servlets

问题 I'm new and just developing on J2EE. I am modifying an existing application (an OpenSource project). I need to save an image on a client sent by the server, but I do not know how. This activity must be done in a transparent manner without affecting the existing operation of the application. From the tests done I get this error: java.lang.IllegalStateException: getWriter () has Already Been Called for this response. How should carry out this task, according to your own opinion? How do I save

问题 My technology stack is Tomcat (servlet 3.0), Jersey for JAX-RS, Spring and Hibernate. When something unexpect goes wrong like some data conversion error in Hibernate, I do not want the clients to see my stacktrace for those exceptions that the Tomcat tries to print by default. However I would like to log those exceptions so I can find what is wrong and fix things. My first try was using ExceptionMapper from JAX-RS and naively thinking that would solve my problems. But then I noticed that

问题 suppose that I want to accept the following urls: http://myserver/myapplication/posts http://myserver/myapplication/posts/<id> http://myserver/myapplication/posts/<id>/delete how can I use the servlet decorator @WebServlet to do so? I'm investigating value and urlPatterns but I don't get how to do so. For example, @WebServlet(urlPatterns={"/posts", "/posts/*"}) [..] String param = request.getPathInfo(); gives me some result, but how to use it? Also, request.getPathInfo() seems to return the

问题 I'm using tomcat 7 to run my servlets on my Dynamic web project in java (eclipse ee). I've added to my web.xml file the following paragraph (from https://tomcat.apache.org/tomcat-7.0-doc/config/filter.html#CORS_Filter/Introduction): <filter> <filter-name>CorsFilter</filter-name> <filter-class>org.apache.catalina.filters.CorsFilter</filter-class> </filter> <filter-mapping> <filter-name>CorsFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>" I am trying to use the post request

问题 How to link a JSP ,servlet and a Java view bean? I donot want to have any scriplet in JSP. How can i ask my JSP to invoke servlet to set the Implicit request and response objects and then display the properties from view bean on the jsp. I need to pass request and response objects from jsp to servlet and then i want to display the properties defined in view bean to a JSP page. JSP -> Servlet -> View Bean -> JSP How to achieve this? 回答1: No need to pass request and response to the bean/model

问题 I read this other posting about how to add a servlet filter in Spring Boot, but I am getting a No Default Constructor error when I try to follow its example of adding an inner WebConfig class within the UiApplication.java class file. I am trying this because adding ignoring(/api-url to the app's SecurityConfig class caused a message stating the /api-url has an empty filter list . I want to add a servlet filter for /api-url so that its filter list is no longer empty. The code for the WebConfig

问题 I am studying servlets I read that servlets are java programs but there are no constructor in servlet... Can anybody elaborate on it? 回答1: There are as in any other java class, but you don't need to invoke it. The webcontainer will call it for you. Most servlets do not hold instance data, hence, most of adding code in the constructor doesn't make any sense. 回答2: If you need to initialize your servlet you'll have to override the init method. 回答3: There is a constructor in servlet (take a look

问题 I am studying servlets I read that servlets are java programs but there are no constructor in servlet... Can anybody elaborate on it? 回答1: There are as in any other java class, but you don't need to invoke it. The webcontainer will call it for you. Most servlets do not hold instance data, hence, most of adding code in the constructor doesn't make any sense. 回答2: If you need to initialize your servlet you'll have to override the init method. 回答3: There is a constructor in servlet (take a look

问题 I'm trying to get the windows user name of the user in my web application. Can any one suggest how to get it? I'm developing a web application. So if a user is accessing my application, then I need to get the user's windows id and his host name. I tried a few different ways but it never worked. Any suggestions are highly appreciated. 回答1: Windows user details are not sent in plain HTTP requests, which makes it impossible for you to derive them from a user in a web application without

问题 This question already has an answer here : How to download file from httpServlet with Jquery? (1 answer) Closed 2 years ago . I'm pretty new to jQuery and ajax and i have a question. In a jsp I call function downloadDocument(documentId){ var action = "attachment.do"; var method = "downloadDocument"; var url = action + "?actionType="+method+"&documentId=" + documentId; $.ajax({ url: url, dataType: "json", type: 'POST', success: function(data){ alert("downloaded!"); }, error: function (request,