConfig.MAPPER_LOCATION));
        sessionFactory.setConfigLocation(new PathMatchingResourcePatternResolver().getResource(MultiDataSourceConfig.CONFIG_LOCATION));
        return sessionFactory.getObject();
    }
}

4.7 通过 ThreadLocal 来存储当前线程的 数据库 key 变量

具体如下

import com.ckjava.entity.DbEnum;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 通过 ThreadLocal 来存储当前线程的 数据库 key 变量
 */
public class MultiDataSourceHolder {

    private static final Logger logger = LoggerFactory.getLogger(MultiDataSourceHolder.class);

    /**
     * 通过 ThreadLocal 来存储当前线程的 dataSource key
     */
    private static final ThreadLocal<DbEnum> contextHolder = new ThreadLocal<>();

    public static void setDataSource(DbEnum dataSource) {
        logger.info("Thread {} set datasource {}", Thread.currentThread().getName(), dataSource);
        contextHolder.set(dataSource);
    }

    public static DbEnum getDataSource() {
        return contextHolder.get();
    }

    public static void clearDataSource() {
        logger.info("Thread {} unset datasource {}", Thread.currentThread().getName(), contextHolder.get());
        contextHolder.remove();
    }
}

4.8 在 TUserService 和 TOrderService 上使用

import com.ckjava.aop.annotation.MultiDataSource;
import com.ckjava.dao.TUserDao;
import com.ckjava.entity.DbEnum;
import com.ckjava.entity.TUserEntity;
import com.ckjava.entity.base.PageParamer;
import com.ckjava.service.base.BaseMybatisCrudService;
import com.ckjava.xutils.http.Page;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Optional;

@Service
public class TUserService extends BaseMybatisCrudService<TUserEntity, TUserDao> {
    @Override
    public Class<TUserEntity> getClassType() {
        return TUserEntity.class;
    }

    @Override
    @MultiDataSource(DbEnum.user)
    public Optional<TUserEntity> get(long id) {
        return super.get(id);
    }

    @Override
    @MultiDataSource(DbEnum.user)
    public Optional<List<TUserEntity>> getAll() {
        return super.getAll();
    }

    @Override
    @MultiDataSource(DbEnum.user)
    public Optional<List<TUserEntity>> getByParam(TUserEntity entity) {
        return super.getByParam(entity);
    }

    @Override
    @MultiDataSource(DbEnum.user)
    public Optional<Page<TUserEntity>> getPage(PageParamer pageParamer) {
        return super.getPage(pageParamer);
    }

    @Override
    @MultiDataSource(DbEnum.user)
    public Optional<Long> save(TUserEntity entity) {
        return super.save(entity);
    }

    @Override
    @MultiDataSource(DbEnum.user)
    public Optional<Long> update(TUserEntity entity) {
        return super.update(entity);
    }

    @Override
    @MultiDataSource(DbEnum.user)
    public Optional<Long> saveOrUpdate(TUserEntity entity) {
        return super.saveOrUpdate(entity);
    }

    @Override
    @MultiDataSource(DbEnum.user)
    public Optional<Integer> delete(Long id) {
        return super.delete(id);
    }

    @Override
    @MultiDataSource(DbEnum.user)
    public Optional<Integer> deletePhysical(Long id) {
        return super.deletePhysical(id);
    }
}

import com.ckjava.aop.annotation.MultiDataSource;
import com.ckjava.dao.TOrderDao;
import com.ckjava.entity.DbEnum;
import com.ckjava.entity.TOrderEntity;
import com.ckjava.entity.base.PageParamer;
import com.ckjava.service.base.BaseMybatisCrudService;
import com.ckjava.xutils.http.Page;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Optional;

@Service
public class TOrderService extends BaseMybatisCrudService<TOrderEntity, TOrderDao> {

    @Override
    public Class<TOrderEntity> getClassType() {
        return TOrderEntity.class;
    }

    @Override
    @MultiDataSource(DbEnum.order)
    public Optional<TOrderEntity> get(long id) {
        return super.get(id);
    }

    @Override
    @MultiDataSource(DbEnum.order)
    public Optional<List<TOrderEntity>> getAll() {
        return super.getAll();
    }

    @Override
    @MultiDataSource(DbEnum.order)
    public Optional<List<TOrderEntity>> getByParam(TOrderEntity entity) {
        return super.getByParam(entity);
    }

    @Override
    @MultiDataSource(DbEnum.order)
    public Optional<Page<TOrderEntity>> getPage(PageParamer pageParamer) {
        return super.getPage(pageParamer);
    }

    @Override
    @MultiDataSource(DbEnum.order)
    public Optional<Long> save(TOrderEntity entity) {
        return super.save(entity);
    }

    @Override
    @MultiDataSource(DbEnum.order)
    public Optional<Long> update(TOrderEntity entity) {
        return super.update(entity);
    }

    @Override
    @MultiDataSource(DbEnum.order)
    public Optional<Long> saveOrUpdate(TOrderEntity entity) {
        return super.saveOrUpdate(entity);
    }

    @Override
    @MultiDataSource(DbEnum.order)
    public Optional<Integer> delete(Long id) {
        return super.delete(id);
    }

    @Override
    @MultiDataSource(DbEnum.order)
    public Optional<Integer> deletePhysical(Long id) {
        return super.deletePhysical(id);
    }
}

5 测试

import com.ckjava.entity.TOrderEntity;
import com.ckjava.service.TOrderService;
import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import java.util.Date;
import java.util.List;

@RunWith(SpringRunner.class)
@SpringBootTest
public class TestOrderService {

	@Autowired
	private TOrderService tOrderService;

	@Test
	public void test_get() {
		tOrderService.get(1L).ifPresent(entity -> {
			System.out.println(entity.getId());
		});
	}

}

12:43:06.033 [main] INFO  c.c.config.MultiDataSourceHolder - Thread main set datasource order
12:43:06.042 [main] INFO  com.zaxxer.hikari.HikariDataSource - HikariPool-1 - Starting...
12:43:06.359 [main] INFO  com.zaxxer.hikari.HikariDataSource - HikariPool-1 - Start completed.
12:43:06.516 [main] INFO  c.c.config.MultiDataSourceHolder - Thread main unset datasource order
1

从上面可见，在数据源加载前，先修改了 datasource key 为 order 数据库。

import com.ckjava.service.TUserService;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@SpringBootTest
public class TestUserService {

	@Autowired
	private TUserService tUserService;

	@Test
	public void test_get() {
		tUserService.get(1L).ifPresent(entity -> {
			System.out.println(entity.getId());
		});
	}

}


12:45:30.389 [main] INFO  c.c.config.MultiDataSourceHolder - Thread main set datasource user
12:45:30.403 [main] INFO  com.zaxxer.hikari.HikariDataSource - HikariPool-1 - Starting...
12:45:30.906 [main] INFO  com.zaxxer.hikari.HikariDataSource - HikariPool-1 - Start completed.
12:45:31.159 [main] INFO  c.c.config.MultiDataSourceHolder - Thread main unset datasource user
1

从输出结果看，在数据源加载前，先修改了 datasource key 为 user 数据库。

6 代码

例子的完整代码：gitee spring-boot-multidb

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