com.spotify.it.frontend.Main.java Source code

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Here is the source code for com.spotify.it.frontend.Main.java
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/*-
 * -\-\-
 * Dockerfile Maven Plugin
 * --
 * Copyright (C) 2016 Spotify AB
 * --
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * -/-/-
 */

package com.spotify.it.frontend;

import com.google.common.io.CharStreams;

import java.io.InputStream;
import java.io.InputStreamReader;
import java.math.BigInteger;
import java.net.URI;
import java.nio.charset.StandardCharsets;
import java.security.SecureRandom;
import java.util.Random;

import spark.Spark;

public class Main {

    public static void main(String[] args) {
        if (args.length < 1) {
            System.err.println("Needs backend URL as command-line argument");
            System.exit(1);
            return;
        }

        URI backendUri = URI.create(args[0]);

        Random random = new SecureRandom();

        Spark.port(1338);
        Spark.get("/", (req, res) -> {
            String uppercase = new BigInteger(130, random).toString(32).toUpperCase();

            String version;
            try (InputStream versionStream = backendUri.resolve("/api/version").toURL().openStream()) {
                version = CharStreams.toString(new InputStreamReader(versionStream, StandardCharsets.UTF_8));
            }

            String lowercase;
            try (InputStream lowercaseStream = backendUri.resolve("/api/lowercase/" + uppercase).toURL()
                    .openStream()) {
                lowercase = CharStreams.toString(new InputStreamReader(lowercaseStream, StandardCharsets.UTF_8));
            }

            return "<!DOCTYPE html><html>" + "<head><title>frontend</title></head>" + "<body>"
                    + "<p>Backend version: " + version + "</p>" + "<p>Lower case of " + uppercase
                    + " is according to backend " + lowercase + "</p>" + "</body></html>";
        });
    }
}