public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {
        // 目標(biāo)數(shù)據(jù)源 map 集合，存儲(chǔ)將要切換的多數(shù)據(jù)源 bean 信息，可以通過(guò) setTargetDataSource(Map<Object, Object> mp) 設(shè)置
        @Nullable
        private Map<Object, Object> targetDataSources;
        // 未指定數(shù)據(jù)源時(shí)的默認(rèn)數(shù)據(jù)源對(duì)象，可以通過(guò) setDefaultTargetDataSouce(Object obj) 設(shè)置
        @Nullable
        private Object defaultTargetDataSource;
  ...
        // 數(shù)據(jù)源查找接口，通過(guò)該接口的 getDataSource(String dataSourceName) 獲取數(shù)據(jù)源信息
        private DataSourceLookup dataSourceLookup = new JndiDataSourceLookup();
        //解析 targetDataSources 之后的 DataSource 的 map 集合
        @Nullable
        private Map<Object, DataSource> resolvedDataSources;
        @Nullable
        private DataSource resolvedDefaultDataSource;

        //將 targetDataSources 的內(nèi)容轉(zhuǎn)化一下放到 resolvedDataSources 中，將 defaultTargetDataSource 轉(zhuǎn)為 DataSource 賦值給 resolvedDefaultDataSource
        public void afterPropertiesSet() {
            //如果目標(biāo)數(shù)據(jù)源為空，會(huì)拋出異常，在系統(tǒng)配置時(shí)應(yīng)至少傳入一個(gè)數(shù)據(jù)源
            if (this.targetDataSources == null) {
                throw new IllegalArgumentException("Property 'targetDataSources' is required");
            } else {
                //初始化 resolvedDataSources 的大小
                this.resolvedDataSources = CollectionUtils.newHashMap(this.targetDataSources.size());
                //遍歷目標(biāo)數(shù)據(jù)源信息 map 集合，對(duì)其中的 key，value 進(jìn)行解析
                this.targetDataSources.forEach((key, value) -> {
                    // resolveSpecifiedLookupKey 方法沒(méi)有做任何處理，只是將 key 繼續(xù)返回
                    Object lookupKey = this.resolveSpecifiedLookupKey(key);
                    // 將目標(biāo)數(shù)據(jù)源 map 集合中的 value 值（Druid 數(shù)據(jù)源信息）轉(zhuǎn)為 DataSource 類型
                    DataSource dataSource = this.resolveSpecifiedDataSource(value);
                    // 將解析之后的 key，value 放入 resolvedDataSources 集合中
                    this.resolvedDataSources.put(lookupKey, dataSource);
                });
                if (this.defaultTargetDataSource != null) {
                    // 將默認(rèn)目標(biāo)數(shù)據(jù)源信息解析并賦值給 resolvedDefaultDataSource
                    this.resolvedDefaultDataSource = this.resolveSpecifiedDataSource(this.defaultTargetDataSource);
                }

            }
        }

        protected Object resolveSpecifiedLookupKey(Object lookupKey) {
            return lookupKey;
        }

        protected DataSource resolveSpecifiedDataSource(Object dataSource) throws IllegalArgumentException {
            if (dataSource instanceof DataSource) {
                return (DataSource)dataSource;
            } else if (dataSource instanceof String) {
                return this.dataSourceLookup.getDataSource((String)dataSource);
            } else {
                throw new IllegalArgumentException("Illegal data source value - only [javax.sql.DataSource] and String supported: " + dataSource);
            }
        }

        // 因?yàn)?AbstractRoutingDataSource 繼承 AbstractDataSource，而 AbstractDataSource 實(shí)現(xiàn)了 DataSource 接口，所有存在獲取數(shù)據(jù)源連接的方法
        public Connection getConnection() throws SQLException {
            return this.determineTargetDataSource().getConnection();
        }

        public Connection getConnection(String username, String password) throws SQLException {
            return this.determineTargetDataSource().getConnection(username, password);
        }

