vincentkong.com » Tomcat

Problem using MySQL JDBC on Tomcat 5.5 and Ubuntu 8.04

Vincent Kong — Wed, 05 Nov 2008 03:36:39 +0000

Normally when I build a web application that connects to a MySQL database, I would place the mysql-connector-java-bin.jar file into the WEB-INF/lib of the web application.

However, when I deployed the application on Tomcat 5.5 on Ubuntu 8.04 I got an exception: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver

I couldn’t find the reason which caused the exception, so I did a quick fix by placing the jar file into the Tomcat’s common lib directory.

$ cp mysql-connector-java-bin.jar /usr/share/java $ cd /usr/share/tomcat5.5/common/lib $ ln -s ../../../java/mysql-connector-java-bin.jar mysql-connector-java-bin.jar

Problems with Ubuntu 7.10 and Tomcat 5.5

Vincent Kong — Tue, 15 Jan 2008 02:51:32 +0000

Ubuntu 7.10 (Gutsy Gibbon) was released on Oct 18, 2007, and like most administrators I decided to take advantage of the release and upgraded my current system 7.04 (Feisty Fawn). Overall, the upgrade went well and I didn’t run into any trouble during the upgrade process. However, afterwards I found some side effect on the my web applications running on Tomcat:

Log4j was no longer logging anything into the log files.
I was getting the following exception in the catalina.log file when attempting to dynamically render an image with a java servlet.
java.lang.UnsatisfiedLinkError: /usr/lib/jvm/java-1.5.0-sun-1.5.0.13/jre/lib/i386/libawt.so: Can't load IA 32-bit .so on a IA 32-bit platform at java.lang.ClassLoader$NativeLibrary.load(Native Method) at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1751) at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1668) at java.lang.Runtime.loadLibrary0(Runtime.java:822) at java.lang.System.loadLibrary(System.java:993) at sun.security.action.LoadLibraryAction.run(LoadLibraryAction.java:50) at java.security.AccessController.doPrivileged(Native Method) at java.awt.Toolkit.loadLibraries(Toolkit.java:1509) at java.awt.Toolkit.(Toolkit.java:1530) at java.awt.Font.(Font.java:141) ....

It turned out that the Java JVM was upgraded to 1.5.0_13-b05 which contained several bugs. Not knowing of anyway to downgrade my JVM to it’s preivous version, I decided to install Java 6 and use it as the JVM for Tomcat.

To install Java 6 for Ubuntu:
$ apt-get install sun-java6-jdk

To configuring Tomcat to run on the Java 6 JVM:
$ nano /etc/default/tomcat5.5

Uncomment or add the following line:
JAVA_HOME=/usr/lib/jvm/java-6-sun

Restart the Tomcat server:
$ /etc/init.d/tomcat5.5 restart

Afterwards, everything was running back to normal!

Tomcat 5.5 Doesn’t Start in Ubuntu 7.10

Vincent Kong — Wed, 31 Oct 2007 01:15:28 +0000

This is related to one of the web application deployed in Tomcat containing the
Apache Common Loggings jar file inside the WEB-INF/lib directory. To
fix this issue, place a copy of the commons-logging jar file inside the
Tomcat’s common endorsed directory.

$ cp commons-logging-1.1.jar /usr/share/java
$ cd /usr/share/tomcat5.5/common/endorsed
$ ln -s ../../../java/commons-logging-1.1.jar commons-logging-1.1.jar

Tomcat 5.5 Doesn’t Start in Ubuntu 7.04

Vincent Kong — Tue, 30 Oct 2007 16:11:32 +0000

For the Ubuntu installation, Tomcat’s log file is set to be a pipe, but

Tomcat can’t seem to start with it. A quick fix will be to recreate it
as a regular file with the same security settings and restart Tomcat.

$ cd /var/log/tomcat5.5
$ sudo rm catalina.out
$ sudo touch catalina.out
$ sudo chown tomcat55:nogroup catalina.out
$ sudo chmod 600 catalina.out

Integrating Tomcat and Apache with mod_jk Connector

Vincent Kong — Fri, 08 Jun 2007 16:09:13 +0000

Using the mod_jk connector is an alternative but more complex method of integrating Tomcat and Apache together. The concept behind this method is to have Apache serve the static content of the website, and Tomcat to serve the Java related content. This could be a better alternative if your website contains mostly HTML pages.

