SpringBoot多数据源切换（十二）-阿里云开发者社区

在开发过程中我们经常会遇到一个项目有需要使用多个数据源，下面就来搭建一个多数据源的项目。

项目结构

创建spring boot聚合工程可以参考：

https://blog.csdn.net/tianshuhao521/article/details/83353392

该项目是一个spring boot的聚合工程

bushro-web——>bushro-service——>bushro-mapper——>bushro-pojo

在数据库中分别创建两个数据库，master,slave，用来测试，分别创建user表，写入测试数据。

项目配置yml

bushro-web中application.yml配置

server:
  port: 8080
spring:
  datasource:
    hikari:
      master:
        driver-class-name: com.mysql.jdbc.Driver
        type: com.zaxxer.hikari.HikariDataSource
        jdbc-url: jdbc:mysql://localhost/master?useSSL=false&serverTimezone=UTC
        username: root
        password: 671354
        filters: stat,wall,log4j2
        maxActive: 50
        initialSize: 5
        maxWait: 60000
        minIdle: 1
        timeBetweenEvictionRunsMillis: 60000
        minEvictableIdleTimeMillis: 300000
        validationQuery: SELECT 1 FROM DUAL
        testWhileIdle: true
        testOnBorrow: false
        testOnReturn: false
        poolPreparedStatements: true
        maxOpenPreparedStatements: 20
      slave:
        driver-class-name: com.mysql.jdbc.Driver
        type: com.zaxxer.hikari.HikariDataSource
        jdbc-url: jdbc:mysql://localhost/slave?useSSL=false&serverTimezone=UTC
        username: root
        password: 671354
        filters: stat,wall,log4j2
        maxActive: 10
        initialSize: 5
        maxWait: 60000
        minIdle: 1
        timeBetweenEvictionRunsMillis: 60000
        minEvictableIdleTimeMillis: 300000
        validationQuery: SELECT 1 FROM DUAL
        testWhileIdle: true
        testOnBorrow: false
        testOnReturn: false
        poolPreparedStatements: true
        maxOpenPreparedStatements: 20
mybatis:
  mapper-locations: classpath:/mapper/*.xml
  type-aliases-package: com.bushro.pojo
#pagehelper分页插件
pagehelper:
  helperDialect: oracle
  reasonable: true
  supportMethodsArguments: true
  params: count=countSql

配置数据源

DataSourceKey.java，数据库标识类，与bushro-web中的application.yml中的hikari下的名字一致

动态切换数据源的主要配置在bushro-mapper上，有6个类

DataSourceKey:

/**
 * 数据库标识
 */
public enum DataSourceKey {
    /**
     * Master data source key.
     */
    master,
    /**
     * Slave alpha data source key.
     */
    slave,
}

DataSourceRoutingDataSource.java

该类继承自 AbstractRoutingDataSource 类，在访问数据库时会调用该类的 determineCurrentLookupKey() 方法获取数据库实例的 key

package com.bushro.config;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
/**
 * Multiple DataSource Configurer
 *
 */
public class DynamicRoutingDataSource extends AbstractRoutingDataSource {
    private final Logger logger = LoggerFactory.getLogger(getClass());
    /**
     * Set dynamic DataSource to Application Context
     *
     * @return
     */
    @Override
    protected Object determineCurrentLookupKey() {
        logger.debug("Current DataSource is [{}]", DynamicDataSourceContextHolder.getDataSourceKey());
        return DynamicDataSourceContextHolder.getDataSourceKey();
    }
}

