I have to realise a web application, on a Ubuntu server, using the Guacamole application, that has been developped by the Apache foundation. In order to understand how to manipulate it, I followed their official documentation, and tried to code my own application, but I can't manage to reach the said application.
The issue doesn't seem to come from Tomcat itself, for it sucessfully manages to host their original guacamole client, given in the said documentation. However, when I try to put my own code in the tomcat9/webapp/ directory, Tomcat just isn't able to launch the application. The manager is able to recognise it, and the app is actually displayed in the app list, but if I try to hit the "start button", I get an error that says :
FAIL - The application for the given context path [/guacamole-tutorial-1.4.0] can't be started
(The message may not be exact here, for it is displayed in my language, and I had to translate it)
I tried to search on internet some help, but I haven't been able to find any solution so far. I've seen a lot of people saying that one should check the logs whenever such issue occurs, but mine doesn't have any error entry. The file just ends up with the two following lines :
2022 06:47:10,753 INFOS [http-nio-8080-exec-29] org.apache.catalina.core.ApplicationContext.log HTMLManager : start: Starting web application '/guacamole-tutorial-1.4.0'
2022 06:47:10,753 INFOS [http-nio-8080-exec-35] org.apache.catalina.core.ApplicationContext.log HTMLManager : list Listing contexts for virtual host 'localhost'
My application is deployed as a .war file, in the same location as the guacamole clients, that actually works. I use Maven to compile the project, as told in Guacamole's documentation, and Nginx as a reverse proxy for Tomcat.
Thanks in advance.
After a few days of research, I managed to find the origin of the error, that happened because of my web.xml file. First, unlike what the tutorial said, it shouldn't begin with the tag, but with :
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">
Then, I also found out that the way the Guacamole documentation tells how to declare the servlet is wrong. After fixing it, my application worked out.
I hope that this will help any other person that struggles with that part of Guacamole. I'll also add two pages that helped me understanding how to write the web.xml file :
http://www-igm.univ-mlv.fr/~dr/XPOSE2003/tomcat/tomcat.php?rub=16
https://mkyong.com/maven/how-to-create-a-web-application-project-with-maven/
Related
Experts,
My dynamic web project having 3 JSP page and 3 servlets .. and everthing was working fine till date.
when i executed the same project today, it was showing this below message.
The webpage cannot be found - HTTP 404
I deleted the whole project after trying multiple checks... now in web.xml if i remove the servlets section, its displaying the jsp content. but if i add the servlet back its throwing same page cannot be found :(
no error in project and i dont see any logs in eclipse... can someone please tel me why this is happening?
Appreciate your input. Thanks
Below are a few general suggestions on debugging web apps:
3 and 4 would be the first checks for 404.
Try to start the web app in the debug mode, and place the break point in the servlet method: any hit? (or just put a System.out.println in the Servlet);
Check the structure of the dynamic web project in Eclipse: are the compiled java classes of the servlets in there?
Check the context path (url) of the dynamic web project in eclipse project config: not accidentally changed?
Check the log files of the tomcat (access logs and catalina logs) your dynamic web project is associated with.
First of all, I am aware that there are other questions regarding Tomcat, Eclipse, and the infamous 404 error. However, none of them manages to resolve the issue. I have spent well over 24 hours on this issue.
To save time, when I configured everything (including Tomcat, and creating a server in Eclipse), I:
• Changed the server location from "workspace metadata" to its correct location by using the "Switch Location" button located in the server's Properties window.
• I chose the "Use Tomcat Installation" option in Server Locations, and saved the choice I made.
In both cases, I restarted the server. If you're curious as to what app I'm currently working on, it's a simple Hello World app, found at: http://theopentutorials.com/examples/java-ee/servlet/how-to-create-a-servlet-with-eclipse-and-tomcat/
• I have included the Java file in the "welcome file" list inside web.xml.
Lastly, out of curiosity, why does the Eclipse browser only go to the project directory, and not the servlet itself? (If I add on the servlet name, then "Hello World" appears).
• Yes, if I enter "http://localhost:8080", the default Tomcat page appears, so no issues there.