The mod_jk connector along with mod_proxy_ajp are the only recommend methods of Tomcat and Apache integration. mod_jk is still actively under development, and is very stable for production servers, as well it supports both Apache 1.3, and 2.x. Other past alternatives like mod_webapp, mod_jserv, mod_jk2 are not longer supported and are consider deprecated.

mod_jk Package Issue for Ubuntu

For Ubuntu 7.04 there is an error in the mod_jk package. It currently has two packages for mod_jk:

libapache-mod-jk which depends on apache
libapache2-mod-jk2 which depends on apache2

As mention previously, mod_jk2 is already deprecated and mod_jk works for both Apache 1.3, and 2.x.

To properly configure Tomcat and Apache to use mod_jk the connector must be manually, build and set up from the source.

Installing and Configuring mod_jk

Download and extract the latest connector from the Tomcat website http://tomcat.apache.org/download-connectors.cgi, then configure and build it:

$ cd tomcat-connectors-1.2.23-src/native
$ ./buildconf.sh
$ ./configure --with-apxs=/usr/bin/apxs2
$ make; make install

Verify the mod_jk.so module exist in the apache module directory /usr/lib/apache2/module.

Note: The programs are required to configure and build the connector: automake, autoconf, libtoolize, and apxs2. To obtain these programs install the following packages in Ubuntu: libtool, automake, and apache2-threaded-dev

libtool error when compiling

On some systems the 'make' command will fail with the following error:

libtool: compile: unable to infer tagged configuration
libtool: compile: specify a tag with `--tag'

This is due to libtool not using the correct gcc when compiling. A workaround would be to add the parameter '--tag CXX' inside the Makefile.

$ cd  tomcat-connectors-1.2.23-src/native/common
$ nano Makefile

Inside the Makefile the change line from:

LIBTOOL = /usr/share/apr-1.0/build/libtool --silent

to:

LIBTOOL = /usr/share/apr-1.0/build/libtool --silent --tag CXX

Creating the workers.properties

Create a workers.properties file in the Apache configuration directory and add the following lines to it.

$ nano /etc/apache2/workers.properties

# This file provides minimal jk configuration properties needed to
# connect to Tomcat.
workers.tomcat_home=/usr/share/tomcat5.5
workers.java_home=/usr/lib/java-1.5.0-sun
ps=/
# Define 1 real worker using ajp13
worker.list=worker1
# Set properties for worker1 (ajp13)
worker.default.port=8009
worker.default.host=localhost
worker.default.type=ajp13
worker.default.lbfactor=1

Configure Apache for mod_jk

Create the jk module configuration files for Apache

$ nano /etc/apache2/mods-available/jk.load

LoadModule jk_module /usr/lib/apache2/modules/mod_jk.so

$ nano /etc/apache2/mods-available/jk.conf


    # Where to find workers.properties
    JkWorkersFile /etc/apache2/workers.properties

    # Where to put jk logs
    JkLogFile /var/log/apache2/mod_jk.log

    # Set the jk log level [debug/error/info]
    JkLogLevel info

    # Select the log format
    JkLogStampFormat "[%a %b %d %H:%M:%S %Y] "

    # JkOptions indicate to send SSL KEY SIZE,
    JkOptions +ForwardKeySize +ForwardURICompat -ForwardDirectories

    # JkRequestLogFormat set the request format
    JkRequestLogFormat "%w %V %T"

    # Globally deny access to the WEB-INF directory
    
         Order deny,allow
         Deny from all

After creating the configuration files you can now enable the jk module for Apache

$ a2enmod jk

Sending JSP and Servlets through mod_jk

Inside the virtual host you can mount JSP and Servlet context to the worker define in the workers.properties file. For example to mount the JSP and Servlet examples from Tomcat add the following lines:

JkMount /jsp-examples/*.jsp worker1
JkMount /servlets-examples/servlet/* worker1

Apache DirectoryIndex

If your website uses index.jsp it must be download inside the DirectoryIndex of Apache. Modified the file /etc/apache2/mods-enabled/dir.conf and add index.jsp to the list.

Integrating Tomcat and Apache Using Proxy

Vincent Kong — Wed, 30 May 2007 16:07:30 +0000

This easiest way to integrate Tomcat and Apache together is to have Tomcat run behind Apache which behaves like a proxy server.

