Spring项目中使用两种方法动态切换数据源，多数据源切换

电玩女神 2023-07-23 11:55 36阅读 0赞

本文介绍两种动态切换数据库的方法。  
方法一：数据源信息配置在xml中，适用于一般数据库切换。执行完某操作，切换数据库，执行另一个操作。  
方法二：数据源信息配置在默认数据源中，适用于切换数据库操作同一方法，相当于批量执行方法。

两种方法核心都是AbstractRoutingDataSource，由spring提供，用来动态切换数据源。我们需要继承它，来进行操作。源码分析可以看下一篇文章[源码分析][Link 1]

## **方法一：数据源信息都配置在xml中** ##

1…继承AbstractRoutingDataSource，重写determineCurrentLookupKey方法

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
    
    public class MultiDataSource extends AbstractRoutingDataSource{
    
    	/* ThreadLocal,叫线程本地变量或线程本地存储。
    	 * ThreadLocal为变量在每个线程中都创建了一个副本，那么每个线程可以访问自己内部的副本变量。
    	 * 这里使用它的子类InheritableThreadLocal用来保证父子线程都能拿到值。
    	 */
    	private static final ThreadLocal<String> dataSourceKey = new InheritableThreadLocal<String>();
    	
    	/**
    	 * 设置dataSourceKey的值
    	 * @param dataSource
    	 */
    	public static void setDataSourceKey(String dataSource) {
    		dataSourceKey.set(dataSource);
    	}
    	/**
    	 * 清除dataSourceKey的值
    	 */
    	public static void toDefault() {
    		dataSourceKey.remove();
    	}
    	/**
    	 * 返回当前dataSourceKey的值
    	 */
    	@Override
    	protected Object determineCurrentLookupKey() {
    		return dataSourceKey.get();
    	}
    }

2… 配置xml，这里将上面创建的MultiDataSource注入到spring容器中，这里主要用到AbstractRoutingDataSource的两个属性defaultTargetDataSource和targetDataSources。defaultTargetDataSource默认目标数据源，targetDataSources（map类型）存放用来切换的数据源。配置完以后，其他地方用到数据源的话，都引用multiDataSource。

3…手动切换数据源，切换完以后，记得再切回默认数据库。

MultiDataSource.setDataSourceKey("dataSource1");//切换到dataSource1数据源
    XXX在该数据源下的操作XXX
    MultiDataSource.toDefault();//操作完以后，清除dataSourceKey的值，即切回默认数据源，原理后面会讲。

4… 利用aop切换数据源，这里记得开启aop，配置文件中使用<aop:aspectj-autoproxy />  
4.1首先定义一个注解，来调用注解切换数据库

import java.lang.annotation.Documented;
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    @Target({ElementType.METHOD,ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface DynamicRoutingDataSource {
    
    	String value() default "dataSource";//本文默认dataSource
    
    }

4.2 这里使用@Before和@After，在调用目标方法前，进行aop拦截，通过解析注解上的值来切换数据源。在调用方法结束后，切回默认数据源。如果目标方法无返回值，也可以使用@Around，调用ProceedingJoinPoint的proceed()方法前切换数据源，调用proceed()方法后切回默认数据源。

import java.lang.reflect.Method;
    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.aspectj.lang.annotation.Pointcut;
    import org.aspectj.lang.reflect.MethodSignature;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.stereotype.Component;
    
    import com.wbb.annotation.DynamicRoutingDataSource;
    import com.wbb.dataSource.MultiDataSource;
    
    @Aspect
    @Component
    public class HandlerDataSourceAop {
    
    	private static Logger logger = LoggerFactory.getLogger(HandlerDataSourceAop.class);
    	/**
    	 * @within匹配类上的注解
    	 * @annotation匹配方法上的注解
    	 */
    	@Pointcut("@within(com.wbb.annotation.DynamicRoutingDataSource)||@annotation(com.wbb.annotation.DynamicRoutingDataSource)")
    	public void pointcut(){}
    	
