Xml parsing and case simulation of user logon using xpath

Problem: It is troublesome to use dom4j to query nodes (tags, attributes, and text) with deep hierarchies !!! Problem: It is troublesome to use dom4j to query nodes (tags, attributes, and text) with deep hierarchies !!!

Xpath is generated in this case-mainly used to quickly obtain the desired [node object].

How to use xPath technology in dom4j

1) importing xPath supports jar packages. Jaxen-1.1-beta-6.jar

2) use the xpath method

List SelectNodes ("xpath expression"); queries multiple node objects

Node selectSingleNode ("xpath expression"); queries a Node object

XPath syntax

/Absolute path indicates starting from the root position of xml or sub-elements (a hierarchy)

// Relative path indicates the selection element regardless of any hierarchy.

* Wildcard indicates that all elements are matched.

[] Condition indicates the element under which to select

@ Attribute indicates selecting an attribute node

And relationship indicates the relationship between conditions (equivalent &&)

Text () indicates select text content

Case

User logon:

Enter the user name and password-> go to "database" to check whether there is a corresponding user->

Yes: the logon is successful.

No: the logon fails.

Use xml as a database

User. xml is used to store user data.

The code is as follows:

Import java. io. bufferedReader; import java. io. file; import java. io. inputStreamReader; import org. dom4j. document; import org. dom4j. element; import org. dom4j. io. SAXReader;/*** xpath case: simulate user logon effect * @ author APPle **/public class Demo3 {public static void main (String [] args) throws Exception {// 1. obtain the user name and password entered by the user. BufferedReader br = new BufferedReader (new InputStreamReader (System. in); // encapsulate keyboard input and input the stream System. out. print Ln ("Enter the user name:"); String name = br. readLine (); System. out. println ("enter the password:"); String password = br. readLine (); // 2. query "database" to see if there is a corresponding user // corresponding user: in the user. in the xml file, find the user tag Document doc = new SAXReader () whose/name attribute value is 'user input' and whose password attribute value is 'user input (). read (new File (". /src/user. xml "); Element userElem = (Element) doc. selectSingleNode ("// user [@ name = '" + name + "' and @ password = '" + password + "']"); // method for concatenating variables in a string-first add a double quotation mark and move the cursor to the middle of the double quotation mark , Write two plus signs, and move the cursor to the center of the plus sign to write the variable. // System. out. println (userElem. getName (); // view the content of the current node object if (userElem! = Null) {// The user name and password are found in the database. // System. out. println ("logon successful");} else {// logon failed System. out. println ("logon failed ");}}}

The above content is the xml parsing of xpath technology and the simulated user login effect in the case. For more information, see PHP Chinese network (www.php1.cn )!