Can anyone clue me in, as to why I am still getting 404s after all this, and following advice that has been marked as "Accepted" here at SO, such as the following:
HTTP Status 404 - The requested resource (/) is not available
Thanks in advance for any help, it is greatly appreciated.
The error 404 may occur because of large amount of different reasons. In order to resolve that, you should check your tomcat log file out first. It contains by the path:
%PATH_TO_WORKSPACE%\.metadata\.plugins\org.eclipse.wst.server.core\tmp%SERVER_NUMBER%\
logs
Usually it contains some stacktraces which discribes the problem. If not, then you should check your deployed application out there:
%PATH_TO_WORKSPACE%\.metadata\.plugins\org.eclipse.wst.server.core\
tmp%SERVER_NUMBER%\___YOUR_APP____
It might happen that your application was not deployed correctly by eclipse plugin (happens very often) and you should try this:
Project --> clean
'Right click on your server' --> clean
Or just remove your webapp from the directory I mentioned erlier and redeploy it from scratch.
There is something basic you need to understand regarding using tomcat(or application server for that matter). There is a slight difference between using from Eclipse and using from outside
Using From within Eclipse
What happens here is that Eclipse (by default) uses a copy of your tomcat installation and places it in its metadata workplace. This secondary tomcat is used by Eclipse for all deployments, re-deployments and all. Keep in mind that this is not your original copy of tomcat installation.
The difference in this tomcat installation is that is actually a minimal server, meaning that although it has all the deployment capabilities, it does not have some of the extra features that come with the tomcat installation and one main feature is the tomcat's homepage (the only reason why people out there get the infamous 404 resource not found when they try to run-on-server their application).
Workaround
Although not an issue (nor a bug from the Apache's end), you can still view your application by changing the URL to your application's url, homepage or no homepage ! All you have to do is change the url from http://localhost:8080 to http://localhost:8080/yourApplicationName and voila , the default page of your application will be shown that you mentioned in the welcome-page-list. Keep note that if you didn't specify a default page in your web.xml, you will again wind up with, yet again, the dreaded 404 resource not found page. The reason is that Tomcat has found your application, but it doesn't know what to do at the root context of your application. You can either map your servlet to the root of the application (that way it will always run at http://localhost:8080/yourApplicationName) or you can change the URL to the url-pattern that you mapped with the servlet in the web.xml, it must be something like http://localhost:8080/myApplicationName/myServletMappingPattern
I'm trying to deploy my first servlet to my server. There are, of course, many tutorials online. But most of them are very detailed and complicated, and I only need to deploy a few simply servlets to this server.
I found what I think to be the shortest method of deployment: Deployment on Tomcat Startup. I moved my .WAR file (FirstProject.war) into $CATALINA_BASE/webapps folder, but when trying to access it (ServerIP/FirstProject) I get the "The requested resource is not available." error.
Is there anything I forgot in the process of deployment?
I know that deployOnStartup has to be set to true, but I didn't change anything with the server's hosts, so the current host is localhost. I didn't change its settings, so deployOnStartup should be true (It's said that true is the default).
What am I missing?
You are using easiest way but I don't know what you are missing. Here what I would suggest is run your server and access through localhost:8080 then click manage app then enter username and password then you can deploy your war.
If you have any query post command.
Even i used to face this problem while deploying my first web application on Jboss and Apache ..
Even though your code is working properly with all your servlet mappings and paths using in your content files ...some times they kick back in real time environment ..So we have to know the proper deployment folder structure and accordingly we have to change our paths in the code
what i am concluding is check the below lines of code
Examples, assuming root is http://foo.com/site/
Absolute path, no matter where we are on the site
/foo.html
will refer to http://foo.com/site/foo.html
Relative path, assuming the containing link is located in http://foo.com/site/part1/bar.html
../part2/quux.html
will refer to http://foo.com/site/part2/quux.html
or
part2/blue.html
will refer to http://foo.com/site/part1/part2/blue.html
I have a Java EE 5 application which consists of three web projects. I'm using JBoss 5.1 web server and NetBeans 7.2 IDE.
