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Martin Hope
Yeti
Asked: 2014-02-12 09:55:15 +0800 CST
  • 2

Setup

I use Apache Tomcat 7 on an Arch linux distribution, and my webapps directory is located at /usr/share/tomcat7/webapps. In this directory one should create a directory, and put META-INF and WEB-INF directories in it with xml configuration files. Then this directory will be the main path of the webapp. Thus for example:

If /usr/share/tomcat7/webapps/foo/bar.html contains:

<!DOCTYPE html>
<html>
  <body>
    Hello world!
  </body>
</html>

Then http://localhost:8080/foo will show:

Hello world!

However, the goal is to have an external dynamic project (distributed by Netbeans in this case) as a webapp. So in that case I would like to locate my webapp here: /home/user/NetbeansProjects/foo/build/web/ (which contains bar.html).

I've come up with three possible approaches but none are working and I think I'm missing something.

Approach 1 (symlink)

I was thinking, let's put a symlink (symbolic link) in the webapps directory using this command:

$ ln -s /home/user/NetbeansProjects/foo/build/web /usr/share/tomcat7/webapps/foo

This seems like the most elegant approach, but Tomcat is not able to read the directory. Why not?

Approach 2 (mount --bind)

I read that you could also redirect one directory to another using mount --bind. So I tried to do this:

sudo mount --bind /usr/share/tomcat7/webapps/foo /home/user/NetbeansProjects/foo/build/web

Actually, this is the only solution that does work. Unfortunately, if I build the project again the mount will disappear. I have already tried to remount the directory after distributing the project using <exec/> in Ant, but this makes Linux crash for some weird reason. So this is not an option either. Also remounting after every clean-build seems not a clean approach. Mounting is also not really used for this kind of stuff, so I imagine the solution will not involve mounting.

Approach 3 (server.xml)

The last thing I want to do is to go againsts the recommendations of the Apache folks (see here). Which says:

It is NOT recommended to place elements directly in the server.xml file.

So what do I do, I take the default server.xml and add this Context-tag to the Host-tag:

<Context docBase="/home/user/NetbeansProjects/foo/build/web/" path="/foo"></Context>

However, if I restart the Tomcat service it fails to start. In the logfiles I read:

SEVERE: Error starting static Resources
java.lang.IllegalArgumentException: Document base /home/user/NetbeansProjects/foo/build/web does not exist or is not a readable directory

So, obviously this must be some kind of permission problem. Since I double checked for spelling errors the path must be correct. But I am not able to solve this, what I have done to grant tomcat7 (group: tomcat7) permission is:

chown -R tomcat7:tomcat7 /home/user/NetbeansProjects/foo/build/web
chmod -R 755 /home/user/NetbeansProjects/foo/build/web

But after restarting Tomcat, the same error occurs and Tomcat fails to start.

Which approach above is the most sensible, and what am I doing wrong that's preventing it from working?

linux
Martin Hope
Yeti
Asked: 2012-09-21 03:19:28 +0800 CST
  • 2

I want to reload (or restart) one specific web application on an Apache Tomcat (6 or 7) server without Tomcat Manager or the automatic Reloadable attribute. Using the manager would give again another security risk, and reloadable attribute does not work when you need to upload/copy large files since it already reloads when the upload has not yet finished.

Being root, it should be easy to reload a specific web application, instead of doing a Tomcat service restart (which reloads every web application on it), right?

tomcat
Martin Hope
Yeti
Asked: 2012-05-04 07:08:00 +0800 CST
  • 1

I got an Apache Tomcat 7 server. If I change a file on the server (for example stylesheet, javascript file or any plain/text file), for example using vim. Then if I go to the file in an internet browser, and press F5 a few times till I see the actual change, I have to wait (while pressing F5 every 500 ms) a few seconds (~3 seconds) before I see what I just changed.

Thus in short: if a file is changed on the server, I see it ~3 seconds later client side. So somewhere there has to be a cache, probably server side since I use F5 which should discard client side cache. So how can I setup a directory on my Apache Tomcat server so that it will not cache files?

I want to do this because I created a simple Ajax/Servlet based website to chat. But after typing a message, it will appear ~3 secs later. I know this can be way faster, because I have done it before on a PHP free webhost server.

tomcat
Martin Hope
Yeti
Asked: 2012-04-20 12:41:27 +0800 CST
  • 1

I have an Apache Tomcat 7 server. I have a quite complex Java Servlet application running on it which needs some MySQL queries per POST. Thus I need a MySQL Database connection to do the query. Currently I use the following Java code to create the DataSource:

//db is for example: jdbc:mysql://127.0.0.1:3306/databasename
DataSource ds = new DataSource(initPoolProperties(db, user, pass));

private PoolProperties initPoolProperties(String db, String user, String pass)
{
    PoolProperties defaultPoolProperties = new PoolProperties();
    defaultPoolProperties.setUrl(db);
    defaultPoolProperties.setUsername(user);
    defaultPoolProperties.setPassword(pass);
    defaultPoolProperties.setDriverClassName("com.mysql.jdbc.Driver");
    // And a long list of properties here ...

    return defaultPoolProperties;
}

In my whole hierarchical Java Servlet application I only create one DataSource per Database connection per POST (by HTML Form to browse through the website). After this I use a few times ds.getConnection() to get the connection needed for executing some MySQL queries.

Everybody seems to use a JNDI DataSource. Which means they define a tag in the context.xml of their application, and use a JNDI lookup to get the DataSource, and use the connections the way I do it as well.

The question is wether I am actually doing the same thing here. Are the connections I use, pooled and shared between multiple visitors/clients? Because my online website application is going to be used a lot, and some pages contain quite heavy SQL queries. And I do not want to risk a person to be waiting for longer than 0.01 seconds loading the page.

I read about the way I do it (as shown above in the small simplified code example) on this website: http://tomcat.apache.org/tomcat-7.0-doc/jdbc-pool.html Scroll down a bit and you will find the Good ol' Java section, I think it is the same as using the , but I'm not sure. How can I be sure of my application using connection pooling and sharing those between clients anyways?

PS I prefer using the PoolProperties instead of putting something in the context.xml since I use multiple databases which are defined in a configuration database. The database which is selected, depends on the user. Thus I can more easily maintain the databases in a MySQL administration program this way, than putting as well lots of code in the context.xml.

tomcat mysql jdbc connection-pool