Quiz | | | A1: | The different types of tags that can be used in a JSP page are directive, declaration, expression, scriptlet, and custom tags. | | | | A2: | A directive tag to set the MIME type for sending a GIF image file is <%@ page contentType="image/gif"> | | | | A3: | The include directive tag should be used in this case. Here is an example: <%@ include file="/myhost/myapp/mySecondJSP.jsp" > | | | | A4: | To define global variables in a JSP, that is, variables outside the service() method, the declaration tag should be used. An example of this is given here: <%! // java variables instantiated here String myStringVar = new String(); int intVar = 0; %> | | | | A5: | The simplest tag to use for displaying values in a JSP is the expression tag. An example of this is Value of the variable is <%=myStringVar>. | | | | A6: | The scriptlet tag should be used to write Java statements in a JSP. The java statements written in scriptlet tags are placed in the service() method of the generated servlet. An example of this is <% // write java statements here %> | | | | A7: | The different implicit variables available in a JSP are request, response, out, session, pageContext, application, config, and page. |
Exercises | | | A1: | The following code demonstrates the technique to send an image file on the browser. After importing the required files, the response type is set to "image/jpeg". The file is then read into a BufferedInputStream object. The size of the file is obtained using the available() method of BufferedInputStream class. This BufferedInputStream object is then read into a byte array. The OutputStream object is then obtained, and the byte array is written onto this OutputStreamObject. The response object is then sent back to the browser. <html> <head> <title>Display Image File</title> </head> <body bgcolor=#FFFFFF> <center> <strong><font size=3 face='arial' color=#336600> <H1>Image File Display</H1> </font></strong> </center> <p> <%@ page import=" java.io.*, java.sql.*, javax.servlet.*, javax.servlet.http.*, "%> <% String IMAGE_FILE_LOCATION = "C:\\Book1Image.jpg"; //setting content type try{ response.setContentType("image/jpeg"); FileInputStream file = new FileInputStream(IMAGE_FILE_LOCATION); BufferedInputStream bin = new BufferedInputStream(file); int fSize = bin.available(); byte[] buff = new byte[fSize]; bin.read(buff, 0, fSize); bin.close(); OutputStream myOut = response.getOutputStream(); int count=0; while(count < fSize) myOut.write(buff[count++]); } catch(IOException ioe){ out.println("File cannot be read."); } catch(Exception e){ out.println("General error."); } %> </body> </html> | | | | A2: | The getMethod() method of the HttpServletRequest class is used to detect the kind of request. The following code illustrates the use of this method to obtain the request type: <html> <head> <title>Detect request method</title> </head> <body bgcolor=#FFFFFF> <center> <strong><font size=3 face='arial' color=#336600> <H1>Detect Request Method</H1> </font></strong> </center> <p> <%@ page import=" java.io.*, java.sql.*, javax.servlet.*, javax.servlet.http.*, "%> <% String reqType = request.getMethod(); if(reqType.equals("GET")){ out.println("This is a get request."); } else if(reqType.equals("POST")){ out.println("This is a post request."); } %> </body> </html> |
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