Tag: java

Java final modifier keyword

I’ve been a huge fan of the ‘final‘ modifier in Java for function arguments and variables. While there’s some debate on their usefulness for performance, they definitely add in readability and understanding of code as developers are instantly notified by modern IDE’s and when they try to reassign such values as the compiler will indicate the error.

NOTE: Use of final for classes or functions often contradicts the paradigm of Object Oriented programming as you’ll be restricted from extending or overriding those items!

Internationalizing JSP with ResourceBundles

Adding multi-language support to JSP based applications is very simple. In this post we will investigate the method that you can use to externalize your text based content.

NOTE: Additional work is required to establish the Locale, format Dates and Numbers or to support other differences such as text-direction.

JSP:

<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
<fmt:setLocale value="en_US" />
<fmt:setBundle basename="ResourceBundles.TestBundle" scope="request" var="rb" />
<fmt:message bundle="${rb}" key="label.test" />

/src/ResourceBundles/TestBundle.properties:

label.test=test(default)

/src/ResourceBundles/TestBundle_en.properties

label.test=test(en)

/src/ResourceBundles/TestBundle_en_US.properties

label.test=test(en_US)

You can also specify some default Locale information in web.xml if you do not wish to use the in your JSPs.

/WEB-INF/web.xml


<context-param>
<param-name>javax.servlet.jsp.jstl.fmt.locale</param-name>
<param-value>en</param-value>
</context-param>

<context-param>
<param-name>javax.servlet.jsp.jstl.fmt.fallbackLocale</param-name>
<param-value>en</param-value>
</context-param>

Some explanation… in this case we’ve told our JSP that the resources are in the TestBundle properties. As the Locale is set to ‘en_US’ it will first look in the TestBundle_en_US.properties file, if not found it will then look in TestBundle_en.properties and finally in TestBundle.properties. If not found there, the output will generally be in the form ‘???key???‘, in this example: ‘???label.test???‘, my understanding is that this can be suppressed by setting ‘allowNull=true‘ somewhere, but I have never found that setting to date.

REFERENCES:

Javascript try/catch/finally

I’ve found that many developers (including myself) that have been coding javascript for some time don’t realize that javascript added the try/catch pattern from Java quite a while ago and that all modern browsers support it.

Here’s the standard pattern, the ‘finally’ of course is optional for when you require it.

try{
// put your code here that may experience a runtime error/exception, i will show division by zero in this example
var x = 1;
alert(x/0);
}
catch(e){
if(e instanceof Error){
alert(‘an error has occurred:name=’ + e.name + ‘|message=’ + e.message);
} else {
alert(‘an unknown exception has occurred’);
}
}
finally{
alert(‘now we are done’);
}

A little more on this… like in Java, there are types of Errors, and you can rely upon ‘instanceof’ to determine them appropriately, here are a few of the common types in JavaScript 1.5:

  • EvalError
  • RangeError
  • ReferenceError
  • SyntaxError
  • TypeError
  • URIError

REFERENCE:
http://www.devarticles.com/c/a/JavaScript/Exception-Handling-in-JavaScript-Using-Multiple-Exception-Handlers/

Cheers

Apache Tomcat Native Library (APR)

If you have ever looked at the console or logs while starting a Tomcat instance on Windows you have probably seen the following line about APR.

INFO: The Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path

As long as the “tcnative-1.dll”  is in the Windows PATH, generally you can place it in c:\windows\system32, but any other location in the PATH will work should you need it to be portable, or have different versions in use.

NOTE: Other Operating Systems use a similar approach as Windows to add an environmental variable, optionally you can also add the appropriate location to the “java.library.path” attribute used when calling the VM, if you are more technically inclined. Also, be aware of 32 vs. 64 bit architectures when selecting your version!

Cheers

Apache Native Client

If you do any development or even production testing with Apache Tomcat, you may have seen the following message in your logs.

“The Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path”

Here’s a quick solution that will leave you with greatly improved performance.

  1. Go to the following URI’s:
  2. Download the appropriate version of tcnative-1.dll
  3. For Windows, place that file in c:\windows\system32\ 
  4. Restart your Tomcat server
  5. You are done!

Cheers

Enabling the Apache2 – Tomcat5 mod_jk Connector

Often you want to use Apache HTTP for static content, yet use Tomcat for JSP and other Java type work.  This is a very common infrastructure for enterprise applications, particularly when using ‘pools’ of servers for performance, redundancy and security.  

In order to accomplish this, all connections need to be handled by the Apache webserver, which will delegate appropriate requests to Tomcat for it to process.

