ServletConfig is an object containing some initial parameters or configuration information created by Servlet Container and passed to the servlet during initialization. ServletConfig is for a particular servlet, that means one should store servlet specific information in web. xml and retrieve them using this object.
Where does each servlet keep its configuration information?
Each Servlet keeps its configuration in a ServletConfig object. This object is created by the web container for each servlet. A ServletConfig object can be used to get configuration information from the web.xml file. It is easier to manage the web application if the servlet configuration information is in one web.xml file.
What is servletconfig in Java?
Each servlet has an object associated with it called the ServletConfig 19. This object is created by the container and implements the javax.servlet.ServletConfig interface. It is the ServletConfig that contains the initialization parameters. A reference to this object can be retrieved by calling the getServletConfig () method.
How do I define a servlet?
The first entry, under the root servlet element in web.xml, defines a name for the servlet and specifies the compiled class that executes the servlet. (Or, instead of specifying a servlet class, you can specify a JSP.) The servlet element also contains definitions for initialization attributes and security roles for the servlet.
What are initial parameters for a servlet?
A Servlet may have as many initial parameters as needed, and initial parameter information for a specific Servlet should be specified within the servlet element for that particular Servlet. Using initial parameters, the HelloWorld Servlet can be modified to be more internationally correct.
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What is servlet config and context?
ServletConfig and ServletContext, both are objects created at the time of servlet initialization and used to provide some initial parameters or configuration information to the servlet.
What is the use of servlet configuration interface?
Interface ServletConfig A servlet configuration object used by a servlet container to pass information to a servlet during initialization.
What is servlet config xml?
xml defines mappings between URL paths and the servlets that handle requests with those paths. The web server uses this configuration to identify the servlet to handle a given request and call the class method that corresponds to the request method (e.g., the doGet() method for HTTP GET requests).
Which file is used for servlet configuration?
The web. xml file is located in the WEB-INF directory of your Web application. The first entry, under the root servlet element in web. xml, defines a name for the servlet and specifies the compiled class that executes the servlet.
What is the main purpose of servlet?
A servlet is a Java programming language class that is used to extend the capabilities of servers that host applications accessed by means of a request-response programming model. Although servlets can respond to any type of request, they are commonly used to extend the applications hosted by web servers.
What is servlet and how it works?
Servlets are the Java programs that run on the Java-enabled web server or application server. They are used to handle the request obtained from the webserver, process the request, produce the response, then send a response back to the webserver. Properties of Servlets are as follows: Servlets work on the server-side.
What is servlet example?
Simply put, a Servlet is a class that handles requests, processes them and reply back with a response. For example, we can use a Servlet to collect input from a user through an HTML form, query records from a database, and create web pages dynamically.
What is Tomcat in servlet?
Apache Tomcat is a long-lived, open source Java servlet container that implements core Java enterprise (now Jakarta EE) specifications, including the Jakarta Servlet, Jakarta Server Pages, and Jakarta WebSocket specs.
What is Cookies in servlet?
A cookie is a small piece of information that is persisted between the multiple client requests. A cookie has a name, a single value, and optional attributes such as a comment, path and domain qualifiers, a maximum age, and a version number.
What is servlet name in web xml?
The servlet element of a web. xml file defines a servlet instance. The servlet element always contains a servlet-name element and a servlet-class element, and may also contain initialization parameters. The servlet-name element declares a name for this particular servlet instance.
What is a web xml file?
web. xml defines mappings between URL paths and the servlets that handle requests with those paths. The web server uses this configuration to identify the servlet to handle a given request and call the class method that corresponds to the request method. For example: the doGet() method for HTTP GET requests.
What is web xml and server xml?
The server. xml is used for server and context. xml is for application that runs on that server. There may be several context. xml files (per application) on a server but only one server.
Which interface is used for in servlet communication?
RequestDispatcher interfaceRequestDispatcher interface is used to forward the request to another resource that can be HTML, JSP or another servlet in the same 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.
What is the role of ServletContext interface of servlet?
Usage of ServletContext Interface The object of ServletContext provides an interface between the container and servlet. The ServletContext object can be used to get configuration information from the web. xml file. The ServletContext object can be used to set, get or remove attribute from the web.
