Java network programming, database programming, XML parsing technology.

Java Network programming

Physical layer.

Data link layer.

Network layer.

Transport layer.

Session layer.

The presentation layer.

Application layer.

The TCP/IP layered interface includes the following functions for the collaboration layer, respectively:

The network interface layer.

Network interconnect layer.

Transport layer.

Application layer.

Socket:

Socket. Sockets. is an abstraction layer.

//Create a client socket to initiate a connection request to the serverSocket socket =NewSocket ("127.0.0.1", 30001); /*Create an input-output stream with an established socket to handle connections to the server side*/        //writing data to the serverBufferedWriter writer =NewBufferedWriter (NewOutputStreamWriter (Socket.getoutputstream ())); Writer.write ("Hello server!!!");        Writer.flush (); //read data from the serverBufferedReader reader =NewBufferedReader (NewInputStreamReader (Socket.getinputstream ())); Char[] ch =New Char[100]; intLen =reader.read (CH); System.out.println ("Information received from the server side:"); System.out.print (NewString (CH, 0, Len)); //Freeing ResourcesReader.close ();        Writer.close (); Socket.close ();

Database programming

JDBC is a set of database programming APIs available in Java.

The DriverManager class is used to manage the JDBC-driven service classes.

The connection interface represents a database connection.

The statement interface represents the SQL statement.

The ResultSet interface represents the returned result set.

Connection conn =NULL;//Connection ObjectStatement stmt =NULL;//Statement ObjectResultSet rs =NULL;//Query Result set        /*Load Driver*/        Try{class.forname ("Com.mysql.jdbc.Driver"); } Catch(ClassNotFoundException e) {e.printstacktrace (); }        /*Create a Connection object*/        //Connection StringString url = "Jdbc:mysql://localhost:3306/java"; //User nameString user = "root"; //PasswordString pwd = "5245"; Try {            //Create a connectionconn =drivermanager.getconnection (URL, user, pwd); System.out.println ("Connection succeeded"); } Catch(SQLException e) {e.printstacktrace (); }        /*Create a statement object*/        Try{stmt=conn.createstatement (); } Catch(SQLException e) {e.printstacktrace (); }        /*send SQL statement execution*/         //Add//String SQL1 =//INSERT into Users (ID,USERNAME,PWD) VALUES (4, ' HXS ', ' 1995 ');//int count = 0;//try {//count = stmt.executeupdate (SQL1);//} catch (SQLException e) {//         //e.printstacktrace ();//         }/// * Process Execution Results * ///if (count = = 1) {//System.out.println ("add Success");//} else {//System.out.println ("Add failed");//         }        //EnquiryString sql = "SELECT ID, username, pwd from users"; Try {            //get query result setrs =stmt.executequery (SQL); } Catch(SQLException e) {//e.printstacktrace ();        }        Try {            //Loop through the next record             while(Rs.next ()) {//get a column value in a rowSYSTEM.OUT.PRINTLN ("id =" + rs.getint ("id") + ", username =" + rs.getstring ("username") + ", pass Word = "+ rs.getstring (" pwd ")); }        } Catch(SQLException e) {//e.printstacktrace ();        }        /*freeing resources: Must-do*/        if(Conn! =NULL)            Try{conn.close (); } Catch(SQLException e) {e.printstacktrace (); } finally {                if(rs! =NULL)                    Try{rs.close (); } Catch(SQLException e) {e.printstacktrace (); } finally {                        if(stmt! =NULL)                            Try{stmt.close (); } Catch(SQLException e) {e.printstacktrace (); }                        }                }        }

XML parsing Technology

XML: Extensible Markup Language.

Form:

Validated processors-check the validity and format specifications of the XML document.

Processor without validation--check the format specification of the XML document.

The XML parser uses two basic APIs:

Document Object Model (DOM): An API based on tree structure.

XML Simple API (SAX): An event-driven API.

<!--Penguin--><penguins>    <penguin id= "1" >        <name> peas </name>    <!--name--        <close>100</close>        <!--intimacy values    --
<! ELEMENT Pet (dogs,penguins) ><! ELEMENT Dogs (dog*) ><! ELEMENT Dog (name,close,health,breed) ><! Attlist Dog ID CDATA #REQUIRED ><! ELEMENT Penguins (penguin*) ><! ELEMENT Penguin (Name,close,health,gender) ><! attlist Penguin ID CDATA #REQUIRED ><! ELEMENT name (#PCDATA) ><! ELEMENT Close (#PCDATA) ><! ELEMENT Health (#PCDATA) ><! ELEMENT Breed (#PCDATA) ><! ELEMENT gender (#PCDATA) >
Java network programming, database programming, XML parsing technology.