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Installing Tomcat 6 on Debian Squeeze

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Posted on 13 March 2010 No comments

This post describes how to setup Tomcat 6 on Debian Squeeze. The configured Tomcat serves requests on port 80 without the need of an additional web server. This is especially good for virtual servers (VPS) providing limit memory. It also has multiple virtual hosts configured, each with it’s own webapp with context root / and optional support for PHP via the Quercus PHP implementation.

Installing Sun Java 6

Ensure the non-free section is enabled for the APT repository configuration in /etc/apt/sources.list, e.g. “deb http://ftp.de.debian.org/debian testing main contrib non-free”
```
apt-get update
apt-get install sun-java6-jdk
echo 'JAVA_HOME="/usr/lib/jvm/java-6-sun"' >> /etc/environment
echo 'JRE_HOME="/usr/lib/jvm/java-6-sun/jre"' >> /etc/environment
```
Installing Tomcat 6
```
apt-get install tomcat6 tomcat6-admin
/etc/init.d/tomcat6 stop
```
Creating standard Tomcat directory layout
```
mkdir /opt/tomcat
cd /opt/tomcat
ln -s /etc/tomcat6/ conf
ln -s /usr/share/tomcat6/bin/ bin
ln -s /usr/share/tomcat6/lib/ lib
ln -s /var/lib/tomcat6/webapps webapps
ln -s /var/log/tomcat6/ logs
```
Creating a Tomcat admin user

In /opt/tomcat/conf/tomcat-users.xml add an entry like:
```
<user name="ADMIN_USERNAME" password="ADMIN_PASSWORD" roles="admin,manager" />
```
Setting up virtual hosts

For each virtual host execute the following command. Replace “mydomain.com” with the desired virtual host name, but omit the “www.” part.
```
mkdir -p /opt/tomcat/webapps.mydomain.com/ROOT
```
In the <Engine> tag of “/opt/tomcat/conf/server.xml” add one host entry for each virtual host.
```
<Host name="mydomain.com" appBase="/opt/tomcat/webapps.mydomain.com">
    <Alias>www.mydomain.com>/Alias>
    <Valve className="org.apache.catalina.valves.AccessLogValve" prefix="mydomain_access_log." suffix=".txt" pattern="common"/>
</Host>
```
The <Alias> tag tells Tomcat to redirect from www.mydomain.com to mydomain.com.
The <Valve> tag enables access logging in the standard logging format.

Using xinetd to configure port 80 for Tomcat

Binding a service on port 80 requires root permissions. Thus we use port forwarding to “bind” Tomcat to port 80. My VPS does not support the use of “iptables -j REDIRECT” therefore I am using xinetd as a web proxy.
Ensure that no other service is listening on port 80/443:
```
netstat -pan | grep ":80\|:443"
```
Register the required xinetd services:
```
echo echo "
service www
{
        socket_type     = stream
        protocol        = tcp
        user            = root
        wait            = no
        bind            = 88.80.198.181
        port            = 80
        redirect        = localhost 8080
        disable         = no
        flags           = REUSE
        log_type        = FILE /var/log/wwwaccess.log
        log_on_success  -= PID HOST DURATION EXIT

        per_source      = UNLIMITED
        instances       = UNLIMITED
}

service https
{
        socket_type     = stream
        protocol        = tcp
        user            = root
        wait            = no
        bind            = 88.80.198.181
        port            = 443
        redirect        = localhost 8443
        disable         = no
        flags           = REUSE
        log_type        = FILE /var/log/httpsaccess.log
        log_on_success  -= PID HOST DURATION EXIT

        per_source      = UNLIMITED
        instances       = UNLIMITED
}
" > /etc/init.d/tomcat
/etc/init.d/xinetd restart
```
If you want to use a different service name, e.g. “tomcat” instead of “www” you must add this service to /var/services, e.g. “tomcat 80/tcp”
In /opt/tomcat/conf/server.xml modify the <Connector> as follows:
```
<Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443" proxyPort="80" address="127.0.0.1" />
```
This binds Tomcat to localhost. It also tells Tomcat that port 80 is the proxy port which is necessary for correct URL generation.
From now on the Tomcat admin applications are only accessible via localhost. You can use SSH port forwarding to still access the applications from your workstation’s web browser. E.g. if you are using PuTTY you can use this command line option “-L 8080:localhost:8080″ to forward the server’s local 8080 port to your workstation’s local 8080 port. On your workstation’s browser you then simply enter http://localhost:8080/manager/html and are connected to the server’s Tomcat admin application.

