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

Java代码


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：

Java代码


public Connection getConnection() throws SQLException {
return determineTargetDataSource().getConnection();
}

原来奥妙就在determineTargetDataSource()里：

Java代码


/**
* 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

Java代码


<bean id="onlineDynamicDataSource" class="com.xx.stat.base.dynamic.DynamicDataSource">
<property name="targetDataSources">
<map key-type="java.lang.String">
<entry key="xx" 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

Java代码


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

Java代码


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

Java代码


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();
}
}