利用Spring的AbstractRoutingDataSource解决多数据源的问题

多数据源问题很常见，例如读写分离数据库配置。

原来的项目出现了新需求，局方要求新增某服务器用以提供某代码，涉及到多数据源的问题。

解决方法如下：

1、首先配置多个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、写一个DynamicDataSource类继承AbstractRoutingDataSource，并实现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解决线程安全问题

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、数据源配置

<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DAOImpl中切换数据源

CustomerContextHolder.setCustomerType(CustomerContextHolder.DATA_SOURCE_B);