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Ans. REST or Representational State Transfer is a flexible architecture style for creating web services that recommends the following guidelines -

1. http for client server communication,
2. XML / JSON as formatiing language ,
3. Simple URI as address for the services and,
4. stateless communication.

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Q3. Difference between GET and POST Requests ?

Ans. GET is supposed to get information from the server. Client sends the minimal information so that Server can respond with the response body on basis of request. For example - You want to get complete employment record for employee id 123

POST is supposed to send the information for submission. Payload or a Body is usually sent so that it can be persisted on the server. For example - Sending the complete information of an employee ( id, name , dept etc ) to the server for persisting it.

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Q4. What will be the output of following Code ?

class BuggyBread {
   public static void main(String[] args) {
      String s2 = "I am unique!";
      String s5 = "I am unique!";

      System.out.println(s2 == s5);
   }
}

Ans. true, due to String Pool, both will point to a same String object.

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Q5. What will be the output of following code ?
class BuggyBread2 {
   private static int counter = 0;
   void BuggyBread2() {
      counter = 5;
   }

   BuggyBread2(int x){
      counter = x;
   }

   public static void main(String[] args) {
      BuggyBread2 bg = new BuggyBread2();
      System.out.println(counter);
   }
}

Ans. Compile time error as it won't find the constructor matching BuggyBread2().
Compiler won't provide default no argument constructor as programmer has already defined one constructor.
Compiler will treat user defined BuggyBread2() as a method, as return type ( void ) has been specified for that.

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Try 3 Question(s) Test

Q6. What is a Webdriver ?

Testing

Ans. Selenium WebDriver is a tool for automating web application testing.It helps in replicating the manual tester behavior like keyboard entry, mouse events etc and then matching the output against the expected.

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Q7. In which cases using SOAP is preferred over REST ?

Ans. SOAP services are better in case we need to establish a formal and detail contract with the client or callers and hence suitable for

1. Services published for much wider unknown audience
2. Require large input payload
3. Requiring different level for authentication

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Q8. What could be the reasons for restricting inheritance using final class ?

Ans. 1. Enforcing composition over inheritance
2. Restricting overriding of certain methods
3. Final methods are faster than regular instance methods
4. Enforcing Immutability

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Q9. If you have access to a function that returns a random integer from one to five, write another function which returns a random integer from one to seven.

Ans. We can do that by pulling binary representation using 3 bits ( random(2) ).

getRandom7() {
   String binaryStr = String.valuesOf(random(2))+String.valuesOf(random(2))+String.valuesOf(random(2));
   binaryInt = Integer.valueOf(binaryStr);
   int sumValue=0;
   int multiple = 1;
   while(binaryInt > 0){
      binaryDigit = binaryInt%10;
      binaryInt = binaryInt /10;
      sumValue = sumValue + (binaryDigit * multiple);
      multiple = multiple * 2;
   }
}

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Q10. Write a method to convert binary to a number ?

Ans.
convert(int binaryInt) {
   int sumValue=0;
   int multiple = 1;
   while(binaryInt > 0){
      binaryDigit = binaryInt%10;
      binaryInt = binaryInt /10;
      sumValue = sumValue + (binaryDigit * multiple);
      multiple = multiple * 2;
   }
   return sumValue;
}

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Q11. Which markup languages can be used in restful web services ?

Ans. XML and JSON ( Javascript Object Notation ).

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Q12. Why Web services use HTTP as the communication protocol ?

Ans. With the advent of Internet, HTTP is the most preferred way of communication. Most of the clients ( web thin client , web thick clients , mobile apps ) are designed to communicate using http only. Web Services using http makes them accessible from vast variety of client applications.

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Q13. Name some Java REST services frameworks ?

Ans. Jersey , Restlet , RestX, Spring , RestEasy ,Restfulie, Play Framework

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Q14. Name few Restriction Methods ?

Hibernate

Ans. eq, ge, gt , between, in , isNull, isEmpty, isNotnull, ne , like, lt , or , not

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Q15. In Spring , Which class handles the Http requests for RESTful web services ?

a. Service
b. Model
c. Controller
d. Util

Spring

Ans. Controller

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Q16. Can we send a request body with the Get Request ? If not, What is the alternate to pass message to the Get Request ?

Ans. Request Body in case of Get Request has no meaning and hence it's not parsed when the request is received. Alternatively Request Parameters are passed as either Path Params or Query Params.

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Frequently asked question in companies using Rest Web services.

Q17. Different between POST and PUT in Rest

Ans. PUT requests are only meant to place the object as it is on server. For example - You want a file to be uploaded and then placed in a particular folder or you want an Employee object to be persisted in the table.

POST requests are also meant to transfer information from client to server but that information once received at the server is evaluated , modified or refactored before persisting.

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Q18. Should a Database Update Request be a POST or PUT Request in Rest

Ans. It should be a POST Request

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Q19. Should a DB Insert Request be a POST or PUT request in Rest

Ans. It depends on whether the request object is persisted as it is

or

its first dismantled, modified or refactored and then inserted into DB.

In first case, it should be a PUT request whereas in second case it should be a POST Request.

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Q20. Is it Necessary to send a POST request with the Payload or a body ?

Ans. No, we can also send an empty body with the POST Request.

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Q21. Can we send payload / body with the GET Request in Rest ?

Ans. We can send it but it's completely ignored by the server.

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Q22. Can I hit the Rest Post Request through a browser address bar if it's not expecting any payload / body ?

Ans. No, even if there is no payload, you can't hit the POST request by typing it into browser address bar. You will need a client that can make a POST Request.

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Q23. What are the different ways in which information can be sent to server in web service call ?

Ans. 1. As Request Param
2. As Path Param
3. Part of Payload / Body in case of PUT and POST Request

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Q24. How to specify the or/and combination restrictions within Criteria in Hibernate ?

Hibernate

Ans. session.createCriteria(Employee.class).add( Restrictions.or(Restrictions.like("name", "A%"),Restrictions.like("name", "B%"))).list();

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Q25. How to create stateful Rest Services ?

Ans. There is no direct way to make stateful REST service but when first time request send to server, generate the token on server and send back to client. When every time new request is send the token is send to identify the request is coming from same client.

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Q26. How would you go about creating a get rest service if it requires multitude of params or inputs ?

Ans. If the number of input values is large, we can go about passing them as query params instead of path params. If the number is even larger and complex , its better to create a post service that behaves like a get service. Though this practice is not recommended but technically it can be accomplished.I dont mind doing it if the exceptionally large number of input would make it much more confusing.

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Q27. Can we discover end points of Rest API without looking at the code ?

Ans. Generally Rest services don't have any registry like we have WSDL is SOAP and hence don't have a way to know the end points without looking at either the url mapping in controller or client code. Some restful service publish WADL (Web Application Description Language) and hence clients can locate the service end points.

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Q28. Can you name few matchers that can be used with hamcrest assertThat method ?

Junit

Ans. is
not
equals
anyOf
hasSize

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Q29. If given a choice , which one would you prefer to send params to the Get service , path params or query param ?

Ans. If the number of params is quite large , I would prefer to either split it with majority of it in query params or all in query params.

If the params are all mandatory , I would keep it as path params. If it's optional , I would keep it as query param so as to keep consistent base url.

If we don't require the param name , then they can be kept as path params as query params necessitates the usage of param name.

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Q30. Is it necessary to specify "employeeId" with @PathParam("employeeId") in this case,

@Path("/{employeeId}")
public String employeeInfo(@PathParam("employeeId") Long employeeId){
}