Head First Servlets and JSP. Passing the Sun Certified Web Component Developer Exam. 2nd Edition

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Spis treści ebooka

• Head First Servlets and JSP
• Dedication
• A Note Regarding Supplemental Files
• Praise for Head First Servlets and JSP
• Praise for the Head First approach
• Perpetrators of the Head First series (and this book)
• How to Use this Book: Intro
  • Who is this book for?
    • Who should probably back away from this book?
  • We know what youre thinking.
  • And we know what your brain is thinking
  • Metacognition: thinking about thinking
  • Heres what WE did
  • Heres what YOU can do to bend your brain into submission
  • What you need for this book
  • Last-minute things you need to know
  • About the SCWCD (for Java EE 1.5) exam
  • Beta testers & technical reviewers
  • Other people to : credit
  • Even more people
• 1. Intro and Overview: Why use Servlets & JSPs?
  • Everybody wants a web site
  • What does your web server do?
  • What does a web client do?
  • Clients and servers know HTML and HTTP
  • Two-minute HTML guide
  • What you write... (the HTML)
  • What the browser creates...
  • What is the HTTP protocol?
  • HTML is part of the HTTP response
  • If thats the response, whats in the request?
  • GET is a simple request, POST can send user data
  • Its true... you can send a little data with HTTP GET
  • Anatomy of an HTTP GET request
  • Anatomy of an HTTP POST request
  • Anatomy of an HTTP response, and what the heck is a MIME type?
  • All the pieces. On one page.
  • URL. Whatever you do, dont pronounce it Earl.
  • Directory structure for a simple Apache web site
  • Web servers love serving static web pages
  • But sometimes you need more than just the web server
  • Two things the web server alone wont do
  • The non-Java term for a web server helper app is CGI program
    • Servlets and CGI both play the role of a helper app in the web server
  • Servlets Demystified (write, deploy, run)
    • Actually, trying to format HTML inside a servlets out.println() pretty much sucks.
  • JSP is what happened when somebody introduced Java to HTML
• 2. High-Level Overview: Web App Architecture
  • What is a Container?
  • What if you had Java, but no servlets or Containers?
  • What does the Container give you?
  • How the Container handles a request
  • How it looks in code (what makes a servlet a servlet)
  • Youre wondering how the Container found the Servlet...
  • A servlet can have THREE names
  • Using the Deployment Descriptor to map URLs to servlets
  • But wait! Theres more you can do with the DD
  • Story: Bob Builds a Matchmaking Site
  • He starts to build a bunch of servlets... one for each page
  • But then it gets ugly, so he adds JSPs
  • But then his friend says, You ARE using MVC, right?
  • The Model-View-Controller (MVC) Design Pattern fixes this
  • Applying the MVC pattern to the matchmaking web app
  • But then his friend Kim takes a look
  • Is there an answer?
  • A working Deployment Descriptor (DD)
  • How J2EE fits into all this
• 3. Hands-on MVC: Mini MVC Tutorial
  • Lets build a real (small) web application
  • The Users View of the web applicationa Beer Advisor
  • Heres the architecture...
  • Creating your development environment
  • Creating the deployment environment
  • Our roadmap for building the app
  • The HTML for the initial form page
  • Deploying and testing the opening page
  • Mapping the logical name to a servlet class file
  • The first version of the controller servlet
  • Compiling, deploying, and testing the controller servlet
  • Building and testing the model class
  • Enhancing the servlet to call the model, so that we can get REAL advice...
  • Servlet version two code
  • Key steps for servlet version two
  • Review the partially completed, MVC beer advice web application
  • Create the JSP view that gives the advice
  • Enhancing the servlet to call the JSP (version three)
  • Code for servlet version three
  • Compile, deploy, and test the final app!
  • There is still so much to learn.
• 4. Request and Response: Being a Servlet
  • Servlets are controlled by the Container
  • But theres more to a servlets life
    • Your servlet inherits the lifecycle methods
  • The Three Big Lifecycle Moments
  • Each request runs in a separate thread!
