springboot实现多数据源切换

多数据切换原理
原理：核心是AbstractRoutingDataSource，在dao访问数据库时，会通过AbstractRoutingDataSource的determineCurrentLookupKey()来获取数据源，所有可以通过AOP（切面）进行动态设置数据源，在dao获取数据源时便可通过determineCurrentLookupKey()返回数据源从而达到动态切换的效果。
上面流程的具体过是：获取yaml文件中的数据来注册保存多个数据源，并将数据源ID放到DynamicDataSourceContextHolder的 List dataSourceIds = new ArrayList<>();中保存，在切面时通过dataSourceIds来判断是非有注册的数据源，要是存在就在注册的数据源中获取并设置到DynamicDataSourceContextHolder的 ThreadLocal HOLDER = new ThreadLocal<>();中。dao获取数据源便通过determineCurrentLookupKey()来获取HOLDER中的数据源，从而达到切换数据源的效果。
以上便是切换数据源的核心原理。下面给出具体的实现代码。

Abstract {@link javax.sql.DataSource} implementation that routes {@link #getConnection()}
 * calls to one of various target DataSources based on a lookup key. The latter is usually
 * (but not necessarily) determined through some thread-bound transaction context.
 public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {

注册数据源类：

package com.yukong.chapter5.register;

import com.yukong.chapter5.config.DynamicDataSourceContextHolder;
import com.yukong.chapter5.config.DynamicRoutingDataSource;
import com.zaxxer.hikari.HikariDataSource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.MutablePropertyValues;
import org.springframework.beans.PropertyValues;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.GenericBeanDefinition;
import org.springframework.boot.context.properties.bind.Bindable;
import org.springframework.boot.context.properties.bind.Binder;
import org.springframework.boot.context.properties.source.ConfigurationPropertyName;
import org.springframework.boot.context.properties.source.ConfigurationPropertyNameAliases;
import org.springframework.boot.context.properties.source.ConfigurationPropertySource;
import org.springframework.boot.context.properties.source.MapConfigurationPropertySource;
import org.springframework.context.EnvironmentAware;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.env.Environment;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.util.StringUtils;

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

/**
 * 动态数据源注册
 * 实现 ImportBeanDefinitionRegistrar 实现数据源注册
 * 实现 EnvironmentAware 用于读取application.yml配置
 */
public class DynamicDataSourceRegister implements ImportBeanDefinitionRegistrar, EnvironmentAware {

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


    /**
     * 配置上下文（也可以理解为配置文件的获取工具）
     */
    private Environment evn;

    /**
     * 别名
     */
    private final static ConfigurationPropertyNameAliases aliases = new ConfigurationPropertyNameAliases();

    /**
     * 由于部分数据源配置不同，所以在此处添加别名，避免切换数据源出现某些参数无法注入的情况
     */
    static {
        aliases.addAliases("url", new String[]{"jdbc-url"});
        aliases.addAliases("username", new String[]{"user"});
    }

    /**
     * 存储我们注册的数据源
     */
    private Map<String, DataSource> customDataSources = new HashMap<String, DataSource>();

    /**
     * 参数绑定工具 springboot2.0新推出
     */
    private Binder binder;

