Multivalued parameters

Multivalued parameters• Some type of parameters may have more than one

value. This is the case for the checkbox.

What IDEs do you use?<BR> <BR><input type=checkbox name=ide value=NB>NetBeans <BR><input type=checkbox name=ide value=EX>Eclipse <BR><input type=checkbox name=ide value=JW>JavaWorkShop <BR><input type=checkbox name=ide value=JP>J++ <BR><input type=checkbox name=ide value=CF>Cafe'

This HTML code will genrate

this output on the web-browser

“ide” will be a mutivalued parameter• The parameter “ide” <name of the input> will receive

as many values as options are selected (from 0 to 5 in this case)

What IDEs do you use?<BR> <BR><input type=checkbox name=ide value=NB>NetBeans <BR><input type=checkbox name=ide value=EX>Eclipse <BR><input type=checkbox name=ide value=JW>JavaWorkShop <BR><input type=checkbox name=ide value=JP>J++ <BR><input type=checkbox name=ide value=CF>Cafe'

These are the values the Parameter “ide” will receive If the option is selected

Retrieving the selected values

• The selected values are retrieved in a String array with the following method

getParameterValues(<parameter name>)

applied on the request parameter of the get or put method. The signature is:

String[] getParamterValues(String)

String[] values = request.getParameterValues(“ide”);for (int i = 0; i < values.length; i++) out.println(i+” “+values[i]);

This will print 1- NB 2- EX and 3- JP in this case

Retrieving All parameters when names are not known

• Sometimes the programmer may not know the names of all parameters which will be passed to the Servlet

• For example when the page was dynamically generated by another servlet according to the results of a query in database or the content of a file

• In these cases we can use the getPatameterNames() method applied to the request parameter, which will return an object of the Enumeration class

• Enumeration en = request.getParameterNames()

Using the Enumeration Object

• To retrieve the value of the unknown we can iterate over the Enumeration object using the nextElement() and hasMoreElement() methods

Enumeration en = request.getParameterNames();

while(en.hasMoreElements()) {

String parameterName = (String)en.nextElement();

String parameterValue =

request.getParameter(parameterName);

out.println(“parametro “+parameterName+

“tiene valor “+parameterValue);

}

Example: products in a file• The information about products to buy is stored in a

file. In each line there is a product code, price and description (separated with a space).

• A first servlet should show this and allow users to specify a quantity to buy

• After the user specifies the quantities, presses a button to see the total

• After pressing the button, a second servlet will receive the information and process it to show the total amount the user has to pay

Processing workflow

Products.txt

111 34347 motores222 760 escoba333 123 lapiz444 224 goma555 322 papel

OrderPage

ProcessPage

Auxiliary classes: Product

public class Product {

public String code; public int price; public String desc;

Product(String x, String y, int z){ code = x; desc = y; price = z; }

}

• First, a class for storing th information about the products

Auxiliary classes: Itemimport java.util.Hashtable;import java.io.*;import java.util.*;public class Item { static public Hashtable getItems() throws Exception { Hashtable v = new Hashtable(); String l; Product p; p = new Product("1111","Honda",250); v.put("1111",p); p = new Product("2222","Mitsubishi",340); v.put("2222",p); p = new Product("4444","BMW",280); v.put("4444",p); p = new Product("5555","Mercedes",400); v.put("5555",p); p = new Product("6666","Ferrari",405); v.put("6666",p); return v; }}

doGet of OrderPageprotected void processRequest(HttpServletRequest request, …. PrintWriter out = response.getWriter(); Hashtable h = Item.getItems(); response.setContentType("text/html"); out.print("<H2 ALIGN=CENTER> Make your order</H2>\n" + "<TABLE BORDER=1 ALIGN=CENTER><TR BGCOLOR=#FFAD00>" + "<TH>Product Number <TH>Product Name<TH>Price <TH> Number"); Enumeration keys = h.keys(); out.print("<form action=ProcessPage method='POST'>"); while(keys.hasMoreElements()) { String k = (String)keys.nextElement(); Product e = (Product)h.get(k); out.print("<TR>"); out.print("<TD>" + e.code); out.print("<TD>" + e.desc ); out.print("<TD>" + e.price+"<TD>"); out.print("<input type=text name="+e.code+" value=0 >"); } out.println("</TABLE>"); out.println("<INPUT TYPE='SUBMIT' VALUE='Process'>"); out.close(); }

Gets the hashtable with the productsby calling the getItems method of the Item class


