Apache Tomcat 7 Essentials: This book takes you from beginner to expert in logical stages, covering all the essentials of Tomcat 7 from trouble-free installation to building your own middleware servers. Packed with examples and illustrations.

Apache Tomcat can be classified based on different components, such as the JDK version, enhancement, stability, and so on. Let's take a real time example, where you want to take a decision on which Apache Tomcat version to deploy for an application. For example, if an application is using Servlet 2.4 and JSP 2.0, then we should always go for the 5.x version. In reality, it's a difficult job to find out which version of Tomcat we should use to utilize the system resource properly.

Normally, these tasks would be done by the company's technical architect, and they are solely responsible for the technical specifications used in any product. Based on the features of Tomcat, let us quickly go through the comparison of Tomcat with different versions:

In the previous table, highly unlikely means that the user using the previous version necessarily needs to have the upgraded higher version to support the new improved features. It also involves security fixes for the current version.

In the previous section, we discussed the various support matrices for Tomcat versions, we are now aware of the support specifications (JDK support, EJB, and Servlet) for Tomcat. Let's try to understand, and quickly review the new features/enhancements for Tomcat 7.

Apache Tomcat 7.x was released with some key improvements over Tomcat 6.x and real time implementation of Servlet 3.0, JSP 2.2, and EL 2.2 specifications. Apart from these, it also solves some major issues from previous releases.

Perform the following steps to download the software:

Once the download is complete, then you have to do the integrity check for the downloaded software using the MD5 checksum.

Following is the process to perform the integrity check using the MD5 checksum:

Tomcat comes with different packages for installation such as binary, source, and RPM. Based on the requirement, the package should be taken from the official site. Let's have a brief discussion on which package should be implemented in real time and why.

Before we begin with the Apache Tomcat 7 installation, we have to configure the prerequisites and they are very important for the Tomcat 7 installation to start. Following are the prerequisites mentioned for Apache Tomcat 7:

Configuration of OS environment variables

After the installation of Java on a different OS, it's now time to set the environment variables for Tomcat at the OS level. In order to run Tomcat, we have to define the JAVA_HOME as an environment variable and set the path for Java so that it can be accessed from any partition of OS.

What is JAVA_HOME?

JAVA_HOME is the JDK install directory, for example, C:\jdk6. It is meant to be set as an environment variable and referenced in Windows batch files or Unix scripts. In Tomcat, JAVA_HOME is defined in catalina.sh under TOMCAT_HOME/bin. The following screenshot shows the definition of JAVA_HOME in Tomcat 7. Once you execute startup.sh, it internally calls catalina.sh and invokes JAVA_HOME. In a production environment, it is always recommended to use the permanent environment variable.

Setting the JAVA_HOME and PATH variable in Windows

The environment variable and path can be set in Windows by performing the following steps:

1. 1. Right-click on the My Computer icon on your desktop and then click Properties, as shown in the following screenshot:

2. 2. Click Advanced | Environment Variables.

3. 3. Under System Variables, click New.

4. 4. In the Variable name field, enter JAVA_HOME, as shown in the following screenshot:

5. 5. In the Variable value field, enter the installation path of the Java Development Kit.

6. 6. Click OK.

7. 7. Click on Apply Changes.

Setting the global path variable in Windows

After setting JAVA_HOME, now it is time to add the Java path in the global path variable. Following is a detailed procedure, which needs to be followed for creating the global path variable in Windows:

1. 1. Right-click on the My Computer icon on your desktop and then click Properties.

2. 2. Click Advanced | Environment Variables.

3. 3. Under System Variables, click on Path.

4. 4. Edit the path and add the Java path in the end.

5. 5. In the Variable value field, enter the installation path of the Java Development Kit, as shown in the previous screenshot.

6. 6. Click OK.

7. 7. Click on Apply Changes.

Setting the JAVA_HOME and the PATH environment variable in Linux

The environment variable and path are set differently in Linux as compared to Windows. Perform the following steps to set the environment variable in Linux:

1. 1. Open the .bash_profile using the vi editor for the root user.