Why we use HttpServlet instead of GenericServlet?
The main difference between GenericServlet and HttpServlet is that the GenericServlet is protocol independent that can be used with any protocol such as HTTP, SMTP, FTP, CGI etc. while HttpServlet is protocol dependent and is only used with HTTP protocol.
Why all servlets should implement the servlet interface?
Servlet interface needs to be implemented for creating any servlet (either directly or indirectly). It provides 3 life cycle methods that are used to initialize the servlet, to service the requests, and to destroy the servlet and 2 non-life cycle methods.
Example
Suppose, one is building a job portal and desires to share different email ids (which may get changed over time) with to recruiter and job applicant. So, he decides to write two servlets one for handling the recruiter’s request and another one for the job applicant.
Methods in the ServletConfig Interface
While configuring Servlet in web.xml we have to give a logical name to our servlet. Let’s say we have a Servlet class TestServlet and we want to configure it in web.xml.
What is request delegation?
Request delegation is a powerful feature of the Servlet API. A single client's request can pass through many Servlets and/or to any other resource in the Web Application. The entire process is done completely on the server-side and, unlike response redirection, does not require any action from a client or extra information sent between the client and server. Request delegation is available through the javax.servlet.RequestDispatcher object. An appropriate instance of a RequestDispatcher object is available by calling either of the following methods of a ServletRequest object:
What is HTTP request?
A client's HTTP request is represented by an HttpServletRequest object. The HttpServletRequest object is primarily used for getting request headers, parameters, and files or data sent by a client. However, the Servlet specification enhances this object to also interact with a Web Application. Some of the most helpful features include session management and forwarding of requests between Servlets.
What is the function of the HttpServletResponse object?
Along with sending content back to a client, the HttpServletResponse object is also used to manipulate the HTTP headers of a response. HTTP response headers are helpful for informing a client of information such as the type of content being sent back, how much content is being sent, and what type of server is sending the content. The HttpServletResponse object includes the following methods for manipulating HTTP response headers:
What is a servlet API?
The Servlet API makes manipulating an HTTP request and response pair relatively simple through use of the HttpServletRequest and HttpServletResponse objects. Both of these objects encapsulate a lot of functionality. Do not worry if it seems like this section is skimming through these two objects. Detailing all of the methods and members would be both tedious and confusing without understanding the rest of the Servlet API, but API discussion has to start somewhere and these two objects are arguably the most important. In this section discussion will only focus on a few of the most commonly used methods of each object. Later chapters of the book cover the other methods in full and in the context of which they are best used.
What are initial parameters?
Initial parameters are a good method of providing simple one-string values that Servlets can use to configure themselves. This approach is simple and effective, but is a limited method of configuring a Servlet. For more complex Servlets it is not uncommon to see a completely separate configuration file created to accompany web.xml. When developing Servlets, keep in mind that nothing stops you from doing this. If the parameter name and parameter values mappings are not adequate, do not use them! It is perfectly OK to create a custom configuration file and package it in a WAR with the rest of a Web Application. A great example of doing this is shown by the Jakarta Struts framework appearing in Chapter 11. The Struts framework relies on a control Servlet that is configured via a custom and usually lengthy XML file.
Is response redirection good?
Response redirection is a good tool to be aware of and works with any implementation of the Servlet API. However, there is a specific bug that tends to arise when using relative response redirection. For instance:
What is the default servlet in WebLogic?
This default servlet can be a servlet that you specify, or, if you do not specify a default servlet, WebLogic Server uses an internal servlet called the FileServlet as the default servlet.
What is servlet element?
The first entry, under the root servlet element in web.xml, defines a name for the servlet and specifies the compiled class that executes the servlet. (Or, instead of specifying a servlet class, you can specify a JSP.) The servlet element also contains definitions for initialization attributes and security roles for the servlet.
What is asynchronous processing?
Asynchronous processing—a servlet no longer has to wait for a response from a resource, such as a database, before its thread can continue. In other words, the thread is not blocked.
What is Oracle's user project directory?
