springboot学习(五)：MyBatis动态数据源配置

冷不防 2022-05-14 12:49 486阅读 0赞

# 说明 #

通过上篇博文[《MyBatis多数据源配置》][MyBatis]，学习了MyBatis多数据源的配置。在实际环境中，数据库一般配置为主从结构的形式，甚至是一主多从的形式，这时，我们希望读操作都在从数据库中进行，增删改操作都在主数据库中进行，希望mybatis能够动态地选择数据库。通过本篇博文，学习记录下通过注解+AOP和只使用AOP两种方式实现动态数据源配置。文中使用主机的mysql作为主数据库，虚机中的mysql作为从数据库。

# 正文 #

## 1.通过spirngboot构建项目 ##

主要依赖 mybatis+mysql+aspect

<dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>1.3.2</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjweaver</artifactId>
        <version>1.8.7</version>
    </dependency>

## 2.在application.properties配置数据库 ##

#主库
    datasource.master.driverClassName=com.mysql.jdbc.Driver
    datasource.master.url=jdbc:mysql://ip:3306/dbname?characterEncoding=UTF-8
    datasource.master.username=**
    datasource.master.password=**
    
    #从库
    datasource.slave.driverClassName=com.mysql.jdbc.Driver
    datasource.slave.url=jdbc:mysql://ip:3306/dbname?characterEncoding=UTF-8
    datasource.slave.username=**
    datasource.slave.password=**

## 3.在启动类关闭自动配置数据源 ##

这个很重要，如果没有关闭，在启动程序时会发生循环依赖的错误

@EnableAutoConfiguration(exclude = {DataSourceAutoConfiguration.class})
    @SpringBootApplication
    public class DynamicDatasourceAnnoApplication { 
    
        public static void main(String[] args) {
            SpringApplication.run(DynamicDatasourceAnnoApplication.class, args);
        }
    }

## 4.配置数据源 ##

要实现数据源的动态选择，AbstractRoutingDataSource这个抽象类很重要，通过阅读源码，发现数据源在该类中以key-value的形式存储在map中，其中在determineTargetDataSource()方法中，通过determineCurrentLookupKey()方法得到key，在map中寻找需要的数据源，而determineCurrentLookupKey()是抽象方法，我们可以通过继承这个抽象类实现该方法，配置我们期望的数据源。

public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {

protected DataSource determineTargetDataSource() {
            Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
            Object lookupKey = this.determineCurrentLookupKey();
            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;
            }
    }

protected abstract Object determineCurrentLookupKey();

在了解了基本原理后，开始配置数据源，继承AbstractRoutingDataSource 类

### DynamicDataSource ###

public class DynamicDataSource extends AbstractRoutingDataSource { 
        @Override
        protected Object determineCurrentLookupKey() {
            return DynamicDataSourceHolder.getType();
        }
    }

实现了该方法后，如何返回一个key，这个key从何而来？  
每个请求都是一个线程，我们可以再创建一个类，其中使用ThreadLocal线程局部变量保存每个线程所请求方法对应的key，通过该类的静态方法返回该请求的key

### DynamicDataSourceHolder ###

public class DynamicDataSourceHolder {
        private static final ThreadLocal<DataSourceType> dataSourceHolder = new ThreadLocal<>();
    
        private static final Set<DataSourceType> dataSourceTypes = new HashSet<>();
        static {
            dataSourceTypes.add(DataSourceType.MASTER);
            dataSourceTypes.add(DataSourceType.SLAVE);
        }
    
        public static void setType(DataSourceType dataSourceType){
            if(dataSourceType == null){
                throw new NullPointerException();
            }
            dataSourceHolder.set(dataSourceType);
        }
    
        public static DataSourceType getType(){
            return dataSourceHolder.get();
        }
    
        public static void clearType(){
            dataSourceHolder.remove();
        }
    
        public static boolean containsType(DataSourceType dataSourceType){
            return dataSourceTypes.contains(dataSourceType);
        }
    }

其中使用了枚举表示不同类型的数据源

### DataSourceType ###

public enum DataSourceType {
        MASTER,
        SLAVE,
    }

创建了关键类DynamicDataSource后，开始配置数据源

### DynamicDataSourceConfig ###

@Configuration
    public class DynamicDataSourceConfig { 
    
        @Bean(name = "masterDataSource")
        @ConfigurationProperties(prefix = "datasource.master")
        public DataSource masterDataSource(){
            return DataSourceBuilder.create().build();
        }
    
        @Bean(name = "slaveDataSource")
        @ConfigurationProperties(prefix = "datasource.slave")
        public DataSource slaveDataSource(){
            return DataSourceBuilder.create().build();
        }
    
