package com.yahoo.rest;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.UnsupportedEncodingException;import java.net.HttpURLConnection;import java.net.URL;import java.net.URLEncoder;import java.util.*;/** * Simple REST client. * * TODO: Handle error codes (http://developer.yahoo.net/documentation/errors.html). * TODO: Parse error XML when error occurs. * TODO: Add request/response logging. * * @author Ryan Kennedy */public class RestClient {    private static final int MAX_URI_LENGTH_FOR_GET = 255;    private static final int ERROR_READ_BUFFER_SIZE = 1024;    private static final String USER_AGENT_STRING;    private static final String DEFAULT_USER_AGENT = "Yahoo-Java-SDK/unknown-version";    static {        String ua = DEFAULT_USER_AGENT;        try {            ResourceBundle bundle = ResourceBundle.getBundle("com.yahoo.rest.RestClient");            if(bundle != null) {                ua = bundle.getString("useragent");            }        }        catch (MissingResourceException mre) {            // It's okay, the bundle just wasn't found. We'll use the default.        }        finally {            USER_AGENT_STRING = ua;        }    }    private RestClient() {    }    /**     * Calls the given REST resource with the given parameters.     *     * @param serviceUrl The URL of the REST resource to call.     * @param parameters The parameters to pass to the call.     * @return The InputStream to the content returned by the resource.     * @throws IOException Thrown if a networking issue occurs.     * @throws RestException Thrown if the call fails. Could be caused by the service or the client. Check the error message for more information.     */    public static InputStream call(String serviceUrl, Map parameters) throws IOException, RestException {        StringBuffer urlString = new StringBuffer(serviceUrl);        String query = RestClient.buildQueryString(parameters);        HttpURLConnection conn;        if((urlString.length() + query.length() + 1) > MAX_URI_LENGTH_FOR_GET) {            // Request is too big, do a POST            URL url = new URL(urlString.toString());            conn = (HttpURLConnection) url.openConnection();            conn.setRequestProperty("User-Agent", USER_AGENT_STRING);            conn.setRequestMethod("POST");            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");            conn.setDoOutput(true);            conn.getOutputStream().write(query.getBytes());        }        else {            // Request is small enough it should fit in a GET            if(query.length() > 0) {                urlString.append("?").append(query);            }            URL url = new URL(urlString.toString());            conn = (HttpURLConnection) url.openConnection();            conn.setRequestProperty("User-Agent", USER_AGENT_STRING);            conn.setRequestMethod("GET");        }        int responseCode = conn.getResponseCode();        if (HttpURLConnection.HTTP_OK != responseCode) {            ByteArrayOutputStream errorBuffer = new ByteArrayOutputStream();            int read;            byte[] readBuffer = new byte[ERROR_READ_BUFFER_SIZE];            InputStream errorStream = conn.getErrorStream();            while (-1 != (read = errorStream.read(readBuffer))) {                errorBuffer.write(readBuffer, 0, read);            }            throw new RestException("Request failed, HTTP " + responseCode + ": " + conn.getResponseMessage(), errorBuffer.toByteArray());        }        return conn.getInputStream();    }    private static String buildQueryString(Map parameters) throws UnsupportedEncodingException {        Set parameterNames = parameters.keySet();        StringBuffer buffer = new StringBuffer();        for (Iterator iterator = parameterNames.iterator(); iterator.hasNext();) {            String parameterName = (String) iterator.next();            Object value = parameters.get(parameterName);            if(value instanceof String) {                buffer.append(URLEncoder.encode(parameterName, "UTF-8"));                buffer.append('=');                buffer.append(URLEncoder.encode((String) parameters.get(parameterName), "UTF-8"));            }            else if(value instanceof List) {                for (Iterator values = ((List) value).iterator(); values.hasNext();) {                    String currentValue = (String) values.next();                    buffer.append(URLEncoder.encode(parameterName, "UTF-8"));                    buffer.append('=');                    buffer.append(URLEncoder.encode(currentValue, "UTF-8"));                    if(values.hasNext()) {                        buffer.append('&');                    }                }            }            if (iterator.hasNext()) {                buffer.append('&');            }        }        return buffer.toString();    }}