The ORACLE_HOMEuser_projectsdomainswl_server directory contains the WebLogic Server examples domain; it contains your applications and the XML configuration files that define how your applications and Oracle WebLogic Server will behave, as well as startup and environment scripts. For more information about the WebLogic Server code examples, see Sample Applications and Code Examples in Understanding Oracle WebLogic Server.
Where are the examples in Java EE 7?
New Java EE 7 servlet examples—When you install WebLogic Server complete with the examples, the examples source code is placed in the EXAMPLES_HOMEexamplessrcexamples directory. The default path is ORACLE_HOMEwlserversamplesserver. From this directory, you can access the source code and instruction files for the Servlet 3.1 examples without having to set up the samples domain.
What is HTTP/1.1 Servlet?
Supports HTTP protocol upgrade processing —HTTP/1.1 allows the client to specify additional communication protocols that it supports and would like to use. Servlet 3.1 supports the HTTP protocol upgrade functionality in servlets.
Where to find source code for WebLogic Server?
You can find the source code and instructions for compiling and running examples in the ORACLE_HOMEwlserversamplesserverexamplessrcexamplessplitdirhelloWorldEar directory of your Web Logic Server distribution, where ORACLE_HOME represents the directory in which you installed WebLogic Server. For more information about the WebLogic Server code examples, see Sample Applications and Code Examples in Understanding Oracle WebLogic Server.
What are Servlets?
Java Servlets are programs that run on a Web or Application server and act as a middle layer between a requests coming from a Web browser or other HTTP client and databases or applications on the HTTP server.
What is a Java servlet?
Java Servlets are Java classes run by a web server that has an interpreter that supports the Java Servlet specification. Servlets can be created using the javax.servlet and javax.servlet.http packages, which are a standard part of the Java's enterprise edition, an expanded version of the Java class library that supports large-scale development ...
Why are servlets platform independent?
Servlets are platform-independent because they are written in Java. Java security manager on the server enforces a set of restrictions to protect the resources on a server machine. So servlets are trusted. The full functionality of the Java class libraries is available to a servlet.
Can you compile servlets with Java?
After you install the servlet packages and add them to your computer's Classpath, you can compile servlets with the JDK's Java compiler or any other current compiler.
Is Java better than CGI?
But Servlets offer several advantages in comparison with the CGI. Performance is significantly better. Servlets execute within the address space of a Web server.
What is the URL used to call a servlet?
The URL you use to call a servlet is determined by: (a) the name of the Web Application containing the servlet and (b) the name of the servlet as mapped in the deployment descriptor of the Web Application. Request parameters can also be included in the URL used to call a servlet.
What is the default servlet in WebLogic?
This default servlet can be a servlet that you specify, or, if you do not specify a default servlet, WebLogic Server uses an internal servlet called the FileServletas the default servlet. You can register any servlet as the default servlet.
What is hostis in WebLogic?
hostis the name of the machine running WebLogic Server.
What is the second entry in web.xml?
The second entry in web.xml, under the servlet-mappingelement, defines the URL pattern that calls this servlet.
What is the function of servlet?
The main function of a servlet is to accept an HTTP request from a Web browser, and return an HTTP response. This work is done by the service()method of your servlet. Service methods include responseobjects used to create output and requestobjects used to receive data from the client.
What is a servletservlet?
ServletServlet can be used to create a default mappings for servlets. For example, to create a default mapping to map all servlets to /myservlet/*, so the servlets can be called using http://host:port/web-app-name/myservlet/com/foo/FooServlet, add the following to your web.xml file. (The web.xmlfile is located in the WEB-INFdirectory of your Web application.)
What is a parameter in servlet?
parametersare one or more name-value pairs containing information sent from the browser that can be used in your servlet.
Servlet Configuration
Each Servlet keeps its configuration in a ServletConfig object. This object is created by the web container for each servlet. A ServletConfig object can be used to get configuration information from the web.xml file. It is easier to manage the web application if the servlet configuration information is in one web.xml file.
Summary
Let’s summarize the difference between the ServletConfig and the Servlet Context. First of all, the ServletConfig object represents a single servlet, it is like a local parameter associated with the particular servlet.
