We Keep Coding

JSP - ArrayList in session attribute null

I am trying to store some data in a arraylist in each users session however when I try and grab the list it is apparently null...
Code:
<%
List<String> attacks = new ArrayList<>();
if (request.getSession().getAttribute("attackList") != null){
attacks = (List<String>) request.getAttribute("attackList");
int x = 1;
for (String attack : attacks){
String[] attacc = attack.split(":");
out.print("" +
"<tr>\n" +
" <th scope=\"row\">"+x+"</th>\n" +
" <td>"+attacc[0]+"</td>\n" +
" <td>"+attacc[1]+"</td>\n" +
" <td>"+attacc[2]+"</td>\n" +
" <td>"+attacc[3]+"</td>\n" +
" </tr>");
x++;
}
}else{
out.print("empty");
}
%>
That ^ is the code I am using to fetch the data, it is printing "empty", so its essentially null...
How I am adding the data:
if (request.getAttribute("attackList") != null) {
attacks = (List<String>) request.getAttribute("attackList");
request.removeAttribute("attackList");
}
attacks.add("data here");
request.setAttribute("attackList", attacks);
I have not tried anything due to me not knowing what to try here.

First, I suggest you, if it is possible, you can start working with expression language, instead of jsp directly, because turn your code more readable.
Look your problem, do you want to work with a List in a Request our a Session scope?
I ask because sometimes you get your list from request scope but your IF is verifying the Session.
And at no time are you adding your list to the session.
You could do this, after your logic, with:
request.getSession().setAttribute("attackList", attacks);
Here is more about session methods:
https://beginnersbook.com/2013/11/jsp-implicit-object-session-with-examples/

using jsp in javascript function

I've searched for this but can't find anything.
Please correct my question if it's incorrect english.
This is my code:
EDIT: The code is within my .jsp file!
function drawChart() {
var data = google.visualization.arrayToDataTable([
['Beoordeling', 'Stage Opleider', 'Student'],
['1', '1', '4'],
<% ArrayList < Stelling > alleStellingenLijst2 = new ArrayList < Stelling > ();
alleStellingenLijst2 = (ArrayList < Stelling > ) request.getAttribute("stellingen");
for (Stelling s: alleStellingenLijst2) {
out.println("['1', '" + s.getDeStelling() + "' , '" + s.getDeWaarde() + "'],");
} %> ]);
var options = {
title: 'Laatste competenties',
hAxis: {
title: 'Score',
titleTextStyle: {
color: 'green'
}
},
vAxis: {
title: 'Beoordeling nummer',
titleTextStyle: {
color: 'green'
}
},
// Allow multiple simultaneous selections.
selectionMode: 'multiple',
colors: ['#BEF781', 'green']
};
var chart = new google.visualization.BarChart(document.getElementById('chart_div'));
chart.draw(data, options);
}
For some reason, it wont execute the code between the <% %> (from the jsp).
This page online: http://project-omega.appspot.com/grafieken.jsp
The google app engine logs say the error is on the last line of my page. It's a nullpointerexception.
I have no idea what it means and I really hope someone can help me.
Thanks a lot and sorry for my english.
EDIT
The rendered output looks as follows
function drawChart() {
var data = google.visualization.arrayToDataTable([
['Beoordeling', 'Stage Opleider', 'Student'],
for (Stelling s : alleStellingenLijst2) {
out.println("['1', '" + s.getDeStelling() + "' , '" + s.getDeWaarde() + "'],");
}
]);
NEW CODE:
function drawChart() {
var data = google.visualization.arrayToDataTable([
['Beoordeling', 'Stage Opleider', 'Student'],
['1', 1, 4],
<%
ArrayList<Stelling> alleStellingenLijst2 =(ArrayList<Stelling>) getServletContext().getAttribute("stellingen");
for (Stelling s : alleStellingenLijst2) {
out.println("['1', " + s.getDeStelling() + " , " + s.getDeWaarde() + "],");
}
%>
['2', 2, 2]
]);

These are JSP markups, you cannot use them in JavaScript!
That's because JSP files are compiled to the .java classes during compilation, and JavaScript is executed on the client side.
You could do the opposite - generate a JavaScript code in the JSP file, that way you could pass some data you want to the JS variables.

