数据库通讯方式有哪些，在数据通信系统中常用数据传输方式有哪些
来源：整理 编辑：黑码技术 2024-05-21 17:25:48
1，在数据通信系统中常用数据传输方式有哪些
并行，串行，异步，同步，单工，半双工，双工，不知道你具体问哪个
2，目前计算机网络中采用的数据通信方式是哪一种
3，数据通信方式的介绍
计算机网络中传输的信息都是数字数据，计算机之间的通信就是数据通信方式，数据通信是计算机和通信线路结合的通信方式。根据所允许的传输方向，数据通信方式可分成单工通信、半双工通信、双工通信三种方式。
4，IT系统中的数据传输方式有哪些
1 socket 开发接口共享--(也包括webService http页面的方式)2 ftp共享同一文件，互相传输数据3 共享出各自的数据库，供对方访问，来达到数据共享的目的请采纳！
5，servlet之间的通信方法有哪些如何具体实现
以下是几种常调用的方法 Servlet to Servlet Communication Listing 1: ServletBase public class ServletBase extends HttpServlet static Connection databaseConnection = null; public void init(ServletConfig _config) throws ServletException super.init(_config); if ( databaseConnection == null ) //- Open up the database connection } protected boolean isLoggedOn( String _username ) return true; } protected boolean logUserOn( String _username ) return true; } } Listing 2: Using the NewSerletBase Class public class logonServlet extends ServletBase public void service(HttpServletRequest _req, HttpServletRe- sponse _res) throws ServletException if ( isLoggedOn( _req.getParameter(襏SERNAME? ) //- Display a message indicating they are already logged on }else logUserOn( _req.getParameter(襏SERNAME? ); } } } Listing 3: Storing an Object public class logonServlet extends HttpServlet public void service(HttpServletRequest _req, HttpServletRe- sponse _res) throws ServletException ServletContext thisContext = getServletContext(); //-- Assume some method creates a new connection class Connection newConnection = createConnection(); thisContext.setAttribute( database.connection? newConnection ); //-- Return some output to the client } } Listing 4: retrieving an Object public class logoffServlet extends HttpServlet public void service(HttpServletRequest _req, HttpServletRe- sponse _res) throws ServletException ServletContext thisContext = getServletContext(); //-- Assume some method creates a new connection class Connection newConnection = thisContext.getAttribute( database.connection?; if ( newConnection == null ) //- Database has not been opened yet //-- Return some output to the client } } Listing 5: Looking at All the Objects public class allServlet extends HttpServlet public void service(HttpServletRequest _req, HttpServletRe- sponse _res) throws ServletException ServletContext thisContext = getServletContext(); //-- Assume some method creates a new Connection class Enumeration E = thisContext.getAttributeNames(); while ( E.hasMoreElements() ) String name = (String)E.nextElement(); System.out.println( "Object: " + name ); } } } Listing 6: Retrieving Remote Contexts public class otherServlet extends HttpServlet public void service(HttpServletRequest _req, HttpServletRe- sponse _res) throws ServletException ServletContext otherContext = getServletContext(http://<otherdomain>/servlet/allServlet?; //-- Assume some method creates a new Connection class Enumeration E = otherContext.getAttributeNames(); while ( E.hasMoreElements() ) String name = (String)E.nextElement(); System.out.println( "Object: " + name ); } } } Listing 7: Forwarding a Request public class forwardServlet extends HttpServlet public void service(HttpServletRequest _req, HttpServletRe- sponse _res) throws ServletException ServletContext xt = getServletContext(); RequestDispatcher xyzServlet = xt.getRequestDispatcher(http://<domain>/servlet/xyzServlet?; //- Do any preliminary processing _req.setAttribute( database.results? new Results() ); xyzServlet.forward( _req, _res ); } } Listing 8: Inserting Content public class insertServlet extends HttpServlet public void service(HttpServletRequest _req, HttpServletRe- sponse _res) throws ServletException ServletContext xt = getServletContext(); RequestDispatcher xyzServlet = xt.getRequestDispatcher(http://<domain>/servlet/xyzServlet?; PrintWriter Out = _res.getWriter(); Out.println( this is from the insertServlet ?); for(int x=0; x < 10; x++ ) xyzServlet.insert( _req, _res ); Out.println( this is the end of the print servlet ?); } } /////////////////////////////////////////forward方法是把请求的内容转发到另外的一个servlet.而include是把另一个servlet处理过后的内容拿过来. 举例来说比如在servlet1打一句out.print("1111"),servlet2打上out.print("22222"),在servlet1中用forward命令会转到servlet2中,显示22222. 而在servlet1中使用include方法会依然在servlet1的页面中,但是在1111后打出22222一个servlet直接调用另一个servlet的doget 或 dopost方法不行吗？ 将所有参数都传过去。forware(String url)和include() 是RequestDispatcher接口定义的方法，前者是直接转到另一个url的。后者是将另一个url的处理过程包含在内转发请求的例子public void doGet(HttpServletRequest request,HttpServletResponse response)throws ServletException, IOException String operation = request.getParameter("operation");if (operation == null) operation = "unknown";}String address;if (operation.equals("order")) address = "/WEB-INF/Order.jsp";} else if (operation.equals("cancel")) address = "/WEB-INF/Cancel.jsp";} else address = "/WEB-INF/UnknownOperation.jsp";}RequestDispatcher dispatcher =request.getRequestDispatcher(address);dispatcher.forward(request, response);}差别：使用sendRedirect时– 用户可以看到JSP的URL（使用RequestDispatcher.forward时用户只能看到servlet的URL）– 客户程序要经过两次往返（而forward只需一次）? sendRedirect的优点– 用户可以单独访问JSP页面? 用户能够保存JSP页面的地址? sendRedirect的缺点– 由于用户可以在不首先经过servlet的情况下访问JSP页面，所以，JSP页面所需的数据有可能不存在。? 因此，JSP页面需要编写代码检查这种情况。楼主你这个功能需要通过javascript来实现,如果图片没有事件加载页面里的话可以通过ajax动态加载图片,不过由于网络延时可能效果不会理想,所以最好是提前把图片加载进来. 通过javascript的事件机制在事件处理函数中对图片进行替换就可以了. 这个功能一个很好的例子就是表单验证,比如在提交之前自动检查用户名是否已经被使用.实现的时候可以捕获一下用户的操作,当光标离开用户名输入框后触发事件,在事件处理函数中通过ajax向服务器发送异步请求,服务器判断该用户名是否已经使用并给予响应,客户端收到响应后修改图片.
文章TAG：
数据 数据库 通讯 方式 数据库通讯方式有哪些