    	@Before(value = "pointcut()")
    	public void beforeOpt(JoinPoint joinPoint) {
    	/** 先查找方法上的注解，没有的话再去查找类上的注解
    	*-----------------------------------------------------------------------
     	* 这里使用的是接口的模式，注解在实现类上，所以不能使用如下方式获取目标方法的对象，
    	* 因为该方式获取的是该类的接口或者顶级父类的方法的对象.
    	* MethodSignature methodSignature = (MethodSignature)point.getSignature();
         * Method method = methodSignature.getMethod();
         * DynamicRoutingDataSource annotation = method.getAnnotation(DynamicRoutingDataSource.class);
         * 通过上面代码是获取不到方法上的注解的，如果真要用上面代码来获取，可以修改aop代理模式，修改为cglib代理
         * 在xml配置文件修改为<aop:aspectj-autoproxy proxy-target-class="true" /> ，
         * proxy-target-class属性true为cglib代理，默认false为jdk动态代理 。
         * ---------------------------------------------------------
         * 本文使用是jdk动态代理， 这里使用反射的方式获取方法
    	*/
    	//反射获取Method 方法一
    	Object target = joinPoint.getTarget();
    	Class<?> clazz = target.getClass();
    	Method[] methods = clazz.getMethods();
    	DynamicRoutingDataSource annotation = null;
    	for (Method method : methods) {
    		if (joinPoint.getSignature().getName().equals(method.getName())) {
    			annotation = method.getAnnotation(DynamicRoutingDataSource.class);
    			if (annotation == null) {
    				annotation = joinPoint.getTarget().getClass().getAnnotation(DynamicRoutingDataSource.class);
    				if (annotation == null) {
    					return;
    				}
    			}
    		}
    	}
    	// 	反射获取Method 方法二
    	//		Object[] args = joinPoint.getArgs();
    	//		Class<?>[] argTypes = new Class[joinPoint.getArgs().length];
    	//		for (int i = 0; i < args.length; i++) {
    	//			argTypes[i] = args[i].getClass();
    	//		}
    	//		Method method = joinPoint.getTarget().getClass().getMethod(joinPoint.getSignature().getName(), argTypes);
    	//		DynamicRoutingDataSource annotation = method.getAnnotation(DynamicRoutingDataSource.class);
    	//		if (annotation == null) {
    	//			annotation = joinPoint.getTarget().getClass().getAnnotation(DynamicRoutingDataSource.class);
    	//			if (annotation == null) {
    	//				return;
    	//			}
    	//		}
    		
    		String dataSourceName = annotation.value();
    		MultiDataSource.setDataSourceKey(dataSourceName);
    		logger.info("切到" + dataSourceName + "数据库");
    	}
    	@After(value="pointcut()")
    	public void afterOpt(){
    		MultiDataSource.toDefault();
    		logger.info("切回默认数据库");
    	}
    }

4.3 使用：只需要把@DynamicRoutingDataSource注解加到方法或者类上即可

@DynamicRoutingDataSource("dataSource1")

方法一到此就结束了。

## 方法二：数据源信息配置在数据库中 ##

1.xml的配置，这里只需要配置一个默认的数据源就行了，因为其他的数据源都是从该数据源的数据源表中读取。

<?xml version="1.0" encoding="UTF-8"?>
    	<beans xmlns="http://www.springframework.org/schema/beans"
    		xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    		xmlns:tx="http://www.springframework.org/schema/tx"
    		xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.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">
    	
    		<context:property-placeholder location="classpath:jdbc.properties" />
    	
    		<bean id="defaultDataSource" class="com.alibaba.druid.pool.DruidDataSource"
    			init-method="init" destroy-method="close">
    			<property name="driverClassName" value="${jdbc.driverClassName}" />
    			<property name="url" value="${jdbc.url}" />
    			<property name="username" value="${jdbc.username}" />
    			<property name="password" value="${jdbc.password}" />
    			<property name="validationQuery" value="select 1"></property>
    			<property name="testOnBorrow" value="true"></property>
    		</bean>
    	
    		
    	    <bean id="dynamicDataSource" class="com.wbb.dataSource.dynamic.DynamicDataSource">
    	        <property name="targetDataSources">
    	            <map key-type="java.lang.String">
    	                <entry key="defaultDataSource" value-ref="defaultDataSource"/>
    	            </map>
    	        </property>
    	        <property name="defaultTargetDataSource" ref="defaultDataSource"/>
    	    </bean>
    		
