org.apache.jasper.JasperException: The absolute uri: http://java.sun.com/jstl/core cannot be resolved in either web.xml or the jar files deployed with this application That URI is for JSTL 1.0, but you’re actually using JSTL 1.2 which uses URIs with an additional /jsp path (because JSTL, who invented EL expressions, was since version 1.1 integrated as part of JSP 2.0 … Read more
JSP (JavaServer Pages) JSP is a Java view technology running on the server machine which allows you to write template text in client side languages (like HTML, CSS, JavaScript, ect.). JSP supports taglibs, which are backed by pieces of Java code that let you control the page flow or output dynamically. A well-known taglib is … Read more
You can and should not disable the browser back button or history. That’s bad for user experience. There are JavaScript hacks, but they are not reliable and will also not work when the client has JS disabled. Your concrete problem is that the requested page is been loaded from the browser cache instead of straight … Read more
All relative URLs in the HTML page generated by the JSP file are relative to the current request URL (the URL as you see in the browser address bar) and not to the location of the JSP file in the server side as you seem to expect. It’s namely the webbrowser who has to download … Read more
A bit decent web application consists of a mix of design patterns. I’ll mention only the most important ones. Model View Controller pattern The core (architectural) design pattern you’d like to use is the Model-View-Controller pattern. The Controller is to be represented by a Servlet which (in)directly creates/uses a specific Model and View based on … Read more
Let’s see in steps what should happen: JSP is basically a view technology which is supposed to generate HTML output. To display an image in HTML, you need the HTML <img> element. To let it locate an image, you need to specify its src attribute. The src attribute needs to point to a valid http:// … Read more
In a well designed MVC approach, the JSP file should not contain any line of Java code and the servlet class should not contain any line of JDBC code. Assuming that you want to show a list of products in a webshop, the following code needs to be created. A Product class representing a real … Read more
2019 modern browsers update This is the approach I’d now recommend with a few caveats: A relatively modern browser is required If the file is expected to be very large you should likely do something similar to the original approach (iframe and cookie) because some of the below operations could likely consume system memory at … Read more
Indeed, the keyword is “Ajax”: Asynchronous JavaScript and XML. However, last years it’s more than often Asynchronous JavaScript and JSON. Basically, you let JavaScript execute an asynchronous HTTP request and update the HTML DOM tree based on the response data. Since it’s pretty tedious work to make it to work across all browsers (especially Internet … Read more
Introduction This can have a lot of causes which are broken down in following sections: Put servlet class in a package Set servlet URL in url-pattern @WebServlet works only on Servlet 3.0 or newer javax.servlet.* doesn’t work anymore in Servlet 5.0 or newer Make sure compiled *.class file is present in built WAR Test the … Read more