  • In the beginning: loading and initializing
    • Servlet Initialization: when an object becomes a servlet
    • But a Servlets REAL job is to handle requests. Thats when a servlets life has meaning.
    • Request and Response: the key to everything, and the arguments to service()
  • The HTTP request Method determines whether doGet() or doPost() runs
  • Actually, one or more of the other HTTP Methods might make a (brief) appearance on the exam...
  • The difference between GET and POST
  • No, its not just about the size
  • The story of the non-idempotent request
  • POST is not idempotent
  • What determines whether the browser sends a GET or POST request?
    • What happens if you do NOT say method=POST in your <form>?
  • POST is NOT the default!
  • Sending and using a single parameter
  • Sending and using TWO parameters
  • Besides parameters, what else can I get from a Request object?
  • Review: servlet lifecycle and API
  • Review: HTTP and HttpServletRequest
  • So thats the Request... now lets see the Response
  • Using the response for I/O
  • Imagine you want to send a JAR to the client...
  • Servlet code to download the JAR
  • Whoa. Whats the deal with content type?
  • Youve got two choices for output: characters or bytes
  • You can set response headers, you can add response headers
  • But sometimes you just dont want to deal with the response yourself...
  • Servlet redirect makes the browser do the work
    • Using relative URLs in sendRedirect()
  • A request dispatch does the work on the server side
  • Redirect vs. Request Dispatch
  • Review: HttpServletResponse
  • Coffee Cram: Mock Exam Chapter 4
  • Coffee Cram: Chapter 4 Answers
• 5. Attributes and Listeners: Being a Web App
  • Kim wants to configure his email address in the DD, not hard-code it inside the servlet class
  • Init Parameters to the rescue
  • You cant use servlet init parameters until the servlet is initialized
  • The servlet init parameters are read only ONCEwhen the Container initializes the servlet
  • Testing your ServletConfig
  • How can a JSP get servlet init parameters?
    • What about the way we did it with the beer app? We passed the model info to the JSP using a request attribute...
  • Setting a request attribute works... but only for the JSP to which you forwarded the request
  • Context init parameters to the rescue
  • Remember the difference between servlet init parameters and context init parameters
  • ServletConfig is one per servlet ServletContext is one per web app
  • So what else can you do with your ServletContext?
  • What if you want an app init parameter thats a database DataSource?
    • What she really wants is a listener.
    • She wants a ServletContextListener
    • Tutorial: a simple ServletContextListener
    • Making and using a context listener
    • We need three classes and one DD
    • Writing the listener class
    • Writing the attribute class (Dog)
    • Writing the servlet class
    • Writing the Deployment Descriptor
    • Compile and deploy
    • Try it out
    • Troubleshooting
    • The full story...
    • Listeners: not just for context events...
    • The eight listeners
    • The HttpSessionBindingListener
  • What, exactly, is an attribute?
    • Attributes are not parameters!
    • The Three Scopes: Context, Request, and Session
    • Attribute API
    • The dark side of attributes...
    • But then something goes horribly wrong...
    • Context scope isnt thread-safe!
    • The problem in slow motion...
    • How do we make context attributes thread-safe?
    • Synchronizing the service method is a spectacularly BAD idea
    • Synchronizing the service method wont protect a context attribute!
    • You dont need a lock on the servlet... you need the lock on the context!
    • Are Session attributes thread-safe?
    • Whats REALLY true about attributes and thread-safety?
    • Protect session attributes by synchronizing on the HttpSession
    • SingleThreadModel is designed to protect instance variables
    • But how does the web container guarantee a servlet gets only one request at a time?
    • Which is the better STM implementation?
    • Only Request attributes and local variables are thread-safe!
    • Request attributes and Request dispatching
    • RequestDispatcher revealed
    • Whats wrong with this code?
    • Youll get a big, fat IllegalStateException!
