Servlets Explain how browsers and servers work Use

Servlets ▮ Explain how browsers and servers work ▮ Use Page Designer to create web pages ▮ Explain how servlets work ▮ Show to define a form to invoke a servlet Chapter 8 © copyright Janson Industries 2014 1

New Source of Documentation Chapter 8 © copyright Janson Industries 2014 http: //download. oracle. com/javaee/7/api/ 2

Servlets and JSPs ▮ Servlets are Java programs that generate HTML which is sent to a browser ▮ JSP’s (Java Server Pages) are HTML with embedded Java commands ▮ The advantage over static web pages: servlets and JSP’s can dynamically build web pages and their content Chapter 8 © copyright Janson Industries 2014 3

Servlets and JSP’s ▮ In actuality, JSP’s are converted into Servlets by the JSP “container” ▮ Need a server that provides Servlet and JSP containers – an application server ▮ Before we can create need to: ▮ Explain how browser, server & servlets work ▮ Show some alternatives for building servlets: ▮ Source code ▮ RAD Page Designer Chapter 8 © copyright Janson Industries 2014 4

Servers ▮ When a link is clicked or a URL is entered, the browser sends a request to the server ▮ There are many type of requests ▮ Primarily, browsers send get and post requests ▮ A browser get request asks for a file’s contents, a post sends HTML FORM info ▮ If the get request identifies a html file, the server sends the html back to the client as part of a response Chapter 8 © copyright Janson Industries 2014 5

Servlets ▮ If a request identifies a servlet, servlet is run i. e. its init() method is run ▮ if a constructor exists, it will be run also ▮ If a get request, server also invokes the do. Get method of the servlet ▮ What method does a post request invoke? ▮ Server also passes 2 objects to the servlet: Http. Servlet. Request Chapter 8 Http. Servlet. Response © copyright Janson Industries 2014 6

Servlets Users PC Browser S/W 1 URL. class Server 2 Get request for servlet Server S/W Req & Resp objects . CLASS 3 Load and run servlet Servlet User Chapter 8 © copyright Janson Industries 2014 7

Servlets ▮ The servlet modifies the response object ▮ When the servlet finishes, the response is passed back to the server ▮ The server returns the modified response object back to the browser Chapter 8 © copyright Janson Industries 2014 8

Servlets Server Users PC Browser S/W 5 Response w/ HTML 6 Display Web Page Server S/W 4 Response object Servlet User Chapter 8 © copyright Janson Industries 2014 9

Server based apps can’t be stored in a Java project We will create and use a Dynamic Web project File, New, Project, Dynamic Web Project Chapter 8 © copyright Janson Industries 2014 10

New project - My. Web Must create an EAR then add My. Web to EAR Chapter 8 © copyright Janson Industries 2014 11

New EAR project - My. Web. EAR Chapter 8 © copyright Janson Industries 2014 12

Chapter 8 © copyright Janson Industries 2014 13

Select JSTL (Java Standard Tag Library) Facet Chapter 8 © copyright Janson Industries 2014 14

Will ask for perspective switch to Web, click Yes Chapter 8 © copyright Janson Industries 2014 15

Opens Technology Quickstarts pane which has links to tutorials/help for common web development actions (They’re OK) Chapter 8 © copyright Janson Industries 2014 16

Create an initial web page: Click on My. Web then File, New, Web Page Specify file name, HTML/XHTML, click Finish Chapter 8 © copyright Janson Industries 2014 17

Servers ▮ Servers require that web app resources be stored in specific locations, i. e. ▮ Web pages are stored in a particular folder ▮ Servlets are stored in a particular folder ▮ RAD picks the correct folder: Web. Content Chapter 8 © copyright Janson Industries 2014 18

Page Designer started - graphical tool Defaults to Split view Click on page & type to insert new text. . . 8 Janson Industries 2014 19 or. Chapter select HTML tags© copyright (page components) from palette. . .

Click Palette tab to display components Multiple trays of components Chapter 8 © copyright Janson Industries 2014 20

Or insert other components (Images, Links, Lines, Tables, etc. )2014 Chapter 8 © copyright Janson Industries 21

Insert a form by clicking on the Form Tags tray Click on Form and then on the page Chapter 8 © copyright Janson Industries 2014 22

Shows form in design view and inserts the HTML Chapter 8 © copyright Janson Industries 2014 23

Must put other visual components in the form Click Text Field then click inside form Specify properties and click OK Name is very important! Chapter 8 © copyright Janson Industries 2014 24

Places component at cursor location Move by click and drag. . . but Web pages are line oriented (as opposed to Frames) Have to put in blank lines and spaces to drag Chapter 8 © copyright Janson Industries 2014 25

Display and change component properties: Select component, switch to Properties view (may need to click Window, Show View, Properties) Chapter 8 © copyright Janson Industries 2014 26

Put in 3 new lines (Enter 3 times) in web page then clicked List. Box and the last line Specify LB properties Must click Add to specify values Chapter 8 © copyright Janson Industries 2014 27

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Click and drag on resize handles to reshape or change properties Chapter 8 © copyright Janson Industries 2014 29

