Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?> |
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Daniel Veillard | 373a475 | 2002-02-21 14:46:29 +0000 | [diff] [blame] | 4 | TD {font-family: Verdana,Arial,Helvetica} |
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Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 9 | A:link, A:visited, A:active { text-decoration: underline } |
William M. Brack | fd9e70d | 2004-02-26 11:01:57 +0000 | [diff] [blame] | 10 | </style><title>A real example</title></head><body bgcolor="#8b7765" text="#000000" link="#000000" vlink="#000000"><table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr><td width="120"><a href="http://swpat.ffii.org/"><img src="epatents.png" alt="Action against software patents" /></a></td><td width="180"><a href="http://www.gnome.org/"><img src="gnome2.png" alt="Gnome2 Logo" /></a><a href="http://www.w3.org/Status"><img src="w3c.png" alt="W3C Logo" /></a><a href="http://www.redhat.com/"><img src="redhat.gif" alt="Red Hat Logo" /></a><div align="left"><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-180x168.gif" alt="Made with Libxml2 Logo" /></a></div></td><td><table border="0" width="90%" cellpadding="2" cellspacing="0" align="center" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3" bgcolor="#fffacd"><tr><td align="center"><h1>The XML C parser and toolkit of Gnome</h1><h2>A real example</h2></td></tr></table></td></tr></table></td></tr></table><table border="0" cellpadding="4" cellspacing="0" width="100%" align="center"><tr><td bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Developer Menu</b></center></td></tr><tr><td bgcolor="#fffacd"><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="20" value="" /><input name="submit" type="submit" value="Search ..." /></form><ul><li><a href="index.html" style="font-weight:bold">Main Menu</a></li><li><a href="examples/index.html" style="font-weight:bold">Code Examples</a></li><li><a href="guidelines.html">XML Guidelines</a></li><li><a href="tutorial/index.html">Tutorial</a></li><li><a href="xmlreader.html">The Reader Interface</a></li><li><a href="XSLT.html">XSLT</a></li><li><a href="python.html">Python and bindings</a></li><li><a href="architecture.html">libxml2 architecture</a></li><li><a href="tree.html">The tree output</a></li><li><a href="interface.html">The SAX interface</a></li><li><a href="xmlmem.html">Memory Management</a></li><li><a href="xmlio.html">I/O Interfaces</a></li><li><a href="library.html">The parser interfaces</a></li><li><a href="entities.html">Entities or no entities</a></li><li><a href="namespaces.html">Namespaces</a></li><li><a href="upgrade.html">Upgrading 1.x code</a></li><li><a href="threads.html">Thread safety</a></li><li><a href="DOM.html">DOM Principles</a></li><li><a href="example.html">A real example</a></li><li><a href="xml.html">flat page</a>, <a href="site.xsl">stylesheet</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>API Indexes</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="APIchunk0.html">Alphabetic</a></li><li><a href="APIconstructors.html">Constructors</a></li><li><a href="APIfunctions.html">Functions/Types</a></li><li><a href="APIfiles.html">Modules</a></li><li><a href="APIsymbols.html">Symbols</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li><li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li><li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li><li><a href="http://www.aleksey.com/xmlsec/">XML-DSig xmlsec</a></li><li><a href="ftp://xmlsoft.org/">FTP</a></li><li><a href="http://www.zlatkovic.com/projects/libxml/">Windows binaries</a></li><li><a href="http://garypennington.net/libxml2/">Solaris binaries</a></li><li><a href="http://www.zveno.com/open_source/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal bindings</a></li><li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml2">Bug Tracker</a></li></ul></td></tr></table></td></tr></table></td><td valign="top" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%"><tr><td><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table border="0" cellpadding="3" cellspacing="1" width="100%"><tr><td bgcolor="#fffacd"><p>Here is a real size example, where the actual content of the application |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 11 | data is not kept in the DOM tree but uses internal structures. It is based on |
| 12 | a proposal to keep a database of jobs related to Gnome, with an XML based |
| 13 | storage structure. Here is an <a href="gjobs.xml">XML encoded jobs |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 14 | base</a>:</p><pre><?xml version="1.0"?> |
| 15 | <gjob:Helping xmlns:gjob="http://www.gnome.org/some-location"> |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 16 | <gjob:Jobs> |
