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Merge pull request iluwatar#42 from joshzambales/master
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‎README.md‎

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# Design pattern samples in Java.
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## Build status:
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* [Callback](#callback)
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* [Execute Around](#execute-around)
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### Presentation Tier Patterns
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Presentation Tier patterns are the top-most level of the application, this is concerned with translating tasks and results to something the user can understand.
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* [Intercepting Filter](#intercepting-filter)
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## <a name="abstract-factory">Abstract Factory</a> [&#8593;](#list-of-design-patterns)
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**Intent:** Provide an interface for creating families of related or dependent objects without specifying their concrete classes.
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**Applicability:** Use the Callback pattern when
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* When some arbitrary synchronous or asynchronous action must be performed after execution of some defined activity.
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## <a name="intercepting-filter">Intercepting Filter</a> [&#8593;](#list-of-design-patterns)
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**Intent:** Provide pluggable filters to conduct necessary pre-processing and post-processing to requests from a client to a target
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![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/intercepting-filter/etc/Intercepting-filter.png "Intercepting Filter")
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**Applicability:** Use the Intercepting Filter pattern when
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* a system uses pre-processing or post-processing requests
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* a system should do the authentication/ authorization/ logging or tracking of request and then pass the requests to corresponding handlers
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* you want a modular approach to configuring pre-processing and post-processing schemes
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**Real world examples:**
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* [CyclicBarrier] (http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/CyclicBarrier.html#CyclicBarrier%28int,%20java.lang.Runnable%29) constructor can accept callback that will be triggered every time when barrier is tripped.
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**Real world examples:**
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* [JavaScript](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain) prototype inheritance
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# Frequently asked questions
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**<a id="Q1">Q: What is the difference between State and Strategy patterns?</a>**
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1. Fork the repository.
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2. Implement the code changes in your fork. Remember to add sufficient comments documenting the implementation.
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3. Create a simple class diagram from your example code.
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4. Add description of the pattern in README.md and link to the class diagram.
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4. Add description of the pattern in README.md and link to the class diagram.
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5. Create a pull request.
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**For creating/editing UML diagrams** you need one of the following:
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* [Let’s Modify the Objects-First Approach into Design-Patterns-First](http://edu.pecinovsky.cz/papers/2006_ITiCSE_Design_Patterns_First.pdf)
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* [Pattern Languages of Program Design](http://www.amazon.com/Pattern-Languages-Program-Design-Coplien/dp/0201607344/ref=sr_1_1)
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* [Martin Fowler - Event Aggregator](http://martinfowler.com/eaaDev/EventAggregator.html)
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* [TutorialsPoint - Intercepting Filter](http://www.tutorialspoint.com/design_pattern/intercepting_filter_pattern.htm)
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* [Presentation Tier Pattern](http://www.javagyan.com/tutorials/corej2eepatterns/presentation-tier-patterns)
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* [Functional Programming in Java: Harnessing the Power of Java 8 Lambda Expressions](http://www.amazon.com/Functional-Programming-Java-Harnessing-Expressions/dp/1937785467/ref=sr_1_1)
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# License
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This project is licensed under the terms of the MIT license.

‎intercepting-filter/etc/Intercepting-filter.png‎

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‎intercepting-filter/pom.xml‎

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<?xml version="1.0"?>
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<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>com.iluwatar</groupId>
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<artifactId>java-design-patterns</artifactId>
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<version>1.0-SNAPSHOT</version>
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</parent>
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<artifactId>intercepting-filter</artifactId>
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<dependencies>
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<scope>test</scope>
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</dependency>
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</dependencies>
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</project>

‎intercepting-filter/src/main/java/com/iluwatar/AddressFilter.java‎

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package com.iluwatar;
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/**
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* Concrete implementation of filter
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* This filter is responsible for checking/filtering the input in the address field, returns null if field is empty
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* @author joshzambales
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*
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*/
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public class AddressFilter implements Filter{
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public String execute(String[] request){
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if(request[2].equals("")){
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return null;
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}else return request[2];
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}
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}

‎intercepting-filter/src/main/java/com/iluwatar/App.java‎

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package com.iluwatar;
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import java.util.*;
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import javax.swing.*;
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import javax.swing.table.*;
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import java.awt.*;
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import java.awt.event.*;
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/**
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*
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* This is an app that checks whether the order request is valid through pre-processing done via Filters
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* Each field has its own corresponding Filter
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* @author joshzambales
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*
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*/
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public class App{
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public static void main(String[] args){
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FilterManager filterManager = new FilterManager(new Target());
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filterManager.setFilter(new NameFilter());
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filterManager.setFilter(new ContactFilter());
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filterManager.setFilter(new AddressFilter());
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filterManager.setFilter(new DepositFilter());
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filterManager.setFilter(new OrderFilter());
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Client client = new Client();
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client.setFilterManager(filterManager);
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}
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}
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‎intercepting-filter/src/main/java/com/iluwatar/Client.java‎

