Access Denied or network error when trying to show file

Thanks to @LuiggiMendoza I was able to find the solution:

First generate a Servlet for download:

<servlet>  
    <servlet-name>DownloadServlet</servlet-name>  
    <servlet-class>org.al.download.DownloadServlet</servlet-class>  
</servlet>
<servlet-mapping>  
    <servlet-name>DownloadServlet</servlet-name>  
    <url-pattern>/DownloadServlet</url-pattern>  
</servlet-mapping>

Then in my Java class that dynamically fills the command data, I call the Servlet in this way:

if(null != fac.getRutaPDF() && !fac.getRutaPDF().equalsIgnoreCase("") && null != fac.getRutaXML() && !fac.getRutaXML().equalsIgnoreCase("")){
        root.addProperty("accion",
            (null != fac.getRutaPDF() ? "<a href=\"DownloadServlet?fileName="+nombreFilePDF+"\" class=\"btn red btn-xs tooltips\"><i class=\"fa fa-file-pdf-o\"></i> PDF</a>" : "") +
            (null != fac.getRutaXML() ? "<a href=\"DownloadServlet?fileName="+nombreFileXML+"\" class=\"btn green btn-xs tooltips\"><i class=\"fa fa-file-excel-o\"></i> XML</a>" : "")
        );
    } else if(null != fac.getRutaPDF() && !fac.getRutaPDF().equalsIgnoreCase("")){
        root.addProperty("accion",
            (null != fac.getRutaPDF() ? "<a href=\"DownloadServlet?fileName="+nombreFilePDF+"\" class=\"btn red btn-xs tooltips\"><i class=\"fa fa-file-pdf-o\"></i> PDF</a>" : "")
        );
    } else if(null != fac.getRutaXML() && !fac.getRutaXML().equalsIgnoreCase("")){
        root.addProperty("accion",
            (null != fac.getRutaXML() ? "<a href=\"DownloadServlet?fileName="+nombreFileXML+"\" class=\"btn green btn-xs tooltips\"><i class=\"fa fa-file-excel-o\"></i> XML</a>" : "")
        );
    }

The magic is done by the ? fileName="+ filenameFilePDF +"

When clicking on automatic, it sends me to the servlet:

import java.io.*;
import javax.servlet.ServletException;
import javax.servlet.http.*;

public class DownloadServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        String fileName = request.getParameter("fileName");
        String filepath = "C:\PortalLeal\";
        response.setContentType("APPLICATION/OCTET-STREAM");
        response.setHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");

        FileInputStream fileInputStream = new FileInputStream(filepath + fileName);

        File file = new File(filepath + fileName);
        if (file.exists()) {
            int i;
            while ((i = fileInputStream.read()) != -1) {
                out.write(i);
            }
            fileInputStream.close();
            out.close();
        } else {
            response.sendRedirect("uploadPDF.jsp"); 
        }
    }
}

It does not access because the resources (PDF / XML) are in a folder that is not accessible to the web server .

All resources that must be shown / used in a web page must be reachable and serviceable by the web server. That is why the images, css files, javascript files, etc. they are usually in the same folder in which you have your HTML or PHP files, because the web server is allowed to access all the files within their child folders.

To serve those PDF and XML files, you must make them available to the web server either on a different web server, a different endpoint (within the same server), or within the folders of the web app that you show us.

I see a problem with what you are proposing as a solution. What is the idea of a web application delivering a link to a file on your local disk (c :)? That system is not going to serve you if some more access, because it will never access the files.

In summary, Tomcat is not accessing the file, but your browser and probably there is a restriction.

In your javascript code, add a file to the URI: // thing your code starts creating the URLs like this:

(null != fac.getRutaPDF() ? "<a onClick=\"downloadURI('file://"+fac.getRutaPDF().replace("\", "\\")+"','"+nombreFilePDF+"');\" class=\"btn red btn-xs tooltips\"><i class=\"fa fa-file-pdf-o\"></i> PDF</a>" : "")

Likewise, in my opinion doing so is incorrect because of what I indicated earlier.