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Resolved issue #1323 Two-Step View pattern
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‎microservices-idempotent-consumer/src/test/java/com/iluwatar/idempotentconsumer/AppTest.java‎

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/*
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* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
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*
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* The MIT License
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* Copyright © 2014-2022 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.idempotentconsumer;
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import org.junit.jupiter.api.Test;

‎microservices-idempotent-consumer/src/test/java/com/iluwatar/idempotentconsumer/RequestStateMachineTests.java‎

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/*
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* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
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*
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* The MIT License
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* Copyright © 2014-2022 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.idempotentconsumer;
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import org.junit.jupiter.api.BeforeEach;

‎pom.xml‎

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<module>function-composition</module>
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<module>microservices-distributed-tracing</module>
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<module>microservices-idempotent-consumer</module>
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<module>two-step-view</module>
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</modules>
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<repositories>
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<repository>

‎two-step-view/README.md‎

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# Book Data Processing and Presentation
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This example demonstrates a simple pipeline for processing book data and rendering it as an HTML view. It involves three main steps: **data preparation**, **business logic processing**, and **presentation**. The structure of the program aligns with the principles of the **Presentation-Abstraction-Control (PAC)** design pattern.
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---
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## Problem Addressed
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This implementation solves the issue described in [Issue #1323](https://github.com/iluwatar/java-design-patterns/issues/1323) of the [java-design-patterns repository](https://github.com/iluwatar/java-design-patterns). The goal is to showcase how to split application logic into phases while keeping the layers loosely coupled.
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---
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## Overview of the Solution
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The program is divided into the following parts:
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1. **Data Layer**
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- The `Book` class represents the raw data for a book.
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- The `BookStore` class holds the processed book data for display.
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2. **Logic Layer**
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- The `DataPreparation` class handles the business logic. It computes whether a discount is applied and checks stock availability.
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3. **Presentation Layer**
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- The `Presentation` class generates an HTML view of the book data.
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---
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## How to Run the Code
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1. Clone the repository:
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```bash
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git clone https://github.com/iluwatar/java-design-patterns.git
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cd java-design-patterns
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```
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2. Compile and run the `App` class:
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```bash
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javac com/iluwatar/*.java
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java com.iluwatar.App
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```
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3. Expected Output:
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The program generates an HTML representation of the book data and prints it to the console:
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```html
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<div class='book'>
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<h1>Batman Vol. 1: The Court of Owls</h1>
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<p>Price: $11.6</p>
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<p>Discounted Price: $8.7</p>
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<p>Status: In Stock</p>
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</div>
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```
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---
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## Code Structure
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- `Book`: Represents raw book data with fields like `name`, `price`, `discount`, and `stock`.
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- `BookStore`: Represents processed data including `discountPrice` and `inStock` status.
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- `DataPreparation`: Contains logic to calculate the discount price and determine stock status.
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- `Presentation`: Generates the HTML view of the book data.
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- `App`: Entry point that orchestrates the flow.
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---
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## Key Features
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- **Layered Architecture**: The application is divided into layers for better separation of concerns.
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- **Scalable Design**: The modular approach makes it easier to extend functionality, such as adding new data preparation rules or presentation formats.
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- **Reusability**: Each layer operates independently, promoting code reuse.
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---
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## Related Resources
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- **GitHub Issue**: [Issue #1323](https://github.com/iluwatar/java-design-patterns/issues/1323)
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- **Repository**: [java-design-patterns](https://github.com/iluwatar/java-design-patterns)
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- **Design Pattern**: [Two-Step-View-Pattern](https://martinfowler.com/eaaCatalog/twoStepView.html)
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‎two-step-view/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<!--
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This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
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The MIT License
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Copyright © 2014-2022 Ilkka Seppälä
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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THE SOFTWARE.
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-->
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<project 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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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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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>1.26.0-SNAPSHOT</version>
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</parent>
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<artifactId>two-step-view</artifactId>
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<properties>
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<maven.compiler.source>17</maven.compiler.source>
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<maven.compiler.target>17</maven.compiler.target>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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</properties>
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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>

‎two-step-view/src/main/java/com/iluwatar/App.java‎

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/*
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* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
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*
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* The MIT License
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* Copyright © 2014-2022 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar;
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import java.util.logging.Logger;
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/** Main class. */
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public class App {
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private static final Logger logger = Logger.getLogger(App.class.getName());
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/** Main function. */
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public static void main(String[] args) {
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// Create a Book instance with sample data
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Book book = new Book("Batman Vol. 1: The Court of Owls", 11.60, true, 10);
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// Convert raw book data into a structured format
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BookStore preparedData = DataPreparation.prepareBook(book);
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String htmlOutput = Presentation.presentBook(preparedData);
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// Output the rendered HTML
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logger.info(htmlOutput);
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}
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}
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‎two-step-view/src/main/java/com/iluwatar/Book.java‎

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/*
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* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
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*
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* The MIT License
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* Copyright © 2014-2022 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar;
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import lombok.AllArgsConstructor;
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import lombok.Data;
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/** Represents a Book. */
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@AllArgsConstructor
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@Data
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public class Book {
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String name;
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double price;
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boolean discount;
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int stock;
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}

‎two-step-view/src/main/java/com/iluwatar/BookStore.java‎

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/*
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* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
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*
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* The MIT License
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* Copyright © 2014-2022 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar;
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import lombok.AllArgsConstructor;
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import lombok.Data;
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/** Represents the processed book data used for display purposes. */
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@AllArgsConstructor
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@Data
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public class BookStore {
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String name;
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double price;
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double discountPrice; // Calculates price if the book is discounted
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boolean inStock; // Indicates if the book is in stock
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}

‎two-step-view/src/main/java/com/iluwatar/DataPreparation.java‎

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/*
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* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
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*
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* The MIT License
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* Copyright © 2014-2022 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar;
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/** class representing phase 1. */
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public class DataPreparation {
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private DataPreparation() {}
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/**
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* Prepares book data for the store.
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* Calculates the discount price if applicable and checks stock availability.
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*/
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public static BookStore prepareBook(Book book) {
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double discountPrice = book.isDiscount() ? book.getPrice() * 0.75 : book.getPrice();
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boolean inStock = book.getStock() > 0;
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return new BookStore(book.getName(), book.getPrice(), discountPrice, inStock);
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}
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}

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