    		<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    			<property name="dataSource" ref="dynamicDataSource"></property>
    			<property name="configLocation" value="classpath:mybatis-config.xml"></property>
    			<property name="mapperLocations" value="classpath:com/wbb/mapper/*.xml"></property>
    		</bean>
    		<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
    			<property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"></property>
    			<property name="basePackage" value="com.wbb.mapper"></property>
    		</bean>
    	
    		
    		<tx:annotation-driven transaction-manager="transactionManager" />
    	
    		<bean id="transactionManager"
    			class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
    			<property name="dataSource" ref="dynamicDataSource"></property>
    		</bean>
    	
    	</beans>

2.数据源表的设计

DROP TABLE IF EXISTS `other_datasource`;
    CREATE TABLE `other_datasource` (
      `id` int(11) NOT NULL AUTO_INCREMENT,
      `datasource_name` varchar(64) DEFAULT NULL,
      `database_ip` varchar(64) DEFAULT NULL,
      `database_port` varchar(64) DEFAULT NULL,
      `database_name` varchar(64) DEFAULT NULL,
      `database_username` varchar(64) DEFAULT NULL,
      `database_password` varchar(64) DEFAULT NULL,
      PRIMARY KEY (`id`)
    ) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;

![è¿éåå¾çæè¿°][70]

3.数据源表对应的bean

/**
     * 数据源bean构建器
     */
    public class DataSourceBean {
    
    	private final String beanName;		//注册在spring中bean名字
    	private final String driverClassName; 
    	private final String url;
    	private final String username;
    	private final String password;
    	private final String validationQuery;
    	private final Boolean testOnBorrow;
    
    	public String getBeanName() {
    		return beanName;
    	}
    
    	public String getDriverClassName() {
    		return driverClassName;
    	}
    
    	public String getUrl() {
    		return url;
    	}
    
    	public String getUsername() {
    		return username;
    	}
    
    	public String getPassword() {
    		return password;
    	}
    
    	public String getValidationQuery() {
    		return validationQuery;
    	}
    
    	public Boolean getTestOnBorrow() {
    		return testOnBorrow;
    	}
    
    	public DataSourceBean(DataSourceBeanBuilder builder) {
    		this.beanName = builder.getBeanName();
    		this.driverClassName = builder.getDriverClassName();
    		this.url = builder.getUrl();
    		this.username = builder.getUsername();
    		this.password = builder.getPassword();
    		this.validationQuery = builder.getValidationQuery();
    		this.testOnBorrow = builder.getTestOnBorrow();
    	}
    
    	public static class DataSourceBeanBuilder {
    		private String beanName;
    		private String driverClassName = "com.mysql.jdbc.Driver";
    		private String url = "jdbc:mysql://%s:%s/%s";
    	    private String databaseIP;
    	    private String databasePort;
    	    private String databaseName;
    		private String username;
    		private String password;
    		private String validationQuery = "select 1";
    		private Boolean testOnBorrow = true;
    		public DataSourceBeanBuilder(String beanName, String databaseIP, String databasePort, String databaseName,
    				String username, String password) {
    			super();
    			this.beanName = beanName;
    			this.databaseIP = databaseIP;
    			this.databasePort = databasePort;
    			this.databaseName = databaseName;
    			this.username = username;
    			this.password = password;
    		}
    		public DataSourceBeanBuilder() {
    			super();
    		}
    		public DataSourceBeanBuilder driverClassName(String driverClassName) {
    			this.driverClassName = driverClassName;
    			return this;
    		}
    		public DataSourceBeanBuilder validationQuery(String validationQuery) {
    			this.validationQuery = validationQuery;
    			return this;
    		}
    		public DataSourceBeanBuilder testOnBorrow(Boolean testOnBorrow) {
    			this.testOnBorrow = testOnBorrow;
    			return this;
    		}
    		public String getUrl() {
    			return String.format(url,this.databaseIP,this.databasePort,this.databaseName);
    		}
    		public String getBeanName() {
    			return beanName;
    		}
    		public String getDriverClassName() {
    			return driverClassName;
    		}
    		public String getDatabaseIP() {
    			return databaseIP;
    		}
    		public String getDatabasePort() {
    			return databasePort;
    		}
    		public String getDatabaseName() {
    			return databaseName;
    		}
    		public String getUsername() {
    			return username;
    		}
    		public String getPassword() {
    			return password;
    		}
    		public String getValidationQuery() {
    			return validationQuery;
    		}
    		public Boolean getTestOnBorrow() {
    			return testOnBorrow;
    		}
    	}