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Text Field List Box Drop Down Menu Notice in DDM that selected item (Inventory) not chosen Chapter 8 © copyright Janson Industries 2014 31

Switch to Preview pane Employee item in list is selected and listed at top and Inventory in DDM is selected and displayed Chapter 8 © copyright Janson Industries 2014 32

To format: select component (or components), click Format Chapter 8 © copyright Janson Industries 2014 33

Choose format options Chapter 8 © copyright Janson Industries 2014 34

You get the idea… I’ll add text and pretty it up a little Chapter 8 © copyright Janson Industries 2014 35

Alternative view: Source Chapter 8 © copyright Janson Industries 2014 36

Of course, you can modify source directly Chapter 8 Forms must have a submit button! © copyright Janson Industries 2014 37

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Chapter 8 © copyright Janson Industries 2014 39

In Class Assg ▮ Create a page called Functions 2 that has form, submit button, and a drop down box with options for: ▮ Customer ▮ Sale ▮ Create two pages (Cust. html and Sale. html) that: ▮ Have forms (with text fields, buttons, and text) to enter customer and transaction info that look like the following. . . Chapter 8 © copyright Janson Industries 2014 40

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A trick to get all the components to line up: Invisible tables (tables with Border = 0) Chapter 8 © copyright Janson Industries 2014 43

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TXServlet Example ▮ Need to change web page such that: ▮ The Functions form calls a servlet ▮ The servlet builds/returns the correct response ▮ Servlet will echo back data entered and selections made by the user on Functions. html Chapter 8 © copyright Janson Industries 2014 45

TXServlet Example ▮ This means the servlet has to: ▮ Read the page components contents from the request ▮ Write html and the page components contents to the response Chapter 8 © copyright Janson Industries 2014 46

To create a servlet for the first time: File, New, Other Expand Web and select Servlet Chapter 8 © copyright Janson Industries 2014 47

Notice RAD knows where to save source Specify name and then click Finish Chapter 8 © copyright Janson Industries 2014 48

Basic methods are created. Need to change so functions and emp num sent back as text on a page Notice that do. Get and do. Post expect Response and Request objects as parameters, will change parameter names to resp and req Chapter 8 © copyright Janson Industries 2014 49

To tie a web page to the servlet, in Design view of page click form outline or in Properties pane the form tab Chapter 8 copyright Janson Industries 2014 Then ©click the Action button 50

RAD will display the available servlets Select a servlet and click the OK button Chapter 8 © copyright Janson Industries 2014 51

Drop Down Menu ■ To retrieve the selected item from the DDM use the request object’s get. Parmeter method ♦ Remember form data imbedded in the request ♦ Each of the forms visual components is a request “parameter” ■ Syntax is: String func = req. get. Parameter(“DDMName"); Chapter 8 © copyright Janson Industries 2014 52

Tieing To Other Pages ■ A response object’s send. Redirect() method allows you to redirect the browser to another url if (func. equals(“other”)) { resp. send. Redirect(“Otherpage. html"); } Chapter 8 © copyright Janson Industries 2014 53

In Class Assg 2 ▮ Create a servlet called Func. Servlet that is ▮ Called by Functions 2. html ▮ Based on the selected function, redirects to either Cust. html or Sale. html User Functions 2. html Func. Servlet Cust or Sale. html Assg 2 Solution Chapter 8 © copyright Janson Industries 2014 54

Writing to a Response ▮ Servlets need two objects to manipulate a Response object: ▮ Print. Writer ▮ Output. Stream ▮ The Print. Writer, Output. Stream, and Response are “tied together” ▮ The Print. Writer feeds the Output. Stream, which writes to the Response Chapter 8 © copyright Janson Industries 2014 55

Servlets ▮ Print. Writer takes Strings and numbers and converts to a text output stream ▮ Output. Stream converts a text output stream to a binary stream Text Print. Writer Stream Primitives & Strings Chapter 8 Output Stream Binary Stream Response © copyright Janson Industries 2014 56

Servlets ▮ The Response object has a method that returns a Output. Stream object that is tied to the repsonse: resp. get. Output. Stream() ▮ Must create a Print. Writer object and pass it the Output. Stream object (ties the two together) ▮ Standard syntax to create Print. Writer object: Print. Writer out = new Print. Writer(resp. get. Output. Stream()); ▮ Don’t forget to import the class import java. io. Print. Writer; Chapter 8 © copyright Janson Industries 2014 57

Servlets ▮ Use the request object to retrieve info from page components then assign to variables: String emp. Num = req. get. Parameter(“Emp. Num. TF”); String func. LB = req. get. Parameter(“Func. LB”); String func. DD = req. get. Parameter(“Func. DD”); ▮ HTML for basic page: out. println("<HTML>"); out. println("<HEAD><Title>Servlet Response</Title></HEAD>"); out. println("<BODY>"); out. println("</HTML>"); Chapter 8 © copyright Janson Industries 2014 58