   Note

   You can put the environment variable in bashrc also. It will also execute at the time of the user login.

2. 2. Add the following environment variable in the file. The following is the code snippet of .bash_profile. The highlighted code shows the declaration of JAVA_HOME and PATH. export will add the JAVA_HOME and PATH to the system parameter for every user login.

   # .bash_profile
   # Get the aliases and functions
   if [ -f ~/.bashrc ];then . ~/.bashrc
   fi
   # User specific environment and start-up programs
   JAVA_HOME=/opt/jdk1.6.0_24
   PATH=$JAVA_HOME/bin:$PATH:$HOME/bin
   export PATH JAVA_HOME
   unset USERNAME
   

3. 3. Save the .bash_profile using the :wq command.

4. 4. Once you have saved the .bash_profile, then you have to logout and re-log in to the environment to activate the changes using the following command:

   su - username
   su - root (as our user is root)
   

   Note

   If we run the previous command for any user, then the profile of that user will be reloaded.

Also, you can run the env command to verify the environment variables are configured properly, as shown in the following screenshot:

Note

It is always best practice to first take the backup of the existing profile. In case there are issues while doing the changes, then we can revert back the changes using the command cp

[root@localhost ~]# cp .bash_profile .bash_profile_backup.

Now we have set the environment variable for Windows and Linux environments, but how can we verify whether the environment is set properly or not?

Before we start installation of Apache Tomcat 7, let's quickly verify the environment variable on both the OSes.

In the Windows environment, variables can be verified using the following command:

echo %VARIABLE_NAME%

For JAVA_HOME:

C:\Users\user>echo %JAVA_HOME%
C:\Program Files\Java\jdk1.6.0_24

For PATH:

C:\Users\user>echo %PATH%
C:\Program Files\PC Connectivity Solution\;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\ Program Files\Broadcom\Broadcom 802.11\Driver;
C:\Program Files\Java\jdk1.6.0_24\bin

In Linux, we can use the following command to verify the environment variables:

echo $VARIABLE_NAME

For JAVA_HOME:

[root@localhost ~]# echo $JAVA_HOME
/opt/jdk1.6.0_24

For PATH:

[root@localhost ~]# echo $PATH
/opt/jdk1.6.0_24/bin:/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/ sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

After verifying the environment variable on both the OSes, we are sure that JAVA_HOME and PATH are properly set in the environment. We have completed the prerequisites of installation of Apache Tomcat 7. Now, we can proceed with the installation of Apache Tomcat 7.

Let's start the installation of Tomcat 7 on different OSes. The steps involved to install the software on Windows are discussed first, and then we move on to the Linux environment.

We have now completed the installation of Apache Tomcat on both the OSes. Now, it's time to start the services and verify the setup we have created up to now. So why waste time, let's rock and roll.

Services in Windows

In Windows, we can start/stop the services using two methods:

• Through the Microsoft Management Console (MMC): Go to Start | Run | services.msc. When the MMC opens, as shown in the following screenshot, you can start/stop services based on the requirement:

• Apache monitor console: Tomcat comes with a very handy tool for administration, which is popularly known as the Apache monitoring console. It's very useful in managing the Tomcat instance (service recycle, enabling logs, and JVM configuration).The following screenshot shows the recycle process using the Tomcat monitoring console. To start/stop services, go to Start | Programs | Apache-Tomcat7 |apache-tomcat monitor Start/Stop.

[root@localhost bin]# ./version.sh
Using CATALINA_BASE: /opt/apache-tomcat-7.0.12
Using CATALINA_HOME: /opt/apache-tomcat-7.0.12
Using CATALINA_TMPDIR: /opt/apache-tomcat-7.0.12/temp
Using JRE_HOME: /opt/jdk1.6.0_24
Using CLASSPATH: /opt/apache-tomcat-7.0.12/bin/bootstrap.jar:/opt/apache-tomcat-7.0.12/bin/tomcat-juli.jar
Server version: Apache Tomcat/7.0.12
Server built: Apr 1 2011 06:13:02
Server number: 7.0.12.0
OS Name: Linux
OS Version: 2.6.18-8.el5
Architecture: i386
JVM Version: 1.6.0_24-b07
JVM Vendor: Sun Microsystems Inc.

