Spring 和 SpringBoot项目分别实现多数据源配置，并动态切换

本是古典何须时尚 2024-04-20 09:44 3阅读 0赞

## 一、前言 ##

随着项目业务的日益复杂，单个数据库有时无法满足项目的需求，比如：数据库的读写分离，集成多个数据库。而多数据源配置的出现就能够很好的解决我们这一难题。

## 二、Spring实现多数据源配置 ##

**1、在pom.xml文件中添加所需依赖**

<properties>
            <log4j.version>2.11.1</log4j.version>
            <spring.version>5.1.5.RELEASE</spring.version>
        </properties>
    
        <dependencies>
    
            
            <dependency>
                <groupId>org.slf4j</groupId>
                <artifactId>slf4j-api</artifactId>
                <version>1.7.25</version>
            </dependency>
    
            
            <dependency>
                <groupId>org.apache.logging.log4j</groupId>
                <artifactId>log4j-slf4j-impl</artifactId>
                <version>${slf4j.log4j.version}</version>
            </dependency>
    
            
            <dependency>
                <groupId>org.apache.logging.log4j</groupId>
                <artifactId>log4j-api</artifactId>
                <version>${log4j.version}</version>
            </dependency>
            
            <dependency>
                <groupId>org.apache.logging.log4j</groupId>
                <artifactId>log4j-core</artifactId>
                <version>${log4j.version}</version>
            </dependency>
    
            
            <dependency>
                <groupId>org.apache.commons</groupId>
                <artifactId>commons-lang3</artifactId>
                <version>3.8.1</version>
            </dependency>
    
    
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.47</version>
            </dependency>
    
            
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>druid</artifactId>
                <version>1.1.10</version>
            </dependency>
    
            
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.4.6</version>
            </dependency>
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis-spring</artifactId>
                <version>1.3.2</version>
            </dependency>
    
            
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>1.16.20</version>
                <scope>provided</scope>
            </dependency>
    
            
            <dependency>
                <groupId>javax.servlet</groupId>
                <artifactId>javax.servlet-api</artifactId>
                <version>3.1.0</version>
                <scope>provided</scope>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-context</artifactId>
                <version>${spring.version}</version>
            </dependency>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-beans</artifactId>
                <version>${spring.version}</version>
            </dependency>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-webmvc</artifactId>
                <version>${spring.version}</version>
            </dependency>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-jdbc</artifactId>
                <version>${spring.version}</version>
            </dependency>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-aspects</artifactId>
                <version>${spring.version}</version>
            </dependency>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-jms</artifactId>
                <version>${spring.version}</version>
            </dependency>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-context-support</artifactId>
                <version>${spring.version}</version>
            </dependency>
    
            
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.11</version>
                <scope>test</scope>
            </dependency>
    
        </dependencies>
    
    
        
        <build>
            <resources>
                <resource>
                    <directory>src/main/java</directory>
                    <includes>
                        <include>**/*.properties</include>
                        <include>**/*.xml</include>
                    </includes>
                </resource>
            </resources>
        </build>

**2、在src/main/resources资源目录下，创建一个properties目录，并创建和编写jdbc.properties配置文件**

#============================================================================
    # 数据源01，数据库为data_source1
    #============================================================================
    jdbc.one.driver=com.mysql.jdbc.Driver
    jdbc.one.url=jdbc:mysql://localhost:3306/data_source1?rewriteBatchedStatements=true&allowMultiQueries=true&useUnicode=true&characterEncoding=utf-8&autoReconnect=true&failOverReadOnly=false&&useSSL=false
    jdbc.one.username=root
    jdbc.one.password=123456
    
    #============================================================================
    #  数据源02，数据库为data_source2
    #============================================================================
    jdbc.two.driver=com.mysql.jdbc.Driver
    jdbc.two.url=jdbc:mysql://localhost:3306/data_source2?rewriteBatchedStatements=true&allowMultiQueries=true&useUnicode=true&characterEncoding=utf-8&autoReconnect=true&failOverReadOnly=false&&useSSL=false
    jdbc.two.username=root
    jdbc.two.password=123456
    
    #============================================================================
    #  数据源03，数据库为data_source3
    #============================================================================
    jdbc.three.driver=com.mysql.jdbc.Driver
    jdbc.three.url=jdbc:mysql://localhost:3306/data_source3?rewriteBatchedStatements=true&allowMultiQueries=true&useUnicode=true&characterEncoding=utf-8&autoReconnect=true&failOverReadOnly=false&&useSSL=false
    jdbc.three.username=root
    jdbc.three.password=123456
    
    
    #============================================================================
    # 通用配置
    #============================================================================
    jdbc.common.initialSize=5
    jdbc.common.minIdle=5
    jdbc.common.maxActive=100
    jdbc.common.maxWait=100000
    jdbc.common.defaultAutoCommit=false
    jdbc.common.removeAbandoned=true
    jdbc.common.removeAbandonedTimeout=600
    jdbc.common.testWhileIdle=true
    jdbc.common.timeBetweenEvictionRunsMillis=60000
    jdbc.common.minEvictableIdleTimeMillis=300000

