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Get and display cookie names and values
Listing 8 calls the getName and getValue methods of the Cookie class to get and display the names and values of each of the cookies saved earlier in the array of cookies.
The first value displayed should be the session ID that was stored in the first cookiesaved. The remaining items in the list should be the field input values previously submitted by the user each time the servlet was called but notincluding the field input value for this invocation of the servlet.
| Listing 8 - Get and display cookie names and values. |
|---|
if(cookies != null){
for(int i = 0; i<cookies.length; i++){
out.println(cookies[i].getName() + ":" +
cookies[i].getValue() + "<br/>");
}//end for loop}//end if |
The output from Listing 8 is shown by the sessionID line and the lines for Tom and Dick in Figure 1 . (The output from Listing 8 does not include the line for Harry.) The large numeric values to the left of Tom and Dick are the cookie namesbased on the number of milliseconds since January 1, 1970.
Display currently submitted field value
Listing 9 displays the field value (Harry) submitted by the user for the current invocation of the servlet. This value is displayed at the end of thelist as shown in Figure 1 . Note that there is no cookie name associated with Harry in Figure 1 . This value was not extracted from a named cookie for display. However, it will be displayed with a cookie name if the user calls the servletagain with a new field value before the cookie with the value Harry expires.
| Listing 9 - Display currently submitted field value. |
|---|
if(name != null){
out.println(name + "<br/>");
}//end if |
The remaining code is typical of what you have seen in earlier modules. You can view that code in Listing 10 .
If you understand the explanation of the servlet code given above and you have understood the explanations of JSP code providedin earlier modules, you should have no difficulty understanding the JSP code provided in Listing 11 . Therefore, I won't bore you with a detailed explanation of that code. The JSPcode is provided simply for comparison with the servlet code.
However, there is one point that is worth noting. If you compare Figure 2 showing the JSP output with Figure 1 showing the servlet output, you will see that the JSP output contains an extra cookie named JSESSIONID . This is a unique session ID value that is automatically created by the JSPcontainer. When writing servlets, you need to take the necessary steps to create a unique session ID. However, when writing JSP, that task is handledautomatically for you so there is no need to create your own unique session ID.
I encourage you to copy the code from Listing 10 and Listing 11 . Install the programs on your server. Experiment with the code,making changes, and observing the results of your changes. Make certain that you can explain why your changes behave as they do.
This section contains a variety of miscellaneous information.
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