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iluwatar#297 Create Spring Boot-backed API Gateway that aggregates calls to the Image and Price microservices
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14 files changed

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lines changed

‎api-gateway/pom.xml

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</parent>
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<modelVersion>4.0.0</modelVersion>
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<artifactId>api-gateway</artifactId>
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<packaging>jar</packaging>
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<properties>
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<spring.version>4.2.5.RELEASE</spring.version>
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<spring-boot.version>1.3.3.RELEASE</spring-boot.version>
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</properties>
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<dependencyManagement>
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<dependencies>
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-dependencies</artifactId>
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<version>${spring-boot.version}</version>
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<type>pom</type>
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<scope>import</scope>
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</dependency>
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</dependencies>
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</dependencyManagement>
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<dependencies>
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<dependency>
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<groupId>org.springframework</groupId>
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<artifactId>spring-webmvc</artifactId>
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<version>${spring.version}</version>
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</dependency>
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-web</artifactId>
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<version>${spring-boot.version}</version>
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</dependency>
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.mockito</groupId>
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<artifactId>mockito-core</artifactId>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.apache.httpcomponents</groupId>
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<artifactId>httpclient</artifactId>
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<version>4.5.2</version>
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</dependency>
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</dependencies>
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<build>
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<plugins>
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<plugin>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-maven-plugin</artifactId>
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<version>${spring-boot.version}</version>
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<executions>
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<execution>
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<goals>
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<goal>repackage</goal>
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</goals>
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</execution>
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</executions>
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</plugin>
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</plugins>
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</build>
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</project>

‎api-gateway/src/main/java/com/iluwatar/api/gateway/ApiGateway.java

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package com.iluwatar.api.gateway;
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import org.springframework.web.bind.annotation.RequestMapping;
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import org.springframework.web.bind.annotation.RestController;
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import javax.annotation.Resource;
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/**
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* The ApiGateway aggregates calls to microservices based on the needs of the individual clients.
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*/
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@RestController
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public class ApiGateway {
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private ImageService imageService = new ImageService();
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private PriceService priceService = new PriceService();
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@Resource
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private ImageClient imageClient;
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@Resource
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private PriceClient priceClient;
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/**
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* Retrieves product information that desktop clients need
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* @return Product information for clients on a desktop
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*/
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@RequestMapping("/desktop")
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public DesktopProduct getProductDesktop() {
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DesktopProduct desktopProduct = new DesktopProduct();
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desktopProduct.setImagePath(imageService.getImagePath());
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desktopProduct.setPrice(priceService.getPrice());
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desktopProduct.setImagePath(imageClient.getImagePath());
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desktopProduct.setPrice(priceClient.getPrice());
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return desktopProduct;
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}
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/**
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* Retrieves product information that mobile clients need
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* @return Product information for clients on a mobile device
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*/
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@RequestMapping("/mobile")
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public MobileProduct getProductMobile() {
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MobileProduct mobileProduct = new MobileProduct();
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mobileProduct.setPrice(priceService.getPrice());
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mobileProduct.setPrice(priceClient.getPrice());
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return mobileProduct;
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}
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}

‎api-gateway/src/main/java/com/iluwatar/api/gateway/App.java

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package com.iluwatar.api.gateway;
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import org.springframework.boot.SpringApplication;
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import org.springframework.boot.autoconfigure.SpringBootApplication;
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/**
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* With the Microservices pattern, a client may need data from multiple different microservices.
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* If the client called each microservice directly, that could contribute to longer load times,
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*
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* <p>
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* This implementation shows what the API Gateway pattern could look like for an e-commerce site.
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* In this case, the (@link ImageService) and (@link PriceService) represent our microservices.
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* Customers viewing the site on a desktop device can see both price information and an image of
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* a product, so the (@link ApiGateway) calls both of the microservices and aggregates the data in
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* the (@link DesktopProduct) model. However, mobile users only see price information; they do not
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* see a product image. For mobile users, the (@link ApiGateway) only retrieves price information,
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* which it uses to populate the (@link MobileProduct).
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* The {@link ApiGateway} makes calls to the Image and Price microservices using the
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* {@link ImageClientImpl} and {@link PriceClientImpl} respectively. Customers viewing the site on a
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* desktop device can see both price information and an image of a product, so the {@link ApiGateway}
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* calls both of the microservices and aggregates the data in the {@link DesktopProduct} model.
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* However, mobile users only see price information; they do not see a product image. For mobile
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* users, the {@link ApiGateway} only retrieves price information, which it uses to populate the
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* {@link MobileProduct}.
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*/
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@SpringBootApplication
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public class App {
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/**
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* command line args
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*/
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public static void main(String[] args) {
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ApiGateway apiGateway = new ApiGateway();
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DesktopProduct desktopProduct = apiGateway.getProductDesktop();
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System.out.println(String.format("Desktop Product \nPrice: %s\nImage path: %s",
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desktopProduct.getPrice(), desktopProduct.getImagePath()));
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MobileProduct mobileProduct = apiGateway.getProductMobile();
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System.out.println(String.format("Mobile Product \nPrice: %s", mobileProduct.getPrice()));
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SpringApplication.run(App.class, args);
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}
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}

