Spark WebServer Template

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>testing-webserver</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>com.sparkjava</groupId>
            <artifactId>spark-core</artifactId>
            <version>2.8.0</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

WebServer.java

import static spark.Spark.*;

import java.io.File;
import java.io.OutputStream;
import java.nio.file.Files;

public class WebServer {
    public static void main(String[] args) {
        enableCORS("*", "GET", "Content-disposition");

        // Hello World http://localhost:4567/hello
        get("/hello", (req, res) -> "Hello World");

        // Download a File Example
        get("/file", ((request, response) -> {
            response.header("Content-disposition", "attachment; filename=seal.jpg;");

            File file = new File("C:\\Users\\jicas\\Pictures\\seal.jpg");
            // OutputStream 101: https://www.baeldung.com/java-outputstream
            OutputStream outputStream = response.raw().getOutputStream();
            outputStream.write(Files.readAllBytes(file.toPath()));
            outputStream.flush();
            return response;
        }));
    }

    private static void enableCORS(final String origin, final String methods, final String headers) {
        options("/*", (request, response) -> {
            String accessControlRequestHeaders = request.headers("Access-Control-Request-Headers");
            if (accessControlRequestHeaders != null) {
                response.header("Access-Control-Allow-Headers", accessControlRequestHeaders);
            }

            String accessControlRequestMethod = request.headers("Access-Control-Request-Method");
            if (accessControlRequestMethod != null) {
                response.header("Access-Control-Allow-Methods", accessControlRequestMethod);
            }

            return "OK";
        });

        before((request, response) -> {
            response.header("Access-Control-Allow-Origin", origin);
            response.header("Access-Control-Request-Method", methods);
            response.header("Access-Control-Allow-Headers", headers);
            response.header("Access-Control-Expose-Headers", headers);
            // Allow by type (if needed)
            // response.type("application/json");
        });
    }
}