I suppose you haven't set the stellingen request attribute.
You usually set the request attributes in a servlet, before forwarding the request to jsp:
#Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
ArrayList<Stelling> list = ...;
req.setAttribute("stellingen", list);
req.getRequestDispatcher("/grafieken.jsp").forward(req, resp);
}
Also make sure the attribute is set in the JSP code:
<%
List<Stelling> stellingen = (List<Stelling>) getServletContext().getAttribute("stellingen");
if(stellingen == null) {
out.println("stellingen attribute not set!");
}else{
for (Stelling s : stellingen) {
out.println("['1', " + s.getDeStelling() + " , " + s.getDeWaarde() + "],");
}
}
%>

how to extract a value of variable from a javascript function in the html page while parsing an html page

I have to parse an html page. I have to extract the value of the name element in the below html which is assigned to a javascript function. How do I do it using JSoup.
<input type="hidden" name="fields.DEPTID.value"/>
JS:
departmentId.onChange = function(value) {
var departmentId = dijit.byId("departmentId");
if (value == null || value == "") {
document.transferForm.elements["fields.DEPTID.value"].value = "";
document.transferForm.elements["fields.DEPTID_DESC.value"].value = "";
} else {
document.transferForm.elements["fields.DEPTID.value"].value = value;
document.transferForm.elements["fields.DEPTID_DESC.value"].value = departmentId.getDisplayedValue();
var locationID = departmentId.store.getValue(departmentId.item, "loctID");
var locationDesc = departmentId.store.getValue(departmentId.item, "loct");
locationComboBox = dijit.byId("locationId");
if (locationComboBox != null) {
if (locationID != "") {
setLocationComboBox(locationID, locationDesc);
} else {
setLocationComboBox("AMFL", "AMFL - AMY FLORIDA");
}
}
}
};

I'll try to teach you form the top:
//Connect to the url, and get its source html
Document doc = Jsoup.connect("url").get();
//Get ALL the elements in the page that meet the query
//you passed as parameter.
//I'm querying for all the script tags that have the
//name attribute inside it
Elements elems = doc.select("script[name]");
//That Elements variable is a collection of
//Element. So now, you'll loop through it, and
//get all the stuff you're looking for
for (Element elem : elems) {
String name = elem.attr("name");
//Now you have the name attribute
//Use it to whatever you need.
}
Now if you want some help with the Jsoup querys to get any other elements you might want, here you go the API documentation to help: Jsoup selector API
Hope that helped =)

Populate dropdown based on another dropdown selection

I have two dropdown fields in a JSP page and I have type4 connection with oracle 10g. I want that based on one dropdown selection I want that second dropdown should get filled by fetching data from database based on data in first dropdown automatically just like refreshing that JSP page or showing an alert something like "please wait". How can I do it in JSP-Servlet?
<select name="dropdown1">
<option value="<%out.println(name);%>"><%out.println(name);%></option>
</select>
My objective is: This below dropdown should get filled base don above selection:
<select name="dropdown2">
<option value="<%out.println(rollno);%>"><%out.println(rollno);%></option>
</select>
I have found one solution :
<body onload="setModels()">
<% // You would get your map some other way.
Map<String,List<String>> map = new TreeMap<String,List<String>>();
Connection con=null;
String vehtypeout="";
String vehtypeout1="";
try{
Class.forName("oracle.jdbc.driver.OracleDriver");
con=DriverManager.getConnection("");
PreparedStatement ps=null;
ResultSet rs=null;
ps=con.prepareStatement("select c1.name, c2.roll from combo1 c1 left join combo2 c2 on c1.name=c2.name order by name");
rs=ps.executeQuery();
while(rs.next()){
vehtypeout=rs.getString(1);
vehtypeout1=rs.getString(2);
map.put(vehtypeout, Arrays.asList((vehtypeout1)));// here i want to show multiple value of vehtypeout1 from database but only one value is coming from databse, how can i fetch multiple value?
map.put("mercedes", Arrays.asList(new String[]{"foo", "bar"}));
}
rs.close();
ps.close();
con.close();
}
catch(Exception e){
out.println(e);
}
%>
<%! // You may wish to put this in a class
public String modelsToJavascriptList(Collection<String> items) {
StringBuilder builder = new StringBuilder();
builder.append('[');
boolean first = true;
for (String item : items) {
if (!first) {
builder.append(',');
} else {
first = false;
}
builder.append('\'').append(item).append('\'');
}
builder.append(']');
return builder.toString();
}
public String mfMapToString(Map<String,List<String>> mfmap) {
StringBuilder builder = new StringBuilder();
builder.append('{');
boolean first = true;
for (String mf : mfmap.keySet()) {
if (!first) {
builder.append(',');
} else {
first = false;
}
builder.append('\'').append(mf).append('\'');
builder.append(" : ");
builder.append( modelsToJavascriptList(mfmap.get(mf)) );
}
builder.append("};");
return builder.toString();
}
%>
<script>
var modelsPerManufacturer =<%= mfMapToString(map) %>
function setSelectOptionsForModels(modelArray) {
var selectBox = document.myForm.models;
for (i = selectBox.length - 1; i>= 0; i--) {
// Bottom-up for less flicker
selectBox.remove(i);
}
for (i = 0; i< modelArray.length; i++) {
var text = modelArray[i];
var opt = new Option(text,text, false, false);
selectBox.add(opt);
}
}
function setModels() {
var index = document.myForm.manufacturer.selectedIndex;
if (index == -1) {
return;
}
var manufacturerOption = document.myForm.manufacturer.options[index];
if (!manufacturerOption) {
// Strange, the form does not have an option with given index.
return;
}
manufacturer = manufacturerOption.value;
var modelsForManufacturer = modelsPerManufacturer[manufacturer];
if (!modelsForManufacturer) {
// This modelsForManufacturer is not in the modelsPerManufacturer map
return; // or alert
}
setSelectOptionsForModels(modelsForManufacturer);
}
function modelSelected() {
var index = document.myForm.models.selectedIndex;
if (index == -1) {
return;
}
// alert("You selected " + document.myForm.models.options[index].value);
}
</script>
<form name="myForm">
<select onchange="setModels()" id="manufacturer">
<% boolean first = true;
for (String mf : map.keySet()) { %>
<option value="<%= mf %>" <%= first ? "SELECTED" : "" %>><%= mf %></option>
<% first = false;
} %>
</select>
<select onChange="modelSelected()" id="models">
<!-- Filled dynamically by setModels -->
</select>
But i am getting only one value in vehtypeout1 where databse contains multiple values. How can i do it?

