I asked a similar question to this recently, but I did a bad job at explaining it, so I am going to try again.
I cannot figure this out for the life of me. I have to do two different java files for this programming assignment, and when running the program from command prompt I get an error that says it cannot find symbol of when I create my object in the second class, and when I run the code in Eclipse I get the error "Error occurred during initialization of boot layer
java.lang.LayerInstantiationException: Package jdk.internal.jrtfs in both module jrt.fs and module java.base".
I even copied an example straight from the textbook to understand it, but it isn't working even though I have exactly what's in the textbook. The pastebin links are for the two classes that come from the textbook examples.
Please someone tell me what's wrong here.
First class: https://pastebin.com/KYHtDHPt
public class Account {
private String name;
public Account(String name) {
this.name = name;
}
public String getName() {
return name;
}
}
Second class: https://pastebin.com/ADUsjjaR
public class AccountTest {
public static void main(String[] args) {
Account account1 = new Account("Brandon Williams");
System.out.printf("Account one is: %s%n",account1.getName());
}
}
I'm searching for a concept to forward an object to subobjects.
Example:
I would like to create log files for several main Objects, that include sub objects (imagine a REST server that would log every single connection by ID).
Creating one big log file is simple ( redirect System.out.println, I already encapsulated that)
Example code:
class SubElementA{
public SubElementA(){
Debugger.debug("I am called, too");
}
}
Application.java
package com.dev4ag;
class Application{
private ElementA elA;
private String prefix;
public Application(String name){
this.elA = new ElementA();
this.prefix = name;
}
public void countUp(){
Debugger.debug(this.prefix+": I will now count up");
this.elA.doSomeStuff();
}
}
ElementA.java
package com.dev4ag;
class ElementA{
private int counter;
private SubElementA subElementA;
public void doSomeStuff(){
counter++;
Debugger.debug("Counter is: "+counter);
}
//Constructor
public ElementA(){
subElementA = new SubElementA();
this.counter = 0;
};
}
SubElementA.java
package com.dev4ag;
class SubElementA{
public SubElementA(){
Debugger.debug("I am called, too");
}
}
Debugger.java
package com.dev4ag;
public class Debugger {
public static void debug(String output){
//Just imagine we would write to a file here ;)
System.out.println(output);
}
}
(it was more easy to write system.out.println than to create a file, just imagine, Debugger.debug would write to a file).
Now I am thinking about a solution to create one Debug output target for each App. I could definitely change debug to not being static and create a debug object within Application.
But is there any way to use this object in the sub classes without forwarding the debug object either through Constructor or setter function, which would mean to have to add an object for the debugger to each class?
What would be the most beautiful solution for that?
Note that this solution might decrease performance a lot and it is pretty dirty way, but some loggers include such data.
But you can use Thread.currentThread().getStackTrace() to get stacktrace like in error and get class and method from where your method was called.
If you are using java9+ then you should probably use StackWalker API instead, especially that it have nice filters and other useful features.
So then you could guess app by class/method names on the stack.
I'm building a Wicket 1.6 application.
In this I have a Parameter class and a FillParameter class to translate org.apache.wicket.PageParameters to my own Parameter class. The Parameter class has defaults (which are set during creation), the FillParameter has min/max values I check on. Both the default values as the min/max values are loaded from a text_resource.properties file using StringResourceModel.
example (line 15):
private int offset = Integer.parseInt((new StringResourceModel("bla.bla.bla.offset", null)).getString());
So far so good. This is working fine in my Wicket application.
Now I'm working on my junit tests and I want to test my FillParameters.class. This is a snippet from my current FillParametersTest.class:
private WicketTester wicketTester;
#Mock
Localizer localizer = mock(Localizer.class);
#Before
public void init() {
wicketTester = new WicketTester(MyApplication.class);
when(localizer.getString(eq("bla.bla.bla.offset"), (Component)anyObject(), anyString())).thenReturn("0");
wicketTester.getApplication().getResourceSettings().setLocalizer(localizer);
}
#Test
public void fillParametersGoodTest() {
PageParameters pageParameters = new PageParameters("pOffset=0");
Parameters parameters = FillParameters.fillParameters(pageParameters, parameters);
Assert.assertEquals(parameters.getOffset(), 0);
}
Alas, this is not working. The test seems to find the resource, but it doesn't get the value from that resource, resulting in:
java.lang.NumberFormatException: null
at java.lang.Integer.parseInt(Integer.java:454)
at java.lang.Integer.parseInt(Integer.java:527)
at bla.bla.bla.Parameters.<init>(Parameters.java:15)
at bla.bla.bla.FillParametersTest.fillParametersGoodTest(FillParametersTest.java:63)
(line 15 in Parameters is the example I've mentioned above)
I've been searching for a solution to my problem, but I can only find good examples on how to read from a resource in the test class, not how to make it work in a application class called by the test class.
