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What is servlet mapping?
A Servlet Mapping is a directive in the web.xml that tells the Servlet Container which class to use when a particular Servlet is called. A Servlet is a class within your Java Web Application. Let's say you have a servlet called MyServlet in the com.example.servlet package. You would need to have a Servlet Mapping pointing the path "/MyServlet" to the "com.example.servlet.MyServlet" class. Without the servlet mapping, you would not be able to invoke your servlet because the Servlet container would not know where it is. JSPs are different - they do not need mappings like this. JSPs exist within the WebRoot of the application, so they are always available. Servlets exist in the WEB-INF\Classes directory once your application is deployed.
What are the servlet config methods?
Methods in the Servlet ContextApart from setting and getting custom attributes used for our application, the context also contains various methods that we can use to retrieve specific information about the application and other aspects. They are:• getAttributeNames() - Returns an Enumeration object containing the attribute names available within this servlet context.• getContext(String uripath) - Returns a ServletContext object that corresponds to a specified URL on the server.• getInitParameter(String name) - Returns a string containing the value of the named context-wide initialization parameter, or null if the parameter does not exist.• getInitParameterNames() - Returns the names of the context's initialization parameters as an Enumeration of string objects, or an empty Enumeration if the context has no initialization parameters.• getMajorVersion() - Returns the major version as an int of the Java Servlet API that this Servlet Container supports.• getMimeType(java.lang.String file) - Returns the MIME type as a string of the specified file, or null if the MIME type is not known.• getMinorVersion() - Returns the minor version as an int of the Servlet API that this Servlet Container supports.• getNamedDispatcher(String name) Returns a RequestDispatcher object that acts as a wrapper for the named servlet.• getRealPath(String path) - Returns a string containing the real path for a given virtual path.• getRequestDispatcher(String path) Returns a RequestDispatcher object that acts as a wrapper for the resource located at the given path.• getResource(String path) - Returns a URL to the resource that is mapped to a specified path.• getResourceAsStream(String path) - Returns the resource located at the named path as an InputStream object.• getServerInfo() Returns the name and version as a String of the Servlet Container on which the servlet is running.
Can you use constructor in servlet?
Yes you can but it is not required. A Servlet is nothing but another .java file and all rules that are applicable to standard Java classes are applicable to them. Note: Even if you write a constructor in a servlet, it will not get executed.
How many interfaces in a java servlet package?
The javax.servlet package defines 12 interfaces, 7 classes, and 2 exceptions. The Interfaces are as follows:• Filter:- Preprocessor of the request before it reaches a servlet. It can also be a postprocessor of the response leaving a servlet. It can modify a request or response (for example, change headers), the request to a resource (a servlet or static content), or the response from a resource.• RequestDispatcher:- This is the servlet version of a redirect. It enables requests to be processed and then forwarded to other components of a Web application, such as another servlet, HTML file, or JSP file.• Servlet:- Defines the life-cycle methods that are implemented by all servlets.• ServletConfig:- This class has the methods for accessing the servlet configuration information such as the servlets name (from the web.xml file), the initialization parameters, and the ServletContext object.• ServletContext:- These methods enable your servlet to communicate with its servlet container. This is how you get the MIME type of a file, dispatch requests, or write to a log file. Notice that this information has application scope. The most important features of the ServletContext are application-scope attributes access, logging, and context initialization parameters.• ServletContextAttributeListener:- Implementations of this interface receive notifications of changes to the attribute list on the servlet context of a Web application. Supports the handling of the ServletContextAttributeEvent class.• ServletContextListener:- An interface that supports the handling of the ServletContextEvent class. Defines a set of methods that a servlet uses to communicate with its servlet container. It can get the MIME type of a file, dispatch requests, or write to a log file. Notice that there is one context per "Web application" per Java Virtual Machine. The specification defines a "Web application" as a collection of servlets and content installed under a specific subset of the server's URL namespace, such as /catalog, and possibly installed via a .war file.• ServletRequest:- This interface forms the base for the class that provides client request information to a servlet. It is protocol-independent.• ServletResponse:- This interface forms the base for the class that represents the response sent from the servlet to the client.• SingleThreadModel:- An interface that ensures a given servlet handles only one request at a time.
Difference between HTTP servlet and Generic servlet?