I have the following problems:
I cannot start application in Debug mode. That I know of, there are two (best) approaches in NetBeans and Java: Remote debugging and debugging via shared memory. I read this post How to debug JBOSS application in netbeans? and I set debug parameters in Jboss configuration(I also know there are different parameter sets for shared memory and remote debugging), but when I go to attach debugger I got following errors:
If I use remote debugging I got error "Connection refused";
If I use shared memory I got error similar to this text "dt_shmem:file path could not be found".
These errors occur when I start JBoss by running run.bat file. If I start JBoss from Netbeans IDE, I can attach to remote process (still have problem with shared memory approach), but then I have other problems, regarding variable primitives and model binding in page life cycle (I will not write about that now).
How can I solve these problems so I can debug application? At least, how can I find a better error message when it fails. I could not find too much on the Net by looking for "Connection refused" error only.
Why I cannot just press run main project(or web project) and that netbeans start application, open it in new browser tab(as localhost) and start debug mode? I'm coming from .net background and VS is offering this as out of the box tool (called ASP .NET development server). Why I have to use external web server and with every change deploy new application and then attach to it? Why Netbeans cannot by default use JVM for running application, and later when I deploy application I will choose which web server to use!?
I hope someone will make this clear to me :)
Thanks
added Note at 03.01.2013.
Well, when I changed VM options in project.properties file of web project (added run.args.extra=-J-Xms256m -J-Xmx756m), I succeeded to debug application and heat breakpoint when executing the code. However, I still have strange problem with Managed Bean properties. I have select list on page, and it is connected to Boolean property. When nothing is selected it should be set to null value by default (and it is when I start JBoss server by running run.bat file), but its value is by default set to false! I checked parameters post values in firebug and there is no problem in posting parameters to bean. It looks to me that problem is when JSF framework is trying to map post values to Managed Beans properties, but I cannot find out why this is happening. I also checked faces-config.xml, but did not find any specific rule for mapping to this specific property. Any tips?
I have installed Tomcat 5.0 in order to execute a web application. How can I show my files which are present in Tomcat to the web browser? I tried http://hostname:8080/myfolder/login.html, but I can't see the files.
One more thing I know about JDBC and other database connectivity and I have developed a HTML page. How can I let a button in the page execute the code written in a Servlet and perform validations?
The simplest thing is to add to the root webapp. That is webapps/ROOT. Any file you put in there will be served unless you change the default configuration.
You should read about the details, of course.
I have installed Tomcat 5.0 in order to execute a web application.
First of all, why are you using the ancient (8 year old) Tomcat 5.0? If you can, rather grab the latest one, Tomcat 6.0.
How can I show my files which are present in Tomcat to the web browser? I tried http://hostname:8080/myfolder/login.html, but I can't see the files.
Is myfolder the context name or just a folder in your webcontent? If it's a context name, then you need to ensure that it's properly deployed. You can find details in the server logs in the /logs folder. If it is a folder in your webcontent and the webapplication is thus supposedly to be the "root" application, then you need to ensure that it's deployed as ROOT.
To learn more about using Tomcat, go through the documentation.
One more thing I know about JDBC and other database connectivity and I have developed a HTML page. How can I let a button in the page execute the code written in a Servlet and perform validations?
To the point, just create a class which extends HttpServlet, implement the doPost() method, define the servlet in web.xml and let the action attribute of the HTML <form> element point to an URL which is covered by the url-pattern of the servlet mapping in the web.xml.
As the question is pretty broad, I have the impression that you haven't learned in any way how to work with Tomcat and JSP/Servlets. I would strongly recommend to go through those tutorials to familarize yourself with JSP/Servlet on Tomcat and Eclipse (an IDE) first: Beginning and Intermediate-Level Servlet, JSP, and JDBC Tutorials
Tomcat is not a web server like, say, Apache. It's a servlet container. You can not just move file in a subfolder which seem to be what you did. You need to pack your web application in a .war and deploy it.
The URL should rather be http://host:8080/webapp/subfolder/login.jsp
Without much information it's hard to help. Please edit your question and describe what you've done so far.