Java SCWCD Exam Cram Notes : Designing Patterns.

Section 13: Design Patterns

13.1 Given a scenario description with a list of issues, select the design pattern (Value Objects, MVC, Data Access Object, or Business Delegate) that would best solve those issues.

13.2 Match design patterns with statements describing potential benefits that accrue from the use of the pattern, for any of the following patterns: Value Objects , MVC , Data Access Object , Business Delegate

Pattern	Description/Benefit/Issues
Value Objects	Reduce network traffic by acting as a caching proxy of a remote object. Total load on the remote object's remote interface is decreased, because data represented by the Value Object are cached on the client by the Value Object instance. All accesses to the properties of the Value Objects are local, and so those accesses cause no remote method invocations. Decreased latency can improve user response time. Potential Liability - Stale data. Whenever a value object is backed by a volatile set of values (such as a stock's price and trading volume, for example) it should only be treated as a snapshot of those values.
MVC	Clarifies design by separating data modeling issues from data display and user interaction. Allows the same data to be viewed in multiple ways and by multiple users. Improves extensibility by simplifying impact analysis. Improves maintainability by encapsulating application functions behind well-known APIs, and decreasing code replication ("copy-paste-and-hack"). Enhances reusability by decoupling application functionality from presentation. Makes applications easier to distribute, since MVC boundaries are natural distribution interface points. Can be used to partition deployment and enable incremental updates. Facilitates testability by forcing clear designation of responsibilities and functional consistency. Enhances flexibility, because data model, user interaction, and data display can be made "pluggable".
Data Access Object	Greater deployment flexibility Resource vendor independence Resource implementation independence Easier migration to CMP Enhanced extensibility Increased complexity because of a level of indirection
Business Delegate	Reduced coupling, improved manageability. Service exception translation Simpler, uniform interface hiding the details. Delegate may cache results - this may improve performance Increased complexity because of a level of indirection
Front Component	Provides centralized dispatching of requests, e.g. via a controller servlet. Enables centralized handling of security, navigation, and presentation formatting
Facade	Provides a layer between clients and subsystems of a complex system. Shields clients from subsystem components, making the subsystems easier to use
Factory	Handles requests for object creation
Singleton	A class which can have at most one instance
Template Method	The key idea is that there is a basic algorithm we want to stay the same, but we want to let subclasses vary how they do the steps. The Template Method says to define the algorithm in the parent class, but implementations of the steps in the subclasses
Bimodal Data Access	Under certain conditions, allows designer to trade off data consistency for access efficiency. JDBC provides read-only, potentially dirty reads of lists of objects, bypassing the functionality, and the overhead, of Entity enterprise beans. At the same time, Entity enterprise beans can still be used for transactional access to enterprise data. Which mechanism to select depends on the requirements of the application operation
Session Entity Facade	Being an instance of the Facade pattern, this pattern shares its applicability. In the context of J2EE application development, use the Session Facade pattern when you want to provide a simple interface to a complex subsystem of enterprise beans or when you want to reduce communication & dependencies b/w client objects and enterprise beans.

