JavaServlet : Force init to create data object on Payara server start?

Question

我正在寻找一种在第一个请求之前在我的java servlet(在Payara上)中生成数据对象的方法，因为创建的数据对象需要一些时间来解析其他网站(大约4秒)。

我认为设置就足够了

@WebServlet(urlPatterns = "/reports/*", loadOnStartup = 1)

首先在 payara 服务器启动时强制 servlet 容器进行初始化(基于 http://www.codejava.net/java-ee/servlet/webservlet-annotation-examples )。然而，它不起作用。我的第一个请求仍然有 4 秒的延迟，后续请求没有延迟。以下代码有效，问题只是第一个请求的延迟。

@WebServlet(urlPatterns = "/reports/*", loadOnStartup = 1)
public class SingleReportServlet extends HttpServlet {

    ReportData m_myData;

    @Override
    public void init() throws ServletException {        
        m_myData = new ReportData(); //This takes about 4 seconds, once
        System.out.println("My servlet has been initialized");        
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        
        String requestPath = request.getPathInfo();
        String[] components = requestPath.split("/");
        String requestedData = components[components.length-1].trim().toUpperCase();
        String report = m_myData.getFullReport(requestedData, Locale.GERMAN, DisplayType.HTML_PARTIAL);
        String headline = "Report for "+requestedData;
        System.out.println(headline);
        System.out.println(report);         
        request.setAttribute("headline", headline);
        request.setAttribute("report", report); 
        request.getRequestDispatcher("/WEB-INF/singleReport.jsp").forward(request, response);       
    }    
}

Answer 1

我建议您使用 ServletContextListener

，而不是在 servlet init 方法中初始化 ReportData

例如

@WebListener
public class ServletContextListenerImpl implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        ReportData m_myData = new ReportData ();
        System.out.println("My ServletContextListenerImpl has been initialized");

        // then add to your session for later use
        sce.getServletContext().setAttribute("RDATA", m_myData);
    }
    ..
 }