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One thing about installing  jdk in *ix remote machines is that , it is not that easy like installing in windows. Here are few things which may be of some use while installing JDK in such operating systems.

• First thing to know about is the architecture of the OS. Whether it is 32 bit or 64 bit. You may need to choose the JDK based on this.
• Next is about the RPM or the bin file. You can download the JDK either in the form of RPM file or as the binary installable.
• I typically prefer the bin file as its installation is available in all *ix OSs
• The next big thing is about pushing this file to the  target system, Most of the times we operate from remote machines. This means either you have to download locally and push it using ftp or sftp or download from that machine itself.
• In bandwidth constrained networks it may be very difficult to push this 70+MB file if we work from remote.
• Alternatively you can use “wget” command with the appropriate URL which gives the download option of the jdk bin file. For example the URL for JDK may look like this “http://cds.sun.com/is-bin/INTERSHOP.enfinity/WFS/CDS-CDS_Developer-Site/en_US/-/USD/VerifyItem-Start/jdk-6u13-linux-x64.bin?BundledLineItemUUID=etNIBe.pqI4AAAEhhFYksD9R&OrderID=EwtIBe.pq1gAAAEhZ1YksD9R&ProductID=_T1IBe.obWYAAAEfqlYcydOO&FileName=/jdk-6u13-linux-x64.bin“
• Once you downloaded this, now choose the location in the system where you want to install the JDK
• Typically this may be /usr/local/bin
• Be the root user to install this
• Ensure that the bin file has X mod for all users (chmod a+x )
• Then now use ./–bin file — under the directory in which you are interested. It may ask to accept the terms and conditions. Enter ‘yes’
• Once the installation is over  use ./java -version in the dir in which it is located.
• Sometimes you have older versions in the path as a result if you use java command it may pick the old installation.

So the next job is to ensure that java’s bin folder is in the path so that we can use the right installation. In windows systems we typically add this to PATH environment variable. Same is true in*ix as well but from a remote location this is how you may add it.

• In case of non-root users use /etc/profile file
• Edit this file and include the PATH content pointing to the bin location of your java installation.
• For root user, the file is different. Use /root/.bash_profile.

Once this is done, reconnect and just merely type java -version. Your installation should reflect. Otherwise one possible thing could be your bin might have defined after the previous installation.

Enjoy!

I often tend to forget so many useful linux commnads I use.

Here are some useful ones of mine

• How to know the system information

cat /proc/cpuinfo   # will reveal the CPU information,

you may see some output like this [user@Host ~]$ cat /proc/cpuinfo
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 65
model name      : Dual-Core AMD Opteron(tm) Processor 8218
stepping        : 3
cpu MHz         : 1000.000
cache size      : 1024 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow pni cx16 lahf_lm cmp_legacy svm extapic cr8_legacy
bogomips        : 2009.31
TLB size        : 1088 4K pages
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management: ts fid vid ttp tm stc

processor       : 1
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 65
model name      : Dual-Core AMD Opteron(tm) Processor 8218
stepping        : 3

• To Split a big file and use it use ” split –lines 10000″ will generate files with 1000 lines each.
• To locate a file with word like java use “locate java”
• Here is the good link to know more about linux CPU utilization
• To know todays date you may use date
• and if you want in format like mmddYYYY formate then u can use “date “+%m%d%Y”  “
• If you want yesterdays date then you can use “date -d yesterday”

Often get into situations where the disk space is eaten up by some logs or uploads. How to find which one swallowed more?

To know mount wise distributions use df command
To know the utilization in a single sub directory, use du command
You can refine this command further by du -h --max-depth=1
where
h is to display in human readable format.
max-depth--> To what level grouping should be done. For example if set to 1, then we will get immediate sub directory wise usage.
The output may look like
7.5G ./SUBDIR1
1.2G ./SUBDIR2
103M ./SUBDIR3


Many of you must be using Maven2 by this time in most of your java projects. I am sure you often would have come across with a problem of how to include the jars which are not built using maven.I  will call them as legacy jars. Here are some of the ways.

The simplest way  is to convert them to maven2 style. We can achieve this using the mvn install:file. For example assuming that you have a legacy jar called mylegacy.jar. And if we need to use as a plain maven dependency then to install this use the following command.

mvn install:install-file -DgroupId=com.mylegacy -DartifactId=mylegacy -Dversion=1.0.0 -Dpackaging=jar -Dfile=[location where the jar exists in the file system]

Note that , we are just converting this jar file in such a way that maven will pick it from the repository appropriately as if like any other maven built artifacts. However the point is it will not provide the pom with the dependencies defined for obvious reasons.

The other way of enabling the legacy jars being is to include them with the concept of System classpath.

For example lets say that the same mylegacy.jar is available under c:\\myproject\mylegacy.jar then the dependency definition for the same may look somthing like

<dependency>

<groupId>com.mylegacy</groupId>
<artifactId>mylegacy</artifactId>
<version>1.0.0</version>
<scope>system</scope>
<systemPath>c:\\myproject\mylegacy.jar</systemPath>

</dependency>

The group Id, artifact Id and versions   are a way define them so as to follow the maven structure. These can be of any arbitrary definition however it is better to have them named appropriately.

Needless to say that both the solutions lack few things.

• We somehow need to preserve the binaries locally or in most of the cases in the source control system and thus increasing the size of the system.
• Dependencies of the included artifact will not be resolved by maven’s transitive dependency resolution. One need to bring all of them and need to define them in the same way as how the legacy jar is defined or if the dependent jar is built based on maven then that may lessen the burden a bit.

Most of the Java projects in the recent times use Maven2 as the default build tool.  One of the good things about Maven is the features are implemented in the form of plugins and pretty friendly to incorporate and  to use them in projects.

In this article we will explore one of the popular static code analyzer tool Checkstyle with respect to Maven2 Integration.

Eventually with eclipse Checkstyle plugin will show how to consistenly use the same Checkstyle configuration xml for both the system build and the eclipse IDE.