引入

现在的企业服务逐渐地呈现出数据的指数级增长趋势，无论从数据库的选型还是搭建，大多数的团队都开始考虑多样化的数据库来支撑存储服务。例如分布式数据库、Nosql数据库、内存数据库、关系型数据库等等。再到后端开发来说，服务的增多，必定需要考虑到多数据源的切换使用来兼容服务之间的调用。为解决这一难题，今天就来分享一个关于多数据源的切换使用配置。

1.maven依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.5.1</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>io.commons.dynamic</groupId>
    <artifactId>datasource</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>dynamic-datasource</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.0</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.13</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.10</version>
        </dependency>
        <!--springBoot的aop-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-aop</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13</version>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

2.配置文件

application.yml

server:
  port: 8080

spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    druid:
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai
      username: root
      password: 123456
      initial-size: 10
      max-active: 100
      min-idle: 10
      max-wait: 60000
      pool-prepared-statements: true
      max-pool-prepared-statement-per-connection-size: 20
      time-between-eviction-runs-millis: 60000
      min-evictable-idle-time-millis: 300000
      #Oracle需要打开注释
      #validation-query: SELECT 1 FROM DUAL
      test-while-idle: true
      test-on-borrow: false
      test-on-return: false
      stat-view-servlet:
        enabled: true
        url-pattern: /druid/*
        #login-username: admin
        #login-password: admin
      filter:
        stat:
          log-slow-sql: true
          slow-sql-millis: 1000
          merge-sql: false
        wall:
          config:
            multi-statement-allow: true

#多数据源的配置
dynamic:
  datasource:
    slave1:
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/shiro?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai
      username: root
      password: 123456
    slave2:
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/shiro?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai
      username: root
      password: 123456


mybatis:
  type-aliases-package: io.commons.dynamic.datasource.entity
  mapper-locations: classpath*:mapper/*.xml

  application.properties

#访问端口号
server.port=8080

spring.datasource.druid.type=com.alibaba.druid.pool.DruidDataSource
#数据库相关配置
spring.datasource.druid.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.druid.url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai
spring.datasource.druid.username=root
spring.datasource.druid.password=123456
# 初始化大小，最小，最大
spring.datasource.druid.initial-size=5
spring.datasource.druid.min-idle=3
spring.datasource.druid.max-active=20
# 配置获取连接等待超时的时间
spring.datasource.druid.max-wait=60000
# 配置间隔多久才进行一次检测，检测需要关闭的空闲连接，单位是毫秒，下面是：1分钟
spring.datasource.druid.time-between-eviction-runs-millis=60000
# 配置一个连接在池中最小生存的时间，单位是毫秒，下面是：5分钟
spring.datasource.druid.min-evictable-idle-time-millis=300000
# 打开PSCache，并且指定每个连接上PSCache的大小
spring.datasource.druid.pool-prepared-statements=true
spring.datasource.druid.max-pool-prepared-statement-per-connection-size=20
# 配置监控统计拦截的filters，去掉后监控界面sql无法统计，'wall'用于防火墙
#spring.datasource.druid.filters=stat,wall,log4j,config
# asyncInit是1.1.4中新增加的配置，如果有initialSize数量较多时，打开会加快应用启动时间
spring.datasource.druid.asyncInit=true
#druid监控相关配置
#用户名
druid.login.username=root
#密码
druid.login.password=root
#白名单
druid.allow=127.0.0.1
#黑名单(共同存在时，deny优先于allow)
druid.deny=root


#多数据源的配置
dynamic.datasource.slave1.driver-class-name=com.mysql.jdbc.Driver
dynamic.datasource.slave1.url=jdbc:mysql://localhost:3306/test?characterEncoding=utf-8&serverTimezone=UTC&useSSL=false
dynamic.datasource.slave1.username=root
dynamic.datasource.slave1.password=123456
dynamic.datasource.slave2.driver-class-name=com.mysql.jdbc.Driver
dynamic.datasource.slave2.url=jdbc:mysql://localhost:3306/shiro?characterEncoding=utf-8&serverTimezone=UTC&useSSL=false
dynamic.datasource.slave2.username=root
dynamic.datasource.slave2.password=123456


#mybatis相关配置
mybatis.type-aliases-package=io.commons.dynamic.datasource.entity
#配置mapper对应的xml映射
mybatis.mapper-locations=classpath:mapper/*.xml

3.动态切换数据源

通过AbstractRoutingDataSource实现数据源动态切换
Springboot提供了AbstractRoutingDataSource 根据用户定义的规则选择当前的数据源，这样我们可以在执行查询之前，切换到需要的数据源。实现可动态路由的数据源，在每次数据库查询操作前执行。它的抽象方法 determineCurrentLookupKey() 决定使用哪个数据源。
 

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

/**
 * DynamicRoutingDataSource 动态切换数据源
 */
public class DynamicDataSource extends AbstractRoutingDataSource {

