Here's an example that looks up all the parameter names that were sent and puts them in a table. It highlights parameters that have zero values as well as ones that have multiple values. First, it looks up all the parameter names via the
getParameterNames method of HttpServletRequest. This returns an Enumeration. Next, it loops down the Enumeration in the standard manner, using hasMoreElements to determine when to stop and using nextElement to get each entry. Since nextElement returns an Object, it casts the result to a String and passes that to getParameterValues, yielding an array of Strings. If that array is one entry long and contains only an empty string, then the parameter had no values, and the servlet generates an italicized "No Value" entry. If the array is more than one entry long, then the parameter had multiple values, and they are displayed in a bulleted list. Otherwise the one main value is just placed into the table. ShowParameters.java
package hall; import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.util.*; /** Shows all the parameters sent to the servlet via either * GET or POST. Specially marks parameters that have no values or * multiple values. * * Part of tutorial on servlets and JSP that appears at * http://www.apl.jhu.edu/~hall/java/Servlet-Tutorial/ * 1999 Marty Hall; may be freely used or adapted. */ public class ShowParameters extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); String title = "Reading All Request Parameters"; out.println(ServletUtilities.headWithTitle(title) + "<BODY BGCOLOR=\"#FDF5E6\">\n" + "<H1 ALIGN=CENTER>" + title + "</H1>\n" + "<TABLE BORDER=1 ALIGN=CENTER>\n" + "<TR BGCOLOR=\"#FFAD00\">\n" + "<TH>Parameter Name<TH>Parameter Value(s)"); Enumeration paramNames = request.getParameterNames(); while(paramNames.hasMoreElements()) { String paramName = (String)paramNames.nextElement(); out.println("<TR><TD>" + paramName + "\n<TD>"); String[] paramValues = request.getParameterValues(paramName); if (paramValues.length == 1) { String paramValue = paramValues[0]; if (paramValue.length() == 0) out.print("<I>No Value</I>"); else out.print(paramValue); } else { out.println("<UL>"); for(int i=0; i<paramValues.length; i++) { out.println("<LI>" + paramValues[i]); } out.println("</UL>"); } } out.println("</TABLE>\n</BODY></HTML>"); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
No comments:
Post a Comment