There is only one servlet instance per registered servlet. Normally, when concurrent requests are handled by the web server, threads are spawned which executes the service() method of the servlet. Instance variables are not thread safe, but local variables within the service() method are. The request object is also "localized" per thread. According to the Servlet specs, when a servlet implements ... |
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As I mentioned my servlets currently implement SingleThreadModel. They connect to an Access database. From what little I learned about Access, it wont allow access if it is open. I am thinking I have a problem. Since I can have more than one instance of each servlet, if more than one client tries to access the data base at the same ... |
Peter's explanation is right on target, although strictly speaking java.lang.Comparable and java.lang.Runnable do define methods. Whenever I see SingleThreadModel, however, the red flags go up. Almost invariably it is an attempt to plug holes in a faulty design. The only real advantage of SingleThreadModel (or the equivalent JSP page directive isThreadSafe="false") is that it prevents two requests from modifying an instance ... |
I'll explain this from the beginning. If this is dumbing it down too much for you i appologise but it's a concept that took me a while to get hold of. For the sake of efficiency, there is only ever one instance of each Servlet. If you have 3 servlets: BobServlet, JohnServlet, BettyServlet, you will have a total of 3 servlet ... |
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What's an acceptable performance concession today may not be tomorrow. Don't use single-threading just as a "easy way out"! On a purely theoretical viewpoint, any need to limit myself to a single-thread approach implies that I wasn't clever enough to get the job done multi-threaded - though I'm sure that sooner or later in the real world, I'll find exceptional cases ... |
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A servlet container may send concurrent requests through the service method of the servlet. To handle the requests the developer of the servlet must make adequate provisions for concurrent processing with multiple threads in the service method. An alternative for the developer is to implement the SingleThreadModel interface which requires the container to guarantee that there is only one request thread ... |
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Yes, SingleThreadModel is getting deprecated as of J2EE 1.4 and I've never used it in my life, nor do I intend to do so. But, there is something that is bugging me about it. And that is what was the reason it was put in there (i.e. in the API) in the first place. From the Servlet spec, we have that, ... |
Originally posted by Gayathri Prasad: Single Thread Model might choke the web server .. i.e typically in a Single thread model what happens is the web server assigns a client to a single instance of a Servlet and when the requests go up... it finally bogs down the web server and thats the reason ( I think) Sun wants to do ... |
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Is from an exam or homework question? If so, I suggest that you have a go at working out the answer yourself and let us know here. Then we can help you clear up any confusion or misunderstandings. I'm not sure that just telling you the answer will help you learn and understand. |
When we mention our servlet to be of a singleThreadModel, the container is going to create a new (or an existing one from the pool) instance of the servlet for every client request (even for the same client session). Isn't it going to be tricky for the container to get the data in sync with other instances of the servlet for ... |
It was generally agreed that SingleThreadModel was a false friend that allowed a servlet developer to believe that they did not need to be concerned about synchronization and threading. Unfortunately this mechanism only makes this true for instance variables of the servlet itself and does not offer any protection for access to sessions, datasources or any other shared resources. As passing ... |
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Sitaram It's Deprecated. As of Java Servlet API 2.4, with no direct replacement. public interface SingleThreadModel Ensures that servlets handle only one request at a time. This interface has no methods. If a servlet implements this interface, you are guaranteed that no two threads will execute concurrently in the servlet's service method. The servlet container can make this guarantee by synchronizing ... |
It was actually deprecated because it was a little misleading. The servlet itself is threadsafe but your not guaranteed thread safety when accessing session or context scoped objects. They perform quite well in app servers that pool them (like Tomcat). Nevertheless... They're depreprecated and that's reason enough not to start using them. |
Hi there, I wanted to get input on a matter of thread safety for a servlet that processes online tests. The basic question is, "Should I implement the SingleThreadModel on the servlet since many students maybe trying to submit their tests symultaneously for processing?" The servlet does contain three instance variables which perhaps need to remain as such so that an ... |
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In one E - Book i have read that -: " Recall that multiple client requests to the same servlet result only in multiple threads calling the service method of a single servlet instance. They do not result in the creation of multiple servlet instances except possibly when the servlet implements SingleThreadModel." In above it is written that it will create ... |
The multi-threading aids efficiency but the servlet code must be coded in a thread safe manner. The shared resources (e.g. instance variables, utility or helper objects etc) should be appropriately synchronized or should only use variables in a read-only manner. Having large chunks of code in synchronized blocks in your service methods can adversely affect performance and makes the code more ... |
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I found this for tomcat : Class ContainerBase.ContainerBackgroundProcessor java.lang.Object org.apache.catalina.core.ContainerBase.ContainerBackgroundProcessor All Implemented Interfaces: java.lang.Runnable and , backgroundProcessorDelay: This value represents the delay in seconds between the invocation of the backgroundProcess method on this host and its child containers, including all contexts. Child containers will not be invoked if their delay value is not negative (which would mean they are using their ... |
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Hi i am trying to run a genericservlet(not httpservlet) implementing a singlethreadmodel.But everytime i make a new request i am getting new thread id.Here is the code.Can you tell me why?? import javax.servlet.*; import java.io.*; public class SingleThreadedServlet2 extends GenericServlet implements SingleThreadModel { public void service(ServletRequest request, ServletResponse response) throws ServletException, IOException { int counter = 0; // get saved value ... |
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Basically, to be avoided. The only reason to use SingleThreadModel is if you store data in fields of the Servlet during the course of a transaction, which you can always avoid doing. If you must have "global variables" during transaction processing use a ThreadLocal object which will give you a unique version for each transaction. |
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