4.这里将操作抽离出，建立数据源操作类，方便操作

/**
     * 数据源操作类
     */
    public class DataSourceContext {
    
    	private static ThreadLocal<DataSourceBean> threadLocal = new InheritableThreadLocal<DataSourceBean>();
    
    	/**
    	 * 获取数据源
    	 */
    	public static DataSourceBean getDataSource() {
    		return threadLocal.get();
    	}
    	/**
    	 * 设置数据源
    	 */
    	public static void setDataSource(DataSourceBean dataSourceBean) {
    		threadLocal.set(dataSourceBean);
    	}
    	/**
    	 * 清除数据源
    	 * 清除后,数据源为默认时间
    	 */
    	public static void toDefault() {
    		threadLocal.remove();
    	}
    }

5.定义AbstractRoutingDataSource的继承类DynamicDataSource，同时实现ApplicationContextAware接口，因为该方法切换数据源，需要到spring上下文中生成和获取数据源bean。

import java.lang.reflect.Field;
    import java.util.HashMap;
    import java.util.Map;
    
    import org.springframework.beans.BeansException;
    import org.springframework.beans.factory.support.BeanDefinitionBuilder;
    import org.springframework.beans.factory.support.DefaultListableBeanFactory;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.ApplicationContextAware;
    import org.springframework.context.ConfigurableApplicationContext;
    import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
    
    import com.alibaba.druid.pool.DruidDataSource;
    
    
    public class  DynamicDataSource extends AbstractRoutingDataSource implements ApplicationContextAware{
    
    	private ApplicationContext applicationContext ;
    