Title and header of the table


Get the keys from the hashtable(codes of products)

doGet of OrderPagepublic void doGet( .. request, ... response) throws . . . { protected void processRequest(HttpServletRequest request, …. PrintWriter out = response.getWriter(); Hashtable h = Item.getItems(); response.setContentType("text/html"); out.print("<H2 ALIGN=CENTER> Make your order</H2>\n" + "<TABLE BORDER=1 ALIGN=CENTER><TR BGCOLOR=#FFAD00>" + "<TH>Product Number <TH>Product Name<TH>Price <TH> Number"); Enumeration keys = h.keys(); out.print("<form action=ProcessPage method='POST'>"); while(keys.hasMoreElements()) { String k = (String)keys.nextElement(); Product e = (Product)h.get(k); out.print("<TR>"); out.print("<TD>" + e.code); out.print("<TD>" + e.desc ); out.print("<TD>" + e.price+"<TD>"); out.print("<input type=text name="+e.code+" value=0 >"); } out.println("</TABLE>"); out.println("<INPUT TYPE='SUBMIT' VALUE='Process'>"); out.close(); }

Iterate over the Enumeration object to obtain each element (a Product object)


Show each field (number, name, price)Of the product in a table row

doGet of OrderPagepublic void doGet( .. request, ... response) throws . . . {

out.print("<input type=text name="+e.code+" value=0 >");}

This puts at the end of the row a text inputIts name will be the number (code) of the product

The name of the input field is the product’s code

Now lets generate the following page with ProcessOrder servlet

doGet of ProcessOrderpublic void doGet( .. request, ... response) throws . . . { PrintWriter out = response.getWriter(); Hashtable h = Item.getItems(); response.setContentType("text/html"); out.print("<H2 ALIGN=CENTER> Your choice was</H2>\n" + "<TABLE BORDER=1 ALIGN=CENTER><TR BGCOLOR=#FFAD00>" + "<TH>Product Number <TH>Product Name<TH>Price <TH> Total"); Enumeration en = request.getParameterNames(); int total = 0; out.print("<form action=ProcessPayment method='POST'>"); while(en.hasMoreElements()) { String number = (String)en.nextElement(); String qtty = request.getParameter(number); int nqtty = Integer.parseInt(qtty); Product e = (Product)h.get(number); out.print("<TR> <TD>" + e.code+"<TD>" + e.desc ); out.print("<TD>" + e.price+"<TD>"+e.price*nqtty); total = total+e.price*nqtty; } out.println("<TR> <TD> FINAL TOTAL<TD> <TD> <TD>"+total); out.println("</TABLE>"); out.println("<INPUT TYPE='SUBMIT' VALUE='Process'>");}

The same with checkbox public void doGet( .. request, ... response) throws . . . { Hashtable items = Item.getItems(); response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.print("<H2 ALIGN=CENTER> Make your order</H2>\n" + "<TABLE BORDER=1 ALIGN=CENTER><TR BGCOLOR=#FFAD00>" + "<TH>Product Number <TH>Product Name<TH>Price <TH> Number"); Enumeration enum = h.getKeys(); out.print("<form action=ProcessPage method='POST'>"); while(enum.hasMoreElements()) { Product e = (Product)enum.nextElement(); out.print("<TR>"); out.print("<TD>" + e.number); out.print("<TD>" + e.name ); out.print("<TD>" + e.price+"<TD>"); out.print("<input type=checkbox SIZE=3 "+ out.print(" name=selection value="+e.number+" >"); } out.println("</TABLE>"); out.println("<INPUT TYPE='SUBMIT' VALUE='Process'>");}

Selection means buy only 1 item<H2 ALIGN=CENTER> Make your order</H2><TABLE BORDER=1 ALIGN=CENTER><TR BGCOLOR=#FFAD00><TH>Product Number <TH>Product Name<TH>Price <TH> Number<TR><TD> 1111 <TD> motores <TD> 34347 <TD><input type=checkbox name=selection value=1111 ><TR><TD> 2222 <TD> escoba <TD> 760 <TD><input type=checkbox name=selection value=2222 ><TR><TD> 3333 <TD> lapiz <TD> 1237 <TD><input type=checkbox name=selection value=3333 ><TR><TD> 4444 <TD> goma <TD> 224 <TD><input type=checkbox name=selection value=4444 ><TR><TD> 5555 <TD> papel <TD> 322 <TD><input type=checkbox name=selection value=5555 >

ProcessOrder for checkboxpublic void doGet( .. request, ... response) throws . . . { Hashtable items = Item.getItems(); response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.print("<H2 ALIGN=CENTER> Your choice was</H2>\n" + "<TABLE BORDER=1 ALIGN=CENTER><TR BGCOLOR=#FFAD00>" + "<TH>Product Number <TH>Product Name<TH>Price <TH> Total"); String[] values = request.getParameterValues(“selection”); out.print("<form action=ProcessPayment method='POST'>"); for (int i = 0; i < values.length; i++){ String number = values[i]; Product e = (Product)item.get(number); out.print("<TR> <TD>" + e.number+"<TD>" + e.name ); out.print("<TD>" + e.price+"<TD>“+e.price*nqtty); total = total*e.price*nqtty; } out.println(“<TR> <TD> <TD> <TD> <TD>”+total); out.println("</TABLE>"); out.println("<INPUT TYPE='SUBMIT' VALUE='Process'>");}

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Multivalued parameters