Here are some bullet points to understand the working of RMI registry in Java:-

RMIRegistry is run on the server machine.

RMIRegistry is a remote object itself binding to a well known port 1099.

When the server is run, in the UnicastRemoteObject’s constructor it exports itself on an anonymous port on the server machine.( This port is unknown to the client).

When Naming.rebind() is called, a reference to the Implementation class is passed as the second parameter.
Naming.rebind(“rmi://localhost:1099/refName”,inst);

The naming class uses the getClass() method to get the name of the server class and adds _Stub to it to get the name of the stub class.

It then loads the stub class into the JVM.

A RemoteRef object is obtained from the server implementation class instance (inst) passes to it. RemoteRef ref = inst.getRef();
This RemoteRef object encapsulated all the details about the server (hostname, port etc)

A stub instance is created by passing the RemoteRef object to it.
ServerImpl_Stub stub = new ServerImpl_Stub(ref);

This instance is passed to the RMIRegistry for binding along with the public name (refName).

When the client executes Naming.lookup() it passes the public name to the RMIRegistry. The registry then returns the stub object stored against that name to the client.

Installation on Windows

Here I will detail the steps required to get your PHP + Apache2 + MYSQL setup up and running.

Steps:
1. Download Apache2 from the location: http://httpd.apache.org/download.cgi
2. Install Apache2 server to the desired location (say: C:\Apache2\).
3. Test that the server is installed properly by starting Apache and opening the url http://localhost/ in a browser. If you get an apache welcome screen, you have successfully installed Apache2 server else check your installation.
4. Download PHP interpreter from http://www.php.net/downloads.php You can either download the auto-installer or the binary zip pack. I prefer zip pack it exposes you to the internal configurations required.
5. Extract the files from the PHP binary zip to the directory which you want to make PHP home (say: C:\PHP\).
6. Add the PHP home directory (‘C:\PHP\’) to the PATH environment variable. (Right click ‘My Computer’ -> select properties -> Go to Advanced tab -> Select the ‘Environment Variables’ button -> Edit the ‘path’ variable’).
7. Restart your system for the PATH variable changes to come in effect.
8. Test your PHP setup by typing ‘php -v’ in a command prompt. If you get any error message please check you installation, else you are ready to proceed further.
9. Now move to your PHP home directory (‘C:\PHP\’) and rename the file php.ini-recommended to php.ini.
10. If you are going to use this setup for testing purpose perform this step else skip to the next step. Open the ‘php.ini’ file in text editor and set ‘display_errors = On’ this will enable easy debugging.
11. Open the ‘php.ini’ file and set ‘doc_root’ to your \htdocs directory. (doc_root = C:\Apache2\htdocs).
12. Set the ‘extension_dir’ property to the \ext directory. (extension_dir = C:\PHP\ext\).
13. Save the changes done to ‘php.ini’ file in Steps 10-12.
14. Open the ‘httpd.conf’ file present in your \conf directory (‘C:\Apache2\conf\httpd.conf’) in a text editor and perform the following changes.
15. Add line ‘LoadModule php5_module /php5apache2.dll’ (‘LoadModule php5_module C:/PHP/php5apache2.dll’) to the LoadModule section in the ‘httpd.conf’ file. *Note those are foward slashes, not backslashes, in the path.
16. Add line ‘AddType application/x-httpd-php .php’ (as it is) to the ‘AddType’ section in the httpd.conf file.
17. Add line ‘PHPIniDir ‘ (PHPIniDir C:/PHP/) to any location in your httpd.conf file. *Again note those are foward slashes, not backslashes, in the path.
18. Save your ‘httpd.conf’ file with the changes done in Step 16-18.
19. Restart your Apache2 server.
20. Create an html page (say: phpinfo.php) containing line ” as part of the body, in your \htdocs directory (C:\Apache2\htdocs). Now open the browser and point it to this page (‘http://localhost/phpinfo.php’).
21. If you get page containing details of your PHP installion then your setup is correct and running fine, else please check your setup by repeating the above steps.
22. Now we will setup the PHP for MYSQL database.
23. Download the MYSQL server and install it to your prefered location.
24. Now check the page that you created in step-20 to see if it contains details of MYSQL. If it dows then your PHP is already configured for MYSQL no need to read further you can start coding/testing in PHP now.
25. If you are not getting MYSQL details, you need to do some more configurations.
26. Open the file ‘php.ini’ present in your PHP home directory (‘C:\PHP\’) in a text editor and uncomment the line ‘extension=php_mysql.dll’ save the file and restart your Apache2 server.
27. Now recheck the page created in step-20. This time you should see a section on MYSQL. If so your setup is successfully done and ready for use else check your installation again.