        @Bean(name = "dynamicDataSource")
        @Primary
        public DataSource dynamicDataSource(@Qualifier(value = "masterDataSource") DataSource masterDataSource,
                                            @Qualifier(value = "slaveDataSource") DataSource slaveDataSource){
            DynamicDataSource dynamicDataSource = new DynamicDataSource();
            dynamicDataSource.setDefaultTargetDataSource(masterDataSource);
            Map<Object,Object> dataSourceMap = new HashMap<>();
            dataSourceMap.put(DataSourceType.MASTER,masterDataSource);
            dataSourceMap.put(DataSourceType.SLAVE,slaveDataSource);
            dynamicDataSource.setTargetDataSources(dataSourceMap);
            return dynamicDataSource;
        }
    
    }

配置好数据源后，开始配置mybatis

### MyBatisConfig ###

@Configuration
    @MapperScan(basePackages = "com.example.dynamic_datasource_anno.db.dao")
    public class MyBatisConfig { 
    
        @Autowired
        private DataSource dataSource;
    
        @Bean(name = "sqlSessionFactory")
        public SqlSessionFactory sqlSessionFactory() throws Exception {
            SqlSessionFactoryBean sessionFactoryBean = new SqlSessionFactoryBean();
            sessionFactoryBean.setDataSource(dataSource);
            sessionFactoryBean.setTypeAliasesPackage("com.example.dynamic_datasource_anno.db.pojo");
            Resource[] resources = new PathMatchingResourcePatternResolver()
                    .getResources("classpath:com/example/dynamic_datasource_anno/db/mapper/*Mapper.xml");
            sessionFactoryBean.setMapperLocations(resources);
    
            return sessionFactoryBean.getObject();
        }
    
    }

数据源和mybatis配置好后，开始配置切面，动态地选择都在此类中完成。

### 第一种 Anno+Aspect ###

创建注解DBType,默认为主数据库

@Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.METHOD)
    public @interface DBType {
        DataSourceType value() default DataSourceType.MASTER;
    }

切面DynamicDataSourceAspect

@Aspect
    @Component
    public class DynamicDataSourceAspect {
    
        private static final Logger logger = LoggerFactory.getLogger(DynamicDataSourceAspect.class);
    
        @Before("@annotation(dbType)")
        public void changeDataSourceType(JoinPoint joinPoint, DBType dbType){
            DataSourceType curType = dbType.value();
            if(!DynamicDataSourceHolder.containsType(curType)){
                logger.info("指定数据源[{}]不存在，使用默认数据源-> {}",dbType.value(),joinPoint.getSignature());
            }else{
                logger.info("use datasource {} -> {}",dbType.value(),joinPoint.getSignature());
                DynamicDataSourceHolder.setType(dbType.value());
            }
    
        }
    
        @After("@annotation(dbType)")
        public void restoreDataSource(JoinPoint joinPoint, DBType dbType){
            logger.info("use datasource {} -> {}",dbType.value(),joinPoint.getSignature());
            DynamicDataSourceHolder.clearType();
        }
    
    }

配置好切面后，可以在Mapper接口的方法上使用@DBType指定要使用的数据源，使用自动代码生成插件将表中数据生成对应的实体类，mapper文件，mapper接口，关于插件的使用，请看之前的博文[《使用c3p0连接池集成mybatis及mybatis自动代码生成插件》][c3p0_mybatis_mybatis]。  
此处，我在service层使用注解

@DBType(DataSourceType.SLAVE)
     public void select(){
          User user = userMapper.selectByPrimaryKey(1);
          System.out.println(user.getId() + "--" + user.getName() + "==" + user.getGender());
     }
    
     @DBType(DataSourceType.MASTER)
     public void insert(User user){
          userMapper.insertSelective(user);
     }

### 第二种 只使用Aspect，判断sql类型 ###

在此方式中，没有再使用枚举、注解，数据源和mybatis的配置与之前相似，不再赘述，详细配置可以查看此方式的源码。主要不同在于切面的配置，此配置中通过切点判断请求的SqlCommandType来选择数据源  
DynamicDataSourceAspect

@Aspect
    @Component
    public class DynamicDataSourceAspect { 
    
        private static final Logger logger = LoggerFactory.getLogger(DynamicDataSourceAspect.class);
        @Autowired
        @Qualifier("sqlSessionFactory")
        private SqlSessionFactory sqlSessionFactory;
    
        // first * any return value
        // second * any class name of the dao package
        // third * any method name of the class
        // (..) any number of parameters
        // @Pointcut("within(com.example.dynamic_datasource_method.db.dao..*)")
        @Pointcut("execution(* com.example.dynamic_datasource_method.db.dao.*.*(..))")
        public void declareJoinPoint(){
        }
    
        @Before("declareJoinPoint()")
        public void matchDataSoruce(JoinPoint point){
    
            //得到被代理对象
            Object target = point.getTarget();
            //目标方法名
            String methodName = point.getSignature().getName();
    