**3、在src/main/resources资源目录下，创建一个spring目录，并创建和编写applicationContext-spring.xml**

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.2.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.2.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.2.xsd">
    
        
        <context:component-scan base-package="com.multiple"/>
      
        
        <aop:aspectj-autoproxy />
    
        
        <context:property-placeholder location="classpath:properties/jdbc.properties" />
    
        
        <bean id="dataSourceOne" class="com.alibaba.druid.pool.DruidDataSource" destroy-method="close">
            <property name="url" value="${jdbc.one.url}" />
            <property name="username" value="${jdbc.one.username}" />
            <property name="password" value="${jdbc.one.password}" />
            <property name="driverClassName" value="${jdbc.one.driver}"/>
            <property name="initialSize" value="${jdbc.common.initialSize}"/>
            <property name="minIdle" value="${jdbc.common.minIdle}"/>
            <property name="maxActive" value="${jdbc.common.maxActive}"/>
            <property name="maxWait" value="${jdbc.common.maxWait}"/>
            <property name="defaultAutoCommit" value="${jdbc.common.defaultAutoCommit}"/>
            <property name="removeAbandoned" value="${jdbc.common.removeAbandoned}"/>
            <property name="removeAbandonedTimeout" value="${jdbc.common.removeAbandonedTimeout}"/>
            <property name="testWhileIdle" value="${jdbc.common.testWhileIdle}"/>
            <property name="timeBetweenEvictionRunsMillis" value="${jdbc.common.timeBetweenEvictionRunsMillis}"/>
            <property name="minEvictableIdleTimeMillis" value="${jdbc.common.minEvictableIdleTimeMillis}"/>
        </bean>
    
        
        <bean id="dataSourceTwo" class="com.alibaba.druid.pool.DruidDataSource" destroy-method="close">
            <property name="url" value="${jdbc.two.url}" />
            <property name="username" value="${jdbc.two.username}" />
            <property name="password" value="${jdbc.two.password}" />
            <property name="driverClassName" value="${jdbc.two.driver}"/>
            <property name="initialSize" value="${jdbc.common.initialSize}"/>
            <property name="minIdle" value="${jdbc.common.minIdle}"/>
            <property name="maxActive" value="${jdbc.common.maxActive}"/>
            <property name="maxWait" value="${jdbc.common.maxWait}"/>
            <property name="defaultAutoCommit" value="${jdbc.common.defaultAutoCommit}"/>
            <property name="removeAbandoned" value="${jdbc.common.removeAbandoned}"/>
            <property name="removeAbandonedTimeout" value="${jdbc.common.removeAbandonedTimeout}"/>
            <property name="testWhileIdle" value="${jdbc.common.testWhileIdle}"/>
            <property name="timeBetweenEvictionRunsMillis" value="${jdbc.common.timeBetweenEvictionRunsMillis}"/>
            <property name="minEvictableIdleTimeMillis" value="${jdbc.common.minEvictableIdleTimeMillis}"/>
        </bean>
    
        
        <bean id="dataSourceThree" class="com.alibaba.druid.pool.DruidDataSource" destroy-method="close">
            <property name="url" value="${jdbc.three.url}" />
            <property name="username" value="${jdbc.three.username}" />
            <property name="password" value="${jdbc.three.password}" />
            <property name="driverClassName" value="${jdbc.three.driver}"/>
            <property name="initialSize" value="${jdbc.common.initialSize}"/>
            <property name="minIdle" value="${jdbc.common.minIdle}"/>
            <property name="maxActive" value="${jdbc.common.maxActive}"/>
            <property name="maxWait" value="${jdbc.common.maxWait}"/>
            <property name="defaultAutoCommit" value="${jdbc.common.defaultAutoCommit}"/>
            <property name="removeAbandoned" value="${jdbc.common.removeAbandoned}"/>
            <property name="removeAbandonedTimeout" value="${jdbc.common.removeAbandonedTimeout}"/>
            <property name="testWhileIdle" value="${jdbc.common.testWhileIdle}"/>
            <property name="timeBetweenEvictionRunsMillis" value="${jdbc.common.timeBetweenEvictionRunsMillis}"/>
            <property name="minEvictableIdleTimeMillis" value="${jdbc.common.minEvictableIdleTimeMillis}"/>
        </bean>
    
    
        
        <bean id="multipleDataSource" class="com.multiple.pool.MultipleDataSource">
            
            <property name="defaultTargetDataSource" ref="dataSourceOne"/>
            <property name="targetDataSources">
                <map>
                    
                    <entry key="dataSourceOneKey" value-ref="dataSourceOne"/>
                    <entry key="dataSourceTwoKey" value-ref="dataSourceTwo"/>
                    <entry key="dataSourceThreeKey" value-ref="dataSourceThree"/>
                </map>
            </property>
    
        </bean>
    
    
        
        <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
            
            <property name="dataSource" ref="multipleDataSource" />
        </bean>
    
        
    
    
        