TurboGear setup

Python come pre-installed with most of the linux version. To install the TurboGear pack just type

• yum install TurboGears

This will install the TurboGears package on your system. Use the following command to check if the installation was success.

• tg-admin info

Now we will install easy_install utility that will make the installation of other TurboGear modules a breeze.
To install easy_install utility download the ez_setup.py script and run it.

• python ez_setup.py

This will install the easy_install utility on your system.

Some of the turbo gear modules that are necessary are SQLObject and database specific modules ( as mysql-python ).You can install these by simply invoking the easy_install utility with the module name as parameter.

• easy_install SQLObject
• easy_install mysql-python

Your TurboGear setup is ready for use.
Have a look at the following tutorial for getting started with TurboGears.

• TurboGears Tutorial: Social Bookmarking Application | Ayman Hourieh’s Blog

Secure login without HTTPS

HTTPS is used on www to provide secured encrypted message communication between the browser and the web server. Though we can not match HTTPS in terms of the security provided, but still we can provide some level of security to the users by encrypting the data sent over HTTP. We can easily encrypt the sensitive user data such as username and password, by using asynchronous/public-key encryption mechanism.

This can be achieved by using javascript or java-applets to encrypt the login data submitted by the users. This simple encryption ensures that an eavesdropper is not able to comprehend the information sent over the network. To prevent the replay attack we should add some unique server generated information to the user data before encryption.

The simplest example will be to use the GnuPG to generate public-private key pairs. On the client side ( i.e. for the browser pages ) we can use javascripts to encrypt the data and on the server side we can directly call the gpg utililty to obtain the original message from the encrypted data.

Short simple questions — Set 8

1 Why do u use Session Tracking in HttpServlet ?

2 Can u use javaScript in Servlets ?

3 What is the capacity the doGet can send to the server ?

4 What are the type of protocols used in HttpServlet ?

5 Difference between TCP/IP and IP protocol ?

6 Why do you use UniCastRemoteObject in RMI ?
In order to get functionalities related to being remote .

7 How many interfaces are used in RMI?

8 Can Rmi registry be written in the code, without having to write it in the command prompt and if yes where?
9 Why is Socket used ?

