File Name: tomcat interview questions and answers .zip
- Apache Tomcat Interview Questions & Answers
- 50 Servlet Interview Questions and Answers
- Tomcat Interview Questions And Answers Pdf
For the Tomcat job perspective , you may be asked a number of questions like up gradation, server maintenance, managing users and about the new features.
Are you looking for Apache Tomcat developer job? If you are a java professional and looking to upgrade your skills then we provide guidance how to prepare for Apache tomcat job interviews. Many companies are looking to hire Devops engineers, Apache tomcat administrators, Linux Apache Tomcat jobs and Hadoop developers for various experience levels across locations.
Apache Tomcat Interview Questions & Answers
Servlets is a very important topic of Java EE and all of the web applications frameworks such as Spring and Struts is built on top of it.
This makes servlet interview questions a hot topic in interviews. Here I am providing a list of 50 servlet interview questions with answers to help you tackle most of the interview questions related to servlets and web applications in java. Apache Web Server is kind of a web server and then we have specific containers that can execute servlets and JSPs known as the servlet container, for example, Tomcat.
So we can say that the Application server is a web server with additional functionalities to help developers with enterprise applications. An HTTP method is said to be idempotent if it returns the same result every time. For example, to access an HTML page or image, we should use GET because it will always return the same object but if we have to save customer information to the database, we should use the POST method.
It helps client in rendering the data for user. Web Applications are modules that run on the server to provide both static and dynamic content to the client browser. Java provides web application support through Servlets and JSPs that can run in a servlet container and provide dynamic content to the client browser.
Read more about web applications at Java Web Application. Java Servlet is server side technologies to extend the capability of web servers by providing support for dynamic response and data persistence. The javax. All servlets must implement the javax.
Servlet interface, which defines servlet lifecycle methods. Servlet API hierarchy is shown in the below image. Read more at Servlet Tutorial. Servlet containers are also known as web container, for example, Tomcat.
Some of the important tasks of servlet container are:. ServletConfig is used to pass configuration information to Servlet. We can provide servlet init parameters in web. We can use getServletConfig method to get the ServletConfig object of the servlet. ServletContext interface provides access to web application parameters to the servlet. The ServletContext is unique object and available to all the servlets in the web application. When we want some init parameters to be available to multiple or all of the servlets in the web application, we can use ServletContext object and define parameters in web.
Servlet containers may also provide context objects that are unique to a group of servlets and which is tied to a specific portion of the URL path namespace of the host.
ServletContext is enhanced in Servlet Specs 3 to introduce methods through which we can programmatically add Listeners and Filters and Servlet to the application. We can also use this to include the content of another resource to the response.
This interface is used for inter-servlet communication in the same context. PrintWriter is a character-stream class whereas ServletOutputStream is a byte-stream class. We can use PrintWriter to write character based information such as character array and String to the response whereas we can use ServletOutputStream to write byte array data to the response. IllegalStateException at runtime with message as other method has already been called for this response.
We can create deadlock in servlet by making a loop of method invocation, just call doPost method from doGet method and doGet method to doPost method to create deadlock situation in servlet. Read more about deadlock in multithreading at Java Deadlock Example. These wrapper classes are provided to help developers with custom implementation of servlet request and response types.
We can extend these classes and override only specific methods we need to implement for custom request and response objects. These classes are not used in normal servlet programming. However, SingleThreadModel does not solve all thread-safety issues. For example, session attributes and static variables can still be accessed by multiple requests on multiple threads at the same time, even when SingleThreadModel servlets are used.
When servlet container receives client request, it invokes the service method which in turn invokes the doGet , doPost methods based on the HTTP method of request. The whole purpose of service method is to forward to request to corresponding HTTP method implementations. If we have to do some pre-processing of request, we can always use servlet filters and listeners. Ideally, if we have to initialize any resource for the servlet, we should override init method where we can access servlet init parameters using ServletConfig object.
When we want to invoke another servlet from a servlet service methods, we use inter-servlet communication mechanisms. We can invoke another servlet using RequestDispatcher forward and include methods and provide additional attributes in request for other servlet use. But service methods such as doGet or doPost are getting called in every client request and since servlet uses multithreading, we should provide thread safety in these methods. The thread safety mechanisms are similar to thread safety in standalone java application, read more about them at Thread Safety in Java.
Servlet attributes are used for inter-servlet communication, we can set, get and remove attributes in web application. There are three scopes for servlet attributes — request scope, session scope and application scope.
