深入理解spring多数据源配置

项目中我们经常会遇到多数据源的问题，尤其是数据同步或定时任务等项目更是如此。本篇文章主要介绍了spring多数据源配置，有兴趣的可以了解一下。

项目中我们经常会遇到多数据源的问题，尤其是数据同步或定时任务等项目更是如此。多数据源让人最头痛的，不是配置多个数据源，而是如何能灵活动态的切换数据源。例如在一个spring和hibernate的框架的项目中，我们在spring配置中往往是配置一个dataSource来连接数据库，然后绑定给sessionFactory，在dao层代码中再指定sessionFactory来进行数据库操作。

正如上图所示，每一块都是指定绑死的，如果是多个数据源，也只能是下图中那种方式。

可看出在Dao层代码中写死了两个SessionFactory，这样日后如果再多一个数据源，还要改代码添加一个SessionFactory，显然这并不符合开闭原则。

那么正确的做法应该是

代码如下：

1. applicationContext.xml

      classpath:com/resource/config.properties         org.hibernate.dialect.MySQLDialectorg.springframework.orm.hibernate4.SpringSessionContextfalsetruecreate  com.po

2. DynamicDataSource.class

 package com.core; import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource; public class DynamicDataSource extends AbstractRoutingDataSource{ @Override protected Object determineCurrentLookupKey() { return DatabaseContextHolder.getCustomerType(); } }

3. DatabaseContextHolder.class

 package com.core; public class DatabaseContextHolder { private static final ThreadLocal contextHolder = new ThreadLocal(); public static void setCustomerType(String customerType) { contextHolder.set(customerType); } public static String getCustomerType() { return contextHolder.get(); } public static void clearCustomerType() { contextHolder.remove(); } }

4. DataSourceInterceptor.class

 package com.core; import org.aspectj.lang.JoinPoint; import org.springframework.stereotype.Component; @Component public class DataSourceInterceptor { public void setdataSourceOne(JoinPoint jp) { DatabaseContextHolder.setCustomerType("dataSourceOne"); } public void setdataSourceTwo(JoinPoint jp) { DatabaseContextHolder.setCustomerType("dataSourceTwo"); } }

5. po实体类

 package com.po; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.Table; @Entity @Table(name = "BTSF_BRAND", schema = "hotel") public class Brand { private String id; private String names; private String url; @Id @Column(name = "ID", unique = true, nullable = false, length = 10) public String getId() { return this.id; } public void setId(String id) { this.id = id; } @Column(name = "NAMES", nullable = false, length = 50) public String getNames() { return this.names; } public void setNames(String names) { this.names = names; } @Column(name = "URL", length = 200) public String getUrl() { return this.url; } public void setUrl(String url) { this.url = url; } }

 package com.po; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.Table; @Entity @Table(name = "CITY", schema = "car") public class City { private Integer id; private String name; @Id @Column(name = "ID", unique = true, nullable = false) public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } @Column(name = "NAMES", nullable = false, length = 50) public String getName() { return name; } public void setName(String name) { this.name = name; } }

6. BrandDaoImpl.class

 package com.dao.one; import java.util.List; import javax.annotation.Resource; import org.hibernate.Query; import org.hibernate.SessionFactory; import org.springframework.stereotype.Repository; import com.po.Brand; @Repository public class BrandDaoImpl implements IBrandDao { @Resource protected SessionFactory sessionFactory; @SuppressWarnings("unchecked") @Override public List findAll() { String hql = "from Brand"; Query query = sessionFactory.getCurrentSession().createQuery(hql); return query.list(); } }

7. CityDaoImpl.class

 package com.dao.two; import java.util.List; import javax.annotation.Resource; import org.hibernate.Query; import org.hibernate.SessionFactory; import org.springframework.stereotype.Repository; import com.po.City; @Repository public class CityDaoImpl implements ICityDao { @Resource private SessionFactory sessionFactory; @SuppressWarnings("unchecked") @Override public List find() { String hql = "from City"; Query query = sessionFactory.getCurrentSession().createQuery(hql); return query.list(); } }

8. DaoTest.class

 package com.test; import java.util.List; import javax.annotation.Resource; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.test.context.ContextConfiguration; import org.springframework.test.context.junit4.SpringJUnit4ClassRunner; import org.springframework.test.context.transaction.TransactionConfiguration; import com.dao.one.IBrandDao; import com.dao.two.ICityDao; import com.po.Brand; import com.po.City; @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations = "classpath:com/resource/applicationContext.xml") @TransactionConfiguration(transactionManager = "transactionManager", defaultRollback = false) public class DaoTest { @Resource private IBrandDao brandDao; @Resource private ICityDao cityDao; @Test public void testList() { List brands = brandDao.findAll(); System.out.println(brands.size()); List cities = cityDao.find(); System.out.println(cities.size()); } }

利用aop，达到动态更改数据源的目的。当需要增加数据源的时候，我们只需要在applicationContext配置文件中添加aop配置，新建个DataSourceInterceptor即可。而不需要更改任何代码。

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