動態切換數據源(spring+hibernate)

出處：http://www.cnblogs.com/coveted/archive/2011/10/22/2221317.html

起因：在當前我手上的一個項目中需要多個數據源,並且來自於不同類型的數據庫... 因爲很多歷史原因.這個項目的住數據源是MySQL,整個系統的CURD都是操作的這個數據庫.

但是還有另外兩個用於數據採集的數據庫: MSSQL,ACCESS.還好只是用於數據採集，在事務上可以不要跨數據庫了，這一點節省了好多的工作量.

環境：我搭建的測試環境是 spring2.5.6+hibernate3.2

思路：動態切換數據源確切的來說是在同一類型數據庫的情況下的。意思就是說 , 在系統中的使用的數據庫分佈在多臺數據庫服務器或者在同臺服務器上的多個數據庫. 在運行時期間根據某種標識符來動態的選擇當前操作的數據庫.

     1.數據源是相同類型的數據庫: 一個SessionFactory+動態數據源+一個事務管理器

     2.數據源是不同類型的數據庫: 根據類型 配置多套SessionFactory

模擬：兩個mysql數據源+一個Access數據源

實現：

1.切換數據源需要標識符,標識符是Object類型

package lhp.example.context;
public enum DBType {
      dataSource1, dataSource2;
}

2.然後創建一個用於切換數據源(設置或者獲得上下文)的工具類

package lhp.example.context;

public class ContextHolder {
    private static final ThreadLocal<Object> holder = new ThreadLocal<Object>();

    public static void setDbType(DBType dbType) {
        holder.set(dbType);
    }

    public static DBType getDbType() {
        return (DBType) holder.get();
    }

    public static void clearDbType() {
        holder.remove();
    }
}

3.創建動態數據源類,繼承org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource這個類.

package lhp.example.context;

import java.util.logging.Logger;

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

public class DynamicDataSource extends AbstractRoutingDataSource {
    public static final Logger logger = Logger.getLogger(DynamicDataSource.class.toString());

    @Override
    protected Object determineCurrentLookupKey() {
        DBType key = ContextHolder.getDbType();//獲得當前數據源標識符
        //logger.info("當前數據源 :" + key);
        return key;
    }

}

4.然後配置多個數據源

<!-- 數據源1 ： mysql -->
    <bean id="dataSource1" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="driverClass" value="com.mysql.jdbc.Driver" />
        <property name="jdbcUrl" value="jdbc:mysql://127.0.0.1:3306/dec" />
        <property name="user" value="root" />
        <property name="password" value="" />
    </bean>
    <!-- 數據源2 ： mysql  -->
    <bean id="dataSource2" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="driverClass" value="com.mysql.jdbc.Driver" />
        <property name="jdbcUrl" value="jdbc:mysql://127.0.0.1:3306/lms" />
        <property name="user" value="root" />
        <property name="password" value="" />
    </bean>

    <!-- 數據源3 ：  access -->
    <bean id="dataSource3" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="driverClass" value="sun.jdbc.odbc.JdbcOdbcDriver" />
        <property name="jdbcUrl" value="jdbc:odbc:accessTest" />
        <property name="user" value="administrator" />
        <property name="password" value="XLZX0309" />
    </bean>

    <!-- mysql 動態數據源設置-->
    <bean id="mysqlDynamicDataSource" class="lhp.example.context.DynamicDataSource">
        <property name="targetDataSources">
            <!-- 標識符類型 -->
            <map key-type="lhp.example.context.DBType">
                <entry key="dataSource1" value-ref="dataSource1" />
                <entry key="dataSource2" value-ref="dataSource2" />
            </map>
        </property>
        <property name="defaultTargetDataSource" ref="dataSource1" />
    </bean>
    

