In-depth understanding of spring multi-data source configuration-javaTutorial-php.cn

We often encounter the problem of multiple data sources in projects, especially projects such as data synchronization or scheduled tasks. The biggest headache for multiple data sources is not configuring multiple data sources, but how to flexibly and dynamically switch data sources. For example, in a spring and hibernate framework project, we often configure a dataSource to connect to the database in the spring configuration, and then bind it to the sessionFactory, and then specify the sessionFactory in the dao layer code to perform database operations.

In-depth understanding of spring multi-data source configuration

As shown in the picture above, each block is designated to be tied. If there are multiple data sources, it can only be in the way shown in the picture below.

In-depth understanding of spring multi-data source configuration

It can be seen that two SessionFactory are written in the Dao layer code. If there is another data source in the future, the code will have to be changed to add a SessionFactory. Obviously this does not Does not comply with the opening and closing principle.

Then the correct approach should be

In-depth understanding of spring multi-data source configuration

The code is as follows:

1. applicationContext.xml

       classpath:com/resource/config.properties                                    org.hibernate.dialect.MySQLDialect org.springframework.orm.hibernate4.SpringSessionContext false true create     com.po

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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(); } }

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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(); } }

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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"); } }

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5. po entity class

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; } }

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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; } }

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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(); } }

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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(); } }

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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()); } }

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Use aop to dynamically change the data source. When we need to add a data source, we only need to add aop configuration in the applicationContext configuration file and create a new DataSourceInterceptor. without changing any code.

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