Interface / Class	Method	Description
Servlet	init(ServletConfig)	Called by the servlet container to indicate to a servlet that the servlet is being placed into service.
	destroy()	Called by the servlet container to indicate to a servlet that the servlet is being taken out of service.
	service(ServletRequest, ServletResponse)	Called by the servlet container to allow the servlet to respond to a request.
	ServletConfig getServletConfig()	Returns a ServletConfig object, which contains initialization and startup parameters for this servlet.
	String getServletInfo	Returns information about the servlet, such as author, version, and copyright.
ServletConfig	String getInitParameter(String)	Returns a String containing the value of the named initialization parameter, or null if the parameter does not exist.
	Enumeration getInitParameterNames()	Returns the names of the servlet's initialization parameters as an Enumeration of String objects, or an empty Enumeration if the servlet has no initialization parameters.
	ServletContext getServletContext()	Returns a reference to the ServletContext in which the caller is executing.
	String getServletName()	Returns the name of this servlet instance. The name may be provided via server administration, assigned in the web application deployment descriptor, or for an unregistered (and thus unnamed) servlet instance it will be the servlet's class name.
ServletContext	String getInitParameter(String)	Returns a String containing the value of the named context-wide initialization parameter, or null if the parameter does not exist.
	Enumeration getInitParameterNames()	Returns the names of the context's initialization parameters as an Enumeration of String objects, or an empty Enumeration if the context has no initialization parameters.
	Object getAttribute(String)	Returns the servlet container attribute with the given name, or null if there is no attribute by that name.
	setAttribute(String, Object)	Binds an object to a given attribute name in this servlet context.
	removeAttribute(String)	Removes the attribute with the given name from the servlet context.
	Enumeration getAttributeNames()	Returns an Enumeration containing the attribute names available within this servlet context.
	log(String)	Writes the specified message to a servlet log file, usually an event log.
	log(String, Throwable)	Writes an explanatory message and a stack trace for a given Throwable exception to the servlet log file.
	ServletContext getContext(String uripath)	Returns a ServletContext object that corresponds to a specified URL on the server. The given path must be absolute (beginning with "/") and is interpreted based on the server's document root.
	String getRealPath(String path)	Returns a String containing the real path for a given virtual path
	java.net.URL getResource(String path)	Returns a URL to the resource that is mapped to a specified path. The path must begin with a "/" and is interpreted as relative to the current context root.
ServletContext	java.net.URL getResource(String path)	This method allows the servlet container to make a resource available to servlets from any source. Resources can be located on a local or remote file system, in a database, or in a .war file. The resource content is returned directly, so be aware that requesting a .jsp page returns the JSP source code. Use a RequestDispatcher instead to include results of an execution. This method has a different purpose than java.lang.Class.getResource, which looks up resources based on a class loader. This method does not use class loaders.
	java.io.InputStream getResourceAsStream(String path)	Returns the resource located at the named path as an InputStream object.
	RequestDispatcher getRequestDispatcher(String path)	Returns a RequestDispatcher object that acts as a wrapper for the resource located at the given path. The resource can be dynamic or static. The pathname must begin with a "/" and is interpreted as relative to the current context root. Use getContext to obtain a RequestDispatcher for resources in foreign contexts. This method returns null if the ServletContext cannot return a RequestDispatcher.
	RequestDispatcher getNamedDispatcher(String name)	Returns a RequestDispatcher object that acts as a wrapper for the named servlet.
ServletRequest	Object getAttribute(String)	Returns the value of the named attribute as an Object, or null if no attribute of the given name exists.
	setAttribute(String, Object)	Stores an attribute in this request.
	removeAttribute(String)	Removes an attribute from this request.
	Enumeration getAttributeNames()	Returns an Enumeration containing the names of the attributes available to this request. This method returns an empty Enumeration if the request has no attributes available to it.
	String getParameter(String)	Returns the value of a request parameter as a String, or null if the parameter does not exist.
	String[] getParameterValues(String)	Returns an array of String objects containing all of the values the given request parameter has, or null if the parameter does not exist.
	Enumeration getParameterNames()	Returns an Enumeration of String objects containing the names of the parameters contained in this request.