  // 最重要的一個(gè)方法，也是 DynamicDataSource 需要實(shí)現(xiàn)的方法
        protected DataSource determineTargetDataSource() {
            Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
            // 調(diào)用實(shí)現(xiàn)類中重寫的 determineCurrentLookupKey 方法拿到當(dāng)前線程要使用的數(shù)據(jù)源的名稱
            Object lookupKey = this.determineCurrentLookupKey();
            // 去解析之后的數(shù)據(jù)源信息集合中查詢?cè)摂?shù)據(jù)源是否存在，如果沒(méi)有拿到則使用默認(rèn)數(shù)據(jù)源 resolvedDefaultDataSource
            DataSource dataSource = (DataSource)this.resolvedDataSources.get(lookupKey);
            if (dataSource == null && (this.lenientFallback || lookupKey == null)) {
                dataSource = this.resolvedDefaultDataSource;
            }

            if (dataSource == null) {
                throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");
            } else {
                return dataSource;
            }
        }

        @Nullable
        protected abstract Object determineCurrentLookupKey();
    }

<!-- web 模塊依賴 -->
<dependency>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- spring 核心 aop 模塊依賴 -->
<dependency>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-aop</artifactId>
</dependency>
<!-- Druid 數(shù)據(jù)源連接池依賴 -->
<dependency>
 <groupId>com.alibaba</groupId>
 <artifactId>druid-spring-boot-starter</artifactId>
 <version>1.2.8</version>
</dependency>
<!-- mybatis 依賴 -->
<dependency>
 <groupId>org.mybatis.spring.boot</groupId>
 <artifactId>mybatis-spring-boot-starter</artifactId>
 <version>2.2.2</version>
</dependency>
<!-- mysql驅(qū)動(dòng) -->
<dependency>
 <groupId>mysql</groupId>
 <artifactId>mysql-connector-java</artifactId>
 <version>8.0.24</version>
</dependency>
<!-- lombok 模塊依賴 -->
<dependency>
 <groupId>org.projectlombok</groupId>
 <artifactId>lombok</artifactId>
 <optional>true</optional>
</dependency>
<dependency>
 <groupId>org.apache.commons</groupId>
 <artifactId>commons-text</artifactId>
 <version>1.10.0</version>
</dependency>
<dependency>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-test</artifactId>
 <scope>test</scope>
</dependency>

spring:
  datasource:
 type: com.alibaba.druid.pool.DruidDataSource
    url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding-utf8&allowPublicKeyRetrieval=true&useSSL=false&serverTimezone=Asia/Shanghai&allowMultiQueries=true
    driver-class-name: com.mysql.cj.jdbc.Driver
    username: root
    password: root
custom:
  datasource:
    names: ds1,ds2
    ds1:
      type: com.alibaba.druid.pool.DruidDataSource
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/content_center?useUnicode
      username: root
      password: root
    ds2:
   type: com.alibaba.druid.pool.DruidDataSource
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/trade?useUnicode
      username: root
      password: root

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.AllArgsConstructor;

/**
 * @Description: 繼承Spring AbstractRoutingDataSource 實(shí)現(xiàn)路由切換
 */
@Data
@NoArgsConstructor
@AllArgsConstructor
public class DynamicDataSource extends AbstractRoutingDataSource {

 /**
  * 決定當(dāng)前線程使用哪種數(shù)據(jù)源
  * @return 數(shù)據(jù)源 key
  */
    @Override
    protected Object determineCurrentLookupKey() {
        return DynamicDataSourceContextHolder.getDataSourceType();
    }
}

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

/**
 * @Description: 動(dòng)態(tài)數(shù)據(jù)源上下文管理
 */
public class DynamicDataSourceHolder {
    // 存放當(dāng)前線程使用的數(shù)據(jù)源類型信息
    private static final ThreadLocal<String> DYNAMIC_DATASOURCE_KEY = new ThreadLocal<String>();
    // 存放數(shù)據(jù)源 key
    private static final List<String> DATASOURCE_KEYS = new ArrayList<String>();
    // 默認(rèn)數(shù)據(jù)源 key
    public static final String DEFAULT_DATESOURCE_KEY = "master";

    //設(shè)置數(shù)據(jù)源
    public static void setDynamicDataSourceType(String key) {
        DYNAMIC_DATASOURCE_KEY.set(key);
    }

    //獲取數(shù)據(jù)源
    public static String getDynamicDataSourceType() {
        return DYNAMIC_DATASOURCE_KEY.get();
    }

    //清除數(shù)據(jù)源
    public static void removeDynamicDataSourceType() {
        DYNAMIC_DATASOURCE_KEY.remove();
    }

 public static void addDataSourceKey(String key) {
  DATASOURCE_KEYS.add(key)
 }

    /**
     * 判斷指定 key 當(dāng)前是否存在
     *
     * @param key
     * @return boolean
     */
    public static boolean containsDataSource(String key){
        return DATASOURCE_KEYS.contains(key);
    }
}