The difference is that a GenericServlet has no defined protocol (it is "generic"), while HttpServler uses the HTTP protocol. HttpServlet is a subclass of GenericServlet with the purpose of creating a servlet for a web site.
Can servlet object be directly loaded?
Yes it can be.
What is the difference between servletcontext and servletconfig?
ServletContext Defines a set of methods that a servlet uses to communicate with its servlet container.ServletConfig is a servlet configuration object used by a servlet container used to pass information to a servlet during initialization. All of its initialization parameters can ONLY be set in deployment descriptor.The ServletContext object is contained within the ServletConfig object, which the Web server provides the servlet when the servlet is initialized.You can specify param-value pairs for ServletContext object in tags in web.xml file.The ServletConfig parameters are specified for a particular servlet and are unknown to other servlets. The ServletContext parameters are specified for an entire application outside of any particular servlet and are available to all the servlets within that application.By Santanu
How do you call a Servlet from JSP?
I have created a .jsp file, in which, I am calling a class.method() through TagLib. REQUIREMENT is, I want to call a servlet instead of a simple class. And Servlet will get the response, and request object from Jsp, and manipulate that, and produce the response object, and control is transfered back to JSP again.
How do you get ServletContext object in EJB - 38k?
get servlet context path from EJB
What is HttpServletRequest?
ServletRequest provides the functionalities to the classes to access the HTTP requests. The servlet container creates an HttpServletRequest object and an HttpServletResponse object, and passes them as arguments to the servlet's service methods such as doGet, doPost, etc.
How do you Retrieve data from drop down box in one servlet and pass to another servlet?
The data that is present in a web page is available in the Form object of the page which can be accessed from the HTTP Request. If the request object gets passed from one servlet to another the data also would get passed.
What use import javaxservlethttpHttpServletRequest in java?
The Http RequestWhen a user hits a URL with a servlet at the other end, the Servlet Container creates an HttpServletRequest object. It passes this object as an argument to the servlet's service methods (doPut(), doGet(), and doPost()). There is a lot of information in this object, including the login details of the user making this request and the name of the HTTP method with which this request was made.
What is generic servlet class?
GenericServlet defines a generic, protocol-independent servlet whereas HttpServlet Provides an abstract class to be subclassed to create an HTTP servlet suitable for a Web site that uses the Http Protocol.
How does Apache httpd work?
Tomcat is a servlet container, and the following is how a servlet container works The init, service, and destroy methods are the servlet's lifecycle methods. The init method is called once by the servlet container after the servlet class has been instantiated to indicate to the servlet that it being placed into service. The init method must complete successfully before the servlet can receive any requests. A servlet programmer can override this method to write initialization code that needs to run only once, such as loading a database driver, initializing values, and so on. In other cases, this method is normally left blank. The service method is then called by the servlet container to allow the servlet to respond to a request. The servlet container passes a javax.servlet.ServletRequest object and a javax.servlet.ServletResponse object. The ServletRequest object contains the client's HTTP request information and the ServletResponse encapsulates the servlet's response. These two objects enable you to write custom code that determines how the servlet services the client request. The servlet container calls the destroy method before removing a servlet instance from service. This normally happens when the servlet container is shut down or when the servlet container needs some free memory. This method is called only after all threads within the servlet's service method have exited or after a timeout period has passed. After the servlet container calls destroy, it will not call the service method again on this servlet. The destroy method gives the servlet an opportunity to clean up any resources that are being held (for example, memory, file handles, and threads) and make sure that any persistent state is synchronized with the servlet's current state in memory. For Better Picture, Visit below article full of images to clear the concept : http://shivasoft.in/blog/java/servlet/how-container-handles-the-servlet-request/
What are types of servlet?
Http servlet and Generic servlet
How do you get servlet context instance to servlet?
You can get the ServletContext instance in a servlet by using the getServletContext() method provided by the HttpServlet class, which is the base class for servlets. This method returns the ServletContext object associated with the servlet. For example: ServletContext context = getServletContext();
What is java servlet chaining?
Servlet Chaining means the output of one servlet act as a input to another servlet. Servlet Aliasing allows us to invoke more than one servlet in sequence when the URL is opened with a common servlet alias. The output from first Servlet is sent as input to other Servlet and so on. The Output from the last Servlet is sent back to the browser. The entire process is called Servlet Chaining.