[root@localhost bin]# ./configtest.sh
Using CATALINA_BASE: /opt/apache-tomcat-7.0.12
Using CATALINA_HOME: /opt/apache-tomcat-7.0.12
Using CATALINA_TMPDIR: /opt/apache-tomcat-7.0.12/temp
Using JRE_HOME: /opt/jdk1.6.0_24
Using CLASSPATH: /opt/apache-tomcat-7.0.12/bin/bootstrap.jar:/opt/apache-tomcat-7.0.12/bin/tomcat-juli.jar
May 22, 2011 4:06:16 PM org.apache.coyote.AbstractProtocolHandler init
INFO: Initializing ProtocolHandler ["http-bio-8080"]
May 22, 2011 4:06:16 PM org.apache.coyote.AbstractProtocolHandler init
INFO: Initializing ProtocolHandler ["ajp-bio-8009"]
May 22, 2011 4:06:16 PM org.apache.catalina.startup.Catalina load
INFO: Initialization processed in 1401 ms

[root@localhost bin]# cd /opt/apache-tomcat-7.0.12/bin/
[root@localhost bin]# ./shutdown.sh
Using CATALINA_BASE: /opt/apache-tomcat-7.0.12
Using CATALINA_HOME: /opt/apache-tomcat-7.0.12
Using CATALINA_TMPDIR: /opt/apache-tomcat-7.0.12/temp
Using JRE_HOME: /opt/jdk1.6.0_24
Using CLASSPATH: /opt/apache-tomcat- 7.0.12/bin/bootstrap.jar:/opt/apache-tomcat-7.0.12/bin/tomcat-juli.jar

Once we have executed the startup scripts, the next step is the verification of the Tomcat services, to check whether services are coming up fine or not. By default, Tomcat runs on HTTP port 8080 and can be accessed on the web browser using the URL, http://localhost:8080. We then find the Tomcat welcome page, which shows that Tomcat is installed correctly and running fine in the environment, as shown in the following screenshot:

Once the welcome page for Tomcat 7 is displayed, we can verify the server status by clicking on Server Status.

It will prompt for the user ID/password. Remember, we have created a user admin that the user ID will be used here for access, as shown in the following screenshot:

Scenario 1: The Java installation is not working, while executing the Java binary.

[root@localhost opt]# ./jdk-6u24-linux-i586.bin
-bash: ./jdk-6u24-linux-i586.bin: Permission denied

Issue: The Java binary doesn't have execute permissions with a specific user.

Fix: Change the permission to 0755 for ./jdk-6u24-linux-i586.bin using the following command:

chmod 0755 jdk-6u24-linux-i586.bin

Scenario 2: While starting the Tomcat startup script, the following error occurs:

[root@localhost bin]# ./startup.sh
Neither the JAVA_HOME nor the JRE_HOME environment variable is defined
At least one of these environment variables is needed to run this program

Fix: Check the .bash_profile and find out whether the following mentioned entry is present in the file:

JAVA_HOME=/opt/jdk1.6.0_24
PATH=$JAVA_HOME/bin:$PATH:$HOME/bin
export PATH JAVA_HOME

Scenario 3: Tomcat services is not displayed after running startup.sh.

Issue: This service is already running on the server.

Fix: Check for any Java process running in the system using the following command in Linux:

Ps -ef |grep tomcat

This command will show all Tomcat processes. If any process is running on an OS, kill it and run the startup scripts again.

In Windows, go to the Task Manager and check if any Java process is running for Tomcat. If any process is running, then kill the process and restart the Tomcat services.