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.MutablePropertyValues;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.GenericBeanDefinition;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.EnvironmentAware;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.env.Environment;
import org.springframework.core.type.AnnotationMetadata;

import javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;
import org.apache.commons.lang3.StringUtils;
import java.util.Objects;

/**
 * @Description: 注冊(cè)動(dòng)態(tài)數(shù)據(jù)源
 * 初始化數(shù)據(jù)源和提供了執(zhí)行動(dòng)態(tài)切換數(shù)據(jù)源的工具類
 * EnvironmentAware（獲取配置文件配置的屬性值）
 */
public class DynamicDataSourceRegister implements ImportBeanDefinitionRegistrar, EnvironmentAware {
 private static final Logger LOGGER = LoggerFactory.getLogger(DynamicDataSourceRegister.class);
    // 指定默認(rèn)數(shù)據(jù)源類型 (springboot2.0 默認(rèn)數(shù)據(jù)源是 hikari 如何想使用其他數(shù)據(jù)源可以自己配置)
    // private static final String DATASOURCE_TYPE_DEFAULT = "com.zaxxer.hikari.HikariDataSource";
    private static final String DEFAULT_DATASOURCE_TYPE = "com.alibaba.druid.pool.DruidDataSource";
    // 默認(rèn)數(shù)據(jù)源
    private DataSource defaultDataSource;
    // 用戶自定義數(shù)據(jù)源
    private Map<String, DataSource> customDataSources  = new HashMap<>();

    /**
     * 加載多數(shù)據(jù)源配置
     * @param env 當(dāng)前環(huán)境
     */
    @Override
    public void setEnvironment(Environment env) {
        initDefaultDataSource(env);
        initCustomDataSources(env);
    }



    /**
     * 初始化主數(shù)據(jù)源
     * @param env
     */
    private void initDefaultDataSource(Environment env) {
        // 讀取主數(shù)據(jù)源
        Map<String, Object> dsMap = new HashMap<>();
        dsMap.put("type", env.getProperty("spring.datasource.type", DEFAULT_DATASOURCE_TYPE));
        dsMap.put("driver", env.getProperty("spring.datasource.driver-class-name"));
        dsMap.put("url", env.getProperty("spring.datasource.url"));
        dsMap.put("username", env.getProperty("spring.datasource.username"));
        dsMap.put("password", env.getProperty("spring.datasource.password"));
        defaultDataSource = buildDataSource(dsMap);
    }


    /**
     * 初始化更多數(shù)據(jù)源
     * @param env
     */
    private void initCustomDataSources(Environment env) {
        // 讀取配置文件獲取更多數(shù)據(jù)源
        String dsPrefixs = env.getProperty("custom.datasource.names");
        if (!StringUtils.isBlank(dsPrefixs)) {
         for (String dsPrefix : dsPrefixs.split(",")) {
          dsPrefix = fsPrefix.trim()
          if (!StringUtils.isBlank(dsPrefix)) {
           Map<String, Object> dsMap = new HashMap<>();
           dsMap.put("type", env.getProperty("custom.datasource." + dsPrefix + ".type", DEFAULT_DATASOURCE_TYPE));
              dsMap.put("driver", env.getProperty("custom.datasource." + dsPrefix + ".driver-class-name"));
              dsMap.put("url", env.getProperty("custom.datasource." + dsPrefix + ".url"));
              dsMap.put("username", env.getProperty("custom.datasource." + dsPrefix + ".username"));
              dsMap.put("password", env.getProperty("custom.datasource." + dsPrefix + ".password"));
              DataSource ds = buildDataSource(dsMap);
              customDataSources.put(dsPrefix, ds);
          }
         }
        }
    }

    @Override
    public void registerBeanDefinitions(AnnotationMetadata annotationMetadata, BeanDefinitionRegistry registry) {
        Map<Object, Object> targetDataSources = new HashMap<Object, Object>();
        // 將主數(shù)據(jù)源添加到更多數(shù)據(jù)源中
        targetDataSources.put(DynamicDataSourceHolder.DEFAULT_DATASOURCE_KEY, defaultDataSource);
        DynamicDataSourceHolder.addDataSourceKey(DynamicDataSourceHolder.DEFAULT_DATASOURCE_KEY);
        // 添加更多數(shù)據(jù)源
        targetDataSources.putAll(customDataSources);
        for (String key : customDataSources.keySet()) {
            DynamicDataSourceContextHolder.addDataSourceKey(key);
        }