    /**
     * ImportBeanDefinitionRegistrar接口的实现方法，通过该方法可以按照自己的方式注册bean
     *
     * @param annotationMetadata
     * @param beanDefinitionRegistry
     */
    @Override
    public void registerBeanDefinitions(AnnotationMetadata annotationMetadata, BeanDefinitionRegistry beanDefinitionRegistry) {
        // 获取所有数据源配置
        Map config, defauleDataSourceProperties;
        defauleDataSourceProperties = binder.bind("spring.datasource.master", Map.class).get();
        // 获取数据源类型
        String typeStr = evn.getProperty("spring.datasource.master.type");
        // 获取数据源类型
        Class<? extends DataSource> clazz = getDataSourceType(typeStr);
        // 绑定默认数据源参数 也就是主数据源
        DataSource consumerDatasource, defaultDatasource = bind(clazz, defauleDataSourceProperties);
        DynamicDataSourceContextHolder.dataSourceIds.add("master");
        logger.info("注册默认数据源成功");
        // 获取其他数据源配置
        List<Map> configs = binder.bind("spring.datasource.cluster", Bindable.listOf(Map.class)).get();
        // 遍历从数据源
        for (int i = 0; i < configs.size(); i++) {
            config = configs.get(i);
            clazz = getDataSourceType((String) config.get("type"));
            defauleDataSourceProperties = config;
            // 绑定参数
            consumerDatasource = bind(clazz, defauleDataSourceProperties);
            // 获取数据源的key，以便通过该key可以定位到数据源
            String key = config.get("key").toString();
            customDataSources.put(key, consumerDatasource);
            // 数据源上下文，用于管理数据源与记录已经注册的数据源key
            DynamicDataSourceContextHolder.dataSourceIds.add(key);
            logger.info("注册数据源{}成功", key);
        }
        // bean定义类
        GenericBeanDefinition define = new GenericBeanDefinition();
        // 设置bean的类型，此处DynamicRoutingDataSource是继承AbstractRoutingDataSource的实现类
        define.setBeanClass(DynamicRoutingDataSource.class);
        // 需要注入的参数
        MutablePropertyValues mpv = define.getPropertyValues();
        // 添加默认数据源，避免key不存在的情况没有数据源可用
        mpv.add("defaultTargetDataSource", defaultDatasource);
        // 添加其他数据源
        mpv.add("targetDataSources", customDataSources);
        // 将该bean注册为datasource，不使用springboot自动生成的datasource
        beanDefinitionRegistry.registerBeanDefinition("datasource", define);
        logger.info("注册数据源成功，一共注册{}个数据源", customDataSources.keySet().size() + 1);
    }

    /**
     * 通过字符串获取数据源class对象
     *
     * @param typeStr
     * @return
     */
    private Class<? extends DataSource> getDataSourceType(String typeStr) {
        Class<? extends DataSource> type;
        try {
            if (StringUtils.hasLength(typeStr)) {
                // 字符串不为空则通过反射获取class对象
                type = (Class<? extends DataSource>) Class.forName(typeStr);
            } else {
                // 默认为hikariCP数据源，与springboot默认数据源保持一致
                type = HikariDataSource.class;
            }
            return type;
        } catch (Exception e) {
            //无法通过反射获取class对象的情况则抛出异常，该情况一般是写错了，所以此次抛出一个runtimeexception
            throw new IllegalArgumentException("can not resolve class with type: " + typeStr);
        }
    }

    /**
     * 绑定参数，以下三个方法都是参考DataSourceBuilder的bind方法实现的，目的是尽量保证我们自己添加的数据源构造过程与springboot保持一致
     *
     * @param result
     * @param properties
     */
    private void bind(DataSource result, Map properties) {
        ConfigurationPropertySource source = new MapConfigurationPropertySource(properties);
        Binder binder = new Binder(new ConfigurationPropertySource[]{source.withAliases(aliases)});
        // 将参数绑定到对象
        binder.bind(ConfigurationPropertyName.EMPTY, Bindable.ofInstance(result));
    }

    private <T extends DataSource> T bind(Class<T> clazz, Map properties) {
        ConfigurationPropertySource source = new MapConfigurationPropertySource(properties);
        Binder binder = new Binder(new ConfigurationPropertySource[]{source.withAliases(aliases)});
        // 通过类型绑定参数并获得实例对象
        return binder.bind(ConfigurationPropertyName.EMPTY, Bindable.of(clazz)).get();
    }

    /**
     * @param clazz
     * @param sourcePath 参数路径，对应配置文件中的值，如: spring.datasource
     * @param <T>
     * @return
     */
    private <T extends DataSource> T bind(Class<T> clazz, String sourcePath) {
        Map properties = binder.bind(sourcePath, Map.class).get();
        return bind(clazz, properties);
    }

    /**
     * EnvironmentAware接口的实现方法，通过aware的方式注入，此处是environment对象
     *
     * @param environment
     */
    @Override
    public void setEnvironment(Environment environment) {
        logger.info("开始注册数据源");
        this.evn = environment;
        // 绑定配置器
        binder = Binder.get(evn);
    }

}

动态路由数据源类：

package com.yukong.chapter5.config;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

import java.util.*;

/**
 * @Auther: yukong
 * @Date: 2018/8/15 10:47
 * @Description: 动态数据源路由配置
 */
public class DynamicRoutingDataSource extends AbstractRoutingDataSource {



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

    @Override
    protected Object determineCurrentLookupKey() {
        String dataSourceName = DynamicDataSourceContextHolder.getDataSourceRouterKey();
        logger.info("当前数据源是：{}", dataSourceName);
        return DynamicDataSourceContextHolder.getDataSourceRouterKey();
    }
}

数据源处理类：

package com.yukong.chapter5.config;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayList;
import java.util.List;

