Java tutorial
/* * Copyright 2007, MetaDimensional Technologies Inc. * * * This file is part of the RememberTheMilk Java API. * * The RememberTheMilk Java API is free software; you can redistribute it * and/or modify it under the terms of the GNU Lesser General Public License * as published by the Free Software Foundation; either version 3 of the * License, or (at your option) any later version. * * The RememberTheMilk Java API is distributed in the hope that it will be * useful, but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser * General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. */ package org.weloveastrid.rmilk.api; import java.io.IOException; import java.io.UnsupportedEncodingException; import java.net.URLEncoder; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.util.Arrays; import java.util.Collections; import java.util.List; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import org.apache.http.HttpResponse; import org.apache.http.HttpStatus; import org.apache.http.client.HttpClient; import org.apache.http.client.methods.HttpGet; import org.apache.http.impl.client.DefaultHttpClient; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.w3c.dom.Node; import org.xml.sax.SAXException; import android.util.Log; /** * Handles the details of invoking a method on the RTM REST API. * * @author Will Ross Jun 21, 2007 */ @SuppressWarnings("nls") public class Invoker { private static final String SERVICE_UNAVAILABLE_CODE = "105"; private static final String TAG = "rtm-invoker"; //$NON-NLS-1$ private static final DocumentBuilder builder; static { // Done this way because the builder is marked "final" DocumentBuilder aBuilder; try { final DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); factory.setNamespaceAware(false); factory.setValidating(false); aBuilder = factory.newDocumentBuilder(); } catch (Exception exception) { Log.e(TAG, "Unable to construct a document builder", exception); aBuilder = null; } builder = aBuilder; } private static final String ENCODING = "UTF-8"; //$NON-NLS-1$ private static final String API_SIG_PARAM = "api_sig"; //$NON-NLS-1$ private static final long INVOCATION_INTERVAL = 400; private long lastInvocation; private final ApplicationInfo applicationInfo; private final MessageDigest digest; private final String serviceRelativeUri; private final HttpClient httpClient; public Invoker(@SuppressWarnings("unused") String serverHostName, @SuppressWarnings("unused") int serverPortNumber, String serviceRelativeUri, ApplicationInfo applicationInfo) throws ServiceInternalException { this.serviceRelativeUri = serviceRelativeUri; httpClient = new DefaultHttpClient(); lastInvocation = System.currentTimeMillis(); this.applicationInfo = applicationInfo; try { digest = MessageDigest.getInstance("md5"); //$NON-NLS-1$ } catch (NoSuchAlgorithmException e) { throw new ServiceInternalException("Could not create properly the MD5 digest", e); } } private StringBuffer computeRequestUri(Param... params) throws ServiceInternalException { final StringBuffer requestUri = new StringBuffer(serviceRelativeUri); if (params.length > 0) { requestUri.append("?"); } for (Param param : params) { try { requestUri.append(param.getName()).append("=").append(URLEncoder.encode(param.getValue(), ENCODING)) .append("&"); } catch (Exception exception) { final StringBuffer message = new StringBuffer( "Cannot encode properly the HTTP GET request URI: cannot execute query"); Log.e(TAG, message.toString(), exception); throw new ServiceInternalException(message.toString()); } } requestUri.append(API_SIG_PARAM).append("=").append(calcApiSig(params)); return requestUri; } /** Call invoke with a false repeat */ public Element invoke(Param... params) throws ServiceException { return invoke(false, params); } public Element invoke(boolean repeat, Param... params) throws ServiceException { long timeSinceLastInvocation = System.currentTimeMillis() - lastInvocation; if (timeSinceLastInvocation < INVOCATION_INTERVAL) { // In order not to invoke the RTM service too often