/Prototipo/Servlet/lib/xstream-distribution-1.4.1-bin/xstream-1.4.1/docs/architecture.html
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1<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 2<html xmlns="http://www.w3.org/1999/xhtml"> 3<!-- 4 Copyright (C) 2005, 2006 Joe Walnes. 5 Copyright (C) 2006, 2007, 2008 XStream committers. 6 All rights reserved. 7 8 The software in this package is published under the terms of the BSD 9 style license a copy of which has been included with this distribution in 10 the LICENSE.txt file. 11 12 Created on 29. January 2005 by Joe Walnes 13 --> 14 <head> 15 <title>XStream - Architecture Overview</title> 16 <link rel="stylesheet" type="text/css" href="style.css"/> 17 18 19 20 21 <!-- Google analytics --> 22 <script src="http://www.google-analytics.com/urchin.js" type="text/javascript"> 23 </script> 24 <script type="text/javascript"> 25 _uacct = "UA-110973-2"; 26 urchinTracker(); 27 </script> 28 29 </head> 30 <body> 31 32 <div id="banner"> 33 <a href="index.html"><img id="logo" src="logo.gif" alt="XStream"/></a> 34 </div> 35 36 <div id="center" class="Content2Column"> <!-- Content3Column for index --> 37 <div id="content"> 38 <h1 class="FirstChild">Architecture Overview</h1> 39 40 41 42 <p>The architecture of XStream consists of the four main components:</p> 43 44 <ul> 45 <li><b>Converters</b></li> 46 <!-- TODO: Mappers --> 47 <li><b>Drivers (Writer and Reader)</b></li> 48 <li><b>Context</b></li> 49 <li><b>Facade</b></li> 50 </ul> 51 52 <!-- ************ --> 53 54 <h1 id="Converters">Converters</h1> 55 56 <p>Whenever XStream encounters an object that needs to be converted to/from XML, it delegates to a suitable 57 <a href="javadoc/com/thoughtworks/xstream/converters/Converter.html">Converter</a> implementation associated 58 with the class of that Object.</p> 59 60 <p>XStream comes <a href="converters.html">bundled with many converters</a> for common types, including primitives, 61 String, Collections, arrays, null, Date, etc.</p> 62 63 <p>XStream also has a <i>default Converter</i>, that is used when no other Converters match a type. This uses 64 reflection to automatically generate the XML for all the fields in an object.</p> 65 66 <p>If an object is composed of other objects, the Converter may delegate to other Converters.</p> 67 68 <p class="highlight">To customize the XML for particular object type a new Converter should be implemented.</p> 69 70 71 <!-- ************ --> 72 73 <h1 id="Drivers">Drivers (Writer and Reader)</h1> 74 75 <p>XStream is abstracted from the underlying XML data using the 76 <a href="javadoc/com/thoughtworks/xstream/io/HierarchicalStreamWriter.html">HierarchicalStreamWriter</a> 77 and <a href="javadoc/com/thoughtworks/xstream/io/HierarchicalStreamReader.html">HierarchicalStreamReader</a> 78 interfaces for serializing and deserializing respectively.</p> 79 80 <p>This abstraction allows XStream to read XML from direct streams using an XML parser or directly manipulate 81 existing structures (such as DOM). This prevents the overhead of having to reparse if XStream is working from 82 XML that has been partially processed by other libraries (for instance a SOAP library). It also avoids tying XStream 83 to a particular library.</p> 84 85 <p>XStream comes bundled with 86 <a href="javadoc/com/thoughtworks/xstream/io/xml/package-summary.html">reader and writer implementations</a> for 87 most major XML libraries.</p> 88 89 <p class="highlight">Writer and Readers can be implemented allowing XStream to serialize to most XML APIs. 90 Writers and Readers can also be created around tree based non XML structures.</p> 91 92 <!-- 93 note: one reader/writer per context 94 note: why not sax 95 --> 96 97 <!-- ************ --> 98 99 <h1 id="Context">Context</h1> 100 101 <p>When XStream serializes or deserializes some objects, it creates a 102 <a href="javadoc/com/thoughtworks/xstream/converters/MarshallingContext.html">MarshallingContext</a> or 103 <a href="javadoc/com/thoughtworks/xstream/converters/UnmarshallingContext">UnmarshallingContext</a>, 104 which handle the traversing of the data and delegation to the necessary Converters.</p> 105 106 <p class="highlight">The MarshallingContext/UnmarshallingContext is made available to converters allowing them 107 to tell XStream to process objects contained within other objects.</p> 108 109 <p>XStream provides three pairs of context implementations that traverse the object graph with slightly 110 different behaviors. The default can be changed using 111 <a href="javadoc/com/thoughtworks/xstream/XStream.html">XStream.setMode()</a>, passing in one of 112 the following parameters:</p> 113 114 <ul> 115 <li> 116 <b>XStream.XPATH_RELATIVE_REFERENCES</b><br/> 117 <i>(Default)</i> Uses relative XPath references to signify duplicate references. This produces XML with 118 the least clutter. 