DataSourceConfigurer.java

数据源配置类，在该类中生成多个数据源实例并将其注入到 ApplicationContext 中

package com.bushro.config;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.springframework.boot.context.properties.ConfigurationProperties;
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 javax.sql.DataSource;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
/**
 * Multiple DataSource Configurer
 */
@Configuration
public class DataSourceConfigurer {
    /**
     * master DataSource
     * @Primary 注解用于标识默认使用的 DataSource Bean，因为有多个个 DataSource Bean，
     * 该注解可用于 master或 slave DataSource Bean, 但不能用于 dynamicDataSource Bean, 否则会产生循环调用
     * @ConfigurationProperties 注解用于从 application.properties 文件中读取配置，为 Bean 设置属性
     * @return data source
     */
    @Bean("master")
    @Primary
    @ConfigurationProperties(prefix = "spring.datasource.hikari.master")
    public DataSource master() {
        return DataSourceBuilder.create().build();
    }
    /**
     * Slave DataSource
     *
     * @return the data source
     */
    @Bean("slave")
    @ConfigurationProperties(prefix = "spring.datasource.hikari.slave")
    public DataSource slave() {
        return DataSourceBuilder.create().build();
    }
    /**
     * 动态数据源
     *
     * @return the data source
     */
    @Bean("dynamicDataSource")
    public DataSource dynamicDataSource() {
        DynamicRoutingDataSource dynamicRoutingDataSource = new DynamicRoutingDataSource();
        Map<Object, Object> dataSourceMap = new HashMap<>(2);
        dataSourceMap.put(DataSourceKey.master.name(), master());
        dataSourceMap.put(DataSourceKey.slave.name(), slave());
        // 将 master 数据源作为默认指定的数据源
        dynamicRoutingDataSource.setDefaultTargetDataSource(master());
        // 将 master 和 slave 数据源作为指定的数据源
        dynamicRoutingDataSource.setTargetDataSources(dataSourceMap);
        // 将数据源的 key 放到数据源上下文的 key 集合中，用于切换时判断数据源是否有效
        DynamicDataSourceContextHolder.dataSourceKeys.addAll(dataSourceMap.keySet());
        // 将 Slave 数据源的 key 放在集合中，用于轮循
        DynamicDataSourceContextHolder.slaveDataSourceKeys.addAll(dataSourceMap.keySet());
        DynamicDataSourceContextHolder.slaveDataSourceKeys.remove(DataSourceKey.master.name());
        return dynamicRoutingDataSource;
    }
    /**
     * 配置 SqlSessionFactoryBean
     * @ConfigurationProperties 在这里是为了将 MyBatis 的 mapper 位置和持久层接口的别名设置到
     * Bean 的属性中，如果没有使用 *.xml 则可以不用该配置，否则将会产生 invalid bond statement 异常
     * @return the sql session factory bean
     */
    @Bean
    public SqlSessionFactoryBean sqlSessionFactoryBean() throws Exception{
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        // 配置 MyBatis
        sqlSessionFactoryBean.setTypeAliasesPackage("com.bushro.mapper");
        sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/*Mapper.xml"));
        // 配置数据源，此处配置为关键配置，如果没有将 dynamicDataSource 作为数据源则不能实现切换
        sqlSessionFactoryBean.setDataSource(dynamicDataSource());
        return sqlSessionFactoryBean;
    }
    /**
     * 注入 DataSourceTransactionManager 用于事务管理
     */
    @Bean
    public PlatformTransactionManager transactionManager() {
        return new DataSourceTransactionManager(dynamicDataSource());
    }
}

