Servlet concepts Q: What's the difference between applets and servlets?
Code Style: Java servlets frequently asked questions (FAQ)There are many fundamental differences between Applet and Servlet classes, the Java API documentation for the two types will show you they have little in common. Applets are essentially graphical user interface (GUI) applications that run on the client side in a network environment, typically embedded in an HTML page. Applets are normally based on Abstract Windowing Toolkit components to maintain backward-compatibility with the widest range of browsers' Java implementations.
Related QuestionsJSP concepts Q: What's the difference between JSP and servlets?
Code Style: Java Server Pages frequently asked questions (FA...Ultimately, servlets and JSP are the same thing. When you deploy JSP documents, the servlet container generates Java source code from the text and tags, then compiles the source to create servlet classes. The JSP servlet classes are then used to service requests the same way as standard servlets. Servlets tend to be better at providing validation for HTTP requests, interpreting the request parameters and directing the outcome of the interaction.
Related QuestionsWhat types of Servlet are there? Q: What is the class structure of servlets?
Code Style: Java servlet API frequently asked questions (FAQ...The class structure of servlets is fundamentally the same as any other Java class, however they must fulfil the Servlet and GenericServlet interface. These interfaces define a set of so-called lifecycle methods, a service method and various supporting methods for getting servlet configuration parameters and for logging. The lifecycle methods init(ServletConfig) and destroy() are called when the servlet container first puts the servlet into service and ultimately removes it.
Related QuestionsDesign concepts Q: What's the difference between abstraction and encapsulation?
Code Style: Java language frequently asked questions (FAQ)Abstraction and encapsulation are two quite separate concepts in Java. Abstraction is a technique that is used to represent common functionality amongst a set of classes. An analogy is to look at a set of vehicles: Car, Truck and Bus have some common features that all road vehicles share. From a Java perspective, the mechanics of turning four wheels, an engine, could be handled in abstract form through a common superclass. Abstraction allows subclasses to share common code without duplication.
Related QuestionsHow can we use a servlet as a proxy for communications between two applets?
www.adobians.comOne way to accomplish this is to have the applets communicate via TCP/IP sockets to the servlet. The servlet would then use a custom protocol to receive and push information between applets. However, this solution does have firewall problems if the system is to be used over and Internet verses an Intranet.
Related QuestionsStart the servlet container. Q: How do I compile a servlet?
Code Style: Java servlets frequently asked questions (FAQ)To compile a servlet, you will need to have the Java Servlet API classes in your classpath. Most Java servlet containers come with a copy, it may be called servlet.jar or something similar. The basic classes are in the packages javax.servlet and javax.servlet.http.
Related QuestionsHow do I compile a servlet? Q: Why won't my servlet compile?
Code Style: Java servlets frequently asked questions (FAQ)All those "cannot find symbol" error messages mean that you do not have the Java servlet JAR file on your compiler's classpath, so it cannot find the servlet class files. The servlet JAR file is normally distributed with your servlet container. For Apache Tomcat it is a file named {CATALINA_HOME}/common/lib/servlet-api.jar. Add this to your compiler classpath as follows.
Related QuestionsServlet implementation Q: What types of Servlet are there?
Code Style: Java servlet API frequently asked questions (FAQ...In the Java servlet API there are several sub-interfaces and implementations of the Servlet interface. The GenericServlet class has general purpose implementations of servlet methods that are common to all, including getInitParameter(String), init(ServletConfig) and log(String). GenericServlet is abstract and leaves the key method service(ServletRequest, ServletResponse) abstract for sub-class implementation.
Related QuestionsWhich is best, servlets or JSP? Q: Which is faster, servlets or JSP?
Code Style: Java Server Pages frequently asked questions (FA...JSP documents are ultimately compiled to servlets, which are multi-threaded by default and are assumed to be thread-safe. If the code in your JSP is not thread-safe, you can request the container uses a single threaded execution of the resulting servlet using the page directive <%@ page isThreadSafe="false" %>. JSP documents are compiled to servlets when they are placed in service and operate like standard servlets.
