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How to pass the JSON object in java function using JSNI?

I am learning GWT, I am trying following example in which I have tried to pass the JSON object in java function.
public class HomeController implements EntryPoint {
public void onModuleLoad() {
createTestNativeFunction();
Presenter presenter = new PersenterImpl();
presenter.go(RootPanel.get());
}
public native void createTestNativeFunction()/*-{
parser: function() {
var that = this;
var jsonResult = JSON.parse({id:42,name:'yo'});
return this.#com.easylearntutorial.gwt.client.HomeController::onParse(Lorg/sgx/jsutil/client/JsObject;)(jsonResult);
}
void onParse(jsonResult){
System.out.println(jsonResult);
}
}
}-*/;
}
I am getting following errors:
Tracing compile failure path for type 'com.easylearntutorial.gwt.client.HomeController'
[ERROR] Errors in 'file:/C:/Users/ameen/workspace/Tutorial/src/com/easylearntutorial/gwt/client/HomeController.java'
[ERROR] Line 31: missing ; before statement
void onParse(jsonResult){
--------------------------------^
[ERROR] Hint: Check the inheritance chain from your module; it may not be inheriting a required module or a module may not be adding its source path entries properly
[WARN] Server class 'com.google.gwt.dev.shell.jetty.JDBCUnloader' could not be found in the web app, but was found on the system classpath
[WARN] Adding classpath entry 'file:/C:/Program%20Files/gwt-2.7.0/gwt-dev.jar' to the web app classpath for this session
For additional info see: file:/C:/Program%20Files/gwt-2.7.0/doc/helpInfo/webAppClassPath.html

You really should try to avoid JSNI. You can probably write 99% of your code not using JSNI at all. If you really need it, you should use the new JsInterop instead, documentation still in early stage but you can see this documentation here.
If you need to use JsInterop or JSNI it is usually because you need to wrap a JS lib, so first, try to find if it is already wrapped. If it is not you can always use some other wrapper library to learn how to wrap your JS lib.
OpenLayers JsInterop wrapper https://github.com/TDesjardins/gwt-ol3
OpenLayers JSNI wrapper (deprecated) https://github.com/geosdi/GWT-OpenLayers
Or explore github https://github.com/search?q=topic%3Agwt+topic%3Ajsinterop

System.out.println() is a java function, you are looking for console.log().
The body of the native is JavaScript, not Java.

You are declare you variable jsonResult into your parser: function(), jsonResult only exist into that function. Thats why the system say you that
missing ; before statement
Because you never declare the varieble into createTestNativeFunction().
Plus sjakubowski is right System.out.println() is a java function, you need to use console.log() on JavaScript.
Try this:
public native void createTestNativeFunction(){
var jsonResult = {};
parser: function() {
var that = this;
jsonResult = JSON.parse({id:42,name:'yo'});
return this.#com.easylearntutorial.gwt.client.HomeController::onParse(Lorg/sgx/jsutil/client/JsObject;)(jsonResult);
}
void onParse(jsonResult){
console.log(jsonResult);
}
}

I did the following to solve my errors.
public class HomeController implements EntryPoint {
public void onModuleLoad() {
createTestNativeFunction();
Presenter presenter = new PersenterImpl();
presenter.go(RootPanel.get());
}
// var jsonResult = JSON.parse({id:42,name:'yo'});
public native void createTestNativeFunction()/*-{
var that = this;
$wnd.testFunction = function(jsonResult) {
that.#com.easylearntutorial.gwt.client.HomeController::onParse(Lorg/sgx/jsutil/client/JsObject;)(jsonResult);
};
}-*/;
public void onParse(JsObject jsonResult){
int i =42;
}
}

Passing string and variable from one class to another. JAVA

I coded Chat in java with gui. Now I made a simple Login with MySQL. If you login you open main chat class. But problem is I want to pass username string from login class to main class.
How to do it. And how to pass variable from one to another class too. thx guys
CODE:
Here is where you login and it opens new class
Login class. login2.java
if (res.next()) {
JOptionPane.showMessageDialog(this, "Login Sucessfull.");
new ClientGUI("localhost", 1500);
dispose();
}
else {
JOptionPane.showMessageDialog(this, "Invalid User Name/Passw");
}
Thank you for help.

Here is what I would do...create a public variable or a public object like:
public static String keepInfo; // on top of your code
Instantiate it in your code by giving it whatever value you want in the constructor. Then the class that wants to call should create an object of the class. In your case, it would something like:
ClientGUI client = new ClientGUI();
// to call your String you can do something like:
String getInfo = client.keepInfo; // if you don't have get or set methods

gwt/jsni- Pass a String from external JS to Java

How can I call from external JS with JSNI?
For example:
//Some external JS code
...
this.onFeatureClick = function(event) {
...
var name = "Batman";
passToJava(name); //Invoke java method and pass String name
};
I tried this here:
public void onModuleLoad() {
...
nativeVariableName(); //Call native method
}
public static void passToJava(String name) {
System.out.println(name);
}
public native String nativeVariableName() /*-{
$wnd.passToJava = function(name) {
#com.google.myproject.webinterface.client.MyWebInterface::passToJava(Ljava/lang/String;)(name);
}; }-*/;
I don't even know if the call from JavaScript works.
Thanks.

This code works just fine. I don't know where do you expect to see result of invocation of System.out.println, but looks like you are looking into wrong place. Replace System.out.println with Window.alert and see for yourself. If it doesn't work, it means that error is in some other place:
Check if the function is correctly exposed (open console in browser,
and type window.passToJava, if it displays null, function wasn't
exposed)
Check if onFeatureClick is called correctly.

