Sometimes I get error:
java.lang.IllegalStateException: The document element is not available.
when doing a findElements call on the Document. Is there a way to test if the document element is available rather than catching the exception.
You can check whether document element exists or not using the following code:
DOMDocument document = browser.getDocument();
DOMElement documentElement = document.getDocumentElement();
if (documentElement != null) {
DOMElement element = documentElement.findElement(By.className("name"));
}
In general, the following code is doing the same thing, but throws exception if documentElement is null:
DOMDocument document = browser.getDocument();
DOMElement element = document.findElement(By.className("name"));
Related
I am trying to build a dynamic Property Accessor. Want something which is like really fast as close to calling the actually Property. Dont want to go the Reflection route as its very slow. So i opted to using DynamicAssembly and inject IL using ILGenerator. Below is the ILGenerator related code which seems to work
Label nulllabel = getIL.DefineLabel();
Label returnlabel = getIL.DefineLabel();
//_type = targetGetMethod.ReturnType;
if (methods.Count > 0)
{
getIL.DeclareLocal(typeof(object));
getIL.DeclareLocal(typeof(bool));
getIL.Emit(OpCodes.Ldarg_1); //Load the first argument
//(target object)
//Cast to the source type
getIL.Emit(OpCodes.Castclass, this.mTargetType);
//Get the property value
foreach (var methodInfo in methods)
{
getIL.EmitCall(OpCodes.Call, methodInfo, null);
if (methodInfo.ReturnType.IsValueType)
{
getIL.Emit(OpCodes.Box, methodInfo.ReturnType);
//Box if necessary
}
}
getIL.Emit(OpCodes.Stloc_0); //Store it
getIL.Emit(OpCodes.Br_S,returnlabel);
getIL.MarkLabel(nulllabel);
getIL.Emit(OpCodes.Ldnull);
getIL.Emit(OpCodes.Stloc_0);
getIL.MarkLabel(returnlabel);
getIL.Emit(OpCodes.Ldloc_0);
}
else
{
getIL.ThrowException(typeof(MissingMethodException));
}
getIL.Emit(OpCodes.Ret);
So above get the first argument which is the object that contains the property. the methods collection contains the nested property if any. for each property i use EmitCall which puts the the value on the stack and then i try to box it. This works like a charm.
The only issue is if you have a property like Order.Instrument.Symbol.Name and assume that Instrument object is null. Then the code will throw an null object exception.
So this what i did, i introduced a null check
foreach (var methodInfo in methods)
{
getIL.EmitCall(OpCodes.Call, methodInfo, null);
getIL.Emit(OpCodes.Stloc_0);
getIL.Emit(OpCodes.Ldloc_0);
getIL.Emit(OpCodes.Ldnull);
getIL.Emit(OpCodes.Ceq);
getIL.Emit(OpCodes.Stloc_1);
getIL.Emit(OpCodes.Ldloc_1);
getIL.Emit(OpCodes.Brtrue_S, nulllabel);
getIL.Emit(OpCodes.Ldloc_0);
if (methodInfo.ReturnType.IsValueType)
{
getIL.Emit(OpCodes.Box, methodInfo.ReturnType);
//Box if necessary
}
}
Now this code breaks saying That the object/memory is corrupted etc. So what exactly is wrong with this code. Am i missing something here.
Thanks in Advance.
Previously, if you had consecutive properties P returning string and then Q returning int, you would get something like this:
...
call P // returns string
call Q // requires a string on the stack, returns an int
box
...
Now you have something like this:
...
call P // returns string
store // stores to object
... // load, compare to null, etc.
load // loads an *object*
call Q // requires a *string* on the stack
store // stores to object *without boxing*
...
So I see two clear problems:
You are calling methods in such a way that the target is only known to be an object, not a specific type which has that method.
You are not boxing value types before storing them to a local of type object.
These can be solved by reworking your logic slightly. There are also a few other minor details you could clean up:
Rather than ceq followed by brtrue, just use beq.
There's no point in doing Stloc_1 followed by Ldloc_1 rather than just using the value on the stack since that local isn't used anywhere else.