  • Coffee Cram: Mock Exam Chapter 5
  • Coffee Cram: Chapter 5 Answers
• 6. Session Management: Conversational state
  • Kim wants to keep client-specific state across multiple requests
  • Its supposed to work like a REAL conversation...
  • How can he track the clients answers?
  • How sessions work
  • One problem... how does the Container know who the client is?
  • The client needs a unique session ID
  • How do the Client and Container exchange Session ID info?
    • Cookies
  • The best part: the Container does virtually all the cookie work!
  • What if I want to know whether the session already existed or was just created?
  • What if I want ONLY a pre-existing session?
  • You can do sessions even if the client doesnt accept cookies, but you have to do a little more work...
    • URL rewriting: something to fall back on
    • URL rewriting kicks in ONLY if cookies fail, and ONLY if you tell the response to encode the URL
    • URL rewriting works with sendRedirect()
    • Getting rid of sessions
    • How we want it to work...
    • The HttpSession interface
    • Key HttpSession methods
    • Setting session timeout
    • Can I use cookies for other things, or are they only for sessions?
    • Using Cookies with the Servlet API
    • Simple custom cookie example
    • Custom cookie example continued...
    • Key milestones for an HttpSession
    • Session lifecycle Events
  • Dont forget about HttpSessionBindingListener
    • Session migration
    • The Beer Web App distributed across two VMs
    • Session migration in action
  • HttpSessionActivationListener lets attributes prepare for the big move...
    • Listener examples
    • Listener examples
    • Listener examples
    • Session-related Listeners
    • Session-related Event Listeners and Event Objects API overview
  • Session-related Listeners
  • Coffee Cram: Mock Exam Chapter 6
  • Coffee Cram: Chapter 6 Answers
• 7. Using JSP: Being a JSP
  • In the end, a JSP is just a servlet
  • Making a JSP that displays how many times its been accessed
  • She deploys and tests it
  • The JSP doesnt recognize the Counter class
  • Use the page directive to import packages
  • But then Kim mentions expressions
  • Expressions become the argument to an out.print()
  • Kim drops the final bombshell...
  • Declaring a variable in a scriptlet
  • What REALLY happens to your JSP code?
  • We need another JSP element...
  • JSP Declarations
  • Time to see the REAL generated servlet
  • The out variable isnt the only implicit object...
  • A comment...
  • API for the generated servlet
  • Lifecycle of a JSP
  • Translation and compilation happens only ONCE
  • Initializing your JSP
    • Configuring servlet init parameters
    • Overriding jspInit()
  • Attributes in a JSP
  • Using PageContext for attributes
  • Examples using pageContext to get and set attributes
  • While were on the subject... lets talk more about the three directives
    • Attributes to the page directive
  • Scriptlets considered harmful?
  • There didnt used to BE an alternative.
  • EL: the answer to, well, everything.
  • Sneak peek at EL
  • Using <scripting-invalid>
  • You can choose to ignore EL
    • El is enabled by default!
  • But wait... theres still another JSP element we havent seen: actions
  • Coffee Cram: Mock Exam Chapter 7
  • Coffee Cram: Chapter 7 Answers
• 8. Scriptless JSP: Script-free pages
  • Our MVC app depends on attributes
  • But what if the attribute is not a String, but an instance of Person?
  • We need more code to get the Persons name
  • Person is a JavaBean, so well use the bean-related standard actions
  • Deconstructing <jsp:useBean> and <jsp:getProperty>
    • Declare and initialize a bean attribute with <jsp:useBean>
    • Get a bean attributes property value with <jsp:getProperty>
  • <jsp:useBean> can also CREATE a bean!
  • You can use <jsp:setProperty>
  • <jsp:useBean> can have a body!
  • Generated servlet when <jsp:useBean> has a body
  • Can you make polymorphic bean references?
  • Adding a type attribute to <jsp:useBean>
  • Using type without class
  • The scope attribute defaults to page
  • Going straight from the request to the JSP without going through a servlet...