I hope I've made my problem clear, and that someone can help me with it. I'm quite new to wicket, but eager to learn.
Problem: how can I read text_resources during junit test with StringResourceModel?
Answer 27 feb 2015
Ok, so I've refactored my whole application and now I've got the code working, and it's actually very simple
private WicketTester wicketTester;
#Before
public void init() {
tester = new WicketTester(MyApplication.class);
}
#Test
public void fillParametersGoodTest() {
MockRequestParameters pageParameters = new MockRequestParameters();
pageParameters.addParameterValue("offset", "0");
FillParameters fp = new FillParameters();
Parameters parameters = fpo.fillParameters(pageParameters, parameters);
Assert.assertEquals(parameters.getOffset(), 0);
}
I'm pretty sure the problem is in your Mockito rule (the when):
when(localizer.getString(eq("bla.bla.bla.offset"), (Component)anyObject(), anyString())).thenReturn("0");
It doesn't match the real call and thus later the value is null.
Play in this area.
I'm trying to create a Web Service with Axis2 and Tomcat 7. Everything is working great except I don't understand the following behavior:
I've created a Web Service with 2 operations, one sets an int local variable and the other one returns it, code looks like this:
package testServer;
public class service {
public int number;
public void setNumber(int i){ this.number = i; }
public int getNumber(){ return this.number; }
}
Client side looks like this:
package testserver;
import java.rmi.RemoteException;
import testserver.ServiceStub;
import testserver.ServiceStub.*;
public class CallService {
public CallService(){};
public void call() throws RemoteException{
ServiceStub s = new ServiceStub();
ServiceStub.SetNumber params = new ServiceStub.SetNumber();
params.setI(2);
s.setNumber(params);
ServiceStub.GetNumber n = new ServiceStub.GetNumber();
ServiceStub.GetNumberResponse r = s.getNumber(n);
System.out.println("number is: " + r.get_return());
}
}
Now, I'm expecting to get a "number is: 2" but instead I'm getting a "number is: 0". Can Anyone explain that to me please?
Because at each invocation, a different instance of the class is used.
In the client, you only have a ServiceStub instance. But the server is creating a new instance of Service (check CAPITALIZATION!!) for each request you make.
This is not as bad as you may think, think that the server does not really know where the requests are from.
To get the 2, you could make the variable static, just for testing. The "real" solution would be calling your server business logic methods (EJBs, POJOs) and have them store and retrieve the value.
I've run through the Google Web Toolkit StockWatcher Tutorial using Eclipse and the Google Plugin, and I'm attempting to make some basic changes to it so I can better understand the RPC framework.
I've modified the "getStocks" method on the StockServiceImpl server-side class so that it returns an array of Stock objects instead of String objects. The application compiles perfectly, but the Google Web Toolkit is returning the following error:
"No source code is available for type com.google.gwt.sample.stockwatcher.server.Stock; did you forget to inherit a required module?"
It seems that the client-side classes can't find an implementation of the Stock object, even though the class has been imported. For reference, here is a screenshot of my package hierarchy:
I suspect that I'm missing something in web.xml, but I have no idea what it is. Can anyone point me in the right direction?
EDIT: Forgot to mention that the Stock class is persistable, so it needs to stay on the server-side.
After much trial and error, I managed to find a way to do this. It might not be the best way, but it works. Hopefully this post can save someone else a lot of time and effort.
These instructions assume that you have completed both the basic StockWatcher tutorial and the Google App Engine StockWatcher modifications.