	ServletInputStream getInputStream()	Retrieves the body of the request as binary data using a ServletInputStream. Either this method or getReader() may be called to read the body, not both.
	BufferedReader getReader()	Retrieves the body of the request as character data using a BufferedReader. The reader translates the character data according to the character encoding used on the body. Either this method or getInputStream() may be called to read the body, not both.
	RequestDispatcher getRequestDispatcher(String path)	Returns a RequestDispatcher object that acts as a wrapper for the resource located at the given path. A RequestDispatcher object can be used to forward a request to the resource or to include the resource in a response. The resource can be dynamic or static.
ServletRequest	RequestDispatcher getRequestDispatcher(String path)	The pathname specified may be relative, although it cannot extend outside the current servlet context. If the path begins with a "/" it is interpreted as relative to the current context root. This method returns null if the servlet container cannot return a RequestDispatcher. The difference between this method and ServletContext's method is that this method can take a relative path.
	String getRemoteAddr()	Returns the Internet Protocol (IP) address of the client that sent the request.
	String getRemoteHost()	Returns the fully qualified name of the client that sent the request, or the IP address of the client if the name cannot be determined.
	String getServerName()	Returns the host name of the server that received the request.
	int getServerPort()	Returns the port number on which this request was received
	String getProtocol()	Returns the name and version of the protocol the request uses in the form protocol/majorVersion.minorVersion, for example, HTTP/1.1.
	String getScheme()	Returns the name of the scheme used to make this request, for example, http, https, or ftp.
	boolean isSecure()	Returns a boolean indicating whether this request was made using a secure channel, such as HTTPS.
	String getContentType()	Returns the MIME type of the body of the request, or null if the type is not known.
	int getContentLength()	Returns the length, in bytes, of the request body and made available by the input stream, or -1 if the length is not known.
	String getCharecterEncoding()	Returns the name of the character encoding used in the body of this request.
	setCharecterEncoding(String)	Overrides the name of the character encoding used in the body of this request.
ServletResponse	ServletOutputStream getOutputStream()	Returns a ServletOutputStream suitable for writing binary data in the response. The servlet container does not encode the binary data. Calling flush() on the ServletOutputStream commits the response. Either this method or getWriter() may be called to write the body, not both
	PrintWriter getWriter()	Returns a PrintWriter object that can send character text to the client. The character encoding used is the one specified in the charset= property of the setContentType method, which must be called before calling this method for the charset to take effect. Calling flush() on the PrintWriter commits the response. Either this method or getOutputStream may be called to write the body, not both.
	setContentType(java.lang.String type)	Sets the content type of the response being sent to the client. The content type may include the type of character encoding used, for example, text/html;charset=ISO-8859-4. If obtaining a PrintWriter, this method should be called first.
	setContentLength(int)	Sets the length of the content body in the response. In HTTP servlets, this method sets the HTTP Content-Length header.
	boolean isCommitted()	Returns a boolean indicating if the response has been committed. A commited response has already had its status code and headers written.
ServletResponse	reset()	Clears any data that exists in the buffer as well as the status code and headers. If the response has been committed, this method throws an IllegalStateException.
	int getBufferSize()	Returns the actual buffer size used for the response. If no buffering is used, this method returns 0.
	setBufferSize(int)	Sets the preferred buffer size for the body of the response. This method must be called before any response body content is written; if content has been written, this method throws an IllegalStateException.
	flushBuffer()	Forces any content in the buffer to be written to the client. A call to this method automatically commits the response, meaning the status code and headers will be written.
	resetBuffer()	Clears the content of the underlying buffer in the response without clearing headers or status code. If the response has been committed, this method throws an IllegalStateException.
abstract class GenericServlet implements Servlet, ServletConfig, Serializable	init()	A convenience method which can be overridden so that there's no need to call super.init(config).
	log(String)	Writes the specified message to a servlet log file, prepended by the servlet's name.
	log(String, Throwable)	Writes an explanatory message and a stack trace for a given Throwable exception to the servlet log file, prepended by the servlet's name.