Servlet attributes are different from init parameters defined in web. We can use RequestDispatcher forward method to forward the processing of a request to another servlet. If we want to include the another servlet output to the response, we can use RequestDispatcher include method.
If we have to initialize some resource before we want our servlet to process client requests, we should override the init method. If we override init ServletConfig config method, then the first statement should be super config to make sure superclass init ServletConfig config method is invoked first. We should always utilize this method for overriding init method to avoid any issues as we may forget to add super call in overriding init method with ServletConfig argument.
URL Encoding is the process of converting data into CGI form so that it can travel across the network without any issues. URL Encoding strips the white spaces and replaces special characters with escape characters. We can use java. URL Decoding is the reverse process of encoding and we can use java. The session is a conversational state between client and server and it can consist of multiple request and response between client and server.
Since HTTP and Web Server both are stateless, the only way to maintain a session is when some unique information about the session session-id is passed between server and client in every request and response.
Read more about these session management approaches in detail at Servlet Session Management Tutorial. We can use HttpSession for session management in servlets but it works with Cookies and we can disable the cookie in client browser.
Cookies are text data sent by server to the client and it gets saved at the client local machine. Servlet API provides cookies support through javax. Cookie class that implements Serializable and Cloneable interfaces. HttpServletRequest getCookies method is provided to get the array of Cookies from the request, since there is no point of adding Cookie to request, there are no methods to set or add a cookie to request.
Similarly, HttpServletResponse addCookie Cookie c method is provided to attach cookie in the response header, there are no getter methods for a cookie. Read more at Cookies in Servlets. If we have to make sure an object gets notified when session is destroyed, the object should implement javax. HttpSessionBindingListener interface. This interface defines two callback methods — valueBound and valueUnbound that we can define to implement processing logic when the object is added as attribute to the session and when session is destroyed.
Recommended reading Servlet Listener. Servlet Filters are pluggable java components that we can use to intercept and process requests before they are sent to servlets and response after servlet code is finished and before container sends the response back to the client. Read more about filters at Servlet Filter. We know that servlet filters can be used to intercept request between a servlet container and servlet, we can utilize it to create an authentication filter and check if the request contains a valid session or not.
We know that using ServletContext, we can create an attribute with application scope that all other servlets can access but we can initialize ServletContext init parameters as String only in the deployment descriptor web. What if our application is database-oriented and we want to set an attribute in ServletContext for Database Connection. If your application has a single entry point user login , then you can do it in the first servlet request but if we have multiple entry points then doing it everywhere will result in a lot of code redundancy.
To handle these scenarios, servlet API provides Listener interfaces that we can implement and configure to listen to an event and do certain operations. Read more about different types of listeners and example at Servlet Listener. Same goes with other error codes like , etc. Servlet API provides support for custom Exception and Error Handler servlets that we can configure in the deployment descriptor, the whole purpose of these servlets are to handle the Exception or Error raised by application and send HTML response that is useful for the user.
We can provide a link to the application home page or some details to let the user know what went wrong. Read more at Servlet Exception Handling. The deployment descriptor is a configuration file for the web application and its name is web. Servlet container uses this file to configure web application servlets, servlet config params, context init params, filters, listeners, welcome pages and error handlers.
With servlet 3. Usually, servlet container loads a servlet on the first client request. Sometimes the servlet is heavy and takes time to loads, we might want to load it on application startup. We can use a load-on-startup element with servlet configuration in the web.
If there are multiple servlets with load-on-startup value such as 0,1,2,3 then lower integer value servlet will be loaded first. We can use below code snippet to get the servlet information in a servlet through servlet context object. File Upload and Download and common tasks in a java web application.
50 Servlet Interview Questions and Answers
Servlets is a very important topic of Java EE and all of the web applications frameworks such as Spring and Struts is built on top of it. This makes servlet interview questions a hot topic in interviews. Here I am providing a list of 50 servlet interview questions with answers to help you tackle most of the interview questions related to servlets and web applications in java. Apache Web Server is kind of a web server and then we have specific containers that can execute servlets and JSPs known as the servlet container, for example, Tomcat. So we can say that the Application server is a web server with additional functionalities to help developers with enterprise applications. An HTTP method is said to be idempotent if it returns the same result every time.
Tomcat Interview Questions And Answers Pdf
What is Tomcat? What is Jasper? Tomcat 5. Explain the concepts of Tomcat Servlet Container.