10 What are the types of JDBC drivers ?

11 Explain the third driver(Native protocol driver) ?

12 Which among the four driver is pure Java driver ?

13 What are the Isolation level in JDBC transaction ?

14 How do you connect with the database ?

15 How do you connect without the Class.forName (” “) ?

16 What does Class.forName return ?

17 What are the types of statement ?

18 Why is preparedStatement,CallableStatement used for?

19 Difference between AWT and Swing compenents ?

20 Can the Swing application if you upload in net, be compatible with your
browser?

21 What should you do get your browser compatible with swing components?

22 What are the methods in Applet ?

23 When is init(),start() called ?

24 When you navigate from one applet to another what are the methods called ?

25 What is the difference between Trusted and Untrusted Applet ?

26 What is Exception ?

27 What are the ways you can handle exception ?

28 When is try,catch block used ?

29 What is finally method in Exceptions ?

30 What are the types of access modifiers ?

31 What is protected and friendly ?

32 What are the other modifiers ?

33 Is synchronised modifier ?

34 What is meant by polymorphism ?
35 What is inheritance ?

36 What is method Overloading ? What is this in OOPS ?

37 What is method Overriding ? What is it in OOPS ?

38 Does java support multi dimensional arrays ?

39 Is multiple inheritance used in Java ?

40 How do you send a message to the browser in JavaScript ?

41 Does javascript support multidimensional arrays ?

42 Why is XML used mainly?

43 What is DTD ?

44 Is there any tool in java that can create reports ?

45 Describe an object.

46 What are sockets?

47 What are threads?

48 What’s the difference between UDP and TCP?

49 What is the difference between a static and non-static field (Java)

50 What’s the difference between a stack and a Queue?

Short simple questions — Set 8

1 What is meant by RMI ?

2 Explain RMI Architecture ?

3 What is meant by a stub ?

4 What is meant by a skelotn ?

5 What is meant by serialisation and deserialisation ?

6 What is meant by RRL ?
Resilient Routing Layers implementation.

7 What is the use of TL ?

8 What is RMI Registry ?

9 What is rmic ?

10 How will you pass parameter in RMI ?

11 What exceptions are thrown by RMI ?

12 What are the steps involved in RMI ?

13 What is meant by bind(), rebind(), unbind() and lookup() methods

14 What are the advanatages of RMI ?

15 What is JNI ?

16 What is Remote Interface ?

17 What class is used to create Server side object ?

18 What class is used to bind the server object with RMI Registry ?
Naming.rebind( , );

19 What is the use of getWriter method ?

20 What is meant by Javabeans ?

21 What is JAR file ?
An archieve of java classes.
22 What is meant by manifest files ?

23 What is Introspection ??????????

24 What are the steps involved to create a bean ?

25 Say any two properties in Beans ?

26 What is persistence ?

27 What is the use of beaninfo ?

28 What are the interfaces you used in Beans ?

29 What are the classes you used in Beans ?

30 What is Entity Bean and Session Bean ?

31 What are the methods of Entity Bean?

32 How does Stateful Session bean store its state ?

33 Why does Stateless Session bean not store its state even though it has
34 ejbActivate and ejbPassivate ?

35 What are the services provided by the container ?

36 Types of transaction ?

37 What is bean managed transaction ?

38 Why does EJB needs two interface( Home and Remote Interface) ?

39 What are transaction attributes ?

40 What is the difference between Container managed persistent bean and Bean

41 managed persistent entity bean ?