	abstract service()	Called by the servlet container to allow the servlet to respond to a request. This method is declared abstract so subclasses, such as HttpServlet, must override it.
HttpServletRequest	String getHeader(String)	Returns the value of the specified request header as a String. If the request did not include a header of the specified name, this method returns null. The header name is case insensitive. You can use this method with any request header.
	Enumeration getHeaders(String)	Returns all the values of the specified request header as an Enumeration of String objects. If the request did not include any headers of the specified name, this method returns an empty Enumeration. The header name is case insensitive. You can use this method with any request header.
	Enumeration getHeaderNames()	Returns an enumeration of all the header names this request contains. If the request has no headers, this method returns an empty enumeration.
	int getIntHeader(String)	Returns the value of the specified request header as an int. If the request does not have a header of the specified name, this method returns -1. If the header cannot be converted to an integer, this method throws a NumberFormatException.
	long getDateHeader(String)	Returns the value of the specified request header as a long value that represents a Date object. Use this method with headers that contain dates, such as If-Modified-Since. If the request did not have a header of the specified name, this method returns -1
	Cookie getCookies()	Returns an array containing all of the Cookie objects the client sent with this request, or null if no cookies sent.
	HttpSession getSession()	Returns the current session associated with this request, or if the request does not have a session, creates one.
HttpServletRequest	HttpSession getSession(boolean create)	Returns the current HttpSession associated with this request or, if if there is no current session and create is true, returns a new session.
	String getRequestURI()	Returns the part of this request's URL from the protocol name up to the query string in the first line of the HTTP request. requestURI = contextPath + servletPath + pathInfo
	String getContextPath()	Returns the portion of the request URI that indicates the context of the request. The context path always comes first in a request URI. The path starts with a "/" character but does not end with a "/" character. For servlets in the default (root) context, this method returns "".
	String getServletPath()	Returns the part of this request's URL that calls the servlet. This includes either the servlet name or a path to the servlet, but does not include any extra path information or a query string.
	String getPathInfo()	Returns any extra path information associated with the URL the client sent when it made this request. The extra path information follows the servlet path but precedes the query string. This method returns null if there was no extra path information.
	String getPathTranslated()	Returns any extra path information after the servlet name but before the query string, and translates it to a real path.
	String getQueryString()	Returns the query string that is contained in the request URL after the path.
	String getMethod()	Returns the name of the HTTP method with which this request was made, for example, GET, POST, or PUT.
	String getAuthType()	Returns the name of the authentication scheme used to protect the servlet. All servlet containers support BASIC_AUTH, FORM_AUTH, and CLIENT_CERT_AUTH and may support DIGEST_AUTH. If the servlet is not authenticated null is returned.
	String getRemoteUser()	Returns the login of the user making this request, if the user has been authenticated, or null if the user has not been authenticated.
	Principal getUserPrincipal()	Returns a java.security.Principal object containing the name of the current authenticated user. If the user has not been authenticated, the method returns null.
	boolean isUserInRole(String role)	Returns a boolean indicating whether the authenticated user is included in the specified logical "role". Roles and role membership can be defined using deployment descriptors. If the user has not been authenticated, the method returns false.
	String getRequestedSessionId()	Returns the session ID specified by the client. This may not be the same as the ID of the actual session in use. For example, if the request specified an old (expired) session ID and the server has started a new session, this method gets a new session with a new ID. If the request did not specify a session ID, this method returns null.
	boolean isRequestedSessionIdValid()	Checks whether the requested session ID is still valid.
	boolean isRequestedSessionIdFromCookie()	Checks whether the requested session ID came in as a cookie.
	boolean isRequestedSessionIdFromURL()	Checks whether the requested session ID came in as part of the request URL.
HttpServletResponse	addCookie(Cookie)	Adds the specified cookie to the response. This method can be called multiple times to set more than one cookie.