        <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
            
            <property name="dataSource" ref="multipleDataSource" />
        </bean>
    
        
        <tx:advice id="txAdvice" transaction-manager="transactionManager">
            <tx:attributes>
                
                <tx:method name="save*" propagation="REQUIRED" />
                <tx:method name="insert*" propagation="REQUIRED" />
                <tx:method name="add*" propagation="REQUIRED" />
                <tx:method name="create*" propagation="REQUIRED" />
                <tx:method name="delete*" propagation="REQUIRED" />
                <tx:method name="update*" propagation="REQUIRED" />
                <tx:method name="find*" propagation="SUPPORTS" read-only="true" />
                <tx:method name="select*" propagation="SUPPORTS" read-only="true" />
                <tx:method name="get*" propagation="SUPPORTS" read-only="true" />
            </tx:attributes>
        </tx:advice>
    
        
        <aop:config>
            <aop:advisor advice-ref="txAdvice" pointcut="execution(* com.multiple.service.*.*(..))" />
        </aop:config>
    
    </beans>

**4、在src/main/resources目录下，创建并编写一个名为log4j2.xml的日志配置文件**

<?xml version="1.0" encoding="UTF-8"?>
    
    
    
    <configuration status="WARN" monitorInterval="1800">
    
        
        <Appenders>
        
            
            <console name="Console" target="SYSTEM_OUT" follow="true">
                
                <PatternLayout charset="UTF-8" pattern="%d{yyyy-MM-dd HH:mm:ss.SSS} %-5level %class{36}.%M() line:%L - %msg%xEx%n"/>
            </console>
    
        </Appenders>
    
        
        <Loggers>
    
            
            <Root level="info">
                <appender-ref ref="Console"/>
            </Root>
    
        </Loggers>
    </configuration>

**5、创建自己的多数据源管理类 MultipleDataSource**

package com.multiple.pool;
    
    import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
    
    public class MultipleDataSource extends AbstractRoutingDataSource { 
    
        private static final ThreadLocal<String> dataSourceKey = new InheritableThreadLocal<String>();
    
        public static void setDataSourceKey(String dataSource) { 
            dataSourceKey.set(dataSource);
        }
        
        public static void clearDataSourceKey() { 
             dataSourceKey.remove();
        }
        
        @Override
        protected Object determineCurrentLookupKey() { 
            return dataSourceKey.get();
        }
    }

**    这里重点说一下`AbstractRoutingDataSource`类，这个类是实现多数据源的关键，它的作用就是动态切换数据源，实质：把项目中配置的多个数据源存储到该类的`targetDataSources`属性中 (`targetDataSources`属性 是一个Map集合，其中value为每个数据源，key则存储每个数据源的键)，然后根据我们重写该类的`determineCurrentLookupKey()`方法来获取当前数据源所对应的`key`，并通过获得的`key`来获取数据源`dataSource`，如果数据源`dataSource`为`null`，则将其设置为默认的数据源，如果当前数据源为`null`且默认数据源也为`null`则抛出异常，部分关键源码解析如下所示:**

public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean { 
    
        // 多数据源 Map集合
    	@Nullable
    	private Map<Object, Object> targetDataSources;
    
        // 默认数据源
    	@Nullable
    	private Object defaultTargetDataSource;
       
        // 默认为true
    	private boolean lenientFallback = true;
    
        // 设置多数据源
        public void setTargetDataSources(Map<Object, Object> targetDataSources) { 
    		this.targetDataSources = targetDataSources;
    	}
    	
    	// 设置默认数据源
    	public void setDefaultTargetDataSource(Object defaultTargetDataSource) { 
    		this.defaultTargetDataSource = defaultTargetDataSource;
    	}
    
        // 动态获取当前数据源
    	protected DataSource determineTargetDataSource() { 
    		Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
    		
    		// 调用我们自己实现的determineCurrentLookupKey()方法，获取当前数据源在map中所对应的lookupKey
    		Object lookupKey = determineCurrentLookupKey();
           
            // 通过获取到的lookupKey，来获取对应的数据源
    		DataSource dataSource = this.resolvedDataSources.get(lookupKey);
            
           /** * 如果当前数据源dataSource为null，并且对应的lookupKey也为null，则设置为默认数据源。 * 其实只要数据源dataSource为null，则会被设置为默认数据源。因为lenientFallback默认为true */
    		if (dataSource == null && (this.lenientFallback || lookupKey == null)) { 
    			dataSource = this.resolvedDefaultDataSource;
    		}
            
            // 如果默认数据源也为null，则抛出异常
    		if (dataSource == null) { 
    			throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");
    		}
           
            // 返回数据源
    		return dataSource;
    	}
    
        // 获取当前数据源在map中所对应的key，需要我们自己实现
    	@Nullable
    	protected abstract Object determineCurrentLookupKey();
    
    }

**6、定义多数据切换规则，并编写AOP类，这里将讲述两种方式实现动态切换数据源**

**方式一：通过注解方式 实现动态切换数据源**

1、自定义注解DataSourceChange，用于动态切换数据源

package com.multiple.annotation;
    
    import java.lang.annotation.*;
    