5.配置sessionFactory

<!-- mysql sessionFactory -->
    <bean id="mysqlSessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
        <property name="dataSource" ref="mysqlDynamicDataSource" />
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.hbm2ddl.auto">update</prop><!--create validate -->
                <prop key="hibernate.query.substitutions">true 1, false 0</prop>
            </props>
        </property>
    </bean>
    
    <!-- access sessionFactory -->
    <bean id="aceessSessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
        <property name="dataSource" ref="dataSource3" />
        <property name="hibernateProperties">
            <props>
                <!-- access 語法和MSSQL相似 所以用的MSSQL方言，或者可以使用第三方方言 -->
                <prop key="hibernate.dialect">org.hibernate.dialect.SQLServerDialect</prop>
                <prop key="hibernate.jdbc.batch_size">30</prop>
                <prop key="hibernate.jdbc.fetch_size">50</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.format_sql">false</prop>
                <prop key="hibernate.hbm2ddl.auto">update</prop><!--create validate -->
                <prop key="hibernate.query.substitutions">true 1, false 0</prop>
                <prop key="hibernate.cglib.use_reflection_optimizer">true</prop>
                <!-- <prop key="hibernate.cache.use_second_level_cache">true</prop> -->
                <!-- <prop key="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</prop> -->
                <!-- <prop key="hibernate.cache.use_query_cache">true</prop> -->
                <!-- <prop key="hibernate.generate_statistics">true</prop> -->
                <!-- <prop key="hibernate.cache.provider_configuration_file_resource_path">classpath:ehcache.xml</prop> -->
            </props>
        </property>
    </bean>

6.測試用例

package lhp.example.junit;

import static org.junit.Assert.*;
import java.sql.DatabaseMetaData;
import lhp.example.context.ContextHolder;
import lhp.example.context.DBType;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.junit.Before;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class ServiceTest {
    private ApplicationContext context;
    //三個數據源的URL
    private String dataSource1_URL = "jdbc:mysql://127.0.0.1:3306/dec";
    private String dataSource2_URL = "jdbc:mysql://127.0.0.1:3306/lms";
    private String dataSource3_URL = "jdbc:odbc:accessTest";
    private SessionFactory mysqlSessionFactory;
    private SessionFactory aceessSessionFactory;

    @Before
    public void setUp() throws Exception {
        // 選擇數據源初始化spring
        ContextHolder.setDbType(DBType.dataSource1);
        //
        String[] xmlFiles = new String[] { 
                "applicationContext-dataSource.xml",
                "applicationContext-hibernate.xml",
                "applicationContext-spring.xml" };
        //
        context = new ClassPathXmlApplicationContext(xmlFiles);
        //
        mysqlSessionFactory = (SessionFactory) context.getBean("mysqlSessionFactory");
        aceessSessionFactory = (SessionFactory) context.getBean("aceessSessionFactory");
    }

    @SuppressWarnings("deprecation")
    @Test
    public void mysqlDataSourceTest() {
        try {

            Session mysqlSession = mysqlSessionFactory.openSession();
            // 獲得數據庫元數據
            DatabaseMetaData meatData = mysqlSession.connection().getMetaData();

            // 默認啓動數據源 dataSource1
            //斷言當前數據源URL是否是dataSource1的URL
            assertEquals(dataSource1_URL, meatData.getURL());

            // 切換到數據源 dataSource2
            ContextHolder.setDbType(DBType.dataSource2);
            mysqlSession = mysqlSessionFactory.openSession();
            meatData = mysqlSession.connection().getMetaData();
            //斷言當前數據源URL是否是dataSource2的URL
            assertEquals(dataSource2_URL, meatData.getURL());

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    @SuppressWarnings("deprecation")
    @Test
    public void accessDataSourceTest() {
        try {
            Session accessSession = aceessSessionFactory.openSession();
            // 獲得數據庫元數據
            DatabaseMetaData meatData = accessSession.connection().getMetaData();
            //斷言當前數據源URL是否是dataSource3的URL
            assertEquals(dataSource3_URL, meatData.getURL());


        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

7.測試結果