  • The param attribute to the rescue
  • But wait ! It gets even better...
  • If you can stand it, it gets even BETTER...
  • Bean tags convert primitive properties automatically
  • But what if the property is something OTHER than a String or primitive?
  • Trying to display the property of the property
  • Expression Language (EL) saves the day!
  • Deconstructing the JSP Expression Language (EL)
  • Using the dot (.) operator to access properties and map values
  • The [] operator is like the dot only way better
  • The [] gives you more options...
  • Using the [] operator with an array
  • A String index is coerced to an int for arrays and Lists
  • For beans and Maps you can use either operator
  • If its NOT a String literal, its evaluated
  • You can use nested expressions inside the brackets
  • You cant do ${foo.1}
  • EL renders raw text, including HTML
    • The same is true for JSP expression tags...
    • ... and for the jsp:getProperty standard action
  • The EL implicit objects
  • Request parameters in EL
  • What if you want more information from the request?
  • The requestScope is NOT the request object
  • Scope implicit objects can save you
  • Getting Cookies and init params
    • She doesnt know about EL functions
  • Imagine you want your JSP to roll dice
  • Deploying an app with static functions
  • And a few other EL operators...
  • EL handles null values gracefully
  • JSP Expression Language (EL) review
  • Reusable template pieces
  • The include directive
  • The <jsp:include> standard action
  • Theyre NOT the same underneath...
  • The include directive happens at translation time <jsp:include> happens at runtime
  • The include directive at first request
  • The <jsp:include> standard action at first request
  • Uh-oh. Shes right...
  • The way we SHOULD have done it
  • Customizing the included content with <jsp:param>
  • The <jsp:forward> standard action
  • A conditional forward...
  • How it runs...
  • With <jsp:forward>, the buffer is cleared BEFORE the forward
    • She doesnt know about JSTL tags
  • Bean-related standard action review
  • The include review
  • Coffee Cram: Mock Exam Chapter 8
  • Coffee Cram: Chapter 8 Answers
• 9. Using JSTL: Custom tags are powerful
  • EL and standard actions are limited
  • The case of the disappearing HTML (reprised)
  • Theres a better way: use the <c:out> tag
    • You can explicitly declare the conversion of XML entities
    • You can explicitly declare NO conversion of XML entities
    • Conversion happens by default
  • Null values are rendered as blank text
  • Set a default value with the default attribute
    • Or you can do it this way:
  • Looping without scripting
  • <c:forEach>
  • Deconstructing <c:forEach>
  • You can even nest <c:forEach> tags
  • Doing a conditional include with <c:if>
  • But what if you need an else?
  • The <c:if> tag wont work for this
  • The <c:choose> tag and its partners <c:when> and <c:otherwise>
  • The <c:set> tag... so much cooler than <jsp:setProperty>
  • Using <c:set> with beans and Maps
  • Key points and gotchas with <c:set>
  • <c:remove> just makes sense
  • With <c:import>, there are now THREE ways to include content
  • <c:import> can reach OUTSIDE the web app
  • Customizing the thing you include
  • Doing the same thing with <c:param>
  • <c:url> for all your hyperlink needs
  • What if the URL needs encoding?
  • You do NOT want your clients to see this:
  • Make your own error pages
    • She doesnt know about the <error-page> DD tag.
  • Configuring error pages in the DD
  • Error pages get an extra object: exception
  • The <c:catch> tag. Like try/catch...sort of
  • You can make the exception an attribute
  • What if you need a tag thats NOT in JSTL?
  • Using a tag library thats NOT from the JSTL
  • Making sense of the TLD
  • Using the custom advice tag
  • The custom tag handler
  • Pay attention to <rtexprvalue>
  • <rtexprvalue> is NOT just for EL expressions
  • What can be in a tag body
  • The tag handler, the TLD, and the JSP
  • The taglib <uri> is just a name, not a location
  • The Container builds a map
  • Four places the Container looks for TLDs
  • When a JSP uses more than one tag library
  • Coffee Cram: Mock Exam Chapter 9
  • Coffee Cram: Chapter 9 Answers
• 10. Custom Tag Development: When even JSTL is not enough...
