Java tutorial
/** * Copyright (C) 2011 Brian Ferris <bdferris@onebusaway.org> * * 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 org.onebusaway.transit_data_federation.util; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStreamWriter; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; import java.net.URLConnection; import java.util.ArrayList; import java.util.Map.Entry; import javax.net.ssl.HttpsURLConnection; import org.apache.commons.lang.StringUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.google.gson.JsonElement; import com.google.gson.JsonObject; import com.google.gson.JsonParser; public class RestApiLibrary { private static int DEFAULT_READ_TIMEOUT = 60 * 1000; private static int DEFAULT_CONNECTION_TIMEOUT = 60 * 1000; private String _protocol = "http"; private String _host = null; private String _apiPrefix = "/api/"; private int _port = 80; private int readTimeout = DEFAULT_READ_TIMEOUT; private int connectionTimeout = DEFAULT_CONNECTION_TIMEOUT; private static Logger log = LoggerFactory.getLogger(RestApiLibrary.class); public void setReadTimeout(int readTimeout) { this.readTimeout = readTimeout; } public void setConnectionTimeout(int connectionTimeout) { this.connectionTimeout = connectionTimeout; } public RestApiLibrary(String protocol, String host, Integer port, String apiPrefix) { _host = host; _apiPrefix = apiPrefix; if (StringUtils.isNotBlank(protocol)) _protocol = protocol; if (port != null) _port = port; } public RestApiLibrary(String host, Integer port, String apiPrefix) { this("http", host, port, apiPrefix); } public URL buildUrl(String baseObject, String... params) throws MalformedURLException { String url = _apiPrefix; url += baseObject; if (params.length > 0) { url += "/"; for (int i = 0; i < params.length; i++) { String param = params[i]; url += param; if (i < params.length - 1) url += "/"; } } return new URL(_protocol, _host, _port, url); } public String getContentsOfUrlAsString(URL requestUrl) throws IOException { BufferedReader br = null; InputStream inStream = null; URLConnection conn = null; try { conn = requestUrl.openConnection(); conn.setConnectTimeout(connectionTimeout); conn.setReadTimeout(readTimeout); inStream = conn.getInputStream(); br = new BufferedReader(new InputStreamReader(inStream)); StringBuilder output = new StringBuilder(); int cp; while ((cp = br.read()) != -1) { output.append((char) cp); } return output.toString(); } catch (IOException ioe) { String url = requestUrl != null ? requestUrl.toExternalForm() : "url unavailable"; log.error("Error getting contents of url: " + url); throw ioe; } finally { try { if (br != null) br.close(); if (inStream != null) inStream.close(); } catch (IOException ioe2) { log.error("Error closing connection"); } } } public ArrayList<JsonObject> getJsonObjectsForString(String string) { JsonParser parser = new JsonParser(); JsonObject response = null; response = (JsonObject) parser.parse(string); // check status /*if(response.has("status")) { if(!response.get("status").getAsString().equals("OK")) throw new Exception("Response error: status was not OK"); } else throw new Exception("Invalid response: no status element was found.");*/ ArrayList<JsonObject> output = new ArrayList<JsonObject>(); // find "content" in the response for (Entry<String, JsonElement> item : response.entrySet()) { String type = item.getKey(); JsonElement responseItemWrapper = item.getValue(); if (type.equals("status")) continue; // our response "body" is always one array of things try { for (JsonElement arrayElement : responseItemWrapper.getAsJsonArray()) { output.add(arrayElement.getAsJsonObject()); } } catch (Exception e) { continue; } } return output; } /** * Writes config value to the given URL * @param requestUrl URL of remote server * @param value the config value to write * @return response code returned by server * @throws Exception */ public boolean setContents(URL requestUrl, String value) throws Exception { HttpURLConnection conn = getHttpURLConnection(requestUrl); int responseCode = 0; try { String content = "{\"config\":{\"value\":\"" + value + "\"}}"; conn.connect(); OutputStreamWriter outputStreamWriter = new OutputStreamWriter(conn.getOutputStream()); outputStreamWriter.write(content); outputStreamWriter.close(); responseCode = conn.getResponseCode(); } catch (Exception e) { log.error("Error writing value on TDM"); e.printStackTrace(); } finally { if (conn != null) { conn.disconnect(); } } return responseCode == HttpURLConnection.HTTP_OK; } /** * Logs the given message to the remote server. The message is sent as a post request to the server * @param baseIdentifier base url indentifier of the remote resource * @param component chef component/role which initiated logging action * @param priority message priority/severity * @param message the actual message to log * @return response text from the server */ public String log(String baseIdentifier, String component, Integer priority, String message) { String url = _apiPrefix + baseIdentifier; HttpURLConnection conn = null; String response = null; URL requestUrl = null; try { requestUrl = new URL("http", _host, _port, url); conn = getHttpURLConnection(requestUrl); conn.connect(); String content = buildMessage(component, priority, message); log.info("Writing content : {} to http connection", content); OutputStreamWriter outputStreamWriter = new OutputStreamWriter(conn.getOutputStream()); outputStreamWriter.write(content); outputStreamWriter.close(); response = conn.getResponseMessage(); } catch (MalformedURLException e) { log.error("Error building url : {}", requestUrl.toString()); e.printStackTrace(); } catch (IOException e) { log.error("Error opening http connection to url : {}", requestUrl.toString()); e.printStackTrace(); } finally { if (conn != null) { conn.disconnect(); } } return response; } private String buildMessage(String component, Integer priority, String message) { StringBuilder messageBuilder = new StringBuilder("{\"component\":\""); messageBuilder.append(component); messageBuilder.append("\",\"priority\":\""); messageBuilder.append(priority); messageBuilder.append("\",\"message\":\""); messageBuilder.append(message); messageBuilder.append("\"}"); return messageBuilder.toString(); } private HttpURLConnection getHttpURLConnection(URL requestUrl) { HttpURLConnection conn = null; try { if (requestUrl.getProtocol().toLowerCase().equals("https")) { conn = (HttpsURLConnection) requestUrl.openConnection(); } else { conn = (HttpURLConnection) requestUrl.openConnection(); } conn.setRequestMethod("POST"); conn.setRequestProperty("Content-Type", "application/json"); conn.setUseCaches(false); conn.setDoOutput(true); } catch (IOException e) { log.error("Error opening Http Connection for url : {}", requestUrl.toString()); e.printStackTrace(); } finally { if (conn != null) { conn.disconnect(); } } return conn; } }