Using jquery, bind a function to the onchange event of "combobox1" select box.
In that function, send an ajax request (you can use jquery get function) to a jsp page in your server.
In that jsp page, retrieve the relevant data from database and send the response back to the client with those data (may be you need to use JSON format).
In the jquery get function, you can add a callback function to execute after server send you back the response.
Inside that call back function, write the code to fill "combobox2" using response data sent by the server.

You'll want an ajax call like below. Have your function that is called return a html-string of
"<option value='myVal'>myText</option>".
The jQuery/Ajax would be:
$("#ddl1").change(function() {
$.ajax({
url: "URLyouwanttoaddress",
data: "myselection=" + $("#ddl1").val();
type:"get",
success: function(data) {
$("#ddl2").html(data);
}
});
});

json ajax problem

I am sorry to ask this but i've been working on this for hours and I can't figure it out on my own.
I have to use json for part of a project and I was able to get it to work but now it's not returning it back to the right jsp but instead just displaying the json jsp. I am pretty sure it is how I am receiving the json.
here are screen shots of what is happening:
this is the jsp that I need to use ajax on, I am wanting to populate the second dropdown using ajax:
this is what is happening instead, (it's the right data):
here is the code(sorry it's long):
-the jsp I am doing ajax on
<script type="text/javascript">
/**
* Utility function to create the Ajax request object in a cross-browser way.
* The cool thing about this function is you can send the parameters in a two-dimensional
* array. It also lets you send the name of the function to call when the response
* comes back.
*
* This is a generalized function you can copy directly into your code. *
*/
function doAjax(responseFunc, url, parameters) {
// create the AJAX object
var xmlHttp = undefined;
if (window.ActiveXObject){
try {
xmlHttp = new ActiveXObject("MSXML2.XMLHTTP");
} catch (othermicrosoft){
try {
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
} catch (failed) {}
}
}
if (xmlHttp == undefined && window.XMLHttpRequest) {
// If IE7+, Mozilla, Safari, etc: Use native object
xmlHttp = new XMLHttpRequest();
}
if (xmlHttp != undefined) {
// open the connections
xmlHttp.open("POST", url, true);
// callback handler
xmlHttp.onreadystatechange = function() {
// test if the response is finished coming down
if (xmlHttp.readyState == 4 && xmlHttp.status == 200) {
// create a JS object out of the response text
var obj = eval("(" + xmlHttp.responseText + ")");
// call the response function
responseFunc(obj);
}
}
// create the parameter string
// iterate the parameters array
var parameterString = "";
for (var i = 0; i < parameters.length; i++) {
parameterString += (i > 0 ? "&" : "") + parameters[i][0] + "=" + encodeURI(parameters[i][1]);
}
// set the necessary request headers
xmlHttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xmlHttp.setRequestHeader("Content-length", parameterString.length);
xmlHttp.setRequestHeader("Connection", "close");
// send the parameters
xmlHttp.send(parameterString);
}
}//doAjax
/**
* Submits the guess to the server. This is the event code, very much
* like an actionPerformed in Java.
*/
function getSeats() {
// this is how you get a reference to any part of the page
var packInput = document.getElementById("pack");
var pack = packInput.value;
// while (packInput.childNodes.length > 0) { // clear it out
// aSeats.removeChild(aSeats.childNodes[0]);
// }
// an example of how to do an alert (use these for debugging)
// I've just got this here so that we know the event was triggered
//alert("You guessed " + seat);
// send to the server (this is relative to our current page)
// THIS IS THE EXAMPLE OF HOW TO CALL AJAX
doAjax(receiveAnswer, "ttp.actions.Sale3PackAction.action",
[["pack", pack]]);
// change the history div color, just 'cause we can
// var randhex = (Math.round(0xFFFFFF * Math.random()).toString(16) + "000000").replace(/([a-f0-9]{6}).+/, "#$1").toUpperCase();