How to make a link betweeen the name a function and the actual function in java

I am building a user interface in netBeans (coding by hand, more flexible) with multiple toolbars.
What I am trying to do is create an actionListener for each button. I am retrieving names of the functions from XML and parse them to string. I will write implementations for those functions in a separate class, but my problem is the following:
How do I make the link between the function name and the string containing it's name?
Example: String is Open(), function will be Open(someParameter) and in the definitions class there will be static void Open(param).

First of all, consider my comment about your idea of dynamic button behavior resolved from strings being a wrong approach. However if you still need exactly what you asked, what you need is Reflection API.
Here's an example:
Class c = SomeClassWithMethods.class;
Method m = c.getMethod("someMethodName", String.class, Integer.class, Integer.TYPE);
m.invoke(baseObjectFromWhichToCallTheMethod, "stringParam", 10, 5);
Added:
Another option, which is a little bit prettier than reflection, but still a messy design, would be to use a map to link those Strings to methods. The code is a bit longer, but from the Java perspective it is much better than using reflection for your task (unless you have some specific requirement of which I'm not aware). This is how it would work:
//Interface whose instances will bind strings to methods
interface ButtonClickHandler {
void onClick();
}
class SomeClassYouNeed {
//One of the methods that will be bound to "onButtonOneClick()"
public void onButtonOneClick() {
log.info("ButtonOneClick method is called");
}
public void onButtonTwoClick() {
log.info("ButtonTwoClick method is called");
}
//Map that will hold your links
private static Map<String, ButtonClickHandler> buttonActionMap;
//Static constructor to initialize the map
static {
buttonActionMap = new Map<String, ButtonClickHandler>();
buttonActionMap.put("onButtonOneClick()",new ButtonClickHandler() {
#Override
public void onClick() {
onButtonOneClick();
}
});
buttonActionMap.put("onButtonTwoClick()",new ButtonClickHandler() {
#Override
public void onClick() {
onButtonTwoClick();
}
});
}
public void callByName(String methodName) {
final ButtonClickHandler handler = buttonActionMap.get(methodName);
if (handler == null) {
throw new IllegalArgumentException("No handler found by name: "+methodName);
}
handler.onClick();
}
}
After you call callByName("onButtonTwoClick()") it will fetch the respective instance of ButtonClickHandler which will use the static method onButtonTwoClick() to process the click of the button.

It seems to me that you are looking for the equivalent of JS "eval" function in Java. This might help. Nevertheless it is generally not a good idea as #Max stated, you might want to rethink your design.

If i have understood your question correctly you are trying to generate your code files based on some strings taken from a XML file. I can suggest you this library to generate your codes.
For tutorials you can visit this link.
You may even use the Java Reflection API. Here is a link for the tutorial.
Its upto you, that which of the above two you use.

Wicket: make a generated csv available to a dygraphs JavaScript

I'm trying to figure out how to make a dynamically generated csv available to a dygraphs JavaScript.
I'm using a wicket behavior to add the dygraph (JavaScript graph) to my markup like shown in the codesample bellow. Right now I've hardcoded it to use a csv file named "dygraph.csv". I want to change this, and instead make dygraph use the values from String csv, how do I achieve this?
Any help help is greatly appreciated.
public class DygraphBehavior extends AbstractBehavior {
private static final long serialVersionUID = -516501274090062937L;
private static final CompressedResourceReference DYGRAPH_JS = new CompressedResourceReference(DygraphBehavior.class, "dygraph-combined.js");
#Override
public void renderHead(IHeaderResponse response) {
response.renderJavascriptReference(DYGRAPH_JS);
}
#Override
public void onRendered(Component component) {
final String id = component.getId();
Response response = component.getResponse();
response.write(JavascriptUtils.SCRIPT_OPEN_TAG);
response.write("new Dygraph(document.getElementById(\""+id+"\"), \"dygraph.csv\", {rollPeriod: 7, showRoller: true, errorBars: true});");
response.write(JavascriptUtils.SCRIPT_CLOSE_TAG);
}
}
public class Dygraph extends WebPage {
public Dygraph() {
String csv = "Date,ms\n20070101,62\n20070102,62";
add(new ResourceLink<File>("csv", new ByteArrayResource("text/csv", csv.getBytes())));
add(new Label("graphdiv").add(new DygraphBehavior()));
}
}
<div>
<h1>Dygraph:</h1>
<div wicket:id="graphdiv" id="graphdiv" style="width:500px; height:300px;"></div>
<a wicket:id="csv" href="#">dl generated csv</a>
</div>

public class Dygraph extends WebPage {
public Dygraph() {
String csv = "Date,ms\n20070101,62\n20070102,62";
ResourceLink<File> link = new ResourceLink<File>("csv", new ByteArrayResource("text/csv", csv.getBytes()));
add( link );
//this is the url that should be passed to the javascript code
CharSequence url = link.urlFor( IResourceListener.INTERFACE );
add(new Label("graphdiv").add(new DygraphBehavior()));
}
}
There are other solutions based on the scope of your resource, maybe a dynamic shared resource would work better (if your graph parameters can simply be passed as url parameters), but this will work.

The JavaScript needs to see the data in some way after the page has been rendered. So you have two options:
Embed the data in the page (say in a hidden div) and then let JavaScript read the data from there as text.
Create a servlet where the JavaScript can download the data from.
The second option means that your page rendering code has to pass the data somehow to the servlet. You can try to put it into the session but then, it will sit there, occupying RAM. Probably not a problem if it's just a little bit of data and you have only a few users. But if that's not true, option #1 is probably better.