Java Enterprise

Java Enterprise

1. Spring MVC

   • in java classes
     • @Controller
       • @Autowired
         • set the service name
         • @RequestMapping (path="/pathname", method = RequestMethod.POST / RequestMEthod.GET)
           • @RequestMapping(      path = "/add", method = RequestMethod.POST) public ModelAndView addstudent( @RequestParam("name") String name, @RequestParam("email") String email, @RequestParam("dob") String dob) { try { addStudentService.addstudent(name, email, dob);  ModelAndView mv = new ModelAndView("addstudent"); String added = "Student Added!"; mv.addObject("added", added);   return mv; } catch (Exception ex) { ModelAndView mv = new ModelAndView("addstudent"); mv.addObject("error", ex.getMessage());   return mv;
           • ask autowired service to do something
             • servicename.method();
             • ModelAndView mv = new ModelAndView("jsp location");
     • @Service
       • pass action to JPA or JDBC, get result / throw exception
   • import springframework
   • in JSP
     • <%@ taglib prefix="c" uri="java.sun.com....."
       • <c:if test="${error != null}">
       • <c: forEach var="st" items="${studentlist}">

2. Server/Client

   • Socket programming
     • Basic serversocket
       • Server side
         • &nbsp;&nbsp; import java.io.IOException; import java.net.ServerSocket; &nbsp; public class Server { &nbsp; &nbsp; public static void main(String[] args) &nbsp; &nbsp; { &nbsp; &nbsp; &nbsp; &nbsp; ServerSocket server = null; &nbsp; &nbsp; &nbsp; &nbsp; try &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; { &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;server = new ServerSocket(5000);&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; catch(IOException e)&nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; e.printStackTrace();&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }}
         • while(true) { &nbsp; &nbsp; try &nbsp; &nbsp; { &nbsp; &nbsp; &nbsp; &nbsp; Socket socket = server.accept(); &nbsp; &nbsp; &nbsp; &nbsp; InputStream is = socket.getInputStream(); &nbsp; &nbsp; &nbsp; &nbsp; StringBuffer mesg = new StringBuffer(); &nbsp; &nbsp; &nbsp; &nbsp; while(true) &nbsp; &nbsp; &nbsp; &nbsp; { &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; int data = is.read(); &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if (data == -1) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; { &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; break; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; } &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; else &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; { &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;mesg.append((char)data); &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;} &nbsp; &nbsp; &nbsp; &nbsp;System.out.println(mesg); &nbsp;&nbsp; &nbsp; } &nbsp; &nbsp; catch(IOException e) &nbsp; &nbsp; { &nbsp; &nbsp; &nbsp; &nbsp; e.printStackTrace(); &nbsp; &nbsp; } }
         • use socket.getInputStream
         • use socket = server.accept();
         • open server by ServerSocket(5000)
         • decode by StringBuffer
         • is.read();
       • Client side
         • import java.io.IOException; import java.io.OutputStream; import &nbsp;java.net.Socket; &nbsp; public class Client { &nbsp; &nbsp; public static void main(String[] args) &nbsp; &nbsp; { &nbsp; &nbsp; &nbsp; &nbsp; try &nbsp; &nbsp; &nbsp; &nbsp; { &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Socket client = new Socket("localhost",5000); &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;OutputStream os = client.getOutputStream(); &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; os.write("Hello ISCG7425".getBytes());&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; os.close(); &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; client.close(); &nbsp; &nbsp; &nbsp; &nbsp; } &nbsp; &nbsp; &nbsp; &nbsp; catch(IOException e) &nbsp; &nbsp; &nbsp; &nbsp; { &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; e.printStackTrace(); &nbsp; &nbsp; &nbsp; &nbsp; } &nbsp; &nbsp; } }
         • socket client = new socket("localhost",5000);
         • client.getOutputStream
         • os.write("msg".getbytes());
         • os.close();
       • Data Streams
         • Socket socket = server.accept(); DataInputStream dis = new DataInputStream(socket.getInputStream()); DataOutputStream dos = new DataOutputStream(socket.getOutputStream()); while(true) { try { String mesg = dis.readUTF(); dos.writeUTF("Echo response:"+mesg); } catch(EOFException e) { &nbsp; break; } &nbsp;}&nbsp;
         • Socket client = new Socket("localhost",5000); DataOutputStream dos = new DataOutputStream(client.getOutputStream()); DataInputStream dis = new DataInputStream(client.getInputStream()); dos.writeUTF("Test Message"); String resp = dis.readUTF(); System.out.println(resp); client.close();&nbsp;
         • use DataInputStream/DataOutputStream
         • dis = new DataInputStream(socket.getInputStream());
         • dos = new DataOutputStream(socket.getOutputStream());
         • dis.readUTF();
         • dos.writeUTF("msg");
     • Server Threads
       • final &nbsp;Socket socket &nbsp;= server.accept(); Thread &nbsp;serverThread = new Thread() { public &nbsp;void run() { &nbsp; try { &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; InputStream is = socket.getInputStream(); &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; StringBuffer mesg = new StringBuffer(); &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; while(true) { &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; int data = is.read(); &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if(data == -1) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; break; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;else &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; mesg.append((char)data); &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; } &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; System.out.println(this.getName() + "\n"+ mesg); &nbsp; }catch(IOException e) { /* … Handle exceptions … / } } }; serverThread.start();
       • Thread serverThread = new Thread(){the server activities}
       • serverTread.start();
       • should include thread.sleep(1000) method
   • Servlets and JSP
     • http
       • text-base protocol for hypertext (HTML)
       • 20+ years old
       • becomes popular and extended to send other type of data
       • simple to implement
       • request-respond kind of protocol, only client can request
     • Servlets
       • help developer focus on business rules
       • providing resources to handle incoming request and outgoing responds
       • need mapping with html url-pattern
       • can be done by annotations: @WebServlet("/weblocation")
     • JSP
       • JavaServerPages
       • need not to transfer java to html
       • translated to Servlets
       • using <% jave coding %> format to inport code to webpage
       • can directly use some variables:request / response / out / session / application

3. Database connection

   • JDBC
     • JDBCDataSource ds = &nbsp;new JDBCDataSource(); // setup &nbsp;URL according to HSQLDB specs ds.setUrl("jdbc:hsqldb:hsql://localhost/contacts"); // set &nbsp;other data source properties ds.setPassword(""); ds.setUser("SA"); // setup &nbsp;global database connection&nbsp; conn = ds.getConnection(); &nbsp;
     • interface to allow java to access SQL database
     • use Classes and Factory method
     • Driver based model
     • basic setup: port, hostname, schema, database name
     • set JDBCDataSource ds --> setUrl & password & username --> getConnection()
     • conn = DriverManager.getconnnection(url,username,password)
       • PreparedStatement stmt = conn.prepareStatement("SQL Code")
         • stmt.setData(value,value);
           • stmt.executeUpdate();
             • stmt.close(); conn.close();
       • Statement stmt = conn.createStatement();
         • ResultSet rs = stmt.executeQuery("SQL code");
           • String name = rs.getString("name");
             • rs.close(); stmt.close(); conn.close();
       • one conn, many stmt, each stmt one rs
   • JPA
     • Java Persistence Architecture
     • EntityManager em = factory.createEntityManager();
       • em.setFlushMode(FlushModeType.COMMIT);
         • em.getTransaction().begin();
           • em.createQuery("SELECT u FROM User As u").getResultList();
             • em.getTransaction().commit();
               • factory.close();
     • set local dataset item by id
       • @Entity / @Table(name = "table name in database"
         • for mapping
       • @ID
       • setName / getName

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