  • Includes and imports can be messy
  • Tag Files: like include, only better
  • But how do you send it parameters?
  • To a Tag File, you dont send request parameters, you send tag attributes!
  • Arent tag attributes declared in the TLD?
  • Tag Files use the attribute directive
  • When an attribute value is really big
  • Declaring body-content for a Tag File
  • Where the Container looks for Tag Files
  • When you need more than Tag Files... Sometimes you need Java
  • Making a Simple tag handler
  • A Simple tag with a body
  • The Simple tag API
  • The life of a Simple tag handler
  • What if the tag body uses an expression?
  • A tag with dynamic row data: iterating the body
  • A Simple tag with an attribute
  • What exactly IS a JspFragment?
  • SkipPageException: stops processing the page...
  • SkipPageException shows everything up to the point of the exception
  • But what happens when the tag is invoked from an included page?
  • SkipPageException stops only the page that directly invoked the tag
  • You still have to know about Classic tag handlers
  • Tag handler API
  • A very small Classic tag handler
  • A Classic tag handler with TWO methods
  • When a tag has a body: comparing Simple vs. Classic
  • Classic tags have a different lifecycle
  • The Classic lifecycle depends on return values
  • IterationTag lets you repeat the body
  • Default return values from TagSupport
  • OK, lets get real...
  • Our dynamic <select> tag isnt complete...
  • We could just add more custom tag attributes...
  • Son of more tag attributes
  • The return of the son of more tag attributes
  • Im getting sick of these tag attributes!
  • Our tag handler code using the DynamicAttributes interface
  • The rest of the tag handler code
  • OK, there is a little bit of configuration in the TLD
  • What about Tag Files?
  • But what if you DO need access to the body contents?
  • With BodyTag, you get two new methods
  • With BodyTag, you can buffer the body
  • What if you have tags that work together?
  • A Tag can call its Parent Tag
  • Find out just how deep the nesting goes...
  • Simple tags can have Classic parents
  • You can walk up, but you cant walk down...
  • Getting info from child to parent
  • Menu and MenuItem tag handlers
  • Getting an arbitrary ancestor
  • Using the PageContext API for tag handlers
  • Coffee Cram: Mock Exam Chapter 10
  • Coffee Cram: Chapter 10 Answers
• 11. Web App Deployment: Deploying your web app
  • The Joy of Deployment
  • What goes where in a web app
    • What she really wants is a WAR file
  • WAR files
  • What a deployed WAR file looks like
  • Making static content and JSPs directly accessible
  • How servlet mapping REALLY works
  • Servlet mappings can be fake
  • Subtle issues...
  • Configuring welcome files in the DD
  • How the Container chooses a welcome file
  • Configuring error pages in the DD
  • Configuring servlet initialization in the DD
  • Making an XML-compliant JSP: a JSP Document
  • Memorizing the EJB-related DD tags
  • Memorizing the JNDI <env-entry> DD tag
  • Memorizing the <mime-mapping> DD tag
  • Coffee Crem: Mock Exam Chapter 11
  • Coffee Crem: Chapter 11 Answers
• 12. Web App Security: Keep it secret, keep it safe
  • The Bad Guys are everywhere
  • And its not just the SERVER that gets hurt...
  • The Big 4 in servlet security
  • A little security story
  • How to Authenticate in HTTP World: the beginning of a secure transaction
  • A slightly closer look at how the Container does Authentication and Authorization
  • How did the Container do that ?
  • Keep security out of the code!
  • Who implements security in a web app?
  • The Big Jobs in servlet security
  • Just enough Authentication to discuss Authorization
  • Authorization Step 1: defining roles
  • Authorization Step 2: defining resource/method constraints
  • The <security-constraint> rules for <web-resource-collection> elements
  • Picky <security-constraint> rules for <auth-constraint> sub-elements
  • The way <auth-constraint> works
  • How multiple <security-constraint> elements interact
  • Dueling <auth-constraint> elements
  • Alices recipe servlet, a story about programmatic security...