    	/**
    	 * 连接数据源前,调用该方法
    	 */
    	@Override
    	protected Object determineCurrentLookupKey() {
    		//1.获取手动设置的数据源参数DataSourceBean
    		DataSourceBean dataSourceBean = DataSourceContext.getDataSource();
    		if(dataSourceBean == null) {
    			return null;
    		}
    		try {
    			//2.获取AbstractRoutingDataSource的targetDataSources属性,该属性存放数据源属性
    			Map<Object, Object> targetSourceMap = getTargetSource();
    			synchronized(this) {
    				/*
    				 * 3.判断targetDataSources中是否已经存在要设置的数据源bean
    				 * 存在的话,则直接返回beanName
    				 * 
    				 */
    				if(!targetSourceMap.keySet().contains(dataSourceBean.getBeanName())) {
    					/*不存在，则进行以下几步
    					3.1 先在spring容器中创建该数据源bean
    					*/
    					Object dataSource = createDataSource(dataSourceBean);
    					//3.2 在创建后的bean,放入到targetDataSources Map中
    					targetSourceMap.put(dataSourceBean.getBeanName(), dataSource);
    					/*
    					 * 3.3 通知spring有bean更新
    					 * 主要更新AbstractRoutingDataSource的resolvedDefaultDataSource(Map)属性,
    					 * 更新完以后,AbstractRoutingDataSource的determineTargetDataSource()中,才能找到数据源
    					 * 代码如下：
    					 * Object lookupKey = determineCurrentLookupKey();
    					   DataSource dataSource = this.resolvedDataSources.get(lookupKey);
    					 */
    					super.afterPropertiesSet();
    				}
    			}
    			for(Map.Entry<Object, Object> entry : targetSourceMap.entrySet()) {
    				System.out.println(entry.getKey()+"-"+entry.getValue());
    			}
    			return dataSourceBean.getBeanName();
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    		return null;
    	}
    	/**
    	 * 根据数据源信息在spring中创建bean,并返回
    	 * @param dataSourceBean 数据源信息
    	 * @return
    	 * @throws IllegalAccessException
    	 */
    	public Object createDataSource(DataSourceBean dataSourceBean) throws IllegalAccessException {
    		//1.将applicationContext转化为ConfigurableApplicationContext
    		ConfigurableApplicationContext context = (ConfigurableApplicationContext) applicationContext;
    		//2.获取bean工厂并转换为DefaultListableBeanFactory
    		DefaultListableBeanFactory beanFactory =  (DefaultListableBeanFactory) context.getBeanFactory();
    		/*
    		 * 3.本文用的是DruidDataSource,所有在这里我们获取的是该bean的BeanDefinitionBuilder,
    		 * 通过BeanDefinitionBuilder来创建bean定义
    		 */
    		BeanDefinitionBuilder beanDefinitionBuilder = BeanDefinitionBuilder.genericBeanDefinition(DruidDataSource.class);
    		/**
    		 * 4.获取DataSourceBean里的属性和对应值,并将其交给BeanDefinitionBuilder创建bean的定义
    		 */
    		Map<String, Object> propertyKeyValues = getPropertyKeyValues(DataSourceBean.class, dataSourceBean);
    		for(Map.Entry<String,Object> entry : propertyKeyValues.entrySet()) {
    			beanDefinitionBuilder.addPropertyValue(entry.getKey(), entry.getValue());
    		}
    		//5.bean定义创建好以后,将其交给beanFactory注册成bean对象，由spring容器管理
    		beanFactory.registerBeanDefinition(dataSourceBean.getBeanName(), beanDefinitionBuilder.getBeanDefinition());
    		//6.最后获取步骤5生成的bean,并将其返回
    		return context.getBean(dataSourceBean.getBeanName());
    	}
    	//获取类属性和对应的值,放入Map中
        @SuppressWarnings("unused")
    	private <T> Map<String, Object> getPropertyKeyValues(Class<T> clazz, Object object) throws IllegalAccessException {
           Field[] fields = clazz.getDeclaredFields();
           Map<String,Object> map = new HashMap<>();
           for (Field field : fields) {
        	   field.setAccessible(true);
        	   map.put(field.getName(), field.get(object));
           }
           map.remove("beanName");
           return map;
        }
        //通过反射获取AbstractRoutingDataSource的targetDataSources属性
    	@SuppressWarnings("unchecked")
    	public Map<Object, Object> getTargetSource() throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {
    		Field field = AbstractRoutingDataSource.class.getDeclaredField("targetDataSources");
    		field.setAccessible(true);
    		return (Map<Object, Object>) field.get(this);
    	}
    	@Override
    	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
    			this.applicationContext = applicationContext;
    	}
     
    }

6.测试用例测试一下

@Test
    	public void testDynamicDataSource() {
    		1.从表中获取需要切换的数据源信息
    		List<DataSourceDO> dataSourceDOList = dataSourceMapper.getAllDataSources();
    		2.循环遍历,切换数据源,执行操作,切完就得切回默认数据源
    		for (DataSourceDO dataSourceDO : dataSourceDOList) {
    			DataSourceBean dataSourceBean = new DataSourceBean(new DataSourceBeanBuilder(dataSourceDO.getDatasourceName(),
    					dataSourceDO.getDatabaseIp(), dataSourceDO.getDatabasePort(), dataSourceDO.getDatabaseName(),
    					dataSourceDO.getUsername(), dataSourceDO.getPassword()));
    			DataSourceContext.setDataSource(dataSourceBean);
    			XXX你的操作XXX
    			DataSourceContext.toDefault();
    		}
    	}

方法二部分参考https://blog.csdn.net/yizhenn/article/details/53965552该博客的思想。

源码分析可以看下一篇文章https://blog.csdn.net/u013034378/article/details/81661706

讲到这里，本篇文章到此也就结束了,如果文章中有问题,或者有一些不够严谨完善的地方,希望大家体谅体谅。欢迎大家留言,交流交流。  
参考：

[https://blog.csdn.net/laojiaqi/article/details/78964862][https_blog.csdn.net_laojiaqi_article_details_78964862]

[Link 1]: https://blog.csdn.net/u013034378/article/details/81661706
[70]: /images/20230528/4b247e21fdc9490f9ce5d1acad2816dc.png
[https_blog.csdn.net_laojiaqi_article_details_78964862]: https://blog.csdn.net/laojiaqi/article/details/78964862