| 17 | |
| 18 | <gjob:Job> |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 19 | <gjob:Project ID="3"/> |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 20 | <gjob:Application>GBackup</gjob:Application> |
| 21 | <gjob:Category>Development</gjob:Category> |
| 22 | |
| 23 | <gjob:Update> |
| 24 | <gjob:Status>Open</gjob:Status> |
| 25 | <gjob:Modified>Mon, 07 Jun 1999 20:27:45 -0400 MET DST</gjob:Modified> |
| 26 | <gjob:Salary>USD 0.00</gjob:Salary> |
| 27 | </gjob:Update> |
| 28 | |
| 29 | <gjob:Developers> |
| 30 | <gjob:Developer> |
| 31 | </gjob:Developer> |
| 32 | </gjob:Developers> |
| 33 | |
| 34 | <gjob:Contact> |
| 35 | <gjob:Person>Nathan Clemons</gjob:Person> |
| 36 | <gjob:Email>nathan@windsofstorm.net</gjob:Email> |
| 37 | <gjob:Company> |
| 38 | </gjob:Company> |
| 39 | <gjob:Organisation> |
| 40 | </gjob:Organisation> |
| 41 | <gjob:Webpage> |
| 42 | </gjob:Webpage> |
| 43 | <gjob:Snailmail> |
| 44 | </gjob:Snailmail> |
| 45 | <gjob:Phone> |
| 46 | </gjob:Phone> |
| 47 | </gjob:Contact> |
| 48 | |
| 49 | <gjob:Requirements> |
| 50 | The program should be released as free software, under the GPL. |
| 51 | </gjob:Requirements> |
| 52 | |
| 53 | <gjob:Skills> |
| 54 | </gjob:Skills> |
| 55 | |
| 56 | <gjob:Details> |
| 57 | A GNOME based system that will allow a superuser to configure |
| 58 | compressed and uncompressed files and/or file systems to be backed |
| 59 | up with a supported media in the system. This should be able to |
| 60 | perform via find commands generating a list of files that are passed |
| 61 | to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine |
| 62 | or via operations performed on the filesystem itself. Email |
| 63 | notification and GUI status display very important. |
| 64 | </gjob:Details> |
| 65 | |
| 66 | </gjob:Job> |
| 67 | |
| 68 | </gjob:Jobs> |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 69 | </gjob:Helping></pre><p>While loading the XML file into an internal DOM tree is a matter of |
Daniel Veillard | 63d8314 | 2002-05-20 06:51:05 +0000 | [diff] [blame] | 70 | calling only a couple of functions, browsing the tree to gather the data and |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 71 | generate the internal structures is harder, and more error prone.</p><p>The suggested principle is to be tolerant with respect to the input |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 72 | structure. For example, the ordering of the attributes is not significant, |
| 73 | the XML specification is clear about it. It's also usually a good idea not to |
| 74 | depend on the order of the children of a given node, unless it really makes |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 75 | things harder. Here is some code to parse the information for a person:</p><pre>/* |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 76 | * A person record |
| 77 | */ |
| 78 | typedef struct person { |
| 79 | char *name; |
| 80 | char *email; |
| 81 | char *company; |
| 82 | char *organisation; |
| 83 | char *smail; |
| 84 | char *webPage; |
| 85 | char *phone; |
| 86 | } person, *personPtr; |
| 87 | |
| 88 | /* |
| 89 | * And the code needed to parse it |
| 90 | */ |
| 91 | personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) { |
| 92 | personPtr ret = NULL; |
| 93 | |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 94 | DEBUG("parsePerson\n"); |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 95 | /* |
| 96 | * allocate the struct |
| 97 | */ |
| 98 | ret = (personPtr) malloc(sizeof(person)); |
| 99 | if (ret == NULL) { |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 100 | fprintf(stderr,"out of memory\n"); |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 101 | return(NULL); |
| 102 | } |
| 103 | memset(ret, 0, sizeof(person)); |
| 104 | |
| 105 | /* We don't care what the top level element name is */ |
| 106 | cur = cur->xmlChildrenNode; |
| 107 | while (cur != NULL) { |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 108 | if ((!strcmp(cur->name, "Person")) && (cur->ns == ns)) |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 109 | ret->name = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 110 | if ((!strcmp(cur->name, "Email")) && (cur->ns == ns)) |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 111 | ret->email = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); |
| 112 | cur = cur->next; |
| 113 | } |
| 114 | |
| 115 | return(ret); |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 116 | }</pre><p>Here are a couple of things to notice:</p><ul><li>Usually a recursive parsing style is the more convenient one: XML data |
Daniel Veillard | 63d8314 | 2002-05-20 06:51:05 +0000 | [diff] [blame] | 117 | is by nature subject to repetitive constructs and usually exhibits highly |