	addHeader(String name, String value)	Add a response header with the given name and String value / integer value / date value respectively. These methods allow response headers to have multiple values.
	addIntHeader(String name, int value)
	addDateHeader(String name, long value)
	setHeader(String name, String value)	Set a response header with the given name and String value / integer value / date value respectively. If the header had already been set, the new value overwrites the previous one. The containsHeader method can be used to test for the presence of a header before setting its value.
	setIntHeader(String name, int value)
	setDateHeader(String name, long value)
	setStatus(int sc)	Sets the status code for this response. This method is used to set the return status code when there is no error (for example, for the status codes SC_OK or SC_MOVED_TEMPORARILY). If there is an error, and the caller wishes to invoke an error-page defined in the web applicaion, the sendError method should be used instead. If this method is called after the response is committed, the call is ignored.
	sendError(int sc) sendError(int sc, java.lang.String msg)	Sends an error response to the client using the specified status clearing the buffer. The server defaults to creating the response to look like an HTML-formatted server error page, setting the content type to "text/html", leaving cookies and other headers unmodified. If an error-page declaration has been made for the web application corresponding to the status code passed in, it will be served back in preference to the suggested msg parameter. If the response has already been committed, this method throws an IllegalStateException. After using this method, the response should be considered to be committed and should not be written to.
	sendRedirect(java.lang.String location)	Sends a temporary redirect response to the client using the specified redirect location URL. This method can accept relative URLs; the servlet container must convert the relative URL to an absolute URL before sending the response to the client. If the location is relative without a leading '/' the container interprets it as relative to the current request URI. If the location is relative with a leading '/' the container interprets it as relative to the servlet container root. If the response has already been committed, this method throws an IllegalStateException. After using this method, the response should be considered to be committed and should not be written to.
	String encodeURL(java.lang.String url)	Encodes the specified URL by including the session ID in it, or, if encoding is not needed, returns the URL unchanged. For robust session tracking, all URLs emitted by a servlet should be run through this method. Otherwise, URL rewriting cannot be used with browsers which do not support cookies.
	String encodeRedirectURL(String url)	Encodes the specified URL for use in the sendRedirect method or, if encoding is not needed, returns the URL unchanged. All URLs sent to the HttpServletResponse.sendRedirect method should be run through this method. Otherwise, URL rewriting cannot be used with browsers which do not support cookies
HttpSession	Object getAttribute(String)	Returns the object bound with the specified name in this session, or null if no object is bound under the name.
	setAttribute(String, Object)	Binds an object to a given attribute name in this session. If an object of the same name is already bound to the session, the object is replaced. After this method executes, and if the new object implements HttpSessionBindingListener, the container calls HttpSessionBindingListener.valueBound. If an object was already bound to this session of this name that implements HttpSessionBindingListener, its HttpSessionBindingListener.valueUnbound method is called.
	removeAttribute(String)	Removes the attribute with the given name from the session. After this method executes, and if the object implements HttpSessionBindingListener, the container calls HttpSessionBindingListener.valueUnbound.
	Enumeration getAttributeNames()	Returns an Enumeration of String objects containing the names of all the objects bound to this session.
	String getId()	Returns a string containing the unique identifier assigned to this session.
	long getCreationTime()	Returns the time when this session was created
	long getLastAccessedTime()	Returns the last time the client sent a request associated with this session
	int getMaxInactiveInterval()	Returns the maximum time interval, in seconds, that the servlet container will keep this session open between client accesses. After this interval, the servlet container will invalidate the session. The maximum time interval can be set with the setMaxInactiveInterval method. A negative time indicates the session should never timeout.
	setMaxInactiveInterval(int)	Specifies the time, in seconds, between client requests before the servlet container will invalidate this session. A negative time indicates the session should never timeout.
	invalidate()	Invalidates this session then unbinds any objects bound to it.