Create a Client-Side Implementation of the Stock Class
There are a couple of things to keep in mind about GWT:
Server-side classes can import client-side classes, but not vice-versa (usually).
The client-side can't import any Google App Engine libraries (i.e. com.google.appengine.api.users.User)
Due to both items above, the client can never implement the Stock class that we created in com.google.gwt.sample.stockwatcher.server. Instead, we'll create a new client-side Stock class called StockClient.
StockClient.java:
package com.google.gwt.sample.stockwatcher.client;
import java.io.Serializable;
import java.util.Date;
public class StockClient implements Serializable {
private Long id;
private String symbol;
private Date createDate;
public StockClient() {
this.createDate = new Date();
}
public StockClient(String symbol) {
this.symbol = symbol;
this.createDate = new Date();
}
public StockClient(Long id, String symbol, Date createDate) {
this();
this.id = id;
this.symbol = symbol;
this.createDate = createDate;
}
public Long getId() {
return this.id;
}
public String getSymbol() {
return this.symbol;
}
public Date getCreateDate() {
return this.createDate;
}
public void setId(Long id) {
this.id = id;
}
public void setSymbol(String symbol) {
this.symbol = symbol;
}
}
Modify Client Classes to Use StockClient[] instead of String[]
Now we make some simple modifications to the client classes so that they know that the RPC call returns StockClient[] instead of String[].
StockService.java:
package com.google.gwt.sample.stockwatcher.client;
import com.google.gwt.sample.stockwatcher.client.NotLoggedInException;
import com.google.gwt.user.client.rpc.RemoteService;
import com.google.gwt.user.client.rpc.RemoteServiceRelativePath;
#RemoteServiceRelativePath("stock")
public interface StockService extends RemoteService {
public Long addStock(String symbol) throws NotLoggedInException;
public void removeStock(String symbol) throws NotLoggedInException;
public StockClient[] getStocks() throws NotLoggedInException;
}
StockServiceAsync.java:
package com.google.gwt.sample.stockwatcher.client;
import com.google.gwt.sample.stockwatcher.client.StockClient;
import com.google.gwt.user.client.rpc.AsyncCallback;
public interface StockServiceAsync {
public void addStock(String symbol, AsyncCallback<Long> async);
public void removeStock(String symbol, AsyncCallback<Void> async);
public void getStocks(AsyncCallback<StockClient[]> async);
}
StockWatcher.java:
Add one import:
import com.google.gwt.sample.stockwatcher.client.StockClient;
All other code stays the same, except addStock, loadStocks, and displayStocks:
private void loadStocks() {
stockService = GWT.create(StockService.class);
stockService.getStocks(new AsyncCallback<String[]>() {
public void onFailure(Throwable error) {
handleError(error);
}
public void onSuccess(String[] symbols) {
displayStocks(symbols);
}
});
}
private void displayStocks(String[] symbols) {
for (String symbol : symbols) {
displayStock(symbol);
}
}
private void addStock() {
final String symbol = newSymbolTextBox.getText().toUpperCase().trim();
newSymbolTextBox.setFocus(true);
// Stock code must be between 1 and 10 chars that are numbers, letters,
// or dots.
if (!symbol.matches("^[0-9a-zA-Z\\.]{1,10}$")) {
Window.alert("'" + symbol + "' is not a valid symbol.");
newSymbolTextBox.selectAll();
return;
}
newSymbolTextBox.setText("");
// Don't add the stock if it's already in the table.
if (stocks.contains(symbol))
return;
addStock(new StockClient(symbol));
}
private void addStock(final StockClient stock) {
stockService.addStock(stock.getSymbol(), new AsyncCallback<Long>() {
public void onFailure(Throwable error) {
handleError(error);
}
public void onSuccess(Long id) {
stock.setId(id);
displayStock(stock.getSymbol());
}
});
}
Modify the StockServiceImpl Class to Return StockClient[]
Finally, we modify the getStocks method of the StockServiceImpl class so that it translates the server-side Stock classes into client-side StockClient classes before returning the array.
