exportcswqueryservlet.java

esri的ArcGIS Server超级学习模板程序（for java）

package com.esri.solutions.jitk.common.csw;

import com.esri.adf.web.data.WebContext;

import com.esri.solutions.jitk.web.tasks.search.csw.CswSearchTaskBean;

import org.apache.log4j.Logger;

import java.io.IOException;

import javax.faces.FactoryFinder;
import javax.faces.context.FacesContext;
import javax.faces.context.FacesContextFactory;
import javax.faces.lifecycle.Lifecycle;
import javax.faces.lifecycle.LifecycleFactory;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


/**
 * This class handles client requests for exporting CS/W queries by
 * extending {@link HttpServlet}.
 */
@SuppressWarnings("serial")
public class ExportCswQueryServlet extends HttpServlet {
    /**
     * {@link Logger} used to log messages for this class.
     */
    private static final Logger LOG = Logger.getLogger(ExportCswQueryServlet.class);

    /*
     * (non-Javadoc)
     * @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
     */
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
        FacesContext fc = null;
        String taskBeanName = null;
        String webContextName = null;
        CswSearchTaskBean taskBean = null;
        WebContext webContext = null;
        String taskBeanInitParamName = "TaskBeanName";
        String webContextInitParamName = "WebContext";
        String xmlQuery = null;
        ServletOutputStream out = null;
        String filename = null;

        taskBeanName = getServletConfig().getInitParameter(taskBeanInitParamName);
        webContextName = getServletConfig()
                             .getInitParameter(webContextInitParamName);

        if (taskBeanName == null) {
            resp.getWriter()
                .write(generateErrorHtml(
                    "An error has occurred exporting CS/W Query.  Possible configuration problem."));

            LOG.debug("Missing servlet initialization parameter '" +
                taskBeanInitParamName + "' for servlet: " +
                getServletConfig().getServletName() + " - cannot export query");

            resp.getWriter().flush();
            resp.getWriter().close();

            return;
        }

        if (webContextName == null) {
            resp.getWriter()
                .write(generateErrorHtml(
                    "An error has occurred exporting CS/W Query.  Possible configuration problem."));

            LOG.debug("Missing servlet initialization parameter '" +
                webContextInitParamName + "' for servlet: " +
                getServletConfig().getServletName() + " - cannot export query");

            resp.getWriter().flush();
            resp.getWriter().close();

            return;
        }

        fc = getFacesContext(req, resp);

        if (!(fc.getApplication().getVariableResolver()
                    .resolveVariable(fc, taskBeanName) instanceof CswSearchTaskBean)) {
            resp.getWriter()
                .write(generateErrorHtml(
                    "An error has occurred exporting CS/W Query.  Possible configuration problem."));

            LOG.debug("CS/W task bean is not of type '" +
                CswSearchTaskBean.class.getName() + "' - cannot export query");

            resp.getWriter().flush();
            resp.getWriter().close();

            return;
        }

        if (!(fc.getApplication().getVariableResolver()
                    .resolveVariable(fc, webContextName) instanceof WebContext)) {
            resp.getWriter()
                .write(generateErrorHtml(
                    "An error has occurred exporting CS/W Query.  Possible configuration problem."));

            LOG.debug("WebContext bean is not of type '" +
                WebContext.class.getName() + "' - cannot export query");

            resp.getWriter().flush();
            resp.getWriter().close();

            return;
        }

        taskBean = (CswSearchTaskBean) fc.getApplication().getVariableResolver()
                                         .resolveVariable(fc, taskBeanName);
        webContext = (WebContext) fc.getApplication().getVariableResolver()
                                    .resolveVariable(fc, webContextName);

        xmlQuery = taskBean.saveQueryToString(webContext);

        if (xmlQuery == null) {
            resp.getWriter()
                .write(generateErrorHtml(
                    "An error has occurred exporting query to XML."));

            LOG.debug("XML serialization string is null");

            resp.getWriter().flush();
            resp.getWriter().close();

            return;
        }

        filename = taskBean.getSaveQueryName().replace("'", "") + ".xml";

        resp.setContentType("APPLICATION/OCTET-STREAM");
        resp.setContentLength(xmlQuery.length());
        resp.addHeader("Content-Disposition", "attachment;filename=" +
            filename);

        out = resp.getOutputStream();

        out.print(xmlQuery);

        out.flush();
        out.close();
    }

    /**
     * Utility method to get the {@link FacesContext} object via
     * the {@link FacesContextFactory#getFacesContext(Object, Object, Object, Lifecycle)}.
     *
     * @param request Reference to the {@link HttpServletRequest} needed for getting the
     *                 {@link FacesContext}.
     * @param response Reference to the {@link HttpServletResponse} needed for getting the
     *                 {@link FacesContext}.
     * @return {@link FacesContext} reference.
     */
    private FacesContext getFacesContext(HttpServletRequest request,
        HttpServletResponse response) {
        FacesContext facesContext = FacesContext.getCurrentInstance();

        if (facesContext == null) {
            FacesContextFactory contextFactory = (FacesContextFactory) FactoryFinder.getFactory(FactoryFinder.FACES_CONTEXT_FACTORY);
            LifecycleFactory lifecycleFactory = (LifecycleFactory) FactoryFinder.getFactory(FactoryFinder.LIFECYCLE_FACTORY);
            Lifecycle lifecycle = lifecycleFactory.getLifecycle(LifecycleFactory.DEFAULT_LIFECYCLE);

            facesContext = contextFactory.getFacesContext(getServletContext(),
                    request, response, lifecycle);
        }

        return facesContext;
    }

    /**
     * Utility method to generate an HTML message that can be
     * sent back to the client.
     *
     * @param message {@link String} message.
     * @return HTML message that can be viewed in a browser.
     */
    private String generateErrorHtml(String message) {
        StringBuilder errorHtml = null;

        errorHtml = new StringBuilder();

        errorHtml.append("<html>");
        errorHtml.append("<head>");
        errorHtml.append("<title>");
        errorHtml.append("Error Exporting CS/W Query");
        errorHtml.append("</title>");
        errorHtml.append("</head>");
        errorHtml.append("<body>");
        errorHtml.append(message);
        errorHtml.append("</body>");
        errorHtml.append("</html>");

        return errorHtml.toString();
    }
}