1、擴展Spring的AbstractRoutingDataSource抽象類(該類充當了DataSource的路由中介, 能有在運行時, 根據某種key值來動態切換到真正的DataSource上。)
從AbstractRoutingDataSource的源碼中:
public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean
我們可以看到,它繼承了AbstractDataSource,而AbstractDataSource不就是javax.sql.DataSource的子類,So我們可以分析下它的getConnection方法:
public Connection getConnection() throws SQLException {
return determineTargetDataSource().getConnection();
}
public Connection getConnection(String username, String password) throws SQLException {
return determineTargetDataSource().getConnection(username, password);
}
獲取連接的方法中,重點是determineTargetDataSource()方法,看源碼:
/**
* 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 = this.resolvedDataSources.get(lookupKey);
if (dataSource == null && (this.lenientFallback || lookupKey == null)) {
dataSource = this.resolvedDefaultDataSource;
}
if (dataSource == null) {
throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");
}
return dataSource;
}
上面這段源碼的重點在於determineCurrentLookupKey()方法,這是AbstractRoutingDataSource類中的一個抽象方法,而它的返回值是你所要用的數據源dataSource的key值,有了這個key值,resolvedDataSource(這是個map,由配置文件中設置好後存入的)就從中取出對應的DataSource,如果找不到,就用配置默認的數據源。
2、看完源碼,應該有點啓發了吧,沒錯!你要擴展AbstractRoutingDataSource類,並重寫其中的determineCurrentLookupKey()方法,來實現數據源的切換:
package com.datasource.test.util.database;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
/**
* 獲取數據源(依賴於spring)
* @author linhy
*/
public class DynamicDataSource extends AbstractRoutingDataSource{
@Override
protected Object determineCurrentLookupKey() {
return DataSourceHolder.getDataSource();
}
}
DataSourceHolder這個類則是我們自己封裝的對數據源進行操作的類:
package com.datasource.test.util.database;
/**
* 數據源操作
* @author linhy
*/
public class DataSourceHolder {
//線程本地環境
private static final ThreadLocal<String> dataSources = new ThreadLocal<String>();
//設置數據源
public static void setDataSource(String customerType) {
dataSources.set(customerType);
}
//獲取數據源
public static String getDataSource() {
return (String) dataSources.get();
}
//清除數據源
public static void clearDataSource() {
dataSources.remove();
}
}