// document.getElementById("history").style.background = randhex;
}
/**
* Receives the response from the server. Our doAjax() function above
* turns the response text into a Javascript object, which it sends as the
* single parameter to this method.
*/
function receiveAnswer(response) {
// show the response pack. For this one, I'll use the innerHTML property,
// which simply replaces all HTML under a tag. This is the lazy way to do
// it, and I personally don't use it. But it's really popular and you are
// welcome to use it. Just know your shame if you do it...
var messageDiv = document.getElementById("aSeats");
messageDiv.innerHTML = response.aSeats;
// replace our history by modifying the dom -- this is the right way
// for simplicity, I'm just erasing the list and then repopulating it
var aSeats = document.getElementById("aSeats");
while (aSeats.childNodes.length > 0) { // clear it out
aSeats.removeChild(aSeats.childNodes[0]);
}
for (var i = 0; i < response.history.length; i++) { // add the items back in
var option = aSeats.appendChild(document.createElement("option"));
option.appendChild(document.createTextNode(response.history[i]));
}
// reset the input box
//document.getElementById("pack").value = "";
}
</script>
<% Venue v = (Venue)session.getAttribute("currentVenue"); %>
<% List<Conceptual_Package> cpList = Conceptual_PackageDAO.getInstance().getByVenue(v.getId()); %>
What Packages do you want to see?
<form method="post" action="ttp.actions.Sale3PackAction.action">
<select name="packid" id="pack">
<% for (Conceptual_Package cp: cpList) { %>
<option value="<%=cp.getId()%>"><%=cp.getName1()%></option>
<% } %>
</select>
<input type="submit" value=" next " onclick="getSeats();"/>
</form>
<!--new-->
Available Seats:
<select name="eventSeatid" id="aSeats">
<option value="aSeats"></option>
</select>
<input type="button" value=" Add "/>
Selected Seats:
<form method="post" action="ttp.actions.sale4Action.action">
<select name="eventSeat2id" size="10" id="seat2">
<option value="seat2"></option>
</select>
</form>
<jsp:include page="/footer.jsp"/>
-the json jsp
<%#page contentType="text/plain" pageEncoding="UTF-8"%>
<jsp:directive.page import="java.util.*"/>
{
"history": [
<% for (String newSeats: (List<String>)session.getAttribute("newSeats")) { %>
"<%=newSeats%>",
<% } %>
]
}
-the action class
public class Sale3PackAction implements Action{
public String process(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpSession session = request.getSession();
String packid = request.getParameter("packid");
System.out.println("packid is: " + packid);
Conceptual_Package cp = Conceptual_PackageDAO.getInstance().read(packid);
request.setAttribute("cp", cp);
List<Physical_Package> ppList = Physical_PackageDAO.getInstance().getByConceptual_Package(cp.getId());
request.setAttribute("currentPack", ppList);
session.setAttribute("aSeats", null);
//return "sale3Pack_ajax.jsp";
//new
//HttpSession session = request.getSession();
// ensure we have a history
for (Physical_Package pPack: ppList){
try {
if (session.getAttribute("aSeats") == null) {
LinkedList aSeatsList = new LinkedList<String>();
session.setAttribute("aSeats", aSeatsList);
aSeatsList.add("Sec: " + pPack.getVenueSeat().getRowInVenue().getSectionInVenue().getSectionNumber() + " Row: " + pPack.getVenueSeat().getRowInVenue().getRowNumber() + " Seat: " + pPack.getVenueSeat().getSeatNumber());
session.setAttribute("newSeats", aSeatsList);
} else {
LinkedList aSeatsList = (LinkedList) session.getAttribute("aSeats");
aSeatsList.add("Sec: " + pPack.getVenueSeat().getRowInVenue().getSectionInVenue().getSectionNumber() + " Row: " + pPack.getVenueSeat().getRowInVenue().getRowNumber() + " Seat: " + pPack.getVenueSeat().getSeatNumber());
session.setAttribute("newSeats", aSeatsList);
}
} catch (DataException ex) {
Logger.getLogger(Sale3PackAction.class.getName()).log(Level.SEVERE, null, ex);
}
}
// next jsp page to go to
return "AjaxPack_json.jsp";
}
}

Hehe, I think we've all been in your place. Spending hours on something just to eventually realize that we overlooked some simple detail.
Read comments for more information...