119 </li> 120 <li> 121 <b>XStream.XPATH_ABSOLUTE_REFERENCES</b><br/> 122 Uses absolute XPath references to signify duplicate references. This might produce for some situations 123 better readable XML. <i>Note, that XStream will read XML with relative paths as well as with absolute 124 paths independent of the XPATH mode.</i> 125 </li> 126 <li> 127 <b>XStream.ID_REFERENCES</b><br/> 128 Uses ID references to signify duplicate references. In some scenarios, such as when using hand-written 129 XML, this is easier to work with. 130 </li> 131 <li> 132 <b>XStream.NO_REFERENCES</b><br/> 133 This disables object graph support and treats the object structure like a tree. Duplicate references are 134 treated as two separate objects and circular references cause an exception. This is slightly faster and 135 uses less memory than the other two modes. 136 </li> 137 </ul> 138 139 <p class="highlight">A new context is created for each object graph that is serialized. Both the 140 <a href="javadoc/com/thoughtworks/xstream/converters/MarshallingContext.html">MarshallingContext</a> and 141 <a href="javadoc/com/thoughtworks/xstream/converters/UnmarshallingContext.html">UnmarshallingContext</a> 142 implement <a href="javadoc/com/thoughtworks/xstream/converters/DataHolder.html">DataHolder</a>, 143 a hash table passed around whilst processing the object graph that can be used as the user sees fit (in a similar 144 way that the HttpServletRequest attributes are used in a web-application).</p> 145 146 147 <!-- ************ --> 148 149 <h1 id="Facade">XStream facade</h1> 150 151 <p>The main <a href="javadoc/com/thoughtworks/xstream/XStream.html">XStream</a> class is typically used as the 152 entry point. This assembles the necessary components of XStream (as described above; Context, Converter, 153 Writer/Reader and ClassMapper) and provides a simple to use API for common operations.</p> 154 155 <p class="highlight">Remember, the XStream class is just a facade - it can always be bypassed for more advanced 156 operations.</p> 157 158 159 160 161 <br/> 162 163 </div> 164 </div> 165 166 <div class="SidePanel" id="left"> 167 <div class="MenuGroup"> 168 <h1>Software</h1> 169 <ul> 170 <li><a href="index.html">About XStream</a></li> 171 <li><a href="news.html">News</a></li> 172 <li><a href="changes.html">Change History</a></li> 173 <li><a href="versioning.html">About Versioning</a></li> 174 </ul> 175 </div> 176 <div class="MenuGroup"> 177 <h1>Evaluating XStream</h1> 178 <ul> 179 <li><a href="tutorial.html">Two Minute Tutorial</a></li> 180 <li><a href="graphs.html">Object references</a></li> 181 <li><a href="manual-tweaking-output.html">Tweaking the Output</a></li> 182 <li><a href="license.html">License</a></li> 183 <li><a href="download.html">Download</a></li> 184 <li><a href="references.html">References</a></li> 185 <li><a href="parser-benchmarks.html">Parser Benchmarks</a></li> 186 <li><a href="http://www.ohloh.net/projects/3459">Code Statistics</a></li> 187 </ul> 188 </div> 189 <div class="MenuGroup"> 190 <h1>Using XStream</h1> 191 <ul> 192 <li class="currentLink">Architecture Overview</li> 193 <li><a href="converters.html">Converters</a></li> 194 <li><a href="faq.html">Frequently Asked Questions</a></li> 195 <li><a href="list-user.html">Users' Mailing List</a></li> 196 <li><a href="issues.html">Reporting Issues</a></li> 197 </ul> 198 </div> 199 <div class="MenuGroup"> 200 <h1>Javadoc</h1> 201 <ul> 202 <li><a href="javadoc/index.html">XStream Core</a></li> 203 <li><a href="hibernate-javadoc/index.html">Hibernate Extensions</a></li> 204 <li><a href="benchmark-javadoc/index.html">Benchmark Module</a></li> 205 </ul> 206 </div> 207 <div class="MenuGroup"> 208 <h1>Tutorials</h1> 209 <ul> 210 <li><a href="tutorial.html">Two Minute Tutorial</a></li> 211 <li><a href="alias-tutorial.html">Alias Tutorial</a></li> 212 <li><a href="annotations-tutorial.html">Annotations Tutorial</a></li> 213 <li><a href="converter-tutorial.html">Converter Tutorial</a></li> 214 <li><a href="objectstream.html">Object Streams Tutorial</a></li> 215 <li><a href="persistence-tutorial.html">Persistence API Tutorial</a></li> 216 <li><a href="json-tutorial.html">JSON Tutorial</a></li> 217 </ul> 218 </div> 219 <div class="MenuGroup"> 220 <h1>Developing XStream</h1> 221 <ul> 222 <li><a href="how-to-contribute.html">How to Contribute</a></li> 223 <li><a href="list-dev.html">Developers' Mailing List</a></li> 224 <li><a href="team.html">Development Team</a></li> 225 <li><a href="repository.html">Source Repository</a></li> 226 <li><a href="http://bamboo.ci.codehaus.org/browse/XSTREAM">Continuous Integration</a></li> 227 </ul> 228 </div> 229 </div> 230 231 </body> 232</html>