‎api-gateway/src/main/java/com/iluwatar/api/gateway/DesktopProduct.java

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* Encapsulates all of the information that a desktop client needs to display a product.
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*/
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public class DesktopProduct {
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/**
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* The price of the product
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*/
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private String price;
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/**
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* The path to the image of the product
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*/
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private String imagePath;
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public String getPrice() {

‎api-gateway/src/main/java/com/iluwatar/api/gateway/ImageClient.java

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package com.iluwatar.api.gateway;
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/**
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* An interface used to communicate with the Image microservice
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*/
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public interface ImageClient {
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String getImagePath();
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}

‎api-gateway/src/main/java/com/iluwatar/api/gateway/ImageClientImpl.java

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package com.iluwatar.api.gateway;
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import org.apache.http.client.methods.CloseableHttpResponse;
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import org.apache.http.client.methods.HttpGet;
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import org.apache.http.impl.client.CloseableHttpClient;
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import org.apache.http.impl.client.HttpClients;
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import org.apache.http.util.EntityUtils;
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import org.springframework.stereotype.Component;
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import java.io.IOException;
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/**
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* An adapter to communicate with the Image microservice
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*/
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@Component
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public class ImageClientImpl implements ImageClient{
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/**
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* Makes a simple HTTP Get request to the Image microservice
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* @return The path to the image
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*/
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@Override
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public String getImagePath() {
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String response = null;
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try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
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HttpGet httpGet = new HttpGet("http://localhost:50005/image-path");
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try (CloseableHttpResponse httpResponse = httpClient.execute(httpGet)) {
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response = EntityUtils.toString(httpResponse.getEntity());
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}
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} catch (IOException e) {
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e.printStackTrace();
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}
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return response;
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}
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}

‎api-gateway/src/main/java/com/iluwatar/api/gateway/ImageService.java

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‎api-gateway/src/main/java/com/iluwatar/api/gateway/MobileProduct.java

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* Encapsulates all of the information that mobile client needs to display a product.
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*/
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public class MobileProduct {
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/**
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* The price of the product
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*/
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private String price;
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public String getPrice() {

‎api-gateway/src/main/java/com/iluwatar/api/gateway/PriceClient.java

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package com.iluwatar.api.gateway;
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/**
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* An interface used to communicate with the Price microservice
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*/
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public interface PriceClient {
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String getPrice();
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}

‎api-gateway/src/main/java/com/iluwatar/api/gateway/PriceClientImpl.java

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package com.iluwatar.api.gateway;
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import org.apache.http.client.methods.CloseableHttpResponse;
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import org.apache.http.client.methods.HttpGet;
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import org.apache.http.impl.client.CloseableHttpClient;
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import org.apache.http.impl.client.HttpClients;
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import org.apache.http.util.EntityUtils;
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import org.springframework.stereotype.Component;
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import java.io.IOException;
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/**
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* An adapter to communicate with the Price microservice
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*/
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@Component
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public class PriceClientImpl implements PriceClient{
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/**
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* Makes a simple HTTP Get request to the Price microservice
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* @return The price of the product
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*/
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@Override
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public String getPrice() {
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String response = null;
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try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
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HttpGet httpGet = new HttpGet("http://localhost:50006/price");
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try (CloseableHttpResponse httpResponse = httpClient.execute(httpGet)) {
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response = EntityUtils.toString(httpResponse.getEntity());
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}
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} catch (IOException e) {
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e.printStackTrace();
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}
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return response;
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}
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}

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