How can I debug my servlet?
jGuru: Tomcat FAQFirst off, you should always do your own exception handling. An uncaught exception can silently kill your servlet, and if you don't know where to look in the log files, or if your server has a bug in it whereby it silently swallows certain exceptions, you'll have no idea where the trouble is.
Related QuestionsHow do I debug an Apache Tomcat 5.0 Servlet?
JDebugTool - Graphical Java DebuggerFirst make sure you have defined the environment variable JAVA_HOME to point to the root directory where you have the JDK installed. Then simply invoke on Windows Then in JDebugTool, select Attach... from the Target menu in the menubar, to display the Attach to Target dialog. On Windows, select the Shared Memory tab, and enter jdbconn in the Shared Memory Name field. On Unix, select the Socket tab, and enter 8000 in the Port Number field.
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?
Code Style: Java Server Pages frequently asked questions (FA...Use the form below to submit a help request or general enquiry about the Code Style Web site. Before you write read the guidelines on asking the right questions, and check this page for periodic updates. Your email address will not be mis-used. If you include your address you may be sent a personal reply, you will not be added to any mailing list unless you request it. Read the site privacy statement for details.
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 company???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
Start 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 QuestionsHow do you do servlet aliasing with Apache and Tomcat?
www.adobians.comServlet aliasing is a two part process with Apache and Tomcat. First, you must map the request in Apache to Tomcat with the ApJServMount directive, e.g., ApJServMount /myservlet /ROOT Second, you must map that url pattern to a servlet name and then to a servlet class in your web.xml configuration file. Here is a sample exerpt: <servlet> <servlet-name>myservlet</servlet-name> <servlet-class>com.mypackage.
Related QuestionsWhat is a Servlet Filter?
www.adobians.comA filter is basically a component that is invoked whenever a resource is invoked for which the filter is mapped. The resource can be something like a servlet, or a URL pattern. A filter normally works on the request, response, or header attributes, and does not itself send a response to the client. You can use absolute urls like: <BODY> <% String base = request.getContextPath(); %> <IMG src="<%=base%>/img/pic.
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 QuestionsHow to debug LessTif applications ?
LessTif Frequently Asked QuestionsWe have some documents which should help to track down bugs in LessTif-based applications. BUG-HUNTING.html describes some specifics of LessTif's built-in debugging facilities while bugs.html covers more general the topic of debugging X11 applications.
Related QuestionsWhy is DeBug™ so good?
Austin Health DeBug Infection Prevention Program - Frequentl...DeBug™ is a user-friendly alternative to soap and water and results in improved outcomes for patients by reducing hospital-acquired infections. DeBug™ is unique because it contains 70% Isopropyl Alcohol (kills bugs instantly), 0.5% Chlorhexidine Gluconate (provides antibacterial residual effect) in an emollient base (causes less skin drying). Solutions such as DeBug™ are superior to gel-based products.
Related QuestionsWhere should DeBug™ be located in a ward?
Austin Health DeBug Infection Prevention Program - Frequentl...To improve Hand Hygiene compliance DeBug™ is located at the foot of the every bed, using a specifically designed bracket. Studies have shown that bedside availability dramatically improves health care worker compliance. Additionally, DeBug™ is placed in high-use areas including nurse’s stations and on mobile equipment (e.g. IV trolleys). To minimise the likelihood of adverse events, DeBug™ should not be placed at or above eye height.
Related QuestionsHow can usage of DeBug™ be sustained?
Austin Health DeBug Infection Prevention Program - Frequentl...Health care worker acceptance and ownership of DeBug is essential. This can be achieved by implementing a successful “culture change” program similar to our DeBug Infection Prevention Program. In addition, we also developed an interactive Hand Hygiene learning package for credentialling of all health care workers at Austin Health.
Related QuestionsI read somewhere about another debug page. How do I see that?
Frequently Asked Questions about the Garmin Map60C and Map60...From the Trip Computer page, press up, right, down and left on the rocker key. A debug page appears. There is a screen shot in this post and a discussion in the few following posts
Related QuestionsWhat is 'full debug info' anyway?
EMMA: Frequently Asked QuestionsThe minimum amount of information necessary for the most feature-full HTML report is contained in LineNumberAttribute and SourceFile .class attributes. These are produced by -g:lines,source compiler option (-g defaults to complete debug info and will work just as well). In Eclipse, the necessary debug attributes are enabled via "Java Compiler" properties.
Related QuestionsHow can I debug makepp?
Makepp FAQ -- Frequently asked questions about makeppYou can put $(print ) around a suspicious expression. This returns the unchanged expression, while printing it as a side effect. You can dump the current directory's (multiply after -C if you want) makefile with the --dump-makefile=file option, to see how makepp sees it. Makepp writes a log of everything it does and why. You can look at that with makepplog, mppl or makeppgraph, mppg. Makepp records all it knows about a file, for reuse on the next run.
Related QuestionsUnder what circumstances will a servlet be reloaded?
www.adobians.comMost of the Servlet containers reload the servlet only it detects the code change in the Servlet, not in the referenced classes. In Tomcat's server.xml deployment descriptor, if you have mentioned <Context path="/myApp" docBase="D:/myApp/webDev" crossContext="true" debug="0" reloadable="true" trusted="false" > </Context> The reloadable = true makes the magic.
Related QuestionsHow can I get the absolute URL of a servlet/JSP page at runtime ?
www.adobians.comYou can get all the necessary information to determine the URL from the request object. To reconstruct the absolute URL from the scheme, server name, port, URI and query string you can use the URL class from java.net. The following code fragment will determine your page's absolute URL: String file = request.getRequestURI(); if (request.getQueryString() != null) { file += '?' + request.getQueryString(); } URL reconstructedURL = new URL(request.getScheme(), request.getServerName(), request.
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 QuestionsHow do I deal with multi-valued parameters in a servlet?
www.adobians.comInstead of using getParameter() with the ServletRequest, as you would with single-valued parameters, use the getParameterValues() method. This returns a String array (or null) containing all the values of the parameter requested.
Related QuestionsHow can I use a servlet to generate a site using frames?
www.adobians.comIn general, look at each frame as a unique document capable of sending its own requests and receiving its own responses. You can create a top servlet (say, FrameServlet) that upon invocation creates the frame layout you desire and sets the SRC parameters for the frame tags to be another servlet, a static page or any other legal value for SRC.
Related QuestionsServlet 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 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 QuestionsWhat is a Java Servlet?
CSG Q&A, Java Servlets and JSP FAQJava Servlets are special Java classes that can integrate with an enhanced web server and enable you to dynamically generate web pages by executing Java code - effectively running your code "inside the web server". Essentially, a web server can be configured to hand some/all web page requests over to a Servlet Engine which translates these requests into method calls into Java servlet classes, dynamically loading and initialising them as necessary.
Related Questions