Enabling PHP support (optional)

Download Quercus.
```
mkdir -p /opt/downloads
wget -o /opt/downloads/quercus-4.0.3.war http://caucho.com/download/quercus-4.0.3.war
```
Install Quercus as a shared library.
```
unzip -j /opt/downloads/quercus-4.0.3.war \*.jar -d /opt/tomcat/lib
```
Enable PHP support for the virtual hosts by installing the quercus web.xml. For each virtual host execute:
```
unzip /opt/downloads/quercus-4.0.3.war *web.xml -d /opt/tomcat/webapps.mydomain.com/ROOT
```
Starting Tomcat
```
/etc/init.d/tomcat start
```
References
Java, Linux Java, PHP, port 80, port forwarding, quercus, tomcat, vhost, virtual servers, VPS, xinetd
Leveraging PyDev’s auto completion for indirectly created objects

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Posted on 20 February 2010 1 comment

This is just a quick tip how to enable auto completion in PyDev for indirectly created objects.

By default, PyDev has no problems in presenting you the possible object attributes and methods on a variable if that variable gets a new object instance assigned directly in the code.

For example, when you first type …
```
mybook = Book()
```
… and in the next line you enter …
```
mybook.
```
… PyDev will dutifully present you the statically declared features for the Book class in a popup.

If you however get that Book instance as the result of another method, e.g. …
```
mybook = bookstore.findBook("foobar")
```
… PyDev currently seems to be helpless.

Because of Python’s dynamic nature it is of course a bit harder for an IDE to figure out what kind of objects may a method. But PyDev could for example honor the @return / @rtype PyDoc annotations (which you can add to the findBook’s method declaration) but currently it just does not.

To still have autocompletion you have two options:
1. Temporarily instantiate a Book object in the code.
```
mybook = Book()
mybook = bookstore.findBook("foobar")
mybook. #--> now you have auto completion
```
  This has the drawback, that if you forget to remove the first line before you finish coding an unneccessary Book instance will be created on every execution during runtime.
2. Use an assertion to ensure that the mybook variable contains an object of type Book
```
mybook = bookstore.findBook("foobar")
assert isinstance(mybook, Book)
mybook. #--> now you have auto completion
```
Jython Jython, pydev, pydoc, python, rtype
OVal 1.40 released

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Posted on 28 September 2009 No comments

I am happy to announce the immediate availability of Version 1.40 OVal the Object Validation Framework for Java. This release fixes some minor issues and provides the following two new features:

1. Enabling/disabling constraints based on the object state:
Using the newly introduced when attribute for constraints it is possible to specify under which circumstances the constraint will be considered during object validation. The when attribute holds a formula in one of the supported scripting languages. If the formula returns true, the constraint will be activated for the current validation cycle otherwise it is ignored. In the following example the alias attribute must have a value only when the name attribute is not set.
```
public class User {
   private String name;

   @NotNull(when = "groovy:_this.name == null")
   private String alias;

   // . . .
}
```
2. Fine grain control over how constraints are applied on arrays, maps, collections and their elements
The newly introduced attribute appliesTo allows you to specify if and how a constraint declared for a map, a collection or an array is applied to their elements as well or exclusively. See the following example how this works:
```
public class BusinessObject {

   // the ids field may be null, but if it is not null
   // none of it's items must be null
   @NotNull(appliesTo = { ConstraintTarget.VALUES })
   private String[] ids;

   // only the field itself must not be null,
   // the list can contain null values
   @NotNull(appliesTo = { ConstraintTarget.CONTAINER })
   private List items;

   // the field must not be null as well as all keys
   // and values of the map
   @NotNull(appliesTo = { ConstraintTarget.CONTAINER, ConstraintTarget.KEYS, ConstraintTarget.VALUES })
   private Map itemsByGroup;

   // . . .
}
```
Download
You can get the lates binaries and source files of OVal from here: http://sourceforge.net/projects/oval/files/

