利用AbstractRoutingDataSource实现动态数据源切换
最近要为公司多个游戏做类似的统计功能，考虑到模块的复用性，决定做个动态数据源，根据不同的游戏参数切换不同的datasource。
网上查了下，spring2.0以后增加了AbstractRoutingDataSource这个东西。下面是实现方法
?
首先看下AbstractRoutingDataSource类结构，继承了AbstractDataSource
public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {}?既然是AbstractDataSource，当然就是javax.sql.DataSource的子类，于是我们自然地回去看它的getConnection方法：
public Connection getConnection() throws SQLException {return determineTargetDataSource().getConnection();}?原来奥妙就在determineTargetDataSource()里：
/** * Retrieve the current target DataSource. Determines the * {@link #determineCurrentLookupKey() current lookup key}, performs * a lookup in the {@link #setTargetDataSources targetDataSources} map, * falls back to the specified * {@link #setDefaultTargetDataSource default target DataSource} if necessary. * @see #determineCurrentLookupKey() */protected DataSource determineTargetDataSource() {Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");Object lookupKey = determineCurrentLookupKey();DataSource dataSource = (DataSource) this.resolvedDataSources.get(lookupKey);if (dataSource == null) {dataSource = this.resolvedDefaultDataSource;}if (dataSource == null) {throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");}return dataSource;}这里用到了我们需要进行实现的抽象方法determineCurrentLookupKey()，该方法返回需要使用的DataSource的key值，然后根据这个key从resolvedDataSources这个map里取出对应的DataSource，如果找不到，则用默认的resolvedDefaultDataSource
?
<bean id="onlineDynamicDataSource" value-ref="dataSourceXX"/> <entry key="yy" value-ref="dataSourceYY"/> </map> </property> <property name="defaultTargetDataSource" ref="dataSource"/> </bean>?
观察上面的配置文件，发现我们配置的是targetDataSources和defaultTargetDataSource
?
public void afterPropertiesSet() {if (this.targetDataSources == null) {throw new IllegalArgumentException("targetDataSources is required");}this.resolvedDataSources = new HashMap(this.targetDataSources.size());for (Iterator it = this.targetDataSources.entrySet().iterator(); it.hasNext();) {Map.Entry entry = (Map.Entry) it.next();Object lookupKey = resolveSpecifiedLookupKey(entry.getKey());DataSource dataSource = resolveSpecifiedDataSource(entry.getValue());this.resolvedDataSources.put(lookupKey, dataSource);}if (this.defaultTargetDataSource != null) {this.resolvedDefaultDataSource = resolveSpecifiedDataSource(this.defaultTargetDataSource);}}?
下面就是我们自己实现的子类DynamicDataSource
public class DynamicDataSource extends AbstractRoutingDataSource{ @Override public void setTargetDataSources(Map targetDataSources) { super.setTargetDataSources(targetDataSources); } @Override public Object unwrap(Class iface) throws SQLException { return null; } @Override public boolean isWrapperFor(Class iface) throws SQLException { return false; } @Override protected Object determineCurrentLookupKey() { String dataSourceName = DynamicDataSourceHolder.getDataSourceName(); return dataSourceName; }?
DynamicDataSourceHolder
public class DynamicDataSourceHolder { private static final ThreadLocal<String> holder = new ThreadLocal<String>(); public static void putDataSourceName(String name){ holder.set(name); } public static String getDataSourceName(){ return holder.get(); }}??
?
?