    @Override
    protected Object determineCurrentLookupKey() {
        return DynamicContextHolder.peek();
    }

}

4.数据源切换注解

此处设置了在类和方法都可以。方便接口开发。

import java.lang.annotation.*;

/**
 * @author 数据源切换注解
 * 优先级：先方法，后类，如果方法覆盖了类上的数据源类型，以方法的为准，否则以类上的为准
 */
@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
public @interface DataSource {

    String value() default "";
}

5.缓存数据源处理

import java.util.ArrayDeque;
import java.util.Deque;

/**
 * 使用ThreadLocal创建一个线程安全的 多数据源上下文
 *
 * @author
 */
public class DynamicContextHolder {
    @SuppressWarnings("unchecked")
    private static final ThreadLocal<Deque<String>> CONTEXT_HOLDER = new ThreadLocal() {
        @Override
        protected Object initialValue() {
            return new ArrayDeque();
        }
    };

    /**
     * 获得当前线程数据源
     *
     * @return 数据源名称
     */
    public static String peek() {
        return CONTEXT_HOLDER.get().peek();
    }

    /**
     * 设置当前线程数据源
     *
     * @param dataSource 数据源名称
     */
    public static void push(String dataSource) {
        CONTEXT_HOLDER.get().push(dataSource);
    }

    /**
     * 清空当前线程数据源
     */
    public static void clearDataSource() {
        Deque<String> deque = CONTEXT_HOLDER.get();
        deque.poll();
        if (deque.isEmpty()) {
            CONTEXT_HOLDER.remove();
        }
    }
}

6.动态数据源配置类

import com.alibaba.druid.pool.DruidDataSource;
import com.common.dynamic.datasource.properties.DataSourceProperties;
import com.common.dynamic.datasource.properties.DynamicDataSourceProperties;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import java.util.HashMap;
import java.util.Map;

/**
 * 动态数据源配置
 */
@Configuration
@EnableConfigurationProperties(DynamicDataSourceProperties.class)
public class DynamicDataSourceConfig {
    @Autowired
    private DynamicDataSourceProperties properties;

    @Bean
    @ConfigurationProperties(prefix = "spring.datasource.druid")
    public DataSourceProperties dataSourceProperties() {
        return new DataSourceProperties();
    }

    @Bean
    public DynamicDataSource dynamicDataSource(DataSourceProperties dataSourceProperties) {
        DynamicDataSource dynamicDataSource = new DynamicDataSource();
        dynamicDataSource.setTargetDataSources(getDynamicDataSource());

        //默认数据源
        DruidDataSource defaultDataSource = DynamicDataSourceFactory.buildDruidDataSource(dataSourceProperties);
        dynamicDataSource.setDefaultTargetDataSource(defaultDataSource);

        return dynamicDataSource;
    }

    private Map<Object, Object> getDynamicDataSource() {
        Map<String, DataSourceProperties> dataSourcePropertiesMap = properties.getDatasource();
        Map<Object, Object> targetDataSources = new HashMap<>(dataSourcePropertiesMap.size());
        dataSourcePropertiesMap.forEach((k, v) -> {
            DruidDataSource druidDataSource = DynamicDataSourceFactory.buildDruidDataSource(v);
            targetDataSources.put(k, druidDataSource);
        });

        return targetDataSources;
    }
}

7.数据源属性

/**
 * 多数据源属性
 */
@Data
public class DataSourceProperties {
    private String driverClassName;
    private String url;
    private String username;
    private String password;

    /**
     * Druid默认参数
     */
    private int initialSize = 2;
    private int maxActive = 10;
    private int minIdle = -1;
    private long maxWait = 60 * 1000L;
    private long timeBetweenEvictionRunsMillis = 60 * 1000L;
    private long minEvictableIdleTimeMillis = 1000L * 60L * 30L;
    private long maxEvictableIdleTimeMillis = 1000L * 60L * 60L * 7;
    private String validationQuery = "select 1";
    private int validationQueryTimeout = -1;
    private boolean testOnBorrow = false;
    private boolean testOnReturn = false;
    private boolean testWhileIdle = true;
    private boolean poolPreparedStatements = false;
    private int maxOpenPreparedStatements = -1;
    private boolean sharePreparedStatements = false;
    private String filters = "stat,wall";


    

import org.springframework.boot.context.properties.ConfigurationProperties;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 * 动态数据源属性
 */
@ConfigurationProperties(prefix = "dynamic")
public class DynamicDataSourceProperties {

    private Map<String, DataSourceProperties> datasource = new LinkedHashMap<>();

    public Map<String, DataSourceProperties> getDatasource() {
        return datasource;
    }

    public void setDatasource(Map<String, DataSourceProperties> datasource) {
        this.datasource = datasource;
    }
}

8.动态数据源工厂

import com.alibaba.druid.pool.DruidDataSource;
import com.common.dynamic.datasource.properties.DataSourceProperties;

import java.sql.SQLException;