try { Thread.sleep(INVOCATION_INTERVAL - timeSinceLastInvocation); } catch (InterruptedException e) { return null; } } // We compute the URI final StringBuffer requestUri = computeRequestUri(params); HttpResponse response = null; final HttpGet request = new HttpGet("http://" //$NON-NLS-1$ + ServiceImpl.SERVER_HOST_NAME + requestUri.toString()); final String methodUri = request.getRequestLine().getUri(); Element result; try { Log.i(TAG, "Executing the method:" + methodUri); //$NON-NLS-1$ response = httpClient.execute(request); lastInvocation = System.currentTimeMillis(); final int statusCode = response.getStatusLine().getStatusCode(); if (statusCode != HttpStatus.SC_OK) { Log.e(TAG, "Method failed: " + response.getStatusLine()); //$NON-NLS-1$ // Tim: HTTP error. Let's wait a little bit if (!repeat) { try { Thread.sleep(1500); } catch (InterruptedException e) { // ignore } response.getEntity().consumeContent(); return invoke(true, params); } throw new ServiceInternalException("method failed: " + response.getStatusLine()); } final Document responseDoc = builder.parse(response.getEntity().getContent()); final Element wrapperElt = responseDoc.getDocumentElement(); if (!wrapperElt.getNodeName().equals("rsp")) { throw new ServiceInternalException( "unexpected response returned by RTM service: " + wrapperElt.getNodeName()); } else { String stat = wrapperElt.getAttribute("stat"); if (stat.equals("fail")) { Node errElt = wrapperElt.getFirstChild(); while (errElt != null && (errElt.getNodeType() != Node.ELEMENT_NODE || !errElt.getNodeName().equals("err"))) { errElt = errElt.getNextSibling(); } if (errElt == null) { throw new ServiceInternalException( "unexpected response returned by RTM service: " + wrapperElt.getNodeValue()); } else { if (SERVICE_UNAVAILABLE_CODE.equals(((Element) errElt).getAttribute("code")) && !repeat) { try { Thread.sleep(1500); } catch (InterruptedException e) { // ignore } return invoke(true, params); } throw new ServiceException(Integer.parseInt(((Element) errElt).getAttribute("code")), ((Element) errElt).getAttribute("msg")); } } else { Node dataElt = wrapperElt.getFirstChild(); while (dataElt != null && (dataElt.getNodeType() != Node.ELEMENT_NODE || dataElt.getNodeName().equals("transaction") == true)) { try { Node nextSibling = dataElt.getNextSibling(); if (nextSibling == null) { break; } else { dataElt = nextSibling; } } catch (IndexOutOfBoundsException exception) { // Some implementation may throw this exception, // instead of returning a null sibling break; } } if (dataElt == null) { throw new ServiceInternalException( "unexpected response returned by RTM service: " + wrapperElt.getNodeValue()); } else { result = (Element) dataElt; } } } } catch (IOException e) { throw new ServiceInternalException("Error making connection: " + e.getMessage(), e); } catch (SAXException e) { // repeat call if possible. if (!repeat) return invoke(true, params); else throw new ServiceInternalException("Error parsing response. " + "Please try sync again!", e); } finally { httpClient.getConnectionManager().closeExpiredConnections(); } return result; } final String calcApiSig(Param... params) throws ServiceInternalException { try { digest.reset(); digest.update(applicationInfo.getSharedSecret().getBytes(ENCODING)); List<Param> sorted = Arrays.asList(params); Collections.sort(sorted); for (Param param : sorted) { digest.update(param.getName().getBytes(ENCODING)); digest.update(param.getValue().getBytes(ENCODING)); } return convertToHex(digest.digest()); } catch (UnsupportedEncodingException e) { throw new ServiceInternalException("cannot hahdle properly the encoding", e); } } private static String convertToHex(byte[] data) { StringBuffer buf = new StringBuffer(); for (int i = 0; i < data.length; i++) { int halfbyte = (data[i] >>> 4) & 0x0F; int two_halfs = 0; do { if ((0 <= halfbyte) && (halfbyte <= 9)) buf.append((char) ('0' + halfbyte)); else buf.append((char) ('a' + (halfbyte - 10))); halfbyte = data[i] & 0x0F; } while (two_halfs++ < 1); } return buf.toString(); } }