Java tutorial
/* * Copyright(c) 2005 Center for E-Commerce Infrastructure Development, The * University of Hong Kong (HKU). All Rights Reserved. * * This software is licensed under the GNU GENERAL PUBLIC LICENSE Version 2.0 [1] * * [1] http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt */ package hk.hku.cecid.corvus.http; import java.util.Date; import java.util.Map; import java.io.InputStream; import java.io.ByteArrayInputStream; import java.io.BufferedInputStream; import java.io.IOException; import java.io.File; import java.io.FileInputStream; import java.nio.channels.FileChannel; import java.nio.channels.Channels; import org.apache.commons.httpclient.HttpMethod; import org.apache.commons.httpclient.methods.PostMethod; import hk.hku.cecid.corvus.ws.data.KVPairData; import hk.hku.cecid.piazza.commons.data.Data; import hk.hku.cecid.piazza.commons.util.FileLogger; import hk.hku.cecid.piazza.commons.io.IOHandler; /** * The <code>EnvelopSender</code> is abstract base class for sending HTTP remote request * to H2O for querying the message envelop through the administration page. * * @author Twinsen Tsang * @version 1.0.0 * @since H2O 28/11/2007 */ public class EnvelopQuerySender extends HttpSender { /** The constant field representing the standardized outgoing message box representation */ public static final String MSGBOX_OUT = "OUTBOX"; /** The constant field representing the standardized incoming message box representation */ public static final String MSGBOX_IN = "INBOX"; /** The constant field representing the HTTP request parameter name for Message id. */ protected static final String MSGID_FORM_PARAM = "message_id"; /** The constant field representing the HTTP request parameter name for Message box. */ protected static final String MSGBOX_FORM_PARAM = "message_box"; // Get the base path for storing the response. private static String BASE_PATH = System.getProperty("java.io.tmpdir") + File.separator; private static int THRESHOLD = 1048576; /* The message id to query the message envelop. */ private String messageIdToDownload = null; /* The message box to query the message envelop. */ private String messageBoxToDownload = null; /* The message envelop returned stream. */ private InputStream envelopStream; /** * Explicit Constructor. Create an instance of <code>EnvelopQuerySender</code> * * @param logger The logger for log the sending process. * @param d The data used for generate Envelop query request. It must be a kind of Admin data. */ protected EnvelopQuerySender(FileLogger logger, Data d) { super(logger, d); } /** * Get the message box mapping from standardized representation to proprietary representation. * <br/><br/> * It should return a HashMap like this: * <pre> * HashMap m = new HashMap(); * m.put(MSGBOX_IN , "Your Inbox representation"); * m.put(MSGBOX_OUT, "Your outbox representation"); * * @return the message box mapping. * * @see EnvelopQuerySender#MSGBOX_IN * @see EnvelopQuerySender#MSGBOX_OUT */ protected Map getMessageBoxMapping() { return null; } /** * Set the message criteria for down-load the message envelop (and payload). * * @param messageId The message id to down-load the message envelop. * @param messageBox The message box to down-load the message envelop. either INBOX or OUTBOX. * * @throws NullPointerException * When {@link #getMessageIdToDownload()} return null.<br/> * When {@link #getMessageBoxToDownload()} return empty or null. * @throws IllegalArgumentException * When {@link #getMessageBoxToDownload()} return string not equal to 'INBOX' and 'OUTBOX' */ public final void setMessageCriteriaToDownload(String messageId, String messageBox) { this.checkArguments(messageId, messageBox); this.messageBoxToDownload = messageBox; this.messageIdToDownload = messageId; } /** * @return The message id to down-load the message envelop. */ public final String getMessageIdToDownload() { return this.messageIdToDownload; } /** * @return The message box to donw-load the message envelop. either INBOX or OUTBOX. */ public final String getMessageBoxToDownload() { return this.messageBoxToDownload; } /** * This method should be called after executed {@link #run()} successfully. * * @return The message envelop