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package com.iluwatar;
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import java.util.*;
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import javax.swing.*;
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import javax.swing.table.*;
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import java.awt.*;
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import java.awt.event.*;
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/**
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* The Client class is responsible for handling the input and running them through filters inside the filterManager
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*
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* This is where Filters come to play as the client pre-processes the request before being displayed in the Target
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*
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* @author joshzambales
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*
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*/
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public class Client extends JFrame{
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private FilterManager filterManager;
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private JLabel jl;
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private JTextField[] jtFields;
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private JTextArea[] jtAreas;
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private JButton clearButton, processButton;
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public Client(){
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super("Client System");
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setDefaultCloseOperation(EXIT_ON_CLOSE);
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setSize(300,300);
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jl = new JLabel("RUNNING...");
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jtFields = new JTextField[3];
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for(int i = 0; i < 3; i++){
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jtFields[i] = new JTextField();
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}
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jtAreas = new JTextArea[2];
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for(int i = 0; i < 2; i++){
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jtAreas[i] = new JTextArea();
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}
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clearButton = new JButton("Clear");
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processButton = new JButton("Process");
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setup();
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}
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private void setup(){
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setLayout(new BorderLayout());
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JPanel panel = new JPanel();
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add(jl,BorderLayout.SOUTH);
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add(panel, BorderLayout.CENTER);
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panel.setLayout(new GridLayout(6,2));
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panel.add(new JLabel("Name"));
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panel.add(jtFields[0]);
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panel.add(new JLabel("Contact Number"));
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panel.add(jtFields[1]);
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panel.add(new JLabel("Address"));
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panel.add(jtAreas[0]);
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panel.add(new JLabel("Deposit Number"));
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panel.add(jtFields[2]);
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panel.add(new JLabel("Order"));
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panel.add(jtAreas[1]);
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panel.add(clearButton);
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panel.add(processButton);
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clearButton.addActionListener(new ActionListener(){
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@Override
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public void actionPerformed(ActionEvent e){
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for(JTextArea i : jtAreas){
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i.setText("");
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}
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for(JTextField i : jtFields){
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i.setText("");
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}
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}
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});
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processButton.addActionListener(new ActionListener(){
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@Override
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public void actionPerformed(ActionEvent e){
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String request = String.format("%s&%s&%s&%s&%s",jtFields[0].getText(),jtFields[1].getText(),jtAreas[0].getText(),jtFields[2].getText(),jtAreas[1].getText());
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jl.setText(sendRequest(request));
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}
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});
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JRootPane rootPane = SwingUtilities.getRootPane(processButton);
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rootPane.setDefaultButton(processButton);
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setVisible(true);
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}
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public void setFilterManager(FilterManager filterManager){
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this.filterManager = filterManager;
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}
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public String sendRequest(String request){
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return filterManager.filterRequest(request);
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}
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}

‎intercepting-filter/src/main/java/com/iluwatar/ContactFilter.java‎

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package com.iluwatar;
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/**
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* Concrete implementation of filter
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* This filter checks for the contact field in which it checks if the input consist of numbers and it also checks if the input follows the length constraint (11 digits)
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* @author joshzambales
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*
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*/
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public class ContactFilter implements Filter{
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public String execute(String[] request){
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if(request[1].equals("") || request[1].matches(".*[^\\d]+.*") || request[1].length() != 11){
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return null;
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}else return request[1];
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}
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}

‎intercepting-filter/src/main/java/com/iluwatar/DepositFilter.java‎

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package com.iluwatar;
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/**
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* Concrete implementation of filter
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*
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* This checks for the deposit code, returns null when deposit field is empty
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* @author joshzambales
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*
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*/
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public class DepositFilter implements Filter{
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public String execute(String[] request){
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if(request[3].equals("")){
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return null;
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}else return request[3];
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}
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}

‎intercepting-filter/src/main/java/com/iluwatar/Filter.java‎

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package com.iluwatar;
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/**
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* Filter interface
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* Filters perform certain tasks prior or after execution of request by request handler.
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* In this case, before the request is handled by the target, the request undergoes through each Filter
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* @author joshzambales
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*
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*/
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public interface Filter{
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public String execute(String[] request);
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}

‎intercepting-filter/src/main/java/com/iluwatar/FilterChain.java‎

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package com.iluwatar;
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import java.util.*;
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/**
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* Filter Chain carries multiple filters and help to execute them in defined order on target.
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*
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* @author joshzambales
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*/
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public class FilterChain{
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private ArrayList<Filter> filters = new ArrayList<Filter>();
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private final Target target;
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public FilterChain(Target target){
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this.target = target;
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}
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public void addFilter(Filter filter){
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filters.add(filter);
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}
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public String execute(String request){
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String tempout[] = new String[filters.size()];
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String tempin[] = request.split("&");
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int i = 0;
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try{
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for(Filter filter:filters){
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tempout[i] = null;
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tempout[i++] = filter.execute(tempin);
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}
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}catch(Exception e){
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return "NOT ENOUGHT INPUT";
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}
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if(tempout[4] == null){
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return "INVALID ORDER!";
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}else if(tempout[3] == null){
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return "INVALID DEPOSIT NUMBER!";
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}else if(tempout[2] == null){
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return "INVALID ADRDESS!";
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}else if(tempout[1] == null){
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return "INVALID Contact Number!";
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}else if(tempout[0] == null){
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return "INVALID Name!";
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}else{
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target.execute(tempout);
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return "RUNNING...";
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}
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}
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}

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