使用libxml2创建和解析xml文件

毕业设计需要用到xml文件来组织和存放数据，

对于Linux环境下，有libxml2可供使用。

经过一段时间查询文档和网站，

基本掌握创建xml文档和解析xml的操作，

简单做一下记录。

创建xml

例子如下：

 #include <stdio.h>
 #include <libxml/parser.h>
 #include <libxml/tree.h>

 int main(int argc, char **argv)
 {
         xmlDocPtr doc = NULL;
         xmlNodePtr root_node = NULL, node = NULL, node1 = NULL;

         doc = xmlNewDoc(BAD_CAST "1.0"); // create a new xml document.
         root_node = xmlNewNode(NULL, BAD_CAST "root"); // create a root node.
         xmlDocSetRootElement(doc, root_node);

         xmlNewChild(root_node, NULL, BAD_CAST "node1", BAD_CAST "content of node1");
         //xmlNewChild(root_node, NULL, BAD_CAST "node2", NULL);

         node = xmlNewChild(root_node, NULL, BAD_CAST "node3", BAD_CAST "node3 has attributes");
         xmlNewProp(node, BAD_CAST "attribute", BAD_CAST "yes");

         node = xmlNewNode(NULL, BAD_CAST "node4");
         node1 = xmlNewText(BAD_CAST
                    "other way to create content (which is also a node)");
         xmlAddChild(node, node1);
         xmlAddChild(root_node, node);

         xmlSaveFormatFileEnc(argc >  ? argv[] : "-", doc, "UTF-8", );

         xmlFreeDoc(doc);

         xmlCleanupParser();

         xmlMemoryDump();
         return();
 }

libxml的api使用 const unsigned char* 。

而string literal 只能隐式转换到 const char*。

所以libxml提供一个BAD_CAST用来作显示转换。

代码应该不难看懂，生成的xml文件如下：

 <?xml version="1.0" encoding="UTF-8"?>
 <root>
   <node1>content of node1</node1>
   <node3 attribute="yes">node3 has attributes</node3>
   <node4>other way to create content (which is also a node)</node4>
 </root>

xml文件和创建xml的代码对照着看就很容易看懂如何生成节点以及属性了。

解析xml

代码如下：

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <libxml/parser.h>
 #include <libxml/xmlmemory.h>

 int main(int argc, char **argv)
 {
         xmlDocPtr doc;
         xmlNodePtr curNode;

         xmlKeepBlanksDefault();
         doc = xmlReadFile("mine.xml", "UTF-8", XML_PARSE_RECOVER); // open a xml doc.
         curNode = xmlDocGetRootElement(doc); // get root element.

         if (curNode == NULL)
         {
                 fprintf(stderr, "open file failed. \n");
                 xmlFreeDoc (doc);
                 return -;
         }

         if (xmlStrcmp(curNode->name, "root")) // if the same,xmlStrcmp return 0, else return 1
         {
                 fprintf(stderr, "check rootElement failed. \n");
                 xmlFreeDoc (doc);
                 return -;
         }

         curNode = curNode->children; // move to root element's children.
         char *nodeName;
         char *content;

         if (curNode != NULL)
         {
                 nodeName = (char *) curNode->name;
                 content = (char *) xmlNodeGetContent(curNode);
                 printf ("Current node name:%s,\t the content is:%s.\n\n", nodeName, content);
         }

         curNode = curNode->next;
         char *attr;
         if (curNode != NULL)
         {
                 nodeName = (char *) curNode->name;
                 content = (char *) xmlNodeGetContent(curNode);
                 attr = (char *) xmlGetProp(curNode, (const xmlChar *)"attribute"); // get node attribute
                 printf ("Current node name:%s,\t the content is:%s,\t AND THE ATTR IS:%s.\n\n", nodeName, content,attr);
         }

         curNode = curNode->next;
         if (curNode != NULL)
         {
                 nodeName = (char *) curNode->name;
                 content = (char *) xmlNodeGetContent(curNode);
                 printf ("Current node name:%s,\t the content is:%s.\n\n", nodeName, content);
         }

         xmlFree(curNode);
         xmlFreeDoc(doc);
         return ;
 }

上面的代码是简单的按生成的xml结构来解析，

正确的用法应该是写成一个函数来调用，

可以解析任何的已知根节点的xml文件。

解析的结果输入如下：

 [nigelzeng@ubuntu xml-learning]$ ./xml-mine-parse
 Current node name:node1,         the content is:content of node1.

 Current node name:node3,         the content is:node3 has attributes,    AND THE ATTR IS:yes.

 Current node name:node4,         the content is:other way to create content (which is also a node).

参考：

http://xmlsoft.org/index.html

http://www.cppblog.com/lymons/archive/2009/03/30/37553.html

http://www.4ucode.com/Study/Topic/1622022