        // 創(chuàng)建 DynamicDataSource
        GenericBeanDefinition beanDefinition = new GenericBeanDefinition();
        beanDefinition.setBeanClass(DynamicDataSource.class);
        beanDefinition.setSynthetic(true);
        MutablePropertyValues mpv = beanDefinition.getPropertyValues();
        mpv.addPropertyValue("defaultTargetDataSource", defaultDataSource);
        mpv.addPropertyValue("targetDataSources", targetDataSources);
        registry.registerBeanDefinition("dataSource", beanDefinition); // 注冊(cè)到 Spring 容器中
        LOGGER.info("Dynamic DataSource Registry");
    }

    /**
     * 創(chuàng)建 DataSource
     * @param dsMap 數(shù)據(jù)庫(kù)配置參數(shù)
     * @return DataSource
     */
    public DataSource buildDataSource(Map<String, Object> dsMap) {
        try {
            Object type = dsMap.get("type");
            if (type == null)
                type = DEFAULT_DATASOURCE_TYPE;// 默認(rèn)DataSource

            Class<? extends DataSource> dataSourceType = (Class<? extends DataSource>)Class.forName((String)type);
            String driverClassName = String.valueOf(dsMap.get("driver"));
            String url = String.valueOf(dsMap.get("url"));
            String username = String.valueOf(dsMap.get("username"));
            String password = String.valueOf(dsMap.get("password"));

            // 自定義 DataSource 配置
            DataSourceBuilder<? extends DataSource> factory = DataSourceBuilder.create()
                    .driverClassName(driverClassName)
                    .url(url)
                    .username(username)
                    .password(password)
                    .type(dataSourceType);
            return factory.build();
        }catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
}

// 注冊(cè)動(dòng)態(tài)多數(shù)據(jù)源
@Import({ DynamicDataSourceRegister.class })
@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

/**
 * 自定義多數(shù)據(jù)源切換注解
 * 優(yōu)先級(jí)：DynamicDataSourceHolder.setDynamicDataSourceKey() > Method > Class
 */
@Target({ ElementType.METHOD, ElementType.TYPE })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
public @interface DataSource
{
    /**
     * 切換數(shù)據(jù)源名稱
     */
    public String value() default DynamicDataSourceHolder.DEFAULT_DATESOURCE_KEY;
}

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.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
import org.aspectj.lang.reflect.MethodSignature;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.Objects;

@Aspect
// 保證在 @Transactional 等注解前面執(zhí)行
@Order(-1)
@Component
public class DataSourceAspect {

    // 設(shè)置 DataSource 注解的切點(diǎn)表達(dá)式
    @Pointcut("@annotation(com.ayi.config.datasource.DynamicDataSource)")
    public void dynamicDataSourcePointCut(){

    }

    //環(huán)繞通知
    @Around("dynamicDataSourcePointCut()")
    public Object around(ProceedingJoinPoint joinPoint) throws Throwable{
        String key = getDefineAnnotation(joinPoint).value();
        if (!DynamicDataSourceHolder.containsDataSource(key)) {
         LOGGER.error("數(shù)據(jù)源[{}]不存在，使用默認(rèn)數(shù)據(jù)源[{}]", key, DynamicDataSourceHolder.DEFAULT_DATESOURCE_KEY)
         key = DynamicDataSourceHolder.DEFAULT_DATESOURCE_KEY;
        }
        DynamicDataSourceHolder.setDynamicDataSourceKey(key);
        try {
            return joinPoint.proceed();
        } finally {
            DynamicDataSourceHolder.removeDynamicDataSourceKey();
        }
    }

    /**
     * 先判斷方法的注解，后判斷類的注解，以方法的注解為準(zhǔn)
     * @param joinPoint 切點(diǎn)
     * @return TargetDataSource
     */
    private TargetDataSource getDefineAnnotation(ProceedingJoinPoint joinPoint){
        MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
        TargetDataSource dataSourceAnnotation = methodSignature.getMethod().getAnnotation(TargetDataSource.class);
        if (Objects.nonNull(methodSignature)) {
            return dataSourceAnnotation;
        } else {
            Class<?> dsClass = joinPoint.getTarget().getClass();
            return dsClass.getAnnotation(TargetDataSource.class);
        }
    }

}