Question

What is the quickest way to export a very large string (several megabytes) from a Java app to on-page javascript? At the moment it’s taking so long the browser grinds to a halt.

Here is the code I’m using to modify the DOM:

window = JSObject.getWindow(this);
document = (JSObject) window.getMember("document");
for (int i = 0; i < encHexFileUploadStr.length(); i++){
    char c = encHexFileUploadStr.charAt(i); 
    document.eval("document.getElementById('encOutgoingData').value += '"+c+"';");
    if (i % 100 == 0) document.eval("console.log("+i+");");
}

Before this I tried to just assign the encHexFileUploadStr variable directly in one go, that was no better.

Is there any good way to do this that isn’t so slow?

Thanks!

Answer 1

I have not attempted to transfer the amount of data you are mentioning from a Java application to a webpage, however, if you are using document.eval the performance problem you are having is most likely due to the processing required on an eval statement. An alternative approach is to directly invoke a JavaScript method which performs the actual data update work. Here is an example of how you would go about using this approach:

Java

JSObject jso = JSObject.getWindow(this);
// invoke JavaScript method updateData with parameter encHexFileUploadStr
jso.call("updateData", new String[] { encHexFileUploadStr });

JavaScript

function updateData(s) {
    document.getElementById('encOutgoingData').value = s;
}