	isNew()	Returns true if the client does not yet know about the session or if the client chooses not to join the session. For example, if the server used only cookie-based sessions, and the client had disabled the use of cookies, then a session would be new on each request.
abstract class HttpServlet extends GenericServlet Eventhough this class is abstract it provides empty implementations of all methods. Typically servlets extending this class would override one of the doXXX methods.	public service(ServletRequest, ServletResponse)	Dispatches client requests to the protected service method. There's no need to override this method.
	protected service(HttpServletRequest, HttpServletResponse)	Receives standard HTTP requests from the public service method and dispatches them to the doXXX methods defined in this class. There's no need to override this method.
	doGet(HttpServletRequest, HttpServletResponse)	Should be safe and idempotent (repeatable) Override to service GET requests. HEAD requests are also satisfied since doHead internally uses this method with a specialized response.
	doPost(HttpServletRequest, HttpServletResponse)	Need not be safe or idempotent. Override to service POST requests.
	doPut(), doDelete(), doHead(), doTrace(), doOptions()	These methods are not common and service the corresponding requests.
	long getLastModified()	These methods are not common and service the corresponding requests.
RequestDispatcher	forward(ServletRequest, ServletResponse)	Forwards a request from a servlet to another resource (servlet, JSP file, or HTML file) on the server. This method allows one servlet to do preliminary processing of a request and another resource to generate the response. forward should be called before the response has been committed to the client (before response body output has been flushed). If the response already has been committed, this method throws an IllegalStateException. Uncommitted output in the response buffer is automatically cleared before the forward.
RequestDispatcher	include(ServletRequest, ServletResponse)	Includes the content of a resource (servlet, JSP page, HTML file) in the response. In essence, this method enables programmatic server-side includes. The ServletResponse object has its path elements and parameters remain unchanged from the caller's. The included servlet cannot change the response status code or set headers; any attempt to make a change is ignored.
SingleThreadModel	No methods	This is a 'markes' interface
ServletContext Listener	contextInitialized(ServletContextEvent)	Implementations of this interface receive notifications about changes to the servlet context of the web application they are part of. To receive notification events, the implementation class must be configured in the deployment descriptor for the web application
ServletContext Listener	ontextDestroyed(ServletContextEvent)
ServletContext AttributeListener	attributeAdded (ServletContextAttributeEvent)	Implementations of this interface receive notifications of changes to the attribute list on the servlet context of a web application. To receive notification events, the implementation class must be configured in the deployment descriptor for the web application.
	attributeRemoved (ServletContextAttributeEvent)
	attributeReplaced (ServletContextAttributeEvent)
ServletContext AttributeListener	attributeAdded (ServletContextAttributeEvent)	Implementations of this interface receive notifications of changes to the attribute list on the servlet context of a web application. To receive notification events, the implementation class must be configured in the deployment descriptor for the web application.
	attributeRemoved (ServletContextAttributeEvent)
	attributeReplaced (ServletContextAttributeEvent)
HttpSession Listener	sessionCreated(HttpSessionEvent)	Implementations of this interface are notified of changes to the list of active sessions in a web application. To receive notification events, the implementation class must be configured in the deployment descriptor for the web application.
HttpSession Listener	sessionDestroyed(HttpSessionEvent)
HttpSession AttributeListener	attributeAdded (HttpSessionBindingEvent)	This listener interface can be implemented in order to get notifications of changes made to sessions within this web application.
	attributeRemoved (HttpSessionBindingEvent)
	attributeReplaced (HttpSessionBindingEvent)
HttpSession ActivationListener	sessionDidActivate(HttpSessionEvent)	Objects that are bound to a session may listen to container events notifying them that sessions will be passivated and that session will be activated. A container that migrates session between VMs or persists sessions is required to notify all attributes bound to sessions implementing HttpSessionActivationListener.
HttpSession ActivationListener	sessionWillPassivate(HttpSessionEvent)
HttpSession BindingListener	valueBound(HttpSessionBindingEvent)	Causes an object to be notified when it is bound to or unbound from a session. The object is notified by an HttpSessionBindingEvent object. This may be as a result of a servlet programmer explicitly unbinding an attribute from a session, due to a session being invalidated, or die to a session timing out.
HttpSession BindingListener	valueUnbound (HttpSessionBindingEvent)

