所以，我对html，css和框架略有熟悉，我对Java有一个公平的理解。但是，我只能看到如何使用添加到html文件的Javascript进行内置函数和计算。但我不明白它如何工作说你的计算机上的Java程序，网站将从中获取数据和信息。有谁能解释一下？我在互联网上找不到任何好的答案。
假设我想在服务器上使用Java计算值2 + 3，然后获取该值并将其显示在网站上。我该怎么做？
答案 0 :(得分：1)
我通过javascript向服务器上的java servlet发送ajax请求来实现此功能，这是我使用的示例：
说你有一个链接：
<a href="#" onclick = 'shipProduct(1)'>Test</a>
单击此链接时，它将查找相应的javscript函数，在我的例子中是：
/**
*
* @param {type} action
* @param {type} bundleId
* @returns {undefined}
*/
function shipProduct(bundleId)
{
$.ajax
({
url: "/FlcErp-war/ShipmentServlet", //this is the name of the serverlet in your project
type: "GET", // the type of your request
data: _action + "=addToShipped&bundleId=" + bundleId,
success: function (content)
{
if (content.substring(0, 1) == '_')
{
alert(content);
}
else
{
//rebuild shipment tables to show updated
//information about the item
buildShipmentQueue();
}
},
error: function (xhr, status, error) {
alert(xhr.responseText);
alert(status);
alert(error);
}
});
}
我所做的是有一个带注释的java servlet来处理我的请求：
您的doPost和doGet将处理您的帖子并获取请求
/**
*
* @author samo
*/
@WebServlet("/ShipmentServlet")
public class ShipmentServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private static final String _addToShipped = "addToShipped";
private static final String _bundleId = "bundleId";
private static final String _shipmentId = "shipmentId";
private static final String _productId = "productId";
private static final String _updateQueue = "updateQueue";
private static final String _unship = "unship";
private static final String _setInSession = "setInSession";
private static final String _externalBundleId = "externalBundleId";
private static final String _plywood = "P";
private static final String _veneer = "V";
private static final String _lumber = "L";
private static final String _bundle = "Bundle";
private static final String _list = "List";
private boolean multipleActions;
private String[] actions;
/**
* Processes requests for both HTTP <code>GET</code> and <code>POST</code>
* methods.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
protected void processBundleRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException, NamingException, CloneNotSupportedException {
response.setContentType("text/html;charset=UTF-8");
try (PrintWriter out = response.getWriter()) {
this.actions = null;
//this is where we will get the actions to process
//if there is more than one action the string will contain
// a comma as a delimiter
String action = request.getParameter("_action");
InitialContext ctx = new InitialContext();
LoadShipmentController lsc = (LoadShipmentController) ctx.lookup("loadShipmentController");
switch (action) {
case _addToShipped:
shipProduct(request, out);
break;
case _updateQueue:
Shipment shipment = lsc.getCurrent();
String type = shipment.getShipmentType();
String shipmentQueue = "";
switch (type) {
case _veneer:
shipmentQueue = lsc.getVeneerShipmentQueue();
break;
case _plywood:
shipmentQueue = lsc.getShipmentQueue();
break;
case _lumber:
shipmentQueue = lsc.getShipmentQueue();
break;
}
out.println(shipmentQueue);
break;
case _unship:
unshipProduct(request, out);
break;
case _setInSession:
String bundleId = request.getParameter(_bundleId);
lsc.setBundleId(bundleId);
break;
case _list:
out.println(lsc.getBundleAndProductListString());
break;
// setSessionVariable(_externalBundleId, bundleId);
}
}
}
public void shipProduct(HttpServletRequest request, PrintWriter out) throws NamingException, CloneNotSupportedException {
Integer bundleId = Integer.valueOf(request.getParameter(_bundleId));
InitialContext ctx = new InitialContext();
ShipmentController shipmentController = (ShipmentController) ctx.lookup("shipmentController");
LoadShipmentController loadShipmentController = (LoadShipmentController) ctx.lookup("loadShipmentController");
// getting the product from the bundle, because that's all we care about
Product product = shipmentController.loadBundle(bundleId).getProduct();
String type = product.getProductType();
//because the way we ships differs depending on the product type I need to
//check first mainly for veneer shipments because their bundle count is not
//predetermined
boolean loaded = false;
switch (type) {
case _veneer:
loaded = loadShipmentController.loadVeneerProduct(product, bundleId);
break;
case _plywood:
loaded = loadShipmentController.loadPlywoodProduct(product, bundleId);
break;
case _lumber:
loaded = loadShipmentController.loadLumberProduct(product, bundleId);
break;
}
if(!loaded)
{
out.println("_" + loadShipmentController.getErrors());
}
}
public void unshipProduct(HttpServletRequest request, PrintWriter out) throws NamingException {
Integer bundleId = Integer.valueOf(request.getParameter(_bundle));
InitialContext ctx = new InitialContext();
LoadShipmentController loadShipmentController = (LoadShipmentController) ctx.lookup("loadShipmentController");
boolean unship = loadShipmentController.unshipByBundleId(bundleId);
if (!unship) {
String error = loadShipmentController.getErrors();
out.println("Error:" + error);
}
}
private void setSessionVariable(String name, String value) {
FacesContext context = FacesContext.getCurrentInstance();
ExternalContext externalContext = context.getExternalContext();
HttpSession session = (HttpSession) externalContext.getSession(false);
session.setAttribute(name, value);
}
// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
* Handles the HTTP <code>GET</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
try {
processBundleRequest(request, response);
} catch (NamingException ex) {
Logger.getLogger(ShipmentServlet.class.getName()).log(Level.SEVERE, null, ex);
} catch (CloneNotSupportedException ex) {
Logger.getLogger(ShipmentServlet.class.getName()).log(Level.SEVERE, null, ex);
}
}
/**
* Handles the HTTP <code>POST</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
}