    @Retention(RetentionPolicy.RUNTIME)
    @Target({ ElementType.METHOD,ElementType.TYPE})
    @Documented
    public @interface DataSourceChange { 
        // 设置默认数据库为dataSourceOneKey
        String dataSource() default "dataSourceOneKey";
    }

对上面的代码的注解进行如下解释：

*  `@Retention`：指定当前注解保留到运行时；
 *  `@Target`：指定当前自定义注解可以使用在哪些地方，这里仅仅让它使用在方法上和类、接口(包括注解类型) 或enum枚举的声明上；
 *  `@Documented`：表示该注解是否可以生成到 API文档中；

2、编写AOP类，根据注解中指定的数据源Key，切换不同的数据库

package com.multiple.aspect;
    
    import com.multiple.annotation.DataSourceChange;
    import com.multiple.pool.MultipleDataSource;
    import org.apache.commons.lang3.StringUtils;
    import org.aspectj.lang.JoinPoint;
    import org.aspectj.lang.Signature;
    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.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.core.annotation.Order;
    import org.springframework.stereotype.Component;
    
    import java.lang.reflect.Method;
    
    
    @Component
    @Aspect
    @Order(1)
    public class MultipleDataSourceAspectAdvice { 
    
        private static final Logger logger = LoggerFactory.getLogger(MultipleDataSourceAspectAdvice.class);
    
        /** * 定义切面 */
        @Pointcut("execution(* com.multiple.service.*.*(..))")
        public void pointCut() { 
        }
    
        
        /** * 设置数据源 **/
        @Before("pointCut()")
        public void dataSourceChange(JoinPoint joinPoint) throws NoSuchMethodException { 
    
            // 获取当前目标的方法签名
            Signature signature = joinPoint.getSignature();
            MethodSignature methodSignature = (MethodSignature)signature;
            // 通过方法签名 获取方法对象（该方法对象为代理方法对象）
            Method method = methodSignature.getMethod();
    
            DataSourceChange data = null;
            // 数据源Key
            String dataSource;
            Method realMethod = null;
    
    
            if(method != null){ 
    
                // 获取真正的目标方法对象
                realMethod = joinPoint.getTarget().getClass().getDeclaredMethod(signature.getName(), method.getParameterTypes());
                data = realMethod.getAnnotation(DataSourceChange.class);
    
                if (data !=null){ 
                    // 获得数据源key
                    dataSource = data.dataSource();
    
                    if (StringUtils.isNotBlank(dataSource)){ 
                        logger.info("使用的数据源key为："+dataSource);
                        MultipleDataSource.setDataSourceKey(dataSource);
                    }
                }
            }
        }
    
        
        /** * 清除数据源 **/
        @After("pointCut()")
        public void dataSourceClear(JoinPoint joinPoint) { 
    
            MultipleDataSource.clearDataSourceKey();
        }
    }

对上面的代码的注解进行如下解释：

*  `@Component`：表明一个类会作为组件类，并告知Spring要为这个类创建bean；
 *  `@Aspect`：把当前类标识为一个切面；
 *  `@Order(1)`：定义Spring IOC容器中Bean的执行顺序的优先级，`而不是定义Bean的加载顺序`，数值越小优先级越高，优先级设置到最高，`是因为在所有service方法调用dao前都必须把数据源确定好`；

踩坑环节：  
  使用aop代理通过 Method类的 `public <T extends Annotation> T getAnnotation(Class<T> annotationClass)`方法获取到的Annotation注解对象为null问题，问题代码如下所示：

// 获取当前目标的方法签名
    Signature signature = joinPoint.getSignature();
    MethodSignature methodSignature = (MethodSignature)signature;
    // 通过方法签名 获取方法对象（该方法对象为代理方法对象）
    Method method = methodSignature.getMethod();
    //此处method是代理对象（由代理模式生成的），结果为null
    DataSourceChange  data = method.getAnnotation(DataSourceChange.class);

有人就会说了，为什么获取的注解对象会为null呢？其实这是代理对象和目标对象的问题，因为通过代理模式生成的代理方法对象上是不会有注解的，这就导致我们通过代理方法对象获取注解对象为null的问题。

那该怎么获取注解对象呢？其实也很简单，通过反射获取到目标对象，而目标对象上是有我们添加的注解，解决方案代码如下所示：

// 获取当前目标的方法签名
    Signature signature = joinPoint.getSignature();
    MethodSignature methodSignature = (MethodSignature)signature;
    // 通过方法签名 获取方法对象（该方法对象为代理对象）
    Method method = methodSignature.getMethod();
    
    // 通过反射获取真正的方法目标对象
    Method realMethod = joinPoint.getTarget().getClass().getDeclaredMethod(signature.getName(), method.getParameterTypes());
    // 结果不为null
    DataSourceChange data = realMethod.getAnnotation(DataSourceChange.class);

3、创建Service接口—UserService

package com.multiple.service;
    
    public interface UserService { 
        String getUserMessageOne();
        