StockServiceImpl.java
import com.google.gwt.sample.stockwatcher.client.StockClient;
We need to change the addStock method slightly so that the generated ID is returned:
public Long addStock(String symbol) throws NotLoggedInException {
Stock stock = new Stock(getUser(), symbol);
checkLoggedIn();
PersistenceManager pm = getPersistenceManager();
try {
pm.makePersistent(stock);
} finally {
pm.close();
}
return stock.getId();
}
All other methods stay the same, except getStocks:
public StockClient[] getStocks() throws NotLoggedInException {
checkLoggedIn();
PersistenceManager pm = getPersistenceManager();
List<StockClient> stockclients = new ArrayList<StockClient>();
try {
Query q = pm.newQuery(Stock.class, "user == u");
q.declareParameters("com.google.appengine.api.users.User u");
q.setOrdering("createDate");
List<Stock> stocks = (List<Stock>) q.execute(getUser());
for (Stock stock : stocks)
{
stockclients.add(new StockClient(stock.getId(), stock.getSymbol(), stock.getCreateDate()));
}
} finally {
pm.close();
}
return (StockClient[]) stockclients.toArray(new StockClient[0]);
}
Summary
The code above works perfectly for me when deployed to Google App Engine, but triggers an error in Google Web Toolkit Hosted Mode:
SEVERE: [1244408678890000] javax.servlet.ServletContext log: Exception while dispatching incoming RPC call
com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract com.google.gwt.sample.stockwatcher.client.StockClient[] com.google.gwt.sample.stockwatcher.client.StockService.getStocks() throws com.google.gwt.sample.stockwatcher.client.NotLoggedInException' threw an unexpected exception: java.lang.NullPointerException: Name is null
Let me know if you encounter the same problem or not. The fact that it works in Google App Engine seems to indicate a bug in Hosted Mode.
GWT needs the .java file in addition to the .class file. Additionally, Stock needs to be in the "client" location of a GWT module.
The GWT compiler doesn't know about Stock, because it's not in a location it looks in. You can either move it to the client folder, or if it makes more sense leave it where it is and create a ModuleName.gwt.xml that references any other classes you want, and get your Main.gwt.xml file to inherit from that.
eg: DomainGwt.gwt.xml
<module>
<inherits name='com.google.gwt.user.User'/>
<source path="javapackagesabovethispackagegohere"/>
</module>
and:
<module rename-to="gwt_ui">
<inherits name="com.google.gwt.user.User"/>
<inherits name="au.com.groundhog.groundpics.DomainGwt"/>
<entry-point class="au.com.groundhog.groundpics.gwt.client.GPicsUIEntryPoint"/>
</module>
There's a better answer here: GWT Simple RPC use case problem : Code included
Basically, you can add parameters to your APPNAME.gwt.xml file so the compiler to give the compiler a path to the server-side class.
I was getting the same issue and the "mvn gwt:compile" output was not very helpful.
Instead, when I tried deploying to tomcat (via the maven tomcat plugin: mvn tomcat:deploy) I got helpful error messages.
A few things I had to fix up:
Make the object that is sent from the client to the server implement Serializable
Add an empty-arg constructor to that same object
Yes, it is sure that we need to use the Serialization for getting the server objects to the client. These modile?? file settings won't work to use the Stock class in the client side.
In your case you have only one class Stock and you can create a StockClient in client side. It is easy. But what will be the solution if anyone having more classes. Something like the properties of this class are also some other type of classes.
Example: stock.getEOD(date).getHigh();
getEOD will return another class with the given date and that class has the getHigh method.
What to do in such big cases? I don't think creating all classes implementing serialization in client side is good for that. Then we have to write code in both server and client. all classes two times.
Keying off of rustyshelf's answer above ...
In my case I needed to edit the ModuleName.gwt.xml file and add the following:
<source path='client'/>
<source path='shared'/>
I created my project with the New->Web Application Project wizard but unchecked the Generate project sample code option. I then created the shared package. Had I not unchecked that, the package would have been created for me and the xml file modified per the above.
There is a far more simple and easy solution for that. If you want to send an object of your custom designed class from server side to client side you should define this custom class in shared package.
For example for your case the you just have to carry the Stock.java class (by drag and drop) into
com.google.gwt.sample.stockwatcher.shared
package. However from your package hierarchy screenshot it seems that you had deleted this shared package. Just re-create this package and drop the Stock.java inside it and let the game begin.