Develop Reference

Stopping RMI Server (Java)

I created a sucessful RMI server, thank god for that :)
It works perfectly..
I have a JForm and it gets activated clicking on a button.
Altough i wanted to create too a button to deactivate it, but i am having a problems to unexport it.
Ok then and this is the way i was trying to exporting and terminating the RMI Server
private void btStopServerActionPerformed(java.awt.event.ActionEvent evt) {
try {
// Nome do objecto
String objectname = txtObjectName.getText();
// obtem o número da porta
int port = Integer.parseInt(txtServerPort.getText());
RemoteMessageObject remote = new RemoteMessageObject();
Registry registry = LocateRegistry.getRegistry(port);
UnicastRemoteObject.unexportObject(LocateRegistry.getRegistry(port), true);
registry.unbind(objectname);
System.out.println("Server offline");
} catch (IOException ex) {
Logger.getLogger(ServerGUI.class.getName()).log(Level.SEVERE, null, ex);
} catch (NotBoundException ex) {
Logger.getLogger(ServerGUI.class.getName()).log(Level.SEVERE, null, ex);
}
}
I get this exception:
java.rmi.NoSuchObjectException: object not exported
at the line:
UnicastRemoteObject.unexportObject(LocateRegistry.getRegistry(port), true);
What am i doing wrong here?
Solved................
I discovered it before :P
Anywway thanks #EJP for the correct answer.
So the solution for me was to create the Register when the class starts as a public variable, so it could be use inside both click events (Start server and stop server).
I removed too a lot of nonsense stuff that was not necessary for disabling the RMI server just like #EJP sayed.
Its now working this way:
private void btStopServerActionPerformed(java.awt.event.ActionEvent evt) {
try {
// Nome do objecto
String objectname = txtObjectName.getText();
// obtem o número da porta
int port = Integer.parseInt(txtServerPort.getText());
Registry registry = LocateRegistry.getRegistry(port);
UnicastRemoteObject.unexportObject(this.registry, true);
registry.unbind(objectname);
System.out.println("Server offline");
} catch (IOException ex) {
GuiUtils.addText(txtLog, "Erro", "Servidor desligado");
btStopServer.setEnabled(false);
btStartServer.setEnabled(true);
} catch (NotBoundException ex) {
Logger.getLogger(ServerGUI.class.getName()).log(Level.SEVERE, null, ex);
}
}

You need to unexport the object returned by LocateRegistry.createRegistry(). The object returned by getRegistry() isn't the actual Registry object, it is a stub, and you can't unexport those.
But unexporting the Registry and then calling unbind() doesn't make sense. Doing it the other way round makes a little sense, but not much.
And you also have to unexport your own remote object.
And creating a new remote object in a method that is trying to unexport the existing one doesn't make sense either.

How to handle exception in my servlet correct

I have some problems making the exception do that i want!. I have created a servlet, which i want to handle all exceptions. My class building for this scenario that i need help too you see under here:
Servlet:
This exception handling is only for 1 method,
try {
completed = func.addNewOperator(userId, name, ini, cpr, password, role);
}catch (Exception e) {
Error = "There was a problem with database access";
response.sendRedirect("SystemError.jsp?Error_resultat=" + Error);
} catch (IOException e) {
Error = "Error found with connection";
response.sendRedirect("SystemError.jsp?Error_resultat=" + Error);
} catch (RuntimeException e) {
Error = "Error found with entered values";
response.sendRedirect("SystemError.jsp?Error_resultat=" + Error);
} catch (Exception e) {
Error = "Serious error found!";
response.sendRedirect("SystemError.jsp?Error_resultat=" + Error);
The func.addNewOperator is called in my function class:
Function:
A small example from my function method you see under here:
public boolean addNewOperator(String userId, String name, String ini, String cpr, String password, String role ) throws Exception {
int id = Integer.parseInt(userId);
}
So lets say if it can't parse it to and integer, it should throws the exception to my servlet, but this is not working. I want to throw the exception to the servlet, and then the servlet should send a response to open SystemError.jsp with an error message as parameter.
Can anyone see if i forgot something??

The order is whatever matches first, get's executed (as the JLS clearly explains).
If the first catch matches the exception, it executes, if it doesn't, the next one is tried and on and on until one is matched or none are.
So, when catching exceptions you want to always catch the most specific first and then the most generic (as RuntimeException or Exception).
Read more Order of catching exceptions in Java
catch (Exception e) should be last catch block in the chain.
It's worth reading Oracle Java Tutorial - Exceptions
Try in this way and don't forget to log the exception in log file.
try {
completed = func.addNewOperator(userId, name, ini, cpr, password, role);
}catch (SQLException e) {
Error = "There was a problem with database access";
} catch (IOException e) {
Error = "Error found with connection";
} catch (RuntimeException e) {
Error = "Error found with entered values";
} catch (Exception e) {
Error = "Serious error found!";
}
if(Error != null){
response.sendRedirect("SystemError.jsp?Error_resultat=" + Error);
}
NumberFormatException is a RuntimeException.

First, you should never redirect to a jsp page, but forward to it. Normally, jsp files are placed under WEB-INF and are never called directly but allways through server. Here is one example of forwarding (derived from from Java Tips - How to forward requests from Servlet to JSP :) :
request.setAttribute("error", error);
getServletConfig().getServletContext().getRequestDispatcher("/WEB-INF/SystemError.jsp")
.forward(request,response);
and your get error (first letter lowercased because it's a variable) in your jsp via ${error}
And anyway, you shouldn't deal with that at your servlet level but delegates this low level job to the container as explained in that other post from SO : How to Properly Handle Exceptions in a JSP/Servlet App?.

