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

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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

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    <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

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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);}}

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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;    }

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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();    }}

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