Incorporating these changes, here's what I'd do:
Type finalType = null;
foreach (var methodInfo in methods)
{
finalType = methodInfo.ReturnType;
getIL.EmitCall(OpCodes.Call, methodInfo, null);
if (!finalType.IsValueType)
{
getIL.Emit(OpCodes.Dup);
getIL.Emit(OpCodes.Ldnull);
getIL.Emit(OpCodes.Beq_S, nulllabel);
}
}
if (finalType.IsValueType)
{
getIL.Emit(OpCodes.Box, methodInfo.ReturnType);
//Box if necessary
}
getIL.Emit(OpCodes.Br_S, returnLabel);
getIL.MarkLabel(nulllabel);
getIL.Emit(OpCodes.Pop);
getIL.Emit(OpCodes.Ldnull);
getIL.MarkLabel(returnlabel);
Note that we can get rid of both locals since we now just duplicate the top value on the stack before comparing against null.
I have used this code for extracting urls from web page.But in the line of 'foreach' it is showing
Object reference not set to an instance of an object
exception. What is the problem? how can i correct that?
WebClient client = new WebClient();
string url = "http://www.google.co.in/search?hl=en&q=java&start=10&sa=N";
string source = client.DownloadString(url);
HtmlDocument doc = new HtmlDocument();
doc.LoadHtml(source);
foreach (HtmlNode link in doc.DocumentNode.SelectNodes("//a[#href and #rel='nofollow']"))
{
Console.WriteLine(link.Attributes["href"].Value);
}
First, you should look up the NullReferenceException in the documentation. It says
The exception that is thrown when there is an attempt to dereference a null object reference.
This means you did the equivalent of
SomeClass reference = null;
reference.Method(); // or reference.Property;
Next, look at the line of code that has the error and figure out what you are derefencing:
foreach (HtmlNode link in doc.DocumentNode.SelectNodes("//a[#href and #rel='nofollow']"))
doc.DocumentNode
doc.DocumentNode.SelectNodes
So either doc is null, or doc.DocumentNodes is null. Since you just assigned a new instance of HtmlDocument to doc, doc can't be the problem. That implies that you loaded an empty document, such that there is no doc.DocumentNode.
Check before the loop to see if doc.DocumentNode is null.
Which line is the exception being thrown from; the actual foreach line, or the contents of the loop?
Probably the easiest method to deal with this one is to use the debugger - pop a breakpoint in front of the foreach, and when the runtime pauses, inspect the contents of the various variables, such as link, doc.DocumentNode, etc. If link is non-null, then check whether link.Attributes["href"] is, and so on.
Below is part of my code interacting with data grid...!
This lists the children of the particular node if i click on it after refreshing the datagrid..
But if i click on an empty space of the datagrid i get an error saying
"ReferenceError: Error #1069: Property data not found on mx.controls.listClasses.ListBaseContentHolder and there is no default value."
How to avoid that ?
if(event.target.data.children != null)
{
resultSet.removeAll();
var tempChildObj:ArrayCollection;
tempChildObj=event.target.data.children as ArrayCollection;
var childLength:int;
childLength=tempChildObj.length;
for(var i:int =0;i<childLength;i++)
{
resultSet.addItem(tempChildObj.getItemAt(i));
}
resultSet.addItem(tempChildObj);
}
}
What the error is telling you is that the event's target property doesn't have a property called data in your error case. This makes sense since you're clicking on a blank row - a blank row won't contain any data.