        String getUserMessageTwo();
    
        String getUserMessageThree();
    }

4、创建Service实现类—UserServiceImpl，为了方便，这里就不再给出dao层

package com.multiple.service.impl;
    
    import com.multiple.annotation.DataSourceChange;
    import com.multiple.service.UserService;
    import org.springframework.stereotype.Service;
    
    
    @Service
    public class UserServiceImpl implements UserService { 
    
         /** * 通过自定义注解@DataSourceChange，使用默认数据源dataSourceOne **/
        @DataSourceChange
        public String getUserMessageOne() { 
    
            return "通过数据源dataSourceOne，获取用户名为张三的用户信息";
        }
    
        /** * 通过自定义注解@DataSourceChange，指定使用数据源dataSourceTwo **/
        @DataSourceChange(dataSource = "dataSourceTwoKey")
        public String getUserMessageTwo() { 
    
            return "通过数据源dataSourceTwo，获取用户名为李四的用户信息";
        }
        
        /** * 通过自定义注解@DataSourceChange，指定使用数据源dataSourceThree **/
        @DataSourceChange(dataSource = "dataSourceThreeKey")
        public String getUserMessageThree() { 
    
            return "通过数据源dataSourceThree，获取用户名为王五的用户信息";
        }
    }

5、编写执行类—MainApplication

package com.multiple;
    
    import com.multiple.service.UserService;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    public class MainApplication { 
    
        public static void main(String[] args) { 
    
            ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("spring/applicationController-spring.xml");
            UserService userService = (UserService) context.getBean("userServiceImpl");
            
            // 使用默认数据源dataSourceOne
            String userMessageOne = userService.getUserMessageOne();
            System.out.println(userMessageOne);
    
            // 使用了数据源dataSourceTwo
            String userMessageTwo = userService.getUserMessageTwo();
            System.out.println(userMessageTwo);
    
            //使用了数据源dataSourceThree
            String userMessageThree = userService.getUserMessageThree();
            System.out.println(userMessageThree);
        }
    
    }

执行结果如下所示：

2019-09-21 16:19:47.001 INFO  com.multiple.aspect.MultipleDataSourceAspectAdvice.dataSourceChange() line:70 - 使用的数据源key为：dataSourceOneKey
    通过数据源dataSourceOne，获取用户名为张三的用户信息
    
    2019-09-21 16:19:47.016 INFO  com.multiple.aspect.MultipleDataSourceAspectAdvice.dataSourceChange() line:70 - 使用的数据源key为：dataSourceTwoKey
    通过数据源dataSourceTwo，获取用户名为李四的用户信息
    
    2019-09-21 16:19:47.031 INFO  com.multiple.aspect.MultipleDataSourceAspectAdvice.dataSourceChange() line:70 - 使用的数据源key为：dataSourceThreeKey
    通过数据源dataSourceThree，获取用户名为王五的用户信息

**方式二：通过接口方式 实现动态切换数据源**

1、创建三个接口，分别代表不同的数据源

package com.multiple.source;
    
    // 表示使用数据源 dataSourceOne
    public interface DataSourceOne { 
    
    }

package com.multiple.source;
    
    // 表示使用数据源 dataSourceTwo
    public interface DataSourceTwo { 
    
    }

package com.multiple.source;
    
    // 表示使用数据源 dataSourceThree
    public interface DataSourceThree { 
    
    }

2、编写AOP类，根据其实现接口的不同，指定不同的数据源Key，切换不同的数据库

package com.multiple.aspect;
    
    import com.multiple.pool.MultipleDataSource;
    import com.multiple.source.DataSourceOne;
    import com.multiple.source.DataSourceThree;
    import com.multiple.source.DataSourceTwo;
    import org.aspectj.lang.JoinPoint;
    import org.aspectj.lang.annotation.Aspect;
    import org.aspectj.lang.annotation.Before;
    import org.aspectj.lang.annotation.Pointcut;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.core.annotation.Order;
    import org.springframework.stereotype.Component;
    
    
    @Component
    @Aspect
    @Order(1)
    public class MultipleDataSourceAspectAdvice { 
    
        private static final Logger logger = LoggerFactory.getLogger(MultipleDataSourceAspectAdvice.class);
    
        /** * 定义切面 */
        @Pointcut("execution(* com.multiple.service.*.*(..))")
        public void pointCut() { 
        }
    
    
        @Before("pointCut()")
        public void dataSourceChange(JoinPoint joinPoint) { 
    
            if (joinPoint.getTarget() instanceof DataSourceOne) { 
                logger.info("使用数据源：DataSourceOne");
                MultipleDataSource.setDataSourceKey("dataSourceOneKey");
                
            } else if (joinPoint.getTarget() instanceof DataSourceTwo) { 
                logger.info("使用数据源：DataSourceTwo");
                MultipleDataSource.setDataSourceKey("dataSourceTwoKey");
                
            } else if (joinPoint.getTarget() instanceof DataSourceThree) { 
                logger.info("使用数据源：DataSourceThree");
                MultipleDataSource.setDataSourceKey("dataSourceThreeKey");
                