Enable the proxy module for Apache.

$ a2enmod proxy $ a2enmod proxy_http (To allow Apache to forward to Tomcat HTTP Connector)

Include the following in the Apache configuration file:

ServerName tomcat.example.com

ProxyPass / http://localhost:8080/
ProxyPassReverse  /  http://localhost:8080/

The above example tells Apache to forward URLs from http://tomcat.example.com/* to Tomcat’s Http Connector which is setup to be listening on port 8080 and assumes that you have setup a virtual host in Tomcat for tomcat.example.com.

When you are running behind a proxy server, you will sometimes prefer to manage the values returned by:

ServletRequest.getServerName(): Returns the host name of the server to which the request was sent.
ServletRequest.getServerPort(): Returns the host name of the server to which the request was sent.

In general, you may want the port number to reflect that specified in the original request, not the one on which the HTTP Connector itself is listening. You can use the proxyName and proxyPort attributes on the element to configure these values.

In the server.xml you can uncomment the line similar to the one below, if you still want to keep the HTTP Connector to continue listening on 8080.

After you have restarted Tomcat, ServletRequest.getServerName(), and ServletRequest.getServerPort() will return www.mycompany.com and 80 respectively.

Using the AJP Connector

AJP is an optimized version of the HTTP protocol to allow a web server such as Apache talk to Tomcat. When integrating Tomcat with Apache, the AJP connector will provide faster performance than proxied HTTP.

Enable APJ proxy module in Apache:

$ a2enmod proxy_ajp

In the Apache configuration file add the following:

ProxyPass / ajp://localhost:8009/
ProxyPassReverse  /  ajp://localhost:8009/

The default port used by the AJP connector in Tomcat is 8009, and can be enable using the following line inside the server.xml file.

Tomcat 5.5 for Ubuntu Quickstart Guide

Vincent Kong — Tue, 29 May 2007 16:05:13 +0000

Apache Tomcat is a web container developed at the Apache Software Foundation (ASF). Tomcat implements the servlet and the JavaServer Pages (JSP) specifications from Sun Microsystems, providing an environment for Java code to run in cooperation with a web server.

Installing Tomcat for Ubuntu

$ sudo apt-get install tomcat5.5

Starting and Stopping Tomcat

The /etc/init.d/tomcat5.5 script and the following options {start | stop | restart | try-restart | force-reload | status} is use to control the server.

Directories and Configuration Files

/etc/tomcat5.5 Configuration directory for Tomcat
/var/lib/tomcat5.5 Base directory (CATALINA_BASE) for Tomcat
/usr/share/tomcat5.5 Home directory (CATALINA_HOME) for Tomcat

The default configuration can be found at /etc/default/tomcat5.5 as well the directory /etc/tomcat5.5 contains other configuration files:

server.xml The server configuration file for Tomcat.
web.xml The default deployment descriptor.
policy.d This directory contains several policy files for SecurityManager. During start up these files will be appended together to auto generate the catalina.policy in the $CATALINA_BASE/conf/ directory.

Running Tomcat’s Servlet and JSP Examples

To install Tomcat’s example applications

$ apt-get install tomcat5.5-webapps

The examples will be installed in the /usr/share/tomcat5.5-webapps directory. To view the examples point your browser to http://localhost:8180, where 8180 is the default port for the Tomcat installation. To change it, modify the HTTP Connector in the server.xml file:

For more information on the HTTP Connector refer to http://tomcat.apache.org/tomcat-5.5-doc/config/http.html

Enabling/Disabling SecurityManager

The default installation of Tomcat has SecurityManager is enabled in the startup script. To enable/disable SecurityManager edit the file /etc/init.d/tomcat5.5 and set the variable TOMCAT5_SECURITY to yes/no.

An alternative is to modified the file /etc/default/tomcat5.5.

Defining Virtual Host

To define a new virtual host modify the server.xml and add a new host inside the Catalina Engine container.


    
        example.com

If the Context is not defined the default docBase would be ROOT, i.e. you will need to deploy you application in /path/to/webapp/ROOT.

For more information on the Host configuration attributes refer to http://tomcat.apache.org/tomcat-5.5-doc/config/host.html.
For more informaton on the Context configuration attributes refer to http://tomcat.apache.org/tomcat-5.5-doc/config/context.html