Java
Installing WebSphere Portal in a local network

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Posted on 6 July 2009 3 comments

Recently I had to setup some WebSphere Portal 6.1 installations in VMWares within a private network. Unfortunately the portal installer aborted with the following message “EJPIC0067E: Portal requires a fully qualified host name that is recoganized by the DNS Server.” Even when adding the fully qualified hostname to the hosts file the installer may still fail with the same message.
The workaround is to disable the hostname check by invoking the portal installer with the following parameter specified: -W nodeHost.active=”False”. You should however only do this for test or development installations.

WebSphere Portal deployment, websphere portal, workaround

Comparing version numbers in Jython / Python

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Posted on 14 March 2009 No comments

Here comes a function to compare version numbers of e.g. Maven artifacts in Jython / Python.

import re

def cmpver(vA, vB):
    """
    Compares two version number strings
    @param vA: first version string to compare
    @param vB: second version string to compare
    @author Sebastian Thomschke
    @return negative if vA < vB, zero if vA == vB, positive if vA > vB.

    Examples:
    >>> cmpver("0", "1")
    -1
    >>> cmpver("1", "0")
    1
    >>> cmpver("1", "1")
    0
    >>> cmpver("1.0", "1.0")
    0
    >>> cmpver("1.0", "1")
    0
    >>> cmpver("1", "1.0")
    0
    >>> cmpver("1.1.0", "1.0.1")
    1
    >>> cmpver("1.0.1", "1.1.1")
    -1
    >>> cmpver("0.3-SNAPSHOT", "0.3")
    -1
    >>> cmpver("0.3", "0.3-SNAPSHOT")
    1
    >>> cmpver("1.3b", "1.3c")
    -1
    >>> cmpver("1.14b", "1.3c")
    1
    """
    if vA == vB: return 0

    def num(s):
        if s.isdigit(): return int(s)
        return s

    seqA = map(num, re.findall('\d+|\w+', vA.replace('-SNAPSHOT', '')))
    seqB = map(num, re.findall('\d+|\w+', vB.replace('-SNAPSHOT', '')))

    # this is to ensure that 1.0 == 1.0.0 in cmp(..)
    lenA, lenB = len(seqA), len(seqB)
    for i in range(lenA, lenB): seqA += (0,)
    for i in range(lenB, lenA): seqB += (0,)

    rc = cmp(seqA, seqB)

    if rc == 0:
        if vA.endswith('-SNAPSHOT'): return -1
        if vB.endswith('-SNAPSHOT'): return 1
    return rc

Theoretically lines 43 – 49 could be written in a more compact way but using the short circuit evaluations (as below) lead to wrong results – at least in Jython 2.1:

    seqa = map(lambda s: s.isdigit() and int(s) or s, re.findall('\d+|\w+', vA.replace('-SNAPSHOT', '')))
    seqb = map(lambda s: s.isdigit() and int(s) or s, re.findall('\d+|\w+', vB.replace('-SNAPSHOT', '')))

Jython Jython, python

Running TomCat 6 in Debug Mode under Windows

(3 votes)

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Posted on 11 March 2009 No comments

While tracing some problems in one of my grails applications I had the need to do step debugging on a remote Tomcat server. Eventually I came up with the following lines to launch TomCat in debug mode:
```
@echo off
set JPDA_TRANSPORT="dt_socket"
set JPDA_ADDRESS="8000"
set JPDA_SUSPEND="y"
catalina.bat jpda start
```
Simply create a debug.bat file in TomCat’s bin directory and add these lines.

Java
« Older Entries

Sebastian Thomschke

Installing Tomcat 6 on Debian Squeeze

Installing Sun Java 6

Installing Tomcat 6

Creating standard Tomcat directory layout

Creating a Tomcat admin user

Setting up virtual hosts

Using xinetd to configure port 80 for Tomcat

Enabling PHP support (optional)

Starting Tomcat

References

Leveraging PyDev’s auto completion for indirectly created objects

OVal 1.40 released

Installing WebSphere Portal in a local network

Comparing version numbers in Jython / Python

Running TomCat 6 in Debug Mode under Windows

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