Servlets ▮ HTML for page body content out. println("The Employee Number passed was: " + emp. Num); out. println("The List Box function was: " + func. LB); out. println("The Drop Down List function was: " + func. DD); Chapter 8 © copyright Janson Industries 2014 59

import java. io. Print. Writer; : : public void do. Get(javax. servlet. http. Http. Servlet. Request req, javax. servlet. http. Http. Servlet. Response resp) { resp. set. Content. Type("text/html"); try { Print. Writer out = new Print. Writer(resp. get. Output. Stream()); String emp. Num = req. get. Parameter("Emp. Num. TF"); String func. LB = req. get. Parameter("Func. LB"); String func. DD = req. get. Parameter("Func. DD"); out. println("<HTML>"); out. println("<HEAD><Title>Servlet Response</Title></HEAD>"); out. println("<BODY>"); out. println("The Employee Number passed was: " + emp. Num); out. println("The List Box function was: " + func. LB); out. println("The Drop Down List function was: " + func. DD); out. println("</BODY>"); out. println("</HTML>"); out. close(); } catch (Exception e) { System. out. println("Sample Servlet failed: "); e. print. Stack. Trace(); Chapter 8 © copyright Janson Industries 2014 } } 60

Don't forget to tie Web page and servlet together: Chapter 8 copyright Janson Industries

Start by clicking form outline in Design view or form tab in Properties pane

RAD will display the available servlets Select Tx. Servlet and click the OK button

Will not work in Preview pane Must run the web page on server In

If a server isn't already defined. . . Chapter 8 © copyright Janson Industries

If first time or in lab, create a new Test server Chapter 8 ©

Deselect RMI and IPC. Soap plays nicer with the firewall. Chapter 8 © copyright

If not first time or not in lab, use existing server Chapter 8 ©

If you get an error, click the Details button and follow instructions Chapter 8

Server Problems ▮ How to fix server errors when running servlets ▮ Turn off your firewall ▮ Turn off anti-virus s/w (or configure it so RAD has total authority) ▮ Run RAD as an administrator ▮ Right click RAD icon/menu item ▮ Select Run as administrator Chapter 8 © copyright Janson Industries 2014 70

Server Problems ▮ Profile name App. Srv 1 is invalid. Specify a profile name that exists on the server. ▮ Click here for document with instructions on how to create server profile name Chapter 8 © copyright Janson Industries 2014 71

Server Problems ▮ If resource not found error ▮ In Servers pane, right click server ▮ Select Add and Remove ▮ Click Remove All then Finish ▮ This forces the server to reload the project the next time it is run ▮ In Explorer pane select the project ▮ In Command bar click on Project ▮ Select Clean ▮ Forces RAD to rebuild the project Chapter 8 © copyright Janson Industries 2014 72

First time will take a while! Page (eventually) displayed in browser pane If not,

Enter info, click Submit Chapter 8 © copyright Janson Industries 2014 74

Chapter 8 © copyright Janson Industries 2014 75

In Class Assg 3 - Sale. Servlet ▮ Sale. html should invoke Sale. Servlet ▮ Create Sale. Servlet to: ▮ Echo back the data from the Sale Web Page Sale. html User Chapter 8 HTML (response) With Sale info © copyright Janson Industries 2014 Sale Servlet 76

In Class Assg 3 - Sale. Servlet Solution Chapter 8 © copyright Janson Industries

In Class Assg 4 - Servlets co Creates Func 2 Servlet Cust. html User Chapter 8 HTML (response) With Cust info Customer object Creates co request response © copyright Janson Industries 2014 Retrieves info Cust Servlet 78

Display Functions 2, choose Customer Enter some info Click Submit Func 2 Servlet creates

In Class Assg 4 - Cust. Servlet ▮ Cust. html should invoke Func 2 Servlet that: ▮ Creates a Customer object, assigns to a variable called co, populates object with page data ▮ Must copy Customer class into My. Web ▮ Code Cust. Servlet such that: ▮ do. Get also expects a Customer variable ▮ Echoes back data from Customer object Chapter 8 © copyright Janson Industries 2014 80

In Class Assg 4 - Cust. Servlet ▮ Func 2 Servlet will invoke Cust. Servlet differently ▮ Instead of Func 2 Servlet redirecting to Cust. Servlet, Func 2 Servlet: ▮ Instantiates a Cust. Servlet object (cs) ▮ Invokes cs. do. Get method passing co, the request, and the response Solution Chapter 8 © copyright Janson Industries 2014 81

All In Class Assgs Example CO Func. Servlet Cust. html Functions 2. html Creates Func 2 Servlet Cust or Sale. html Request Response CO HTML (response) With Cust info User Sale. html HTML (response) With Sale info Chapter 8 © copyright Janson Industries 2014 Customer object Retrieves info Cust Servlet Sale Servlet 82

Chapter 8 Tutorial ▮ To turn in the C 8 (and C 9) tutorial: ▮ Export the dynamic web project as a WAR file ▮ Give the WAR file the same name as the project with your initials at the end ▮ Send the WAR as an email attachment to me at rjanson@fscj. edu ▮ I will let you know within 1 business day that I received it, if you don’t hear from me I didn’t get it Chapter 8 © copyright Janson Industries 2014 83