Javase Learning Notes Sax parsing (6)

The Sax-Simple API for XML is simply a set of sun-provided API mechanisms that manipulate XML data.

The parsing principle used by Sax is based on the mechanism of event triggering.

Sax technology can only be read by XML data.

 1. Prepare XML file to parse Linkmans.xml 
 <?xml version= " 1.0   " encoding="   UTF-8   standalone="  no  ?><linkmans> <linkman> <name>jack</name&        Gt <phone>18663243245  </phone> <email>[email protected] 163  .com</email> </linkman> <linkman> <name> Zhang San < ;/name> <phone>1353243247  </phone> <EMAIL>[EMAIL&NB Sp;protected]126  .com</email> </linkman></linkmans> 

 2   //  2. Get the SAX parser  public  static   SAXParser Getparser () Throws exception{  2.1 get Parser factory class object 
      saxparserfactory factory = Saxparserfactory.newinstance ();       SAXParser parser  = Factory.newsaxparser ();    return   parser; }

3 .    Parse data //  3. Parse data public   staticvoid  getelement (file file, DefaultHandler dh) throws exception{       //  3.1 Get parser       saxparser parser =  Getparser ();        // 3.2 Calling the Parse method        parser.parse (file, DH);   }

4. Create a Myhandler.java that inherits from the DefaultHandler class Public classMyHandler extends DefaultHandler {//automatically executes when the document starts parsing     Public voidstartdocument () throws Saxexception {super.startdocument (); System. out. println ("XML document start parsing ..."); }    //encountered a start element automatic execution     Public voidstartelement (String uri, String localname, string name, Attributes Attributes) throws Saxexception {        Super.startelement (URI, LocalName, name, attributes); System. out. println ("Elements"+name+"start ..."); }    //encountered text content automatic execution     Public voidCharacters (Char[] ch,intStartintlength) throws saxexception {super.characters (ch, start, length); System. out. println ("text content"+NewString (ch,start,length)); }    //encountered element end automatic execution     Public voidendElement (String uri, String localname, String name) throws Saxexception {super.endelement (URI, L        Ocalname, name); System. out. println ("Elements"+name+"End ..."); }    //custom execution When document parsing is complete     Public voidenddocument () throws Saxexception {super.enddocument (); System. out. println ("XML document parsing end ..."); }}

5 methods for invoking parsing elements in the main function  Public Static void Main (string[] args) throws Exception {       new File ("linkmans.xml" );        New MyHandler ();       GetElement (File,handler);   }

Through the above procedures found that in fact, sax parsing only requires the developer to pass the corresponding event handler object (inherit from the DefaultHandler Class).

Example 1: Create an event handler to get the specified node data from the XML.  Public classOptiondatahandler extends DefaultHandler {//defines the name of a member variable record label    PrivateString name =NULL; //A variable that defines a statistic number    Private intCount =0; //encountered a start element automatic execution     Public voidstartelement (String uri, String localname, string name, Attributes Attributes) throws Saxexception {        Super.startelement (URI, LocalName, name, attributes);  This. Name =name; if("name". Equals ( This. Name)) {             This. count++; }    }    //encountered text content automatic execution     Public voidCharacters (Char[] ch,intStartintlength) throws saxexception {super.characters (ch, start, length); //determine if the name element        if("name". Equals ( This. Name) && This. Count = =2) {System. out. println (NewString (ch,start,length)); }    }}

Case one: Parsing XML data with sax and encapsulating the collection of data

In fact, the use of any XML parsing technology to parse XML data requires later data encapsulation, if it is only a separate to get the value of a node does not have any meaning. It is therefore necessary to parse the XML data so that it is encapsulated into the specified collection as an object to facilitate the processing of other applications.

1. Implement a Linkman.java JavaBean object Public classLinkman {PrivateString name; PrivateString Phone; PrivateString Email;  PublicLinkman () {super (); }     PublicLinkman (string name, string phone, string email) {super ();  This. Name =name;  This. Phone =phone;  This. email =email; }    //omit get and set methods}

3. Create an event handler for encapsulation Listhandler.java Public classListhandler extends DefaultHandler {//Defining JavaBean Objects    PrivateLinkman Linkman =NULL; //defining a collection encapsulates a JavaBean object    Privatelist<linkman> list =NULL; //defines the name of the parsed element    PrivateString name =NULL; @Override Public voidstartdocument () throws Saxexception {super.startdocument (); //to create an object of the list collection         This. List =NewArraylist<linkman>(); } @Override Public voidstartelement (String uri, String localname, string name, Attributes Attributes) throws Saxexception {        Super.startelement (URI, LocalName, name, attributes); //record the name of the parsed element         This. Name =name; //if it's linkman, then create a Linkman object        if("Linkman". Equals ( This. Name)) {             This. Linkman =NewLinkman (); }} @Override Public voidCharacters (Char[] ch,intStartintlength) throws saxexception {super.characters (ch, start, length); //if the element name is name at this time get text value        if("name". Equals ( This. Name)) {             This. Linkman.setname (NewString (ch,start,length)); }        //if the element name is phone, get text value        if("Phone". Equals ( This. Name)) {             This. Linkman.setphone (NewString (ch,start,length)); }        //if the element name is an email get text value        if("Email". Equals ( This. Name)) {             This. Linkman.setemail (NewString (ch,start,length)); }} @Override Public voidendElement (String uri, String localname, String name) throws Saxexception {super.endelement (URI, L        Ocalname, name); //release THIS.name         This. Name =NULL; //if the element name at this time is Linkman        if("Linkman". Equals (name)) {            //to add a Linkman object to a collection             This. List.add ( This. Linkman); //emptying the Linkman object             This. Linkman =NULL; }    }    //provide a way to get the packaged Linkman collection     PublicList<linkman>getList () {returnlist; }}

Summary: It must be a good choice if you use Sax to read data, but this parsing technique cannot do other things such as: Add, delete, and change.

Solution: There can be a technology award DOM and sax combine to efficiently query and perform actual data manipulation (add, delete, and change). Even with third-party XML parsing techniques dom4j.

Javase Learning Notes Sax parsing (6)