What is the significance of url-pattern in web xml and how to configure servlet

Question

I have manually configured web xml for my application  Now  I m facing issues while running my application  I m trying to access my servlet from my jsp page  But  it is throwing error as page not found   The servlets are placed under below folder location    lt application folder gt  WEB-INF classes  lt package gt    So  what should be the entries for servlets in url-pattern and servlet-mapping  So that  servlet can be accessible through URL

User · Answer

url-pattern is used in web xml to map your servlet to specific URL  Please see below xml code  similar code you may find in your web xml configuration file    lt servlet gt       lt servlet-name gt AddPhotoServlet lt  servlet-name gt     servlet name      lt servlet-class gt upload AddPhotoServlet lt  servlet-class gt     servlet class  lt  servlet gt    lt servlet-mapping gt       lt servlet-name gt AddPhotoServlet lt  servlet-name gt      servlet name      lt url-pattern gt  AddPhotoServlet lt  url-pattern gt     how it should appear  lt  servlet-mapping gt    If you change url-pattern of AddPhotoServlet from  AddPhotoServlet to  MyUrl  Then  AddPhotoServlet servlet can be accessible by using  MyUrl  Good for the security reason  where you want to hide your actual page URL    Java Servlet url-pattern Specification         A string beginning with a     character and ending with a        suffix    is used for path mapping     A string beginning with a        prefix is    used as an extension mapping     A string containing only the        character indicates the  default  servlet of the application  In this    case the servlet path   is the request URI minus the context path and    the path info is   null     All other strings are used for exact matches    only       Reference   Java Servlet Specification  You may also read this Basics of Java Servlet

User · Answer

Servlet-mapping has two child tags  url-pattern and servlet-name  url-pattern specifies the type of urls for which  the servlet given in servlet-name should be called  Be aware that  the container will use case-sensitive for string comparisons for servlet matching   First specification of url-pattern a web xml file for the server context on the servlet container at server  com  matches the pattern in  lt url-pattern gt  status   lt  url-pattern gt  as follows   http   server com server status synopsis                 Matches http   server com server status complete date today      Matches http   server com server status                          Matches http   server com server server1 status                  Does not match   Second specification of url-pattern A context located at the path  examples on the Agent at example com matches the pattern in  lt url-pattern gt   map lt  url-pattern gt  as follows    http   server com server US Oregon Portland map      Matches  http   server com server US server Seattle map       Matches  http   server com server Paris France map            Matches  http   server com server US Oregon Portland MAP      Does not match  the extension is uppercase  http   example com examples interface description mail mapi   Does not match  the extension is mapi rather than map    Third specification of url-mapping A mapping that contains the pattern  lt url-pattern gt   lt  url-pattern gt  matches a request if no other pattern matches  This is the default mapping  The servlet mapped to this pattern is called the default servlet   The default mapping is often directed to the first page of an application  Explicitly providing a default mapping also ensures that malformed URL requests into the application return are handled by the application rather than returning an error   The servlet-mapping element below maps the server servlet instance to the default mapping    lt servlet-mapping gt     lt servlet-name gt server lt  servlet-name gt     lt url-pattern gt   lt  url-pattern gt   lt  servlet-mapping gt    For the context that contains this element  any request that is not handled by another mapping is forwarded to the server servlet   And Most importantly we should Know about Rule for URL path mapping   The container will try to find an exact match of the path of the request to the path of the servlet  A successful match selects the servlet  The container will recursively try to match the longest path-prefix  This is done by stepping down the path tree a directory at a time  using the         character as a path separator  The longest match determines the servlet selected  If the last segment in the URL path contains an extension  e g   jsp   the servlet container will try to match a servlet that handles requests for the extension  An extension is defined as the part of the last segment after the last         character  If neither of the previous three rules result in a servlet match  the container will attempt to serve content appropriate for the resource requested  If a    default    servlet is defined for the application  it will be used    Reference URL Pattern

[java] What is the significance of url-pattern in web.xml and how to configure servlet?

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