How to connect JSF(h:commandButton) with Servlet

Question

In my project(JSF+ MAVEN) i want to download PDF Files from my DB using servlet,(i.e. than i click the button,servlet must download file from DB) but all what i am writing in JSF 'commandButton' don't work.CommandButton don't see servlet.

This is form with 'commandButton' in content.xhtml

 <h:form>
     <h:commandButton action="/DownloadFile" value="#{msg.download}"styleClass="download-Button">
                    <f:param name="file_id=#{b.id} "/>
     </h:commandButton>
  </h:form>

This is 'Downloadfile' servlet, which download PDF files from DB. PDF files saves in column 'content' in DB as relative path.

public class DownloadFile extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet {

private String content;
private String name;
private Connection conn;
private  PreparedStatement ps;
private ResultSet rs;
private void getFileFromDb(HttpServletRequest request, HttpServletResponse response) throws ServletException,
        IOException {
    try {
        Map<String, String> params = FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap();
        int selectedFileID = Integer.valueOf(params.get("file_id"));
        System.out.println("Id====" + selectedFileID);

        conn = DataBase.getConnection();
         ps = conn.prepareStatement("SELECT content,name FROM book WHERE id= "+ selectedFileID);
        rs = ps.executeQuery();
        while (rs.next()){
            content = rs.getString("content");
            name = rs.getString("name");
        }
    } catch (SQLException e) {
        e.printStackTrace();
    }

    String contextPath = "D:\\IdeaProjects\\Books\\";
    File pdfFile = new File(contextPath + content);

    response.setContentType("application/pdf");
    response.addHeader("Content-Disposition", "attachment; filename=" + name+".pdf");
    response.setContentLength((int) pdfFile.length());

    FileInputStream fileInputStream = new FileInputStream(pdfFile);
    OutputStream responseOutputStream = response.getOutputStream();
    int bytes;
    while ((bytes = fileInputStream.read()) != -1) {
        responseOutputStream.write(bytes);
    }

}

}

This is my project structure. Project structure

How to correctly write navigation to this servlet? I have tried many ways, but they also don't works.Will be gratefull for all answers.

Why do you think you need a commandButton for this? Or the other way around, if you use a commandButton, why do you use a servlet? You are trying to mix solutions that are not intended to be use together (in one call). And off-topic: Read https://stackoverflow.com/questions/30639785/jsf-controller-service-and-dao and apply it to your code. Where you read 'jsf controller' you can also read 'servlet'. Separation of concerns. And if you 'wrapped' the real logic in a service, https://stackoverflow.com/questions/9391838/how-to-provide-a-file-download-from-a-jsf-backing-bean becomes easily possible — Kukeltje, Jun 13 '18 at 18:17
Thank you so much. This examples https://stackoverflow.com/questions/9391838/how-to-provide-a-file-download-from-a-jsf-backing-bean helped me solve my problem. — Maxim Sukhodolets, Jun 13 '18 at 19:07
Possible duplicate of [How to provide a file download from a JSF backing bean?](https://stackoverflow.com/questions/9391838/how-to-provide-a-file-download-from-a-jsf-backing-bean) — Kukeltje, Jun 13 '18 at 19:55

Allan Braga · Answer 1 · 2018-06-13T18:54:15.697

For create a servlet you don´t need to implement the Servelet only extend.

public class HelloWorld extends HttpServlet {}

Change your method name to doGet and change for public not private.

Then call the Servlet with this simple way, don´t forget to add target="_blank"

<h:outputLink value="/DownloadFile?param=param_value" target="_blank">
    <f:param name="param1" value="value1" />
</h:outputLink>

Or pure HTML:

<a href="/DownloadFile?param=" target="_blank">
    #{node.reportName}
</a>

How to connect JSF(h:commandButton) with Servlet

1 Answers1