PDF handling

Read and open the PDF in a new browser window

The goal is to use JSF to open a PDF file inline in a new browser window without showing the full PDF path and filename for some (security) reasons. You can use either a h:commandLink or a h:commandButton for this:

<h:form>
    <h:commandLink value="Download PDF" action="#{myBean.downloadPDF}" target="_blank" />
</h:form>

<h:form target="_blank">
    <h:commandButton value="Download PDF" action="#{myBean.downloadPDF}" />
</h:form>

Note: when using an ajax-capable command button/link from a library such as PrimeFaces, then don't forget to turn off the ajax capability by e.g. adding ajax="false" in case of PrimeFaces command components. It's namely not possible to download files using ajax, for the simple reason that JavaScript is due to security restrictions not capable of forcing a Save As dialogue from the client side on.

The downloadPDF() method of the backing bean MyBean.java sends the PDF to the HttpServletResponse as follows:

package mypackage;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.Closeable;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

import javax.faces.context.ExternalContext;
import javax.faces.context.FacesContext;
import javax.servlet.http.HttpServletResponse;

public class MyBean {

    // Constants ----------------------------------------------------------------------------------

    private static final int DEFAULT_BUFFER_SIZE = 10240; // 10KB.

    // Actions ------------------------------------------------------------------------------------

    public void downloadPDF() throws IOException {

        // Prepare.
        FacesContext facesContext = FacesContext.getCurrentInstance();
        ExternalContext externalContext = facesContext.getExternalContext();
        HttpServletResponse response = (HttpServletResponse) externalContext.getResponse();

        File file = new File(getFilePath(), getFileName());
        BufferedInputStream input = null;
        BufferedOutputStream output = null;

        try {
            // Open file.
            input = new BufferedInputStream(new FileInputStream(file), DEFAULT_BUFFER_SIZE);

            // Init servlet response.
            response.reset();
            response.setHeader("Content-Type", "application/pdf");
            response.setHeader("Content-Length", String.valueOf(file.length()));
            response.setHeader("Content-Disposition", "inline; filename=\"" + getFileName() + "\"");
            output = new BufferedOutputStream(response.getOutputStream(), DEFAULT_BUFFER_SIZE);

            // Write file contents to response.
            byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
            int length;
            while ((length = input.read(buffer)) > 0) {
                output.write(buffer, 0, length);
            }

            // Finalize task.
            output.flush();
        } finally {
            // Gently close streams.
            close(output);
            close(input);
        }

        // Inform JSF that it doesn't need to handle response.
        // This is very important, otherwise you will get the following exception in the logs:
        // java.lang.IllegalStateException: Cannot forward after response has been committed.
        facesContext.responseComplete();
    }

    // Helpers (can be refactored to public utility class) ----------------------------------------

    private static void close(Closeable resource) {
        if (resource != null) {
            try {
                resource.close();
            } catch (IOException e) {
                // Do your thing with the exception. Print it, log it or mail it. It may be useful to 
                // know that this will generally only be thrown when the client aborted the download.
                e.printStackTrace();
            }
        }
    }

}

The names of the getFilePath() and getFileName() are self-explaining, so there is no need to describe those methods.

If you don't care about showing request parameters or filenames in the URL, then you can also consider to use a FileServlet.

Copyright - There is no copyright on the code. You can copy, change and distribute it freely. Just mentioning this site should be fair.

(C) May 2006, BalusC