Coverage Report - org.mule.providers.tcp.protocols.XmlMessageProtocol
 
Classes in this File Line Coverage Branch Coverage Complexity
XmlMessageProtocol
0%
0/26
0%
0/7
3
 
 1  
 /*
 2  
  * $Id: XmlMessageProtocol.java 7976 2007-08-21 14:26:13Z dirk.olmes $
 3  
  * --------------------------------------------------------------------------------------
 4  
  * Copyright (c) MuleSource, Inc.  All rights reserved.  http://www.mulesource.com
 5  
  *
 6  
  * The software in this package is published under the terms of the CPAL v1.0
 7  
  * license, a copy of which has been included with this distribution in the
 8  
  * LICENSE.txt file.
 9  
  */
 10  
 
 11  
 package org.mule.providers.tcp.protocols;
 12  
 
 13  
 import java.io.IOException;
 14  
 import java.io.InputStream;
 15  
 import java.io.PushbackInputStream;
 16  
 
 17  
 import edu.emory.mathcs.backport.java.util.concurrent.ConcurrentHashMap;
 18  
 
 19  
 /**
 20  
  * <p>
 21  
  * The XmlMessageProtocol is an application level tcp protocol that can be used to
 22  
  * read streaming xml documents. The only requirement is that each document include
 23  
  * an xml declaration at the beginning of the document of the form "<?xml...". In
 24  
  * section 2.8, the xml 1.0 standard contains "Definition: XML documents
 25  
  * <strong>SHOULD</strong> begin with an XML declaration which specifies the version
 26  
  * of XML being used" while the xml 1.1 standard contains "Definition: XML 1.1
 27  
  * documents <strong>MUST</strong> begin with an XML declaration which specifies the
 28  
  * version of XML being used". The SHOULD indicates a recommendation that, if not
 29  
  * followed, needs to be carefully checked for unintended consequences. MUST
 30  
  * indicates a mandatory requirement for a well-formed document. Please make sure
 31  
  * that the xml documents being streamed begin with an xml declaration when using
 32  
  * this class.
 33  
  * </p>
 34  
  * <p>
 35  
  * Data are read until a new document is found or there are no more data
 36  
  * (momentarily).  For slower networks,
 37  
  * {@link org.mule.providers.tcp.protocols.XmlMessageEOFProtocol} may be more reliable.
 38  
  * </p>
 39  
  * <p>
 40  
  * Also, the default character encoding for the platform is used to decode the
 41  
  * message bytes when looking for the XML declaration. Some caution with message
 42  
  * character encodings is warranted.
 43  
  * </p>
 44  
  * <p>
 45  
  * Finally, this class uses a PushbackInputStream to enable parsing of individual
 46  
  * messages. The stream stores any pushed-back bytes into it's own internal buffer
 47  
  * and not the original stream. Therefore, the read buffer size is intentionally
 48  
  * limited to insure that unread characters remain on the stream so that all data may
 49  
  * be read later.
 50  
  * </p>
 51  
  */
 52  
 public class XmlMessageProtocol extends ByteProtocol
 53  
 {
 54  
     private static final String XML_PATTERN = "<?xml";
 55  
 
 56  
     private static final int READ_BUFFER_SIZE = 4096;
 57  
     private static final int PUSHBACK_BUFFER_SIZE = READ_BUFFER_SIZE * 2;
 58  
 
 59  0
     private ConcurrentHashMap pbMap = new ConcurrentHashMap();
 60  
 
 61  
     public XmlMessageProtocol()
 62  
     {
 63  0
         super(STREAM_OK);
 64  0
     }
 65  
 
 66  
     public Object read(InputStream is) throws IOException
 67  
     {
 68  0
         PushbackInputStream pbis = (PushbackInputStream) pbMap.get(is);
 69  0
         if (null == pbis)
 70  
         {
 71  0
             pbis = new PushbackInputStream(is, PUSHBACK_BUFFER_SIZE);
 72  0
             PushbackInputStream prev = (PushbackInputStream) pbMap.putIfAbsent(is, pbis);
 73  0
             pbis = null == prev ? pbis : prev;
 74  
         }
 75  
 
 76  0
         int len = -1;
 77  
         try
 78  
         {
 79  
             // read until xml pattern is seen (and then pushed back) or no more data
 80  
             // to read. return all data as message
 81  0
             byte[] buffer = new byte[READ_BUFFER_SIZE];
 82  0
             StringBuffer message = new StringBuffer(READ_BUFFER_SIZE);
 83  0
             int patternIndex = -1;
 84  
             boolean repeat;
 85  
             do
 86  
             {
 87  0
                 len = safeRead(pbis, buffer);
 88  0
                 if (len >= 0)
 89  
                 {
 90  
                     // TODO take encoding into account, ideally from the incoming XML
 91  0
                     message.append(new String(buffer, 0, len));
 92  
                     // start search at 2nd character in buffer (index=1) to
 93  
                     // indicate whether we have reached a new document.
 94  0
                     patternIndex = message.toString().indexOf(XML_PATTERN, 1);
 95  0
                     repeat = isRepeat(patternIndex, len, pbis.available());
 96  
                 }
 97  
                 else
 98  
                 {
 99  
                     // never repeat on closed stream (and avoid calling available)
 100  0
                     repeat = false;
 101  
                 }
 102  
 
 103  
             }
 104  0
             while (repeat);
 105  
 
 106  0
             if (patternIndex > 0)
 107  
             {
 108  
                 // push back the start of the next message and
 109  
                 // ignore the pushed-back characters in the return buffer
 110  0
                 pbis.unread(message.substring(patternIndex, message.length()).getBytes());
 111  0
                 message.setLength(patternIndex);
 112  
             }
 113  
 
 114  
             // TODO encoding here, too...
 115  0
             return nullEmptyArray(message.toString().getBytes());
 116  
 
 117  
         }
 118  
         finally
 119  
         {
 120  
             // TODO - this doesn't seem very reliable, since loop above can end
 121  
             // without EOF.  On the other hand, what else can we do?  Entire logic
 122  
             // is not very dependable, IMHO.  XmlMessageEOFProtocol is more likely
 123  
             // to be correct here, I think.
 124  
 
 125  
             // clear from map if stream has ended
 126  0
             if (len < 0)
 127  
             {
 128  0
                 pbMap.remove(is);
 129  
             }
 130  
         }
 131  
     }
 132  
 
 133  
     /**
 134  
      * Show we continue reading?  This class, following previous implementations, only
 135  
      * reads while input is saturated.
 136  
      * @see XmlMessageEOFProtocol
 137  
      *
 138  
      * @param patternIndex The index of the xml tag (or -1 if the next message not found)
 139  
      * @param len The amount of data read this loop (or -1 if EOF)
 140  
      * @param available The amount of data available to read
 141  
      * @return true if the read should continue
 142  
      */
 143  
     protected boolean isRepeat(int patternIndex, int len, int available)
 144  
     {
 145  0
         return patternIndex < 0 && len == READ_BUFFER_SIZE && available > 0;
 146  
     }
 147  
 
 148  
 }