            Class<?>[] interfaces = target.getClass().getInterfaces();
            Class<?>[] parametersTypes = ((MethodSignature)point.getSignature()).getMethod().getParameterTypes();
    
            try {
                Method method = interfaces[0].getMethod(methodName,parametersTypes);
                String key = interfaces[0].getName() + "." + method.getName();
                //sql 的类型
                SqlCommandType type = sqlSessionFactory.getConfiguration().getMappedStatement(key).getSqlCommandType();
                //查询从库 增删改主库
                if(type == SqlCommandType.SELECT){
                    logger.info("use slaveDataSource");
                    DynamicDataSourceHolder.setType("slave");
                }
                if(type == SqlCommandType.DELETE || type == SqlCommandType.UPDATE || type == SqlCommandType.INSERT){
                    logger.info("use masterDataSource");
                    DynamicDataSourceHolder.setType("master");
                }
            } catch (NoSuchMethodException e) {
                e.printStackTrace();
            }
        }
    
        @After("declareJoinPoint()")
        public void restoreDataSource(JoinPoint joinPoint){
            logger.info(DynamicDataSourceHolder.getType() + " change to master" + joinPoint.getSignature());
            DynamicDataSourceHolder.clearType();
        }
    }

通过此方式，可以直接调用mapper接口的方法而不需要注解直接动态地选择数据源

## 问题 ##

当在启动类没有关闭数据源的自动配置时，启动项目会报以下错误：

Description:
    
    The dependencies of some of the beans in the application context form a cycle:
    
       dynamicDataSourceAspect (field private org.apache.ibatis.session.SqlSessionFactory com.example.dynamic_datasource_method.config.mybatis.DynamicDataSourceAspect.sqlSessionFactory)
          ↓
       myBatisConfig (field private javax.sql.DataSource com.example.dynamic_datasource_method.config.mybatis.MyBatisConfig.dataSource)
    ┌─────┐
    |  dynamicDataSource defined in class path resource [com/example/dynamic_datasource_method/config/mybatis/DynamicDataSourceConfig.class]
    ↑     ↓
    |  masterDataSource defined in class path resource [com/example/dynamic_datasource_method/config/mybatis/DynamicDataSourceConfig.class]
    ↑     ↓
    |  dataSourceInitializer
    └─────┘
    
    
    2018-09-08 10:04:09.537 ERROR 20372 --- [ main] o.s.test.context.TestContextManager : Caught exception while allowing TestExecutionListener [org.springframework.test.context.web.ServletTestExecutionListener@68ceda24] to prepare test instance [com.example.dynamic_datasource_method.DynamicDatasourceMethodApplicationTests@65ae095c]
    
    java.lang.IllegalStateException: Failed to load ApplicationContext
        at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:124) ~[spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.test.context.support.DefaultTestContext.getApplicationContext(DefaultTestContext.java:83) ~[spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.test.context.web.ServletTestExecutionListener.setUpRequestContextIfNecessary(ServletTestExecutionListener.java:189) ~[spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.test.context.web.ServletTestExecutionListener.prepareTestInstance(ServletTestExecutionListener.java:131) ~[spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:230) ~[spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:228) [spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:287) [spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) [junit-4.12.jar:4.12]
        at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:289) [spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:247) [spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94) [spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) [junit-4.12.jar:4.12]
        at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) [junit-4.12.jar:4.12]
        at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) [junit-4.12.jar:4.12]
        at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) [junit-4.12.jar:4.12]
        at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) [junit-4.12.jar:4.12]
        at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61) [spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70) [spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.junit.runners.ParentRunner.run(ParentRunner.java:363) [junit-4.12.jar:4.12]
        at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191) [spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.junit.runner.JUnitCore.run(JUnitCore.java:137) [junit-4.12.jar:4.12]
        at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68) [junit-rt.jar:na]
        at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47) [junit-rt.jar:na]
        at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242) [junit-rt.jar:na]
        at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70) [junit-rt.jar:na]
    Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'dynamicDataSourceAspect': Unsatisfied dependency expressed through field 'sqlSessionFactory'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'myBatisConfig': Unsatisfied dependency expressed through field 'dataSource'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'dynamicDataSource' defined in class path resource [com/example/dynamic_datasource_method/config/mybatis/DynamicDataSourceConfig.class]: Unsatisfied dependency expressed through method 'dynamicDataSource' parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'masterDataSource' defined in class path resource [com/example/dynamic_datasource_method/config/mybatis/DynamicDataSourceConfig.class]: Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSourceInitializer': Invocation of init method failed; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'dynamicDataSource': Requested bean is currently in creation: Is there an unresolvable circular reference?
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:588) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:366) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1272) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:312) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:308) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) ~[spring-boot-1.5.16.BUILD-20180902.070551-14.jar:1.5.16.BUILD-SNAPSHOT]
        at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) ~[spring-boot-1.5.16.BUILD-20180902.070551-14.jar:1.5.16.BUILD-SNAPSHOT]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) ~[spring-boot-1.5.16.BUILD-20180902.070551-14.jar:1.5.16.BUILD-SNAPSHOT]
        at org.springframework.boot.test.context.SpringBootContextLoader.loadContext(SpringBootContextLoader.java:121) ~[spring-boot-test-1.5.16.BUILD-20180902.070551-14.jar:1.5.16.BUILD-SNAPSHOT]
        at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:98) ~[spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:116) ~[spring-test-4.3.18.RELEASE.jar:4.3.18.RELEASE]
        ... 24 common frames omitted

