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Filters Inter-Servlet Communication

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Objectives Introduction to Filters Filter API Configuring Filter Manipulating Request and Responses Servlet Communication

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Introduction Filter

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Filters

Components that add functionality to the request and response processing of a Web Application

Intercept the requests and responses that flow between a client and a Servlet/JSP.

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Filter Participation

User FilterWeb Resource(Servlet / JSP)

Request

Response

Filter Participating in Request-Response Process

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Filter Life CycleInstantiation and Loading

Initialization init()

doFilter()

destroy()

Unavailable GC

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Filter Chain Invoke a series of filters If the Calling filter is last filter, will invoke web resource

Filter 1

ClientFilter

2Filter

3

Web Resourc

e

Working of Filter Chain

Filter Chain

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Usage of Filter

Authentication Logging and auditing filter Image conversion filters Data compression Encryption filters Filters that trigger resource access events

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Benefits of Filter

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Compress Filter

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Working of Filter

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Working of Filter

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Filter API

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“Filter” InterfaceA filter is an object than perform filtering tasks

on either the request to a resource (a servlet or static content), or on the response from a resource, or both.

Init() doFilter() Destroy()

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“FilterConfig” Interface A filter configuration object used by a servlet

container used to pass information to a filter during initialization

Methods– getFilterName()– getInitParameter()– getInitParameterNames()– getServletContext()

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“FilterChain” Interface A FilterChain is an object provided by the

servlet container to the developer giving a view into the invocation chain of a filtered request for a resource

Methods– doFilter()

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Configuring Filter<?xml version="1.0" encoding="UTF-8"?><web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

<filter> <filter-name>TimerFilter</filter-name> <filter-class>filters.TimerFilter</filter-class> </filter> <filter-mapping> <filter-name>TimerFilter</filter-name> <url-pattern>/TimerFilter</url-pattern> </filter-mapping> <session-config> <session-timeout> 30 </session-timeout> </session-config> <welcome-file-list> <welcome-file>Timer.html</welcome-file> </welcome-file-list></web-app>

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Filter Element <icon> <filter-name> <display-name> <description> <filter-class> <init-param>

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Filter-Mapping Element <filter-name> <url-name> <servlet-name>

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Configuring Filter Chain

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Manipulating Request and Response

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Manipulating Request and Response

ServletRequestWrapper ServletResponseWrapper

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Inter-Servlet Communication

A process where two or more Servlets communicates with each other to process the client request.

A Servlet can forward the request to another Servlet to process the client request.

A Servlet can include the output of another Servlet to process the client request.

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Applet – Servlet Communication

Developing Applet front end application Establishing connection between applet and

servlet Communicasting throught object

serialisation Sending objects from applet to servlet Sending objects from servlet to applet

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Summary Introduction to Filters Filter API Configuring Filter Manipulating Request and Responses Servlet Communication