Related QuestionsWhat is the difference between applets loaded over the net and applets loaded via the file system?
Applet SecurityThere are two different ways that applets are loaded by a Java system. The way an applet enters the system affects what it is allowed to do. If an applet is loaded over the net, then it is loaded by the applet class loader, and is subject to the restrictions enforced by the applet security manager. If an applet resides on the client's local disk, and in a directory that is on the client's CLASSPATH, then it is loaded by the file system loader.
Related QuestionsServlet start up Q: What are the basic steps to run a servlet?
Code Style: Java servlets frequently asked questions (FAQ)The key steps in creating and running a servlet are outlined below in the simplest form. There are different techniques that can be used to complete these stages, described in other FAQ answers. Create a Web application directory structure under the webapp directory of your servlet container (or use an existing one), e.g.
Related QuestionsWhy won't my servlet compile? Q: Can I use a constructor in my servlet?
Code Style: Java servlets frequently asked questions (FAQ)A servlet is a normal Java class, so when there are no custom constructors, there is an implicit default constructor with no arguments. Servlet containers typically use the Class.newInstance() method to load servlets, so you must be careful to add an explicit default constructor if you add non-default constructors.
Related QuestionsServlet techniques Q: Can I access a servlet from a stand alone client?
Code Style: Java servlets frequently asked questions (FAQ)URL-rewriting is a way of maintaining a session between an HTTP client and a servlet container which does not use cookies. Rather than exchange a session ID in a cookie, the servlet container includes it in the hyperlink URLs it generates for servlets and JSP.
Related QuestionsWhen should one use applets and when should one use servlets?
jGuru: Applets FAQAuthor: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by swati m (http://www.jguru.com/guru/viewbio.jsp?EID=64343 Applets run inside browsers, and servlets run inside servers. So broadly speaking, use applets when you need dynamism on the client side, and use servlets when you need dynamism on the server side. Servlets can produce any HTML (or indeed, any file type), and therefore are much more versatile than applets.
Related QuestionsHow can I write an "error page" -- that is, a servlet or JSP to report errors of other servlets?
www.adobians.comThe Servlet 2.2 specification allows you to specify an error page (a servlet or a JSP) for different kinds of HTTP errors or ServletExceptions. You can specify this in deployment descriptor of the web application as: <error-page> <exception-type>FooException</exception-type> <location>/error.
Related QuestionsCompiler concepts Q: What is the source code for the compiler?
Code Style: Java compiler frequently asked questions (FAQ)The source code for a Java program is also known as a compilation unit, which contains the code for a top level Java class or interface. A Java compilation unit is usually created in the form of a file with a .java extension and is passed to the compiler as a file path reference. The Java source file naming convention is not a standard specified by the Java language but is a common feature of Java compilers, such as javac, to help locate source code.
Related QuestionsWhat is the class structure of servlets? Q: Why is HttpServlet declared abstract?
Code Style: Java servlet API frequently asked questions (FAQ...The GenericServlet is an abstract class that is extended by HttpServlet to provide HTTP protocol-specific methods. Java application developers normally extend the HttpServlet because it implements all the HTTP features necessary to create a Web application. The GenericServlet does not include protocol-specific methods for handling request parameters, cookies, sessions and setting response headers.
Related QuestionsDo you support Java applets or Java servlets (JSP)?
Hostito Web Hosting - software and systems faqsYes, we support JSP by running Tomcat on our servers. JSP is available with any hosting account, but there is an additional fee per domain running JSP due to the high demand it puts on server resources.
Related QuestionsHow do I run a servlet in Tomcat? Q: Should the Tomcat bootstrap classes be in my classpath?