            } else { 
                logger.info("默认使用数据源：dataSourceOneKey");
                MultipleDataSource.setDataSourceKey("dataSourceOneKey");
            }
        }
    }

3、创建Service接口—UserService

package com.multiple.service;
    
    public interface UserService { 
        
        String getUserMessage();  
    }

4、创建Service实现类—UserServiceImpl，并实现DatasourceOne接口

package com.multiple.service.impl;
    
    import com.multiple.service.UserService;
    import com.multiple.source.DataSourceOne;
    import org.springframework.stereotype.Service;
    
    
    @Service
    public class UserServiceImpl implements UserService, DataSourceOne { 
        
        public String getUserMessage() { 
        
            return "获取用户名为张三的用户信息";
        }
    }

5、编写执行类—MainApplication

执行结果如下所示：

2019-09-21 16:46:25.192 INFO  com.multiple.aspect.MultipleDataSourceAspectAdvice.dataSourceChange() line:45 - 使用数据源：DataSourceOne
    获取用户名为张三的用户信息

如果需要更换数据源，只需要把UserServiceImpl实现的DatasourceOne接口，更改为其他接口即可实现数据源的切换。

## 三、SpringBoot实现多数据源配置 ##

**1、在pom.xml文件中添加所需依赖**

<properties>
            <druid.version>1.1.10</druid.version>
        </properties>
    
        <dependencies>
           
           
           <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
    
                
                <exclusions>
                    <exclusion>
                        <groupId>org.springframework.boot</groupId>
                        <artifactId>spring-boot-starter-logging</artifactId>
                    </exclusion>
                </exclusions>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-log4j2</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>com.lmax</groupId>
                <artifactId>disruptor</artifactId>
                <version>3.4.2</version>
            </dependency>
    
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <scope>runtime</scope>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-jdbc</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>druid</artifactId>
                <version>${druid.version}</version>
            </dependency>
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>druid-spring-boot-starter</artifactId>
                <version>${druid.version}</version>
            </dependency>
    
            
            <dependency>
                <groupId>org.mybatis.spring.boot</groupId>
                <artifactId>mybatis-spring-boot-starter</artifactId>
                <version>2.1.0</version>
            </dependency>
    
            
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <optional>true</optional>
            </dependency>
    
            
            <dependency>
                <groupId>org.apache.commons</groupId>
                <artifactId>commons-lang3</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-configuration-processor</artifactId>
                <optional>true</optional>
            </dependency>
    
            
            <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>
        </dependencies>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
    
            <resources>
                <resource>
                    <directory>src/main/java</directory>
                    <includes>
                        <include>**/*.properties</include>
                        <include>**/*.xml</include>
                    </includes>
                </resource>
            </resources>
        </build>

**2、在src/main/resources资源目录下，编写application.properties配置文件**

#============================================================================
    # 数据源dataSourcePrimary，数据库为data_source1
    #============================================================================
    spring.datasource.primary.driverClassName=com.mysql.jdbc.Driver
    spring.datasource.primary.username=root
    spring.datasource.primary.password=vms123
    spring.datasource.primary.url=jdbc:mysql://localhost:3316/data_source1?rewriteBatchedStatements=true&allowMultiQueries=true&useUnicode=true&characterEncoding=utf-8&autoReconnect=true&failOverReadOnly=false&&useSSL=false
    spring.datasource.primary.type=com.alibaba.druid.pool.DruidDataSource
    
    spring.datasource.primary.initialSize=5
    spring.datasource.primary.minIdle=5
    spring.datasource.primary.maxActive=100
    spring.datasource.primary.maxWait=100000
    spring.datasource.primary.defaultAutoCommit=false
    spring.datasource.primary.removeAbandoned=true
    spring.datasource.primary.removeAbandonedTimeoutMillis=600
    spring.datasource.primary.testWhileIdle=true
    spring.datasource.primary.timeBetweenEvictionRunsMillis=60000
    spring.datasource.primary.minEvictableIdleTimeMillis=300000
    
    #============================================================================
    #  数据源dataSourceLocal，数据库为data_source2
    #============================================================================
    spring.datasource.local.driverClassName=com.mysql.jdbc.Driver
    spring.datasource.local.username=root
    spring.datasource.local.password=vms123
    spring.datasource.local.url=jdbc:mysql://localhost:3316/data_source2?rewriteBatchedStatements=true&allowMultiQueries=true&useUnicode=true&characterEncoding=utf-8&autoReconnect=true&failOverReadOnly=false&&useSSL=false
    spring.datasource.local.type=com.alibaba.druid.pool.DruidDataSource
    
    spring.datasource.local.initialSize=5
    spring.datasource.local.minIdle=5
    spring.datasource.local.maxActive=100
    spring.datasource.local.maxWait=100000
    spring.datasource.local.defaultAutoCommit=false
    spring.datasource.local.removeAbandoned=true
    spring.datasource.local.removeAbandonedTimeoutMillis=600
    spring.datasource.local.testWhileIdle=true
    spring.datasource.local.timeBetweenEvictionRunsMillis=60000
    spring.datasource.local.minEvictableIdleTimeMillis=300000
    
