Servlet上下文的多个动态数据源

我终于解决了以下由SessionListener和Servlet组成的解决方案，它们的工作方式如下。SessionListener具有以下形式：

public class SessionListener implements HttpSessionListener {  public void sessionCreated(HttpSessionEvent event) {    HttpSession session = event.getSession();    // get list of possible data sources available to this session    List<DataSource> sources = new ArrayList<DataSource>();    ... pre to get the available sources    // get the current data source    DataSource source = null;    ... pre to get the current source  source = sources.get(0); // for example    // setup the session attributes    session.setAttribute("availableSources", sources);    session.setAttribute("currentSource", source);  }}

每当用户登录并创建会话时，可用数据源的列表和当前的数据源都会放入该会话中。这是在会话级别完成的，因为数据源取决于用户登录。现在可以从应用程序内部对其进行访问。要更改当前的数据源，我使用以下简化版本创建了一个Servlet：

public abstract class BoxletServlet extends HttpServlet {  protected void doGet(HttpServletRequest request, HttpServletResponse response)     throws ServletException, IOException {    HttpSession session = request.getSession(true);    String s = request.getParameter("source");    // based on 's' choose from the available DataSource    List<DataSource> sources = (List<DataSource>) session.getParameter("availableSources");    Source source = chooseFrom(sources, s);    session.setParameter("currentSource", source);    // forward to a page saying that the DataSource changed  }

}

通过此实现，现在可以创建以下jsps：

<%@ taglib uri="http://java.sun.com/jstl/sql" prefix="sql" %><sql:query var = "users" dataSource="${sessionScope.currentSource}">  select id, firstName, lastName FROM user</sql:query>

希望它可以帮助别人。