how to call jsp file from java?

Question

I have two jsp file and one java file. My constraints is if jspfile1 call java then java file call the jspfile2. Is it possible? How to achieve this?

Answer 1

jsp files get converted to a servlet. You cannot call them directly.

EDIT : typo fixed.

Answer 2

Do a http web request.

Answer 3

If by "Java file" you mean a Servlet, you can use the RequestDispatcher:

 request.getRequestDispatcher("/my.jsp").include(request, response);

 request.getRequestDispatcher("/my.jsp").forward(request, response);

Answer 4

 import java.io.*; import java.net.*;
> import javax.swing.*; import
> java.io.*;
> 
> public class MyClass {
> 
> public static void
> download(InputStream in, File file)
> throws IOException {
> System.out.println("Creating output
> file"); FileOutputStream out = new
> FileOutputStream(file); byte[] b = new
> byte[1024]; int len; while((len =
> in.read(b)) != -1) { out.write(b, 0,
> len); } out.close();
> System.out.println("Created output
> file"); } public static void
> main(String[] args) throws IOException
> { URL url = new URL("PutHereTheURL");
> HttpURLConnection connection =
> (HttpURLConnection)
> url.openConnection();
> 
> connection.setRequestMethod("POST");
> connection.setDoOutput(true);
> connection.setDoInput(true);
> connection.setUseCaches(false);
> connection.setAllowUserInteraction(false);
> connection.setFollowRedirects(false);
> connection.connect();
> 
> // Send the data String postString =
> "option1=" + ; DataOutputStream dos =
> new DataOutputStream(
> connection.getOutputStream() );
> dos.writeBytes(postString);
> dos.close();
> 
> // Read the resulting data from the
> Post InputStream is =
> connection.getInputStream();
> download(is, new File("myFile.html"));
> connection.disconnect(); } }

Answer 5

The normal way is using a Servlet. Just extend HttpServlet and map it in web.xml with a certain url-pattern. Then just have the HTML links or forms in your JSP to point to an URL which matches the servlet's url-pattern.

E.g. page1.jsp:

<form action="servletUrl">
    <input type"submit">
</form>

or

<a href="servletUrl">click here</a>

The <form> without method attribute (which defaults to method="get") and the <a> links will call servlet's doGet() method.

public class MyServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // Do your Java code thing here.
        String message = "hello";
        request.setAttribute("message", message); // Will be available in ${message}.

        // And then forward the request to a JSP file.
        request.getRequestDispatcher("page2.jsp").forward(request, response);
    }
}

If you have a <form method="post">, you'll have to replace doGet by doPost method.

Map this servlet in web.xml as follows:

<servlet>
    <servlet-name>myServlet</servlet-name>
    <servlet-class>com.example.MyServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>myServlet</servlet-name>
    <url-pattern>/servletUrl</url-pattern>
</servlet-mapping>

so that it's available by http://example.com/contextname/servletUrl. The <form> and <a> URL's have to point either relatively or absolutely to exact that URL to get the servlet invoked.

Now, this servlet example has set some "result" as request attribute with the name "message" and forwards the request to page2.jsp. To display the result in page2.jsp just do access ${message}:

<p>Servlet result was: ${message}</p>