Java Client Example

package com.mycompany.fews.webservices;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.StringWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

public final class RestServiceClient {

    private RestServiceClient() {
    }

    public static void main(String[] args) throws IOException {

        // Example on how to call a GET request with parameters.
        filtersExample();

        // Example on how to run a workflow with a POST request with parameters.
        runTaskExample();

        // Example on how to get warm state times and download a warm state file.
        getWarmStateTimes();
        downloadWarmState();

    }

    private static void getWarmStateTimes() throws IOException {
        List<RequestParameter> requestParameters = new ArrayList<>();
        requestParameters.add(new RequestParameter("moduleInstanceIds", "ModuleInstanceId"));
        requestParameters.add(new RequestParameter("documentFormat", "PI_JSON"));
        String warmStatesUrl = "http://localhost:8080/FewsWebServices/rest/fewspiservice/v1/warmstates/times";
        HttpURLConnection connection = get(warmStatesUrl, requestParameters);
        if (connection.getResponseCode() == 200) {
            String response = getHttpResponse(connection);
            // the response contains the warmstate files in PI_JSON format.
            // JSON can be parsed with for example the jackson json library: https://github.com/FasterXML/jackson.
            System.out.println(response);
        } else {
            // Handle error.
            String errorResponse = getHttpResponse(connection);
            System.out.println(errorResponse);
        }

    }


    private static void downloadWarmState() throws IOException {
        List<RequestParameter> requestParameters = new ArrayList<>();
        requestParameters.add(new RequestParameter("moduleInstanceId", "ModuleInstanceId"));
        requestParameters.add(new RequestParameter("stateTime", "2023-01-24T08:00:00Z"));
        String warmStatesUrl = "http://localhost:8080/FewsWebServices/rest/fewspiservice/v1/warmstates";
        HttpURLConnection connection = get(warmStatesUrl, requestParameters);
        if (connection.getResponseCode() == 200) {
            String tmpdir = Files.createTempDirectory("warmstates").toFile().getAbsolutePath();
            File zipFile = new File(tmpdir, "warmstate.zip");
            downloadFile(connection, zipFile);
            System.out.printf("The Warm State file can be found at: %s%n", zipFile.getAbsolutePath());
        } else {
            // Handle error.
            String errorResponse = getHttpResponse(connection);
            System.out.println(errorResponse);
        }

    }

    private static void filtersExample() throws IOException {
        List<RequestParameter> requestParameters = new ArrayList<>();
        requestParameters.add(new RequestParameter("documentFormat", "PI_XML"));
        String filtersUrl = "http://localhost:8080/FewsWebServices/rest/fewspiservice/v1/filters";
        HttpURLConnection connection = get(filtersUrl, requestParameters);
        if (connection.getResponseCode() == 200) {
            String response = getHttpResponse(connection);
            // the response contains the filters in PI_XML format.
            System.out.println(response);
        } else {
            // Handle error.
            String errorResponse = getHttpResponse(connection);
            System.out.println(errorResponse);
        }
    }

    private static void runTaskExample() throws IOException {
        List<RequestParameter> requestParameters = new ArrayList<>();
        requestParameters.add(new RequestParameter("workflowId", "Import_Forecasts"));
        String runTasksUrl = "http://localhost:8080/FewsWebServices/rest/fewspiservice/v1/runtask";
        List<RequestParameter> bodyParameters = new ArrayList<>();
        HttpURLConnection connection = post(runTasksUrl, requestParameters, bodyParameters);
        if (connection.getResponseCode() == 200) {
            String response = getHttpResponse(connection);
            // the response contains the task id.
            System.out.println(response);
        } else {
            // Handle error.
            String errorResponse = getHttpResponse(connection);
            System.out.println(errorResponse);
        }
    }

    public static HttpURLConnection post(String urlString, List<RequestParameter> requestParameters, List<RequestParameter> bodyParameters) throws IOException {
        URL url = createUrl(urlString, requestParameters);
        var connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("POST");
        connection.setDoOutput(true);
        connection.setDoInput(true);
        try (StringWriter stringWriter = new StringWriter(16)) {
            for (RequestParameter param : bodyParameters) {
                stringWriter.append(URLEncoder.encode(param.getKey(), StandardCharsets.UTF_8));
                stringWriter.append("=");
                stringWriter.append(URLEncoder.encode(param.getValue(), StandardCharsets.UTF_8));
                stringWriter.append("&");
            }
            connection.getOutputStream().write(stringWriter.toString().getBytes());
        }
        connection.connect();
        return connection;
    }

    public static HttpURLConnection get(String urlString, List<RequestParameter> requestParameters) throws IOException {
        URL url = createUrl(urlString, requestParameters);
        var connection = (HttpURLConnection) url.openConnection();
        configureTimeout(connection);
        return connection;
    }

    private static void configureTimeout(HttpURLConnection connection) {
        var connectionTimeout = 60_000;
        connection.setConnectTimeout(connectionTimeout);
        var readTimeout = 60_000;
        connection.setReadTimeout(readTimeout);
        connection.setDoInput(true);
    }

    private static URL createUrl(String urlString, List<RequestParameter> requestParameters) throws MalformedURLException {
        StringBuilder urlBuilder = new StringBuilder(16);
        urlBuilder.append(urlString);
        if (!requestParameters.isEmpty()) urlBuilder.append("?");
        for (var requestParam: requestParameters) {
            urlBuilder.append(URLEncoder.encode(requestParam.getKey(), StandardCharsets.UTF_8));
            urlBuilder.append("=");
            urlBuilder.append(URLEncoder.encode(requestParam.getValue(), StandardCharsets.UTF_8));
            urlBuilder.append("&");
        }
        return new URL(urlBuilder.toString());
    }

    public static String getHttpResponse(HttpURLConnection connection) throws IOException {
        try (var bufferedReader = new BufferedReader(new InputStreamReader(connection.getResponseCode() < HttpURLConnection.HTTP_BAD_REQUEST ? connection.getInputStream() : connection.getErrorStream(), StandardCharsets.UTF_8))) {
            return bufferedReader.lines().collect(Collectors.joining("\n"));
        }
    }

    private static void downloadFile(HttpURLConnection connection, File zipFile) throws IOException {
        try (OutputStream outStream = new FileOutputStream(zipFile)) {
            try (var inputStream = connection.getInputStream()) {
                byte[] buffer = new byte[1024];
                int bytesRead;
                while ((bytesRead = inputStream.read(buffer)) != -1) {
                    outStream.write(buffer, 0, bytesRead);
                }
            }
        }
    }

    private static final class RequestParameter {
        private final String key;
        private final String value;

        private RequestParameter(String key, String value) {
            this.key = key;
            this.value = value;
        }

        private String getKey() {
            return key;
        }

        private String getValue() {
            return value;
        }

    }
}