/**
 * DruidDataSource 动态数据源工厂
 */
public class DynamicDataSourceFactory {

    public static DruidDataSource buildDruidDataSource(DataSourceProperties properties) {
        DruidDataSource druidDataSource = new DruidDataSource();
        druidDataSource.setDriverClassName(properties.getDriverClassName());
        druidDataSource.setUrl(properties.getUrl());
        druidDataSource.setUsername(properties.getUsername());
        druidDataSource.setPassword(properties.getPassword());

        druidDataSource.setInitialSize(properties.getInitialSize());
        druidDataSource.setMaxActive(properties.getMaxActive());
        druidDataSource.setMinIdle(properties.getMinIdle());
        druidDataSource.setMaxWait(properties.getMaxWait());
        druidDataSource.setTimeBetweenEvictionRunsMillis(properties.getTimeBetweenEvictionRunsMillis());
        druidDataSource.setMinEvictableIdleTimeMillis(properties.getMinEvictableIdleTimeMillis());
        druidDataSource.setMaxEvictableIdleTimeMillis(properties.getMaxEvictableIdleTimeMillis());
        druidDataSource.setValidationQuery(properties.getValidationQuery());
        druidDataSource.setValidationQueryTimeout(properties.getValidationQueryTimeout());
        druidDataSource.setTestOnBorrow(properties.isTestOnBorrow());
        druidDataSource.setTestOnReturn(properties.isTestOnReturn());
        druidDataSource.setPoolPreparedStatements(properties.isPoolPreparedStatements());
        druidDataSource.setMaxOpenPreparedStatements(properties.getMaxOpenPreparedStatements());
        druidDataSource.setSharePreparedStatements(properties.isSharePreparedStatements());

        try {
            druidDataSource.setFilters(properties.getFilters());
            druidDataSource.init();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return druidDataSource;
    }
}

9.数据源切面

import com.common.dynamic.datasource.annotation.DataSource;
import com.common.dynamic.datasource.config.DynamicContextHolder;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import java.lang.reflect.Method;

/**
 * 动态数据源切面处理
 */
@Aspect
@Component
@Order(Ordered.HIGHEST_PRECEDENCE)
public class DataSourceAspect {
    protected Logger logger = LoggerFactory.getLogger(getClass());

    @Pointcut("@annotation(com.common.dynamic.datasource.annotation.DataSource) " +
            "|| @within(com.common.dynamic.datasource.annotation.DataSource)")
    public void dataSourcePointCut() {

    }

    @Around("dataSourcePointCut()")
    public Object around(ProceedingJoinPoint point) throws Throwable {
        MethodSignature signature = (MethodSignature) point.getSignature();
        Class targetClass = point.getTarget().getClass();
        Method method = signature.getMethod();

        DataSource targetDataSource = (DataSource) targetClass.getAnnotation(DataSource.class);
        DataSource methodDataSource = method.getAnnotation(DataSource.class);
        if (targetDataSource != null || methodDataSource != null) {
            String value;
            if (methodDataSource != null) {
                value = methodDataSource.value();
            } else {
                value = targetDataSource.value();
            }

            DynamicContextHolder.push(value);
            logger.debug("set datasource is {}", value);
        }

        try {
            return point.proceed();
        } finally {
            DynamicContextHolder.clearDataSource();
            logger.debug("clean datasource");
        }
    }
}

10.使用动态数据源

在想要切换数据源的方法或类上加上@DataSource注解,目标方法和类都可以生效，方法上的注解优先于类上注解

注意事项：@DataSource("slave1") 里面的值跟yml配置要一致，如果@DataSource注解里面值为空，走默认数据源

@Controller
@RequestMapping(value = "sysMenu")
public class SysMenuController {

    @Autowired
    private SysMenuService sysMenuService;

    @DataSource("slave1")
    @RequestMapping(value = "list1")
    @ResponseBody
    public List<SysMenu> selectMenuAll1() {
        return sysMenuService.selectMenuAll();
    }

    @DataSource(value = "slave2")
    @RequestMapping(value = "list2")
    @ResponseBody
    public List<SysMenu> selectMenuAll2() {
        return sysMenuService.selectMenuAll();
    }
}

Spring AOP注解失效及解决

在使用 Spring AOP 的时候，我们从 IOC 容器中获取的 Service Bean 对象其实都是Proxy代理对象，而不是那些 Service Bean 对象this本身，也就是说在同类Service Bean中A方法调用B，本质是 this.B()，而不是Proxy.B()故 Spring AOP 是不能拦截到这些被嵌套调用的方法的。

如果2个数据源同时使用，建议把@DataSource注解标记在service接口实现类的方法上

@Service
public class UserInfoServiceImpl implements UserInfoService {

    @DataSource(value = "defaultDataSource")
    @Override
    public int insertSelective(UserInfo record) {
        return userInfoMapper.insertSelective(record);
    }

    @DataSource(value = "slave2")
    @Override
    public List<UserInfo> selectAll() {
        return userInfoMapper.selectAll();
    }
}