GWT RPC with large data arrays

[Daniel Peterson]

I'm trying to transmit large amounts of data from my server to my
client using the Asynchronous RPC calls. I've noticed that for these
arrays often take quite a long period of time to transmit. I'm only
sending four sets of data, but containing several hundred (to perhaps
a thousand) points each. I'm transmitting a simple class that holds
four parallel double arrays that will be used to populate a DataTable
for a visualization (from the Google Visualization API).

I could restructure my classes and doubtless get a little speed up (by
only having one array that I am transferring), but the entire
transmission process occurs three to four times faster if I parse the
data on the server from a byte array to a string using a string
buffer, than transmit a single string across the RPC.

I've seen that I could manually code the serialing interface for the
RPC call, but, unless I can find a way to send a large blob of data
and escape the arrays, I don't think that will speed up the process
too much.

I been looking into the JSON queries, but am not sure how much faster
they could be since it seems the point of that is to transmit a long
string across as well. As I understand it, the parsing would be faster
because JavaScript natively reads it.

Finally, I've glanced over HTTP requests, but I'm not sure about speed
gains there either, and I don't want to have to entirely retool my
server.

My question is thus: I'm fairly inexperienced at web development and
these sorts of client/server interactions. What would be the best way
to encode this data for quick transmission to the client?

Thanks.

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Re: Auto refresh data grid after x seconds

[Daniel Peterson]

You might try setting all your data into Labels and keeping the
references to the labels in a vector, arraylist, map, whatever.

Attach the labels to the grid using the setWidget method. Updating the
labels you have stored will update the grid entries.

I've done that with a FlexTable, though without the storage structure
for the labels. Hope this helps:

public class OverviewPanel extends Composite {

private FlexTable table;

private Label valFlow;
private Label valPower;
private Label valSource;
private Label valTarget;

public OverviewPanel(double flow, double power, doube source, double
target) {

overviewPanel = new HorizontalPanel();
overviewPanel.setStyleName(gwt-sb-label-no-bkgd);
overviewPanel.setWidth(600px);
initWidget(overviewPanel);

table = new FlexTable();
table.setCellSpacing(5);
overviewPanel.add(table);

valFlow = addDataSet(Flow:, gal, flow, 0, 0);
valPower = addDataSet(Power:, kW, power, 0, 4);
valSource = addDataSet(Source:, ft, source, 0, 6);
valTarget = addDataSet(Target:, ft, target, 0, 8);
}

public void updateData(double flow, double power, double source,
double target) {

valPower.setText(power.value);
valFlow.setText(flow.);
valSource.setText(source);
valTarget.setText(target);
}

public void add(Widget widget) {
overviewPanel.add(widget);
}

private Label addDataSet(String name, String units, double value, int
row, int startColumn) {
Label nameLabel = new Label(name);
table.setWidget(row, startColumn, nameLabel);

nameLabel.setHorizontalAlignment(HasHorizontalAlignment.ALIGN_RIGHT);

Label value = new Label(Double.toString(value));

value.setHorizontalAlignment(HasHorizontalAlignment.ALIGN_RIGHT);
value.setStyleName(gwt-sb-tag-value);
value.setWidth(50px);
table.setWidget(row, startColumn + 1, value);

Label unitsLabel = new Label(units);
table.setWidget(row, startColumn + 2, unitsLabel);

return value;
}
}

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