DynamicDataSourceContextHolder.java

该类为数据源上下文配置，用于切换数据源

package com.bushro.config;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.ArrayList;
import java.util.List;
/**
 * 多个数据源上下文容器
 *
 */
public class DynamicDataSourceContextHolder {
    private static final Logger logger = LoggerFactory.getLogger(DynamicDataSourceContextHolder.class);
    private static int counter = 0;
    /**
     * Maintain variable for every thread, to avoid effect other thread
     */
    private static final ThreadLocal<String> CONTEXT_HOLDER = ThreadLocal.withInitial(DataSourceKey.master::name);
    /**
     * All DataSource List
     */
    public static List<Object> dataSourceKeys = new ArrayList<>();
    /**
     * The constant slaveDataSourceKeys.
     */
    public static List<Object> slaveDataSourceKeys = new ArrayList<>();
    /**
     * To switch DataSource
     *
     * @param key the key
     */
    public static void setDataSourceKey(String key) {
        CONTEXT_HOLDER.set(key);
    }
    /**
     * Use master data source.
     */
    public static void useMasterDataSource() {
        CONTEXT_HOLDER.set(DataSourceKey.master.name());
    }
    /**
     * Use slave data source.
     */
    public static void useSlaveDataSource() {
        try {
            int datasourceKeyIndex = counter % slaveDataSourceKeys.size();
            CONTEXT_HOLDER.set(String.valueOf(slaveDataSourceKeys.get(datasourceKeyIndex)));
            counter++;
        } catch (Exception e) {
            logger.error("Switch slave datasource failed, error message is {}", e.getMessage());
            useMasterDataSource();
            e.printStackTrace();
        }
    }
    /**
     * Get current DataSource
     *
     * @return data source key
     */
    public static String getDataSourceKey() {
        return CONTEXT_HOLDER.get();
    }
    /**
     * To set DataSource as default
     */
    public static void clearDataSourceKey() {
        CONTEXT_HOLDER.remove();
    }
    /**
     * Check if give DataSource is in current DataSource list
     *
     * @param key the key
     * @return boolean boolean
     */
    public static boolean containDataSourceKey(String key) {
        return dataSourceKeys.contains(key);
    }
}

DynamicDataSourceAspect.java

动态数据源切换的切面，切 DAO 层，通过 DAO 层方法名判断使用哪个数据源，实现数据源切换关于切面的 Order 可以可以不设，因为 @Transactional 是最低的，取决于其他切面的设置，并且在 org.springframework.core.annotation.AnnotationAwareOrderComparator 会重新排序

package com.bushro.config;
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.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
@Aspect
// 该切面应当先于 @Transactional 执行
@Order(-1)
@Component
public class DynamicDataSourceAspect {
    /** * Switch DataSource * * @param point * @param targetDataSource */
    @Before("@annotation(targetDataSource))")
    public void switchDataSource(JoinPoint point, TargetDataSource targetDataSource) {
        if (!DynamicDataSourceContextHolder.containDataSourceKey(targetDataSource.value())) {
            System.out.println("DataSource [{}] doesn't exist, use default DataSource [{}] " + targetDataSource.value());
        } else {
            // 切换数据源
            DynamicDataSourceContextHolder.setDataSourceKey(targetDataSource.value());
            System.out.println("Switch DataSource to [{}] in Method [{}] " +
                    DynamicDataSourceContextHolder.getDataSourceKey() + point.getSignature());
        }
    }
    /** * Restore DataSource * * @param point * @param targetDataSource */
    @After("@annotation(targetDataSource))")
    public void restoreDataSource(JoinPoint point, TargetDataSource targetDataSource) {
        // 将数据源置为默认数据源
        DynamicDataSourceContextHolder.clearDataSourceKey();
        System.out.println("Restore DataSource to [{}] in Method [{}] " +
                DynamicDataSourceContextHolder.getDataSourceKey() + point.getSignature());
    }
}

TargetDataSource

注解

package com.bushro.config;
import java.lang.annotation.*;
/**
 *注解来标识使用哪个数据库
 */
@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface TargetDataSource {
    String value();
}

bushro-pojo创建user类，bushro-mapper创建相应的xml,以及dao层接口

服务层

在相应的方法上使用@TargetDataSource注解来表明使用哪个数据库

@Service
public class UserServiceImpl implements UserService {
    @Resource
    UserMapper userMapper;
    @TargetDataSource("master")
    @Override
    public List getUserMaster() {
        return userMapper.getUserList();
    }
    @TargetDataSource("slave")
    @Override
    public List getUserSlave() {
        return userMapper.getUserList();
    }
}

controller

@RestController
public class UserController {
    @Resource
    UserService userService;
    @RequestMapping("/getUserMaster")
    public List getUserMaster(){
        return userService.getUserMaster();
    }
    @RequestMapping("/getUserSlave")
    public List getUserSlave(){
        return userService.getUserSlave();
    }
}

结果

两个方法调用的都是同一个方法，但是从不同数据库取出来的结果就不同了

SpringBoot多数据源切换（十二）

项目结构

项目配置yml

配置数据源

服务层

结果

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