stream. */ public final InputStream getEnvelopStream() throws IOException { if (this.envelopStream == null) throw new IOException("There is no envelop stream available, exeucted run() properly ?."); return this.envelopStream; } /** * [@EVENT] The method <code>onStart</code> log all new configuration. */ protected void onStart() { // Get the data. KVPairData data = (KVPairData) this.properties; super.onStart(); if (this.log != null) { FileLogger l = this.log; // Log all information for this sender. l.log("Envelop Query HTTP Client init at " + new Date().toString()); l.log(""); l.log("Sending Envelop Query HTTP Request with following configuration"); l.log("------------------------------------------------------------------"); if (data != null) l.log(data.toString()); l.log("------------------------------------------------------------------"); l.log(""); } } /** * [@EVENT] This method is invoked when the sender is required to create a HTTP Request from configuration. * <br/><br/> * It generates a form-url-encoded content embedded in the HTTP POST request. It contains * two parameters, message_id and message_box. The value of these parameters are * extracted from {@link #getMessageIdToDownload()} and {@link #getMessageBoxToDownload()} * respectively. * <br/><br/> * <b>NOTE</b>: The values of message_box parameter may differ to what you see because it * may transform {@link #getMessageBoxMapping()}. * * @throws NullPointerException * When {@link #getMessageIdToDownload()} return null.<br/> * When {@link #getMessageBoxToDownload()} return empty or null. * @throws IllegalArgumentException * When {@link #getMessageBoxToDownload()} return string not equal to 'INBOX' and 'OUTBOX' */ protected HttpMethod onCreateRequest() throws Exception { this.checkArguments(this.messageIdToDownload, this.messageBoxToDownload); // Create HTTP Form POST method PostMethod post = new PostMethod(this.getServiceEndPoint().toExternalForm()); // transform the message box value. String mappedMsgBox; Map messageBoxMapping = this.getMessageBoxMapping(); if (messageBoxMapping == null) { this.log.warn("No Message Box mapping found, use NO-OP mapping."); mappedMsgBox = this.messageBoxToDownload; } else { mappedMsgBox = (String) messageBoxMapping.get(this.messageBoxToDownload); } // Assign the message_id, message_box as the post parameter. post.setParameter(MSGID_FORM_PARAM, this.messageIdToDownload); post.setParameter(MSGBOX_FORM_PARAM, mappedMsgBox); return post; } /** * [@EVENT] This method is invoked when received the reply HTTP response from the server. * <br/><br/> * It saves the response body stream and then available to get through by {@link #getEnvelopStream()} */ protected void onResponse() throws Exception { HttpMethod post = this.getExecutedMethod(); InputStream ins = post.getResponseBodyAsStream(); /* * We have to pipe the content to either memory or storage because the response stream * is directly extracted from socket which is going to close upon the connection * has been closed. */ if (ins.available() < THRESHOLD) { byte[] envelop = IOHandler.readBytes(ins); this.envelopStream = new ByteArrayInputStream(envelop); } else { // Create a temporary file at TMP directory. File envelopTmp = new File(BASE_PATH + this.hashCode()); envelopTmp.deleteOnExit(); // Pipe the content to the TMP file. FileChannel fChannel = new FileInputStream(envelopTmp).getChannel(); fChannel.transferFrom(Channels.newChannel(ins), 0, ins.available()); fChannel.close(); // Create an buffered stream to the file. this.envelopStream = new BufferedInputStream(new FileInputStream(envelopTmp)); // InputStream is closed automatically. } } /* * A Helper method to check whether the arguments passed is valid. */ private final void checkArguments(String messageId, String messageBox) { if (messageId == null) throw new NullPointerException("Missing 'messageId' in the argument."); if (messageBox == null || messageBox.equals("")) throw new NullPointerException("Missing 'messageBox' or it should not be empty."); if (!messageBox.equals(MSGBOX_OUT) && !messageBox.equals(MSGBOX_IN)) throw new IllegalArgumentException("Invalid 'messageBox' arugments. It should either INBOX or OUTBOX."); } }