/**
 * @Auther: yukong
 * @Date: 2018/8/15 10:49
 * @Description: 数据源上下文
 */
public class DynamicDataSourceContextHolder {



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

    /**
     * 存储已经注册的数据源的key
     */
    public static List<String> dataSourceIds = new ArrayList<>();

    /**
     * 线程级别的私有变量
     */
    private static final ThreadLocal<String> HOLDER = new ThreadLocal<>();

    public static String getDataSourceRouterKey () {
        return HOLDER.get();
    }

    public static void setDataSourceRouterKey (String dataSourceRouterKey) {
        logger.info("切换至{}数据源", dataSourceRouterKey);
        HOLDER.set(dataSourceRouterKey);
    }

    /**
     * 设置数据源之前一定要先移除
     */
    public static void removeDataSourceRouterKey () {
        HOLDER.remove();
    }

    /**
     * 判断指定DataSrouce当前是否存在
     *
     * @param dataSourceId
     * @return
     */
    public static boolean containsDataSource(String dataSourceId){
        return dataSourceIds.contains(dataSourceId);
    }

}

切面类：

package com.yukong.chapter5.aop;

import com.yukong.chapter5.annotation.DataSource;
import com.yukong.chapter5.config.DynamicDataSourceContextHolder;
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.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;

//@Aspect
//@Component
//@Order(-1900)
public class DynamicDataSourceAspect {
    private static final Logger logger = LoggerFactory.getLogger(DynamicDataSourceAspect.class);

    @Before("@annotation(ds)")
    public void changeDataSource(JoinPoint point, DataSource ds) throws Throwable {
        String dsId = ds.value();
        if (DynamicDataSourceContextHolder.dataSourceIds.contains(dsId)) {
            logger.debug("Use DataSource :{} >", dsId, point.getSignature());
            DynamicDataSourceContextHolder.setDataSourceRouterKey(dsId);
        } else {
            logger.info("数据源[{}]不存在，使用默认数据源 >{}", dsId, point.getSignature());
        }
    }

    @After("@annotation(ds)")
    public void restoreDataSource(JoinPoint point, DataSource ds) {
        logger.debug("Revert DataSource : " + ds.value() + " > " + point.getSignature());
        DynamicDataSourceContextHolder.removeDataSourceRouterKey();

    }
}

拦截器：

package com.yukong.chapter5.aop;

import com.yukong.chapter5.annotation.DataSource;
import com.yukong.chapter5.config.DynamicDataSourceContextHolder;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.annotation.AnnotationUtils;

import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

/**
 * @Auther: yukong
 * @Date: 2018/8/17 09:15
 * @Description:
 */
public class DynamicDataSourceAnnotationInterceptor implements MethodInterceptor {

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


    /**
     * 缓存方法注解值
     */
    private static final Map<Method, String> METHOD_CACHE = new HashMap<>();

    @Override
    public Object invoke(MethodInvocation invocation) throws Throwable {
        try {
            String datasource = determineDatasource(invocation);
            if (! DynamicDataSourceContextHolder.containsDataSource(datasource)) {
                logger.info("数据源[{}]不存在，使用默认数据源 >", datasource);
            }
            DynamicDataSourceContextHolder.setDataSourceRouterKey(datasource);
            return invocation.proceed();
        } finally {
            DynamicDataSourceContextHolder.removeDataSourceRouterKey();
        }
    }

    private String determineDatasource(MethodInvocation invocation) {
        Method method = invocation.getMethod();
        if (METHOD_CACHE.containsKey(method)) {
            return METHOD_CACHE.get(method);
        } else {
            DataSource ds = method.isAnnotationPresent(DataSource.class) ? method.getAnnotation(DataSource.class)
                    : AnnotationUtils.findAnnotation(method.getDeclaringClass(), DataSource.class);
            METHOD_CACHE.put(method, ds.value());
            return ds.value();
        }
    }

}

织入类：

package com.yukong.chapter5.aop;

import com.yukong.chapter5.annotation.DataSource;
import org.aopalliance.aop.Advice;
import org.springframework.aop.Pointcut;
import org.springframework.aop.support.AbstractPointcutAdvisor;
import org.springframework.aop.support.ComposablePointcut;
import org.springframework.aop.support.annotation.AnnotationMatchingPointcut;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;