42 What is J2EE ?

43 What is JTS ?

44 How many entity beans used and how many tables can u use in EJB project ?

45 What is scalable,portability in J2EE?

46 What is Connection pooling?Is it advantageous?

47 Method and class used for Connection pooling ?

48 How to deploy in J2EE(i.e Jar,War file) ?

49 How is entity bean created using Container managed entity bean ?

50 Sotware architechture of EJB ?

51 In Entity bean will the create method in EJB home and ejbCreate in Entity bean have the same parameters ?

52 What methods do u use in Servlet – Applet communication ?

53 What are the types of Servlet ?

54 Difference between HttpServlet and Generic Servlets ?

55 Difference between doGet and doPost ?

56 What are the methods in HttpServlet?

57 What are the types of SessionTracking?

58 What is Cookie ? Why is Cookie used ?

60 If my browser does not support Cookie,and my server sends a cookie instance What will happen ?

Short simple questions — Set 7

1 What is the class in Swing to change the appearance of the Frame in

2 What is JDBC ?

3 How do you connect to the database ? What are the steps ?

4 What are the drivers available in JDBC ? Explain

5 How can you load the driver ?

6 What are the different types of statement s ?

7 How can you created JDBC statements ?

8 How will you perform transactions using JDBC ?

9 What are the two drivers for web apllication?

10 What are the different types of 2 tier and 3 tier architecture ?

11 How can you retrieve warning in JDBC ?

12 What is the exception thrown by JDBC ?

13 What is meant by PreparedStatement ?

14 What is difference between PreparedStatement and Statement ?

15 How can you call the stored procedures ?

16 What is meant by a ResultSet ?

17 What is the difference between ExecuteUpdate and ExecuteQuery ?

18 How do you know which driver is connected to a database ?

19 What is meant by TCP, IP, UDP ?

20 What is the difference between TCP and UDP ?

21 What is a proxy server ?

22 What is meant by URL

23 What is a socket and server sockets ?

24 When MalformedURLException and UnknownHost Exception throws ?

25 What is InetAddress ?

26 What is datagram and datagram packets and datagram sockets ?

27 Write the range of multicast socket IP address ?

28 What is meant by a servlet ?

29 What are the types of servlets ? Explain

30 What is the different between a Servlet and a CGI.

31 What is the difference between 2 types of Servlets ?

32 What is the type of method for sending request from HTTP server ?

33 What are the exceptions thrown by Servlets ? Why ?

34 What is the life cycle of a servlet ?

35 What is meant by cookies ?

36 What is HTTP Session ?

37 What is the difference between GET and POST methods ?

38 How can you run a Servlet Program ?

39 How to communicate between an applet and a servlet ?

40 What is a Servlet-to-Servlet communcation ?

41 What is Session Tracking ?

42 What are the security issues in Servlets ?

43 What is HTTP Tunneling

44 How do you load an image in a Servlet ?

45 What is Servlet Chaining ?

46 What is URL Rewriting ?

47 What is context switching ?

Short simple questions — Set 6

1 What is the life cycle of an Applet ?

2 How do you load an HTML page from an Applet ?

3 What is meant by Applet Stub Interface ?

4 What is meant by getCodeBase and getDocumentBase method ?

5 How can you call an applet from a HTML file

6 What is meant by Applet Flickering ?

7 What is the use of parameter tag ?

8 What is audio clip Interface and what are all the methods in it ?

9 What is the difference between getAppletInfo and getParameterInfo ?

10 How to communicate between applet and an applet ?

11 What is meant by event handling ?

12 What are all the listeners in java and explain ?

13 What is meant by an adapter class ?

14 What are the types of mouse event listeners ?

15 What are the types of methods in mouse listeners ?

16 What is the difference between panel and frame ?

17 What is the default layout of the panel and frame ?

18 What is meant by controls and types ?

19 What is the difference between a scroll bar and a scroll panel.

20 What is the difference between list and choice ?

21 How to place a component on Windows ?

22 What are the different types of Layouts ?

23 What is meant by CardLayout ?

24 What is the difference between GridLayout and GridBagLayout

25 What is the difference between menuitem and checkboxmenu item.

26 What is meant by vector class, dictionary class , hash table class,and property class ?

27 Which class has no duplicate elements ?

28 What is resource bundle ?

29 What is an enumeration class ?

30 What is meant by Swing ?

31 What is the difference between AWT and Swing ?

32 What is the difference between an applet and a Japplet

33 What are all the components used in Swing ?

34 What is meant by tab pans ?

35 What is the use of JTree ?

36 How can you add and remove nodes in Jtree.

37 What is the method to expand and collapse nodes in a Jtree ?

38 What is the use of JTable ?

39 What is meant by JFC ?

Short simple questions — Set 5

1. Name 2 classes that can store arbitrary number of objects ?

2. What is the difference between java.applet.* and java.applet.Applet ?

3. What is a default package ?

4. What is meant by a super class and how can you call a super class ?

5. What is anonymous class ?

6. Name interfaces without a method ?

7. What is the use of an interface ?

8. What is a serializable interface ?
Serializability of a class is enabled by the class implementing the java.io.Serializable interface. Classes that do not implement this interface will not have any of their state serialized or deserialized. All subtypes of a serializable class are themselves serializable. The serialization interface has no methods or fields and serves only to identify the semantics of being serializable.

9. How to prevent field from serialization ?
There are several methods for preventing a field from being serialized:
Declare the field as private transient.
Define the serialPersistentFields field of the class in question, and omit the field from the list of field descriptors.
Write a class-specific serialization method (i.e., writeObject or writeExternal) which does not write the field to the serialization stream (i.e., by not calling ObjectOutputStream.defaultWriteObject).

10. What is meant by exception ?

11. How can you avoid the runtime exception ?

12. What is the difference between throw and throws ?

13. What is the use of finally ?

14. Can multiple catch statements be used in exceptions ?
yes

15. Is it possible to write a try within a try statement ?
yes

16. What is the method to find if the object exited or not ?

17. What is meant by a Thread ?

18. What is meant by multi-threading ?

19. What is the 2 way of creating a thread ? Which is the best way and why ?
Two ways of creating threads are, one can extend from the Java.lang.Thread and can implement the rum method or the run method of a different class can be called which implements the interface Runnable, and the then implement the run() method. The latter one is mostly used as first due to Java rule of only one class inheritance, with implementing the Runnable interface that problem is sorted out.

20. What is the method to find if a thread is active or not ?

21. What are the thread-to-thread communcation ?

22. What is the difference between sleep and suspend ?

23. Can thread become a member of another thread ?

24. What is meant by deadlock ?

25. How can you avoid a deadlock ?

26. What are the three typs of priority ?
MAX_PRIORITY which is 10, MIN_PRIORITY which is 1, NORM_PRIORITY which is 5.

27. What is the use of synchronizations ?

28. Garbage collector thread belongs to which priority ?
In the Sun literature you’ll find many references to garbage collection as a low-priority background process

29. What is meant by time-slicing ?

30. What is the use of ‘this’ ?

31. How can you find the length and capacity of a string buffer ?
A string buffer with no characters in it and an initial capacity of 16 characters. Every string buffer has a capacity. As long as the length of the character sequence contained in the string buffer does not exceed the capacity, it is not necessary to allocate a new internal buffer array. If the internal buffer overflows, it is automatically made larger.