Here’s a simple setup to get you started:

  • First you need to get the connector appropriate to your installation:

    http://tomcat.apache.org/connectors-doc/

  • Next make sure the connector file is in the /conf folder of your Apache installation.

    NOTE: I prefer to use this path and leave the version name to make maintenance and backups easier.

  • Add the following line to httpd.conf

    LoadModule jk_module conf/mod_jk-1.2.26-httpd-2.2.4.so

  • Now, add the following to http.conf

    <IfModule jk_module>
    Include “c:/TOMCATPATH/conf/auto/mod_jk.conf”
    JkWorkersFile conf/workers.properties
    JkLogFile “c:/LOGSPATH/tomcat55_mod_jk.log”
    </IfModule>

  • Add the c:/APACHEPATH/conf/workers.properties file with the following (minimal) contents:

    worker.list=ajp13
    worker.ajp13.port=8009
    worker.ajp13.host=localhost
    worker.ajp13.type=ajp13

  • Finally, restart both Apache and Tomcat
  • The following file should have been created in c:/TOMCATPATH/conf/auto/mod_jk.conf

    ########## Auto generated on …some datetime… ##########

    <IfModule !mod_jk.c>
      LoadModule jk_module “C:/APACHEPATH/conf/mod_jk-1.2.26-httpd-2.2.4.so”
    </IfModule>

    JkWorkersFile “C:/TOMCATPATH/conf/jk/workers.properties”
    JkLogFile “c:/LOGSPATH/mod_jk.log”

    JkLogLevel emerg

    <VirtualHost localhost>
        ServerName localhost

        JkMount /webdav ajp13
        JkMount /webdav/* ajp13

        JkMount /servlets-examples ajp13
        JkMount /servlets-examples/* ajp13

        JkMount /jsp-examples ajp13
        JkMount /jsp-examples/* ajp13

        JkMount /balancer ajp13
        JkMount /balancer/* ajp13

        JkMount /host-manager ajp13
        JkMount /host-manager/* ajp13

        JkMount /tomcat-docs ajp13
        JkMount /tomcat-docs/* ajp13

        JkMount /manager ajp13
        JkMount /manager/* ajp13
    </VirtualHost>

If all went well, you should be able to access  your Tomcat server webapps on the regular HTTP port used by your Apache installation.

Cheers!

Enerjy plugin for Eclipse IDE

I’ve previously written on the benefits of static analysis of java code with the use of PMD and FindBugs.  I was recently turned on to a new tool that performs similar testing of code within the Eclipse IDE.

When I first found this tool it was free, since that time it’s come out of beta and is now a little costly, but it may still be worth it due to the functionality it provides.

The premise of this tool is a little different than other ones, while it covers much of the same need, it also performs many tests that I would previously use CheckStyle to do.  This only provides them at runtime and in a common manner within the IDE.

REFERENCES:

Cheers! 

Eclipse ResourceBundle Editor

I typically use the open-source Eclipse IDE for most of my Java and PHP work. For my corporate work, this means that I use IBM‘s packaged RAD and WSAD offerings that are based on various versions of the Eclipse framework.

When working on Internationalized (I18n) applications, most experienced Java architects rely on ResourceBundles to store the various text that is needed for different languages, problem is that editing these files becomes problematic, especially when dealing with multi-byte character sets as are often used in Unicode (non Latin-1, aka ISO-8859-1) languages.

The best editor I’ve found for this case is, as you may have guessed, free for download.

Here’s the links:

Cheers!

UTF-8 (BOM) prevents java compilation

I had an adventure tracking this one down lately, it seems that if your IDE saves files as UTF-8, the java compiler can’t always resolve the files.

Here’s the errors from the console output:

[INFO] ————————————————————————
[ERROR] BUILD FAILURE
[INFO] ————————————————————————
[INFO] Compilation failure

C:\Sandbox\Jars\example.jar\src\main\java\com\giantgeek\Example.java:[1,0] ‘class’ or ‘interface’ expected

C:\Sandbox\Jars\example.jar\src\main\java\com\giantgeek\Example.java:[1,1] illegal character: \187

C:\Sandbox\Jars\example.jar\src\main\java\com\giantgeek\Example.java:[1,2] illegal character: \191

Those character codes (\187 \191) may look a little familiar to some people, as they represent the Byte Order Mark (BOM) that prefixes a UTF-8 formatted file. If you look at them in a file editor (or text editor that doesn’t interpret UTF-8) they will look odd.

They look like “an i (two dots over), double right arrow, upside down question mark”.

Simple solution is to re-edit and save the file as ISO-8859-1.

An alternate approach that is available in some instances is to use the arguments to javac to allow the file encoding.

References:

Cheers!