What you'll want to do first is check if the event's target contains a data property before you start accessing the child property of data. Either one of the following tests should work:
if( event.target.hasOwnProperty( "data" ) ) {
// rest of your code here
}
or
if( event.target.data ) {
// rest of your code here
}
I"m trying to attached some jquery to checkboxes in a gridview, using document.ready:
$(document).ready(function()
{
var chkBox= document.getElementById("gvTimeSheet_ctl01_chkAll1");
//I can alert chkBox.id, element exists
var name = $("input[name='gvTimeSheet$ctl01$chkAll1']");
//Here, when I alert the id, I get a null
var ID = $("#gvTimeSheet_ctl01_chkAll1");
//Here, when I alert the id, I get a null
var withClass = $(".chkAll1Class");
//Here, when I alert the id, I get a null
var withClass2 = $(".Bill1");
//Here, when I alert the id, I get a null
//This line causes the browswer to crash and gives me the following error
//Microsoft JScript runtime error: 'null' is null or not an object
$("#gvTimeSheet_ctl01_chkAll1").click(function()
{
var checked_status = this.checked;
$("input[class=Bill1]").each(function()
{
this.checked = checked_status;
});
});
});*/
So, why are any attempts at finding an object null in jquery, yet exist in regular javascript within the same method? What am I missing here. I have the jquery js files brought in in a script tag directly above this method. I just can't seem to find any objects on this page with jquery. On other pages, I can.
Objects that result from a jQuery selector are actually wrappers around a DOM object, so you don't access it the same as a DOM object.
If you're alerting just "name.id", from your first example above, there won't be any such property on the jQuery wrapper. Try alerting your ID as follows:
alert(name.attr("id"));
var val = $("input:radio[name$='rdoselect']:checked").val();
if (val == 1) {
$('[id$=divDate]').attr('disabled', true);
}else {
$('[id$=divDate]').attr('disabled', false);
}
var ID = $("#gvTimeSheet_ctl01_chkAll1");
This returns a jQuery object, not an ID. ID.id would also be undefined. To get the ID, you need:
var ID = $("#gvTimeSheet_ctl01_chkAll1").attr("id");
Does the page you're adding this code to already include the Prototype JavaScript library?
jQuery's "$" method never returns null, so this shouldn't be a problem:
// This line causes the browswer to crash and gives me the following error
// Microsoft JScript runtime error: 'null' is null or not an object
$("#gvTimeSheet_ctl01_chkAll1").click(function() { .... });
All the comments about needing to use .attr('id') still stand (though I prefer $('#whatever')[0].id myself.)
I'm newish to flex an have recently hit a snag casting.
this is the code I'm running.
/**
* return background definition depending on time
*/
private function findBackgroundItem( relativeTime : Number ) : CSBackgroundItem
{
if( this.backgroundItems == null ) return null;
var result :CSBackgroundItem = null;
var relative:Date = new Date(relativeTime);
for( var i : Number = 0; i < this.backgroundItems.length; i++ )
{
// backgroundItems is an Ilist of CSBackgroundItem.
var colourItem : CSBackgroundItem = CSBackgroundItem( this.backgroundItems.getItemAt( i ) );
// other stuff here
}
return result;
}
The problem occurs when the IList.getItemsAt() result is cast to the CSBackgroundItem variable colourItem. The following error is thrown
TypeError: Error #1034: Type Coercion failed: cannot convert com.mystuff::CSBackgroundItem#650e8dd1 to com.mystuff.CSBackgroundItem.
If I use the 'as' keyword I get cast results in the colourItem being null. Using the debugger shows that the list is not empty and is indeed populated with CSBackgroundItem objects.
Now this is the wacky bit.. this code works, the first time the module it's in loads.. subsequent loads (after unloading it) throw the exception.
Can anyone shed any light on why this might happen?
FYI, a type loaded into a child ApplicationDomain can be cast to a type (that it extends/implements) in the parent ApplicationDomain.
Eg.
loader.applicationDomain = ApplicationDomain.currentDomain; // parent domain
loader.applicationDomain = new ApplicationDomain(ApplicationDomain.currentDomain); // child domain
loader.applicationDomain = new ApplicationDomain(); // new domain
I think I may have found the answer..
My guess is the module is loading in a different ApplicationDomain.. which would mean you can't cast from the same type in the current domain..
As I understand this is vaguely similart to different Java ClassLoaders loading the same class.
I'll post again once I've confirmed it
Yup.. that works..
here is the fix i used in MXML style..
<mx:ModuleLoader id="loader" x="10" y="10" width="100%" height="100%" applicationDomain="{ApplicationDomain.currentDomain}"/>
the equivilant actionscript would be
loader.applicationDomain = ApplicationDomain.currentDomain;