| 118 | structured patterns.</li> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 119 | <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 120 | i.e. the pointer to the global XML document and the namespace reserved to |
| 121 | the application. Document wide information are needed for example to |
| 122 | decode entities and it's a good coding practice to define a namespace for |
| 123 | your application set of data and test that the element and attributes |
| 124 | you're analyzing actually pertains to your application space. This is |
| 125 | done by a simple equality test (cur->ns == ns).</li> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 126 | <li>To retrieve text and attributes value, you can use the function |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 127 | <em>xmlNodeListGetString</em> to gather all the text and entity reference |
| 128 | nodes generated by the DOM output and produce an single text string.</li> |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 129 | </ul><p>Here is another piece of code used to parse another level of the |
| 130 | structure:</p><pre>#include <libxml/tree.h> |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 131 | /* |
| 132 | * a Description for a Job |
| 133 | */ |
| 134 | typedef struct job { |
| 135 | char *projectID; |
| 136 | char *application; |
| 137 | char *category; |
| 138 | personPtr contact; |
| 139 | int nbDevelopers; |
| 140 | personPtr developers[100]; /* using dynamic alloc is left as an exercise */ |
| 141 | } job, *jobPtr; |
| 142 | |
| 143 | /* |
| 144 | * And the code needed to parse it |
| 145 | */ |
| 146 | jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) { |
| 147 | jobPtr ret = NULL; |
| 148 | |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 149 | DEBUG("parseJob\n"); |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 150 | /* |
| 151 | * allocate the struct |
| 152 | */ |
| 153 | ret = (jobPtr) malloc(sizeof(job)); |
| 154 | if (ret == NULL) { |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 155 | fprintf(stderr,"out of memory\n"); |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 156 | return(NULL); |
| 157 | } |
| 158 | memset(ret, 0, sizeof(job)); |
| 159 | |
| 160 | /* We don't care what the top level element name is */ |
| 161 | cur = cur->xmlChildrenNode; |
| 162 | while (cur != NULL) { |
| 163 | |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 164 | if ((!strcmp(cur->name, "Project")) && (cur->ns == ns)) { |
| 165 | ret->projectID = xmlGetProp(cur, "ID"); |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 166 | if (ret->projectID == NULL) { |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 167 | fprintf(stderr, "Project has no ID\n"); |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 168 | } |
| 169 | } |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 170 | if ((!strcmp(cur->name, "Application")) && (cur->ns == ns)) |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 171 | ret->application = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 172 | if ((!strcmp(cur->name, "Category")) && (cur->ns == ns)) |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 173 | ret->category = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); |
Daniel Veillard | 024f199 | 2003-12-10 16:43:49 +0000 | [diff] [blame] | 174 | if ((!strcmp(cur->name, "Contact")) && (cur->ns == ns)) |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 175 | ret->contact = parsePerson(doc, ns, cur); |
| 176 | cur = cur->next; |
| 177 | } |
| 178 | |
| 179 | return(ret); |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 180 | }</pre><p>Once you are used to it, writing this kind of code is quite simple, but |
Daniel Veillard | 63d8314 | 2002-05-20 06:51:05 +0000 | [diff] [blame] | 181 | boring. Ultimately, it could be possible to write stubbers taking either C |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 182 | data structure definitions, a set of XML examples or an XML DTD and produce |
| 183 | the code needed to import and export the content between C data and XML |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 184 | storage. This is left as an exercise to the reader :-)</p><p>Feel free to use <a href="example/gjobread.c">the code for the full C |
Daniel Veillard | c948420 | 2001-10-24 12:35:52 +0000 | [diff] [blame] | 185 | parsing example</a> as a template, it is also available with Makefile in the |
Daniel Veillard | 1177ca4 | 2003-04-26 22:29:54 +0000 | [diff] [blame] | 186 | Gnome CVS base under gnome-xml/example</p><p><a href="bugs.html">Daniel Veillard</a></p></td></tr></table></td></tr></table></td></tr></table></td></tr></table></td></tr></table></body></html> |