## 思考 ##

关于最后一种方式判断sql类型达到数据源的动态地选择，此时mysql为一主一从的结构，若为一主多从的结构时如何实现动态选择？以下是大体思路：

本项目实现了一主一从动态数据源的选择，使用切面判断sql方法的方式。

这里的多数据的动态选择，主要是一主一从的形式，若有一主多从的方式，怎么实现数据源的动态选择？

增删改可以使用一个主数据库，查则可以有多个从数据库可以选择，对于多个从数据库，如何选择?

当有多个从数据库时，初步设想使用负载均衡，使用轮询的方式将查询分布到多个从数据库中，那如何实现？

动态数据源的实现是继承了抽象类AbstractRoutingDataSource,实现了其中的抽象方法 determineCurrentLookupKey()  
通过方法名可知，该方法返回一个key，通过阅读AbstractRoutingDataSource的源码，多个数据源的存储方式  
是以key-value的形式存储在map中，当动态选择时，使用determineTargetDataSourc()根据key找到对应的DataSource。

现在要实现多个数据库，设想继承AbstractRoutingDataSource类，重写determineTargetDataSource()方法，将原来Map<Object, Object> targetDataSources的存储方式改为Map<Object,List<Object>> slaveDataSources 用来存储从库数据源，当动态选择时，在determineTargetDataSource()方法中 判断 determineCurrentLookupKey()方法的key，若为master，则直接返回resolvedDefaultDataSource,(前提是在配置数据源时，必须将主数据设置为defaultDataSource).若为slave，则得到slave的List<DataSource>,使用轮询的方式得到其中一个DataSource返回，实现多从的动态选择。

项目源码：  
第一种：[https://github.com/Edenwds/springboot\_study/tree/master/dynamic\_datasource\_anno][https_github.com_Edenwds_springboot_study_tree_master_dynamic_datasource_anno]  
第二种：[https://github.com/Edenwds/springboot\_study/tree/master/dynamic\_datasource\_method][https_github.com_Edenwds_springboot_study_tree_master_dynamic_datasource_method]

参考资料：  
[https://blog.csdn.net/neosmith/article/details/61202084][https_blog.csdn.net_neosmith_article_details_61202084]  
[https://www.codeblogbt.com/archives/153425][https_www.codeblogbt.com_archives_153425]  
[http://fedulov.website/2015/10/14/dynamic-datasource-routing-with-spring/][http_fedulov.website_2015_10_14_dynamic-datasource-routing-with-spring]  
[https://stackoverflow.com/questions/47970429/query-is-always-execute-before-than-aop-in-springboot-and-mybatis-application-fo][https_stackoverflow.com_questions_47970429_query-is-always-execute-before-than-aop-in-springboot-and-mybatis-application-fo]

[MyBatis]: https://blog.csdn.net/sinat_36553913/article/details/82317624
[c3p0_mybatis_mybatis]: https://blog.csdn.net/sinat_36553913/article/details/81414965
[https_github.com_Edenwds_springboot_study_tree_master_dynamic_datasource_anno]: https://github.com/Edenwds/springboot_study/tree/master/dynamic_datasource_anno
[https_github.com_Edenwds_springboot_study_tree_master_dynamic_datasource_method]: https://github.com/Edenwds/springboot_study/tree/master/dynamic_datasource_method
[https_blog.csdn.net_neosmith_article_details_61202084]: https://blog.csdn.net/neosmith/article/details/61202084
[https_www.codeblogbt.com_archives_153425]: https://www.codeblogbt.com/archives/153425
[http_fedulov.website_2015_10_14_dynamic-datasource-routing-with-spring]: http://fedulov.website/2015/10/14/dynamic-datasource-routing-with-spring/
[https_stackoverflow.com_questions_47970429_query-is-always-execute-before-than-aop-in-springboot-and-mybatis-application-fo]: https://stackoverflow.com/questions/47970429/query-is-always-execute-before-than-aop-in-springboot-and-mybatis-application-fo