利用Spring的AbstractRoutingDataSource解決多數據源的問題

多數據源問題很常見，例如讀寫分離數據庫配置。

1、首先配置多個datasource

<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
	    <property name="driverClassName" value="net.sourceforge.jtds.jdbc.Driver">
		</property>
		<property name="url" value="jdbc:jtds:sqlserver://10.82.81.51:1433;databaseName=standards">
		</property>
		<property name="username" value="youguess"></property>
		<property name="password" value="youguess"></property>
	</bean>
	<bean id="dataSource2" class="org.apache.commons.dbcp.BasicDataSource">
	    <property name="driverClassName" value="net.sourceforge.jtds.jdbc.Driver">
		</property>
		<property name="url" value="jdbc:jtds:sqlserver://10.82.81.52:1433;databaseName=standards">
		</property>
		<property name="username" value="youguess"></property>
		<property name="password" value="youguess"></property>
</bean>

2、寫一個DynamicDataSource類繼承AbstractRoutingDataSource，並實現determineCurrentLookupKey方法

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

3、利用ThreadLocal解決線程安全問題

package com.standard.core.util;
public class CustomerContextHolder {
	public static final String DATA_SOURCE_A = "dataSource";
	public static final String DATA_SOURCE_B = "dataSource2";
	private static final ThreadLocal<String> contextHolder = new ThreadLocal<String>();
	public static void setCustomerType(String customerType) {
		contextHolder.set(customerType);
	}
	public static String getCustomerType() {
		return contextHolder.get();
	}
	public static void clearCustomerType() {
		contextHolder.remove();
	}
}

4、數據源配置

<bean id="dynamicDataSource" class="com.standard.core.util.DynamicDataSource" >
		<property name="targetDataSources">
			<map key-type="java.lang.String">
				<entry value-ref="dataSource" key="dataSource"></entry>
				<entry value-ref="dataSource2" key="dataSource2"></entry>
			</map>
		</property>
		<property name="defaultTargetDataSource" ref="dataSource" >
		</property>
	</bean> 

5、在Action或ServiceImpl或DAOImpl中切換數據源，HibernateTemplate和SqlMapClientTemplate等操作數組庫都是用到DataSource的

CustomerContextHolder.setCustomerType(CustomerContextHolder.DATA_SOURCE_B);