Deployment Descriptor DTD (web-app_2_3.dtd)

Legend:

? - Optional (0 or 1)
* - Any number (0 - n)
+ - 1 or more (1 - n))

No following character - Required (1)

<!ELEMENT web-app

(icon?, display-name?, description?, distributable?,

context-param*, <!ELEMENT context-param (param-name, param-value, description?)>


filter*,

filter-mapping*,

listener*,  <!ELEMENT listener (listener-class)>

servlet*,  <!ELEMENT servlet (icon?, servlet-name, display-name?, description?, (servlet-class|jsp-file),

 init-param*, <!ELEMENT init-param (param-name, param-value, description?)>

 load-on-startup?, run-as?,

 security-role-ref*)><!ELEMENT security-role-ref (description?, role-name, role-link?)>

servlet-mapping*, <!ELEMENT servlet-mapping (servlet-name, url-pattern)>

session-config?, <!ELEMENT session-config (session-timeout?)>

mime-mapping*, <!ELEMENT mime-mapping (extension, mime-type)>

welcome-file-list?, <!ELEMENT welcome-file-list (welcome-file+)>

error-page*, <!ELEMENT error-page ((error-code | exception-type), location)>

taglib*, <!ELEMENT taglib (taglib-uri, taglib-location)>

resource-env-ref*,

resource-ref*,

security-constraint*,  <!ELEMENT security-constraint (display-name?,web-resource-collection+, <!ELEMENT web-resource-collection

(web-resource-name, description?,

url-pattern*, http-method*)>

auth-constraint?, <!ELEMENT auth-constraint (description?, role-name*)>

user-data-constraint?)> <!ELEMENT user-data-constraint (description?,

transport-guarantee)> NONE, INTEGRAL, or CONFIDENTIAL.

login-config?,<!ELEMENT login-config

(auth-method?, "BASIC", "DIGEST", "FORM", or "CLIENT-CERT"

realm-name?,  Only for BASIC

form-login-config?)><!ELEMENT form-login-config (form-login-page, form-error-page)>

security-role*, <!ELEMENT security-role (description?, role-name)>

env-entry*,

ejb-ref*,

ejb-local-ref*)>

Example 1

<web-app>

<display-name>A Simple Application</display-name>

<context-param>

<param-name>Webmaster</param-name>

<param-value>webmaster@mycorp.com</param-value>

</context-param>

<servlet>

<servlet-name>catalog</servlet-name >

<servlet-class >com.mycorp.CatalogServlet</servlet-class >

<init-param >

<param-name >catalog</param-name >

<param-value >Spring</param-value >

</init-param >

</servlet >

<servlet-mapping >

<servlet-name >catalog</servlet-name >

<url-pattern >/catalog/*</url-pattern >

</servlet-mapping >

<session-config >

<session-timeout >30</session-timeout >

</session-config >

<mime-mapping >

<extension >pdf</extension >

<mime-type >application/pdf</mime-type >

</mime-mapping >

<welcome-file-list >

<welcome-file >index.jsp</welcome-file >

<welcome-file >index.html</welcome-file >

<welcome-file >index.htm</welcome-file >

</welcome-file-list >

<error-page >

<error-code >404</error-code >

<location >/404.html</location >

</error-page >

</web-app >

Example 2

<web-app >

<display-name >A Secure Application</display-name >

<servlet >

<servlet-name >catalog</servlet-name >

<servlet-class >com.mycorp.CatalogServlet</servlet-class >

<init-param >

<param-name >catalog</param-name >

<param-value >Spring</param-value >

</init-param >

<security-role-ref >

<role-name >MGR</role-name > <!-- role name used in code -- >

<role-link >manager</role-link > <!-- role name in security-role-- >

</security-role-ref >

</servlet >

<servlet-mapping >

<servlet-name >catalog</servlet-name >

<url-pattern >/catalog/*</url-pattern >

</servlet-mapping >

<security-constraint >

<web-resource-collection >

<web-resource-name >SalesInfo</web-resource-name >

<url-pattern >/salesinfo/*</url-pattern >

<http-method >GET</http-method >

<http-method >POST</http-method >

</web-resource-collection >

<auth-constraint >

<role-name >manager</role-name >

</auth-constraint >

<user-data-constraint >

<transport-guarantee >CONFIDENTIAL</transport-guarantee >

</user-data-constraint >

</security-constraint >

<security-role >

<role-name >manager</role-name >

</security-role >

</web-app >

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