/**
 * @Auther: yukong
 * @Date: 2018/8/17 09:14
 * @Description: aop织入
 */
public class DynamicDataSourceAnnotationAdvisor extends AbstractPointcutAdvisor implements BeanFactoryAware {

    private Advice advice;

    private Pointcut pointcut;

    public DynamicDataSourceAnnotationAdvisor(DynamicDataSourceAnnotationInterceptor dynamicDataSourceAnnotationInterceptor) {
        this.advice = dynamicDataSourceAnnotationInterceptor;
        this.pointcut = buildPointcut();
    }

    @Override
    public Pointcut getPointcut() {
        return this.pointcut;
    }

    @Override
    public Advice getAdvice() {
        return this.advice;
    }

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        if (this.advice instanceof BeanFactoryAware) {
            ((BeanFactoryAware) this.advice).setBeanFactory(beanFactory);
        }
    }

    private Pointcut buildPointcut() {
        Pointcut cpc = (Pointcut) new AnnotationMatchingPointcut(DataSource.class, true);
        // 类注解
        Pointcut clpc = (Pointcut) AnnotationMatchingPointcut.forClassAnnotation(DataSource.class);
        // 方法注解
        Pointcut mpc = (Pointcut) AnnotationMatchingPointcut.forMethodAnnotation(DataSource.class);
        return new ComposablePointcut(cpc).union(clpc).union(mpc);
    }

}

切面注解：

package com.yukong.chapter5.annotation;

import java.lang.annotation.*;

/**
 * 切换数据注解 可以用于类或者方法级别 方法级别优先级 > 类级别
 */
@Target({ElementType.METHOD, ElementType.TYPE, ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DataSource {
    String value() default "master"; //该值即key值
}

测试类mapper：

package com.yukong.chapter5.repository;


import com.yukong.chapter5.annotation.DataSource;
import com.yukong.chapter5.entity.User;

import java.util.List;

/**
 * @Auther: yukong
 * @Date: 2018/8/13 19:47
 * @Description: UserMapper接口
 */
@DataSource("slave1")
public interface UserMapper {

    /**
     * 新增用户
     * @param user
     * @return
     */
    @DataSource  //默认数据源
    int save(User user);

    /**
     * 更新用户信息
     * @param user
     * @return
     */
    @DataSource("slave1")  //默认数据源
    int update(User user);

    /**
     * 根据id删除
     * @param id
     * @return
     */
    @DataSource  //默认数据源
    int deleteById(Long id);

    /**
     * 根据id查询
     * @param id
     * @return
     */
    @DataSource("slave1")  //slave1
    User selectById(Long id);

    /**
     * 查询所有用户信息
     * @return
     */
    List<User> selectAll();
}

测试主类：

package com.yukong.chapter5;

import com.yukong.chapter5.aop.DynamicDataSourceAnnotationAdvisor;
import com.yukong.chapter5.aop.DynamicDataSourceAnnotationInterceptor;
import com.yukong.chapter5.register.DynamicDataSourceRegister;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Import;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@Import(DynamicDataSourceRegister.class)
@MapperScan("com.yukong.chapter5.repository")
@SpringBootApplication
@EnableTransactionManagement
public class Chapter5Application {
    @Bean
    public DynamicDataSourceAnnotationAdvisor dynamicDatasourceAnnotationAdvisor() {
        return new DynamicDataSourceAnnotationAdvisor(new DynamicDataSourceAnnotationInterceptor());
    }
    public static void main(String[] args) {
        SpringApplication.run(Chapter5Application.class, args);
    }
}

yaml配置:

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server:
  port: 8989
spring:
  datasource:
    master:
      password: abc123
      url: jdbc:mysql://193.112.100.103:3306/master?useUnicode=true&characterEncoding=UTF-8
      driver-class-name: com.mysql.jdbc.Driver
      username: root
      type: com.zaxxer.hikari.HikariDataSource
    cluster:
    - key: slave1
      password: abc123
      url: jdbc:mysql://193.112.100.103:3306/slave1?useUnicode=true&characterEncoding=UTF-8
      idle-timeout: 20000
      driver-class-name: com.mysql.jdbc.Driver
      username: root
      type: com.zaxxer.hikari.HikariDataSource
    - key: slave2
      password: abc123
      url: jdbc:mysql://193.112.100.103:3306/slave2?useUnicode=true&characterEncoding=UTF-8
      driver-class-name: com.mysql.jdbc.Driver
      username: root
mybatis:
  mapper-locations: classpath:/mybatis/mapper/*.xml
  config-location:  classpath:/mybatis/config/mybatis-config.xml

logging:
  level:
    com:
      yukong:
        chapter5:
          repository: debug

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