Java how to find out if a URL is http or https?

I am writing a web crawler tool in Java. When I type the website name, how can I make it so that it connects to that site in http or https without me defining the protocol?
try {
Jsoup.connect("google.com").get();
} catch (IOException ex) {
Logger.getLogger(LinkGUI.class.getName()).log(Level.SEVERE, null, ex);
}
But I get the error:
java.lang.IllegalArgumentException: Malformed URL: google.com
What can I do? Are there any classes or libraries that do this?
What I'm trying to do is I have a list of 165 Courses, each with 65 - 71 html pages with links all throughout them. I am writing a Java program to test if the link is broken or not.

You can write your own simple method to try both protocols, like:
static boolean usesHttps(final String urlWithoutProtocol) throws IOException {
try {
Jsoup.connect("http://" + urlWithoutProtocol).get();
return false;
} catch (final IOException e) {
Jsoup.connect("https://" + urlWithoutProtocol).get();
return true;
}
}
Then, your original code can be:
try {
boolean shouldUseHttps = usesHttps("google.com");
} catch (final IOException ex) {
Logger.getLogger(LinkGUI.class.getName()).log(Level.SEVERE, null, ex);
}
Note: you should only use the usesHttps() method once per URL, to figure out which protocol to use. After you know that, you should connect using Jsoup.connect() directly. This will be more efficient.

retrieve openID-url using openid4java

Consider the following code excerpt:
String openIDProviderURL = "https://www.google.com/accounts/o8/id";
try {
URI loc = getUI().getPage().getLocation();
List discoveries = manager.discover(openIDProviderURL);
DiscoveryInformation discovered = manager.associate(discoveries);
getUI().getSession().setAttribute("openid-disc", discovered);
AuthRequest authReq = manager.authenticate(discovered, "http://"+loc.getHost()+":"+loc.getPort()+loc.getPath());
FetchRequest fetch = FetchRequest.createFetchRequest();
authReq.addExtension(fetch);
System.out.println("DEST URL: "+authReq.getDestinationUrl(true));
getUI().getPage().setLocation(authReq.getDestinationUrl(true));
} catch (DiscoveryException ex) {
Logger.getLogger(NavigatorUI.class.getName()).log(Level.SEVERE, null, ex);
} catch (MessageException ex) {
Logger.getLogger(NavigatorUI.class.getName()).log(Level.SEVERE, null, ex);
} catch (ConsumerException ex) {
Logger.getLogger(NavigatorUI.class.getName()).log(Level.SEVERE, null, ex);
}
}
Authentication with Google works, however, can anyone tell me how to extract the actual openID-identifier-URL from the objects I'm using here? When the authentication succeeds, it lets me now by writing "INFO: Verification succeeded for: https://www.google.com/accounts/o8/id?blablabla", but so far, I haven't found a way to access this very URL in the program. Could someone help me out please?
PS: I have been going through older posts dealing with openID4java. However, they all deal with failed authentication and the likes, which for me isn't the problem. If this very question has been asked before, I apologise.

Jersey: what does "couldn't find grammar element" mean?

After upgrading Jersey from version 1.15 to 1.17 it started to log the following messages:
Apr 2, 2013 5:13:06 PM com.sun.jersey.server.wadl.generators.AbstractWadlGeneratorGrammarGenerator attachTypes
INFO: Couldn't find grammar element for class java.lang.String
An example of a service that produces such a message:
#GET
#Path("/bla/{a}")
#Produces("application/json")
public String doStuff(#PathParam("a") String a) {
return a;
}
My first impression would be to consider this an error message, purely based on the way the message is phrased ("couldn't find"). However, it's logged at a level of INFO, and it doesn't seem to have any effects in practice since all services continue to work.
So my question is whether these log messages indicate a (potential) problem with the way we are configuring or using Jersey. Since it didn't happen with the previous version I already checked the release notes, but didn't find anything related.

I had the same "info" message as well. I didn't manage to fix it (yet) for basic java types (Boolean, String...) but for my own custom classes if I add the #XmlRootElement annotation and a default no-param constructor the message dissapears.
Digging into jersey source code I noticed the class "WadlGeneratorJAXBGrammarGenerator" the following code :
Object parameterClassInstance = null;
try {
Constructor<?> defaultConstructor = type.getDeclaredConstructor();
defaultConstructor.setAccessible(true);
parameterClassInstance = defaultConstructor.newInstance();
} catch (InstantiationException ex) {
LOGGER.log(Level.FINE, null, ex);
} catch (IllegalAccessException ex) {
LOGGER.log(Level.FINE, null, ex);
} catch (IllegalArgumentException ex) {
LOGGER.log(Level.FINE, null, ex);
} catch (InvocationTargetException ex) {
LOGGER.log(Level.FINE, null, ex);
} catch (SecurityException ex) {
LOGGER.log(Level.FINE, null, ex);
} catch (NoSuchMethodException ex) {
//getting here for Boolean/String and some other primitive data type
LOGGER.log(Level.FINE, null, ex);
}
if (parameterClassInstance==null) {
return null;
}
So basically there is no default constructor for String, Boolean and few others then it throws a NoSuchMethodException therefore it return nulls and log the info message.
So still no idea why it happens but in my case the solution was to disable the wadl generation since I was not using it.
Just add the following param to your web.xml
<init-param>
<param-name>com.sun.jersey.config.feature.DisableWADL</param-name>
<param-value>true</param-value>
</init-param>