  • Customizing methods: isUserInRole()
  • The declarative side of programmatic security
  • Authentication revisited
  • Implementing Authentication
  • Form-Based Authentication
  • Summary of Authentication types
  • She doesnt know about J2EEs protected transport layer connection
  • Securing data in transit: HTTPS to the rescue
  • How to implement data confidentiality and integrity sparingly and declaratively
  • Protecting the request data
  • Coffee Cram: Mock Exam Chapter 12
  • Coffee Cram: Chapter 12 Answers
• 13. Filters and Wrappers: The Power of Filters
  • Enhancing the entire web application
  • How about some kind of filter?
  • Filters are modular, and configurable in the DD
  • Three ways filters are like servlets
  • Building the request tracking filter
  • A filters life cycle
  • Think of filters as being stackable
    • A conceptual call stack example
  • Declaring and ordering filters
  • News Flash: As of version 2.4, filters can be applied to request dispatchers
  • Compressing output with a response-side filter
  • Architecture of a response filter
  • But is it really that simple?
  • The output has left the building
  • We can implement our OWN response
    • She doesnt know about the servlet Wrapper classes
  • Wrappers rock
  • Adding a simple Wrapper to the design
  • Add an output stream Wrapper
  • The real compression filter code
    • Off the path
  • Compression wrapper code
  • Compression wrapper, helper class code
  • Coffee Cram: Mock Exam Chapter 13
  • Coffee Cram: Chapter 13 Answers
• 14. Patterns and Struts: Enterprise Design Patterns
  • Web site hardware can get complicated
  • Web application software can get complicated
  • Lucky for us, we have J2EE patterns
    • Common pressures
  • Performance (and the ilities)
  • Aligning our vernaculars...
    • Code to interfaces
    • Separation of Concerns & Cohesion
    • Hide Complexity
  • More design principles...
    • Loose Coupling
    • Remote Proxy
    • Increase Declarative Control
  • Patterns to support remote model components
    • A Fable: The Beer App Grows
  • How the Business Team supports the web designers when the MVC components are running on one JVM
  • How will they handle remote objects?
  • RMI makes life easy
    • What we want...
    • How RMI pulls it off
  • Just a little more RMI review
  • Adding RMI and JNDI to the controller
  • How about a go-between object?
  • The go-between is a Business Delegate
  • Simplify your Business Delegates with the Service Locator
  • Protecting the web designers JSPs from remote model complexity
  • Compare the local model diagram to this remote model diagram
  • Theres good news and bad news...
  • Time for a Transfer Object?
    • Service Locator and Business Delegate both simplify model components
  • Business tier patterns: quick review
  • Our very first pattern revisited... MVC
    • Where we left off...
  • MVC in a real web app
  • Looking at the MVC controller
  • Improving the MVC controllers
    • New and (shorter) controller pseudo-code
  • Designing our fantasy controller
  • Yes! Its Struts in a nutshell
  • Is Struts a container?
  • How does Front Controller fit in?
  • Refactoring the Beer app for Struts
  • The Struts Beer app architecture
  • A form bean exposed
  • How an Action object ticks
  • struts-config.xml: tying it all together
  • Specifying Struts in the web.xml DD
  • Install Struts, and Just Run It!
  • Creating the deployment environment
  • Patterns review for the SCWCD
  • Business Delegate
  • Service Locator
  • Transfer Object
  • Intercepting Filter
  • Model, View, Controller (MVC)
  • Front Controller
  • Coffee Cram: Mock Exam Chapter 14
  • Coffee Cram: Chapter 14 Answers
• A. Final Mock Exam: Coffee Cram
  • Coffee Cram: Final Mock Exam
  • Coffee Cram: Final Exam Answers
• B.
• C.
• Index
• About the Authors
• Copyright

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