32. How to compare two strings ?

33. What are the interfaces defined by Java.lang ?

34. What is the purpose of run-time class and system class

35. What is meant by Stream and Types ?

36. What is the method used to clear the buffer ?
clear() makes a buffer ready for a new sequence of channel-read

37. What is meant by Stream Tokenizer ?

38. What is serialization and de-serialisation ?

39. What is meant by Applet ?

40. How to find the host from which the Applet has originated ?

Short simple questions

Short but tricky …

1. Checked & Unchecked exception
Unchecked exceptions are any class of exception that extends the RuntimeException class at some point in its inheritance hierarchy. Java compilers do not require that you declare or catch unchecked exceptions in your program code. All Exceptions that extend the RuntimeException class are unchecked exceptions.
Checked exceptions are exceptions that do not extend the RuntimeException class. Checked exceptions must be handled by the programmer to avoid a compile-time error.

2. Use of throws exception
Tells the implementing class to handle the exception thrown.

3. What is finally in exception handling
This is the block of code that is always executed whether exception occurs or not.

4. Vector class
The Vector class implements a growable array of objects.

5. What will happen to the Exception object after exception handling

6. Two types of multi-tasking.

7. Two ways to create the thread Synchronization.
Thread synchronization is done by setting locks on objects. coordinating activities and data access among multiple threads.
Java’s monitor supports two kinds of thread synchronization: mutual exclusion and cooperation . Mutual exclusion, which is supported in the Java virtual machine via object locks, enables multiple threads to independently work on shared data without interfering with each other. Cooperation, which is supported in the Java virtual machine via the wait and notify methods of class Object, enables threads to work together towards a common goal.

8. I/O Filter
A stream filter monitors, transforms, or is some way processes the data as the stream flows through it on the way from a source to a destination

9. How can you retrieve warnings in JDBC

10. Can applet in different page communicate with each other

11. List Four driver Manager

12. State Features of JDBC 2.0

13. Explain about stored procedures
A stored procedure is a group of SQL statements that form a logical unit and perform a particular task. Stored procedures are used to encapsulate a set of operations or queries to execute on a database server. For example, operations on an employee database (hire, fire, promote, lookup) could be coded as stored procedures executed by application code. Stored procedures can be compiled and executed with different parameters and results, and they may have any combination of input, output, and input/output parameters. The procedure will be compiled and stored in the database as a database object that can be called, similar to the way you would call a method.

14. Describe Servlet Life cycle

15. Why do you go for servlet rather than CGI

16. How to generate skeleton & Stub classes

17. Explain lazy activation
In the RMI system, we use lazy activation. Lazy activation defers activating an object until a client’s first use (i.e., the first method invocation).

18. What is meant by Java ?

19. What is meant by a class ?

20. What is meant by a method ?

21. What are the OOPS concepts in Java ?

22. What is meant by encapsulation ? Explain with an example

23. What is meant by inheritance ? Explain with an example

24. What is meant by polymorphism ? Explain with an example

25. Is multiple inheritance allowed in Java ? Why ?

26. What is meant by Java interpreter ?
Bytecode is interpreted by JVM.

27. What is meant by JVM ?

28. What is a compilation unit ?

29. What is meant by identifiers ?

30. What are the different types of modifiers ?

31. What are the access modifiers in Java ?

32. What are the primitive data types in Java ?

33. What is meant by a wrapper class ?

34. What is meant by static variable and static method ?

35. What is meant by Garbage collection ?

36. What is meant by abstract class

37. What is meant by final class, methods and variables ?

38. What is meant by interface ?

40. What is meant by a resource leak ?

41. What is the difference between interface and abstract class ?

42. What is the difference between public private, protected and static

43. What is meant by method overloading ?

44. What is meant by method overriding ?

45. What is singleton class ?

46. What is the difference between an array and a vector ?

47. What is meant by constructor ?

48. What is meant by casting ?

49. What is the difference between final, finally and finalize ?

50. What is meant by packages ?