利用AbstractRoutingDataSource实现动态数据源切换

原文地址：http://dsbjoe.iteye.com/blog/1176779

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

 

 "onlineDynamicDataSource" class="com.xx.stat.base.dynamic.DynamicDataSource">
    "targetDataSources">
       "java.lang.String">
          "xx" value-ref="dataSourceXX"/>
          "yy" value-ref="dataSourceYY"/>


    "defaultTargetDataSource" ref="dataSource"/>

 

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 holder = new ThreadLocal();

     public static void putDataSourceName(String name){
         holder.set(name);
     }

     public static String getDataSourceName(){
         return holder.get();
     }
 }