    #============================================================================
    #  数据源dataSourceProduce，数据库为data_source3
    #============================================================================
    spring.datasource.produce.driverClassName=com.mysql.jdbc.Driver
    spring.datasource.produce.username=root
    spring.datasource.produce.password=vms123
    spring.datasource.produce.url=jdbc:mysql://localhost:3316/data_source3?rewriteBatchedStatements=true&allowMultiQueries=true&useUnicode=true&characterEncoding=utf-8&autoReconnect=true&failOverReadOnly=false&&useSSL=false
    spring.datasource.produce.type=com.alibaba.druid.pool.DruidDataSource
    
    spring.datasource.produce.initialSize=5
    spring.datasource.produce.minIdle=5
    spring.datasource.produce.maxActive=100
    spring.datasource.produce.maxWait=100000
    spring.datasource.produce.defaultAutoCommit=false
    spring.datasource.produce.removeAbandoned=true
    spring.datasource.produce.removeAbandonedTimeoutMillis=600
    spring.datasource.produce.testWhileIdle=true
    spring.datasource.produce.timeBetweenEvictionRunsMillis=60000
    spring.datasource.produce.minEvictableIdleTimeMillis=300000
    
    #指定mapper.xml文件的所在路径
    mybatis.mapper-locations=chasspath*:com/multiple/mapper/*.xml

**3、在src/main/resources目录下，创建并编写一个名为log4j2.xml的日志配置文件**

**4、创建配置类MutiplyDataSource**

package com.multiple.config;
    
    import com.alibaba.druid.pool.DruidDataSource;
    import com.multiple.pool.DynamicDataSource;
    import org.springframework.boot.context.properties.ConfigurationProperties;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.context.annotation.Primary;
    import org.springframework.jdbc.datasource.DataSourceTransactionManager;
    import org.springframework.transaction.PlatformTransactionManager;
    
    import javax.sql.DataSource;
    import java.util.HashMap;
    
    
    @Configuration
    public class MutiplyDataSource { 
    
        /** * @ConfigurationProperties: 将配置文件的值映射到bean上，需要保证prefix属性指定前缀后面的属性字段名称， * 要与映射到bean上的属性字段名称一一对应 **/
        @Bean(name = "dataSourcePrimary")
        @ConfigurationProperties(prefix = "spring.datasource.primary")
        public DataSource primaryDataSource(){ 
              return new DruidDataSource();
        }
    
        @Bean(name = "dataSourceLocal")
        @ConfigurationProperties(prefix = "spring.datasource.local")
        public DataSource localDataSource(){ 
            return new DruidDataSource();
        }
    
        @Bean(name = "dataSourceProduce")
        @ConfigurationProperties(prefix = "spring.datasource.produce")
        public DataSource produceDataSource(){ 
            return new DruidDataSource();
        }
    
        /** * @Primary: 该注解表示在同一个接口有多个实现类可以注入的时候，优先选择使用@Primary注解的bean， * 避免@autowire注解自动装配时的歧义性而导致报错 **/
        @Primary
        @Bean(name = "dynamicDataSource")
        public DataSource dynamicDataSource(){ 
    
            DynamicDataSource dynamicDataSource = new DynamicDataSource();
    
            // 配置默认数据源为 dataSourcePrimary
            dynamicDataSource.setDefaultTargetDataSource(primaryDataSource());
    
            // 配置多数据源
            HashMap<Object,Object> dataSourceMap = new HashMap<>(3);
            dataSourceMap.put("primary",primaryDataSource());
            dataSourceMap.put("local",localDataSource());
            dataSourceMap.put("produce",produceDataSource());
            dynamicDataSource.setTargetDataSources(dataSourceMap);
    
            return dynamicDataSource;
        }
    
        /** * 配置@Transactional注解事务 **/
        @Bean
        public PlatformTransactionManager transactionManager(){ 
            return new DataSourceTransactionManager(dynamicDataSource());
        }
    
    }

**5、创建自己的多数据源管理类 DynamicDataSource**

package com.multiple.pool;
    
    import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
    
    
    public class DynamicDataSource extends AbstractRoutingDataSource { 
    
        private static final ThreadLocal<String> dataSourceKey = new InheritableThreadLocal<String>();
    
        public static void setDataSourceKey(String dataSource) { 
            dataSourceKey.set(dataSource);
        }
    
        public static void clearDataSourceKey() { 
             dataSourceKey.remove();
        }
    
        @Override
        protected Object determineCurrentLookupKey() { 
            return dataSourceKey.get();
        }
    }

**6、定义多数据切换规则，并编写AOP类，这里只演示通过注解方式 实现动态切换数据源**

1、自定义注解DataSourceChange，用于动态切换数据源

package com.multiple.annotation;
    
    import java.lang.annotation.*;
    
    
    @Retention(RetentionPolicy.RUNTIME)
    @Target({ ElementType.METHOD,ElementType.TYPE})
    @Documented
    public @interface DataSourceChange { 
    