Code Style: Apache Tomcat frequently asked questions (FAQ)Your compilation classpath only needs to include the classes and libraries necessary for your servlet. It's unlikely you are using Tomcat bootstrap classes in your servlet but, if so, make sure this package is on your classpath. The URL you use partly depends on the port you have configured Tomcat to operate on. This is configured in the HTTP Connector element in server.xml.
Related QuestionsHow does servlet performance compare to applets?
Java Network Programming FAQClient-side Java has been dogged by performance problems due to slow loading times, older JVMs without JIT compilation, and inefficient coding. Applets have gained a reputation of poor performance, which often gives Java itself a bad name. Server-side Java, however, doesn't suffer from the same performance problems. The speed of execution is much better, as the server administrator can install more recent JVMs (some of which are optimized for server-side processing).
Related QuestionsObject concepts Q: What's the difference between a class and an object in Java?
Code Style: Java objects frequently asked questions (FAQ)A Java class is a definition or model of an object type. A class has a specific set of fields, methods and constructors with distinct argument types. Any object that fulfils a class definition directly or by inheritance has a set of properties and behaviour that is common to all instances of the class. In this sense, a class is like a set of things that are alike. In Java concrete classes also provide a code implementation that can be instantiated to create an object reference.
Related QuestionsWhat is the difference between static variables and instance variables in a servlet?
www.adobians.comAccording to the Java Language definition, a static variable is shared among all instances of a class, where a non-static variable -- also called an instance variable -- is specific to a single instance of that class. According to the Servlet specification, a servlet that does not declare SingleThreadModel usually has one and only one instance, shared among all concurrent requests hitting that servlet.
Related QuestionsWhat URL do I use to run my servlet? Q: Can I return custom error pages in Tomcat?
Code Style: Apache Tomcat frequently asked questions (FAQ)You can configure custom error pages in Tomcat using the error-page element in the application's web.xml file, as below. The error-code element contains the HTTP status code number, the location element contains the path to the error document relative to the Web application root. The error document may be a static HTML document or a JSP. The error-page element may be repeated to specify custom pages for any number of error codes.
Related QuestionsCan I use a constructor in my servlet? Q: Can I use a normal class to handle my requests?
Code Style: Java servlets frequently asked questions (FAQ)Servlets are normal Java classes, they compile and run just like any other class. All that is required is that servlets implement the javax.servlet.Servlet interface. Usually, they extend a protocol-specific class such as javax.servlet.http.HttpServlet.
Related QuestionsHow do I call one servlet from another servlet?
www.adobians.comIf the end result needed is to invoke the methods then the simplest mechanism would be to treat the servlet like any java object , create an instance and call the mehods. If the idea is to call the service method from the service method of another servlet, AKA forwarding the request, you could use the RequestDispatcher object. If, however, you want to gain access to the instance of the servlet that has been loaded into memory by the servlet engine, you have to know the alias of the servlet.
Related QuestionsHow can I call a servlet from a JSP?
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Related QuestionsWhat is the difference between an application, and applet and a servlet?
Java Programmer's FAQAn application is a standalone program. An applet is a downloadable program that runs in a web-browser. Typically an applet has restricted access to the client system for reasons of security. Other than that it is virtually no different to a regular Java program. A servlet is a java program whose input comes from a server and whose output goes to a server. Other than that it is virtually no different to a regular Java program.
Related QuestionsWhat is a servlet?
Digital Mesh :: Dynamic websites development :: India, Belgi...A servlet is a program written in the Java programming language that runs on the server, as opposed to the browser (applets). Detailed information can be found at http://java.sun.com/products/servlet.
Related QuestionsServlet FAQs & Java Interview QuestionsServlets are modules that extend request/response-oriented servers,such as Java-enabled web servers. For example, a servlet might be responsible for taking data in an HTML order-entry form and applying the business logic used to update a companyâ??s order database. Servlets are to servers what applets are to browsers. Unlike applets, however, servlets have no graphical user interface. Servlets provide a way to generate dynamic documents that is both easier to write and faster to run.Related Questions