        String dataSource() default "primary";
    }

2、编写AOP类，根据注解中指定的数据源Key，切换不同的数据库

package com.multiple.aspect;
    
    import com.multiple.annotation.DataSourceChange;
    import com.multiple.pool.DynamicDataSource;
    import org.apache.commons.lang3.StringUtils;
    import org.aspectj.lang.JoinPoint;
    import org.aspectj.lang.Signature;
    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.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.core.annotation.Order;
    import org.springframework.stereotype.Component;
    
    import java.lang.reflect.Method;
    
    
    @Component
    @Aspect
    @Order(1)
    public class MultipleDataSourceAspectAdvice { 
    
        private static final Logger logger = LoggerFactory.getLogger(MultipleDataSourceAspectAdvice.class);
    
        /** * 定义切面 */
        @Pointcut("execution(* com.multiple.service.*.*(..))")
        public void pointCut() { 
        }
    
    
        /** * 设置数据源 **/
        @Before("pointCut()")
        public void dataSourceChange(JoinPoint joinPoint) throws Throwable { 
    
            // 获取当前目标的方法签名
            Signature signature = joinPoint.getSignature();
            MethodSignature methodSignature = (MethodSignature) signature;
            // 通过方法签名 获取方法对象（该方法对象为代理对象）
            Method method = methodSignature.getMethod();
    
            DataSourceChange data = null;
            // 数据源Key
            String dataSource;
            Method realMethod = null;
    
    
            if (method != null) { 
    
                // 获取真正的方法目标对象
                realMethod = joinPoint.getTarget().getClass().getDeclaredMethod(signature.getName(), method.getParameterTypes());
                data = realMethod.getAnnotation(DataSourceChange.class);
    
                if (data != null) { 
                    // 获得数据源key
                    dataSource = data.dataSource();
    
                    if (StringUtils.isNotBlank(dataSource)) { 
                        logger.info("使用的数据源key为：" + dataSource);
                        DynamicDataSource.setDataSourceKey(dataSource);
                    }
                }
            }
    
        }
    
    
        /** * 清除数据源 **/
        @After("pointCut()")
        public void dataSourceClear(JoinPoint joinPoint) { 
    
            DynamicDataSource.clearDataSourceKey();
        }
    
    }

3、创建Service接口—UserService

package com.multiple.service;
    
    public interface UserService { 
    
        String getUserMessagePrimary();
    
        String getUserMessageLocal();
    
        String getUserMessageProduce(); 
    }

4、创建Service实现类—UserServiceImpl，为了方便，这里就不再给出dao层

package com.multiple.service.impl;
    
    import com.multiple.annotation.DataSourceChange;
    import com.multiple.service.UserService;
    import org.springframework.stereotype.Service;
    import org.springframework.transaction.annotation.Transactional;
    
    
    @Service
    public class UserServiceImpl implements UserService{ 
    
        /** * 通过自定义注解@DataSourceChange，使用默认数据源primary **/
        @Override
        @Transactional(rollbackFor = Exception.class)
        @DataSourceChange
        public String getUserMessagePrimary() { 
    
            return "通过数据源primary，获取用户名为张三的用户信息";
        }
    
        /** * 通过自定义注解@DataSourceChange，使用数据源local **/
        @Override
        @Transactional(rollbackFor = Exception.class)
        @DataSourceChange(dataSource = "local")
        public String getUserMessageLocal() { 
    
            return "通过数据源local，获取用户名为李四的用户信息";
        }
    
        /** * 通过自定义注解@DataSourceChange，使用数据源produce **/
        @Override
        @Transactional(rollbackFor = Exception.class)
        @DataSourceChange(dataSource = "produce")
        public String getUserMessageProduce() { 
    
            return "通过数据源produce，获取用户名为王五的用户信息";
        }
    }

5、创建UserController

package com.multiple.controller;
    
    import com.multiple.service.UserService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.ResponseBody;
    
    
    @Controller
    public class UserController { 
    
        @Autowired
        private UserService userService;
    
        @RequestMapping("/primary")
        @ResponseBody
        public String primary() { 
    
            String messagePrimary = userService.getUserMessagePrimary();
            return messagePrimary;
        }
    
        @RequestMapping("/local")
        @ResponseBody
        public String local() { 
            String messageLocal = userService.getUserMessageLocal();
            return messageLocal;
        }
    
        @RequestMapping("/produce")
        @ResponseBody
        public String produce() { 
            String messageProduce = userService.getUserMessageProduce();
            return messageProduce;
        }
    }

6、编写SpringMdsourceApplication启动类

package com.multiple;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
    
    /** * 排除ataSourceAutoConfiguration自动配置类,否则会默认自动配置,不会使用我们自定义的DataSource **/
    @SpringBootApplication(exclude = DataSourceAutoConfiguration.class)
    public class SpringMdsourceApplication { 
    
        public static void main(String[] args) { 
            SpringApplication.run(SpringMdsourceApplication.class, args);
        }
    
    }