hasan's blog (বল্গ)

i had a problem with spring framework, as you know while we are defining dependency over the xml documents, it becomes less changeable unless you know about my recent post about ext-util namespace handler and if you know any other alternatives.

before digging inside the problem better i clarify my context -

i have been working with one of my projects, where i have a several configurations which suppose to be different in different deployment environment, for example – to make my service avail, user has to define his database, his content index directory, server port, ip address and few more.

all these configurations were kept within the spring bean declaration scope. though few of them were moved to the properties file through ext-util namespace handler.

previously to make those configuration changeable i kept those files under WEB-INF/classes so it overrides the default bundled resource.

but still it wasn’t user friendly, since my user has to change one xml document to add more index services also he has to edit different configurations from java properties file.

again when i started bundling jetty with my whole application i found it is tricker to keep those xml outside of application, since i don’t wanna make my user confused with lot of xml files. and i have to keep few xml out of  my classpath context, so spring has to load my configuration from my “config/index-configuration/” directory.

though by default spring can do it over “file:///absolute/path/to/file.xml” since spring is using java URL class to locate this resource.  but in my case i can’t put any aboslute path.
so i found a simple way out there to support relative path reference.

previously i had the following xml document -

now i have replaced them with the following change -

if you observe closely you will find “extfile:///” protocol reference, which is not standard url protocol. so to make it work i used the following bunch of code and configuration -

1. i have created a class “Handler” under the “com.ideabase.repository.core.protocols.extfile” package.
this package and class name is conventional, though you can change them lets sun explain about it.

2. i wrote the following code -

public class Handler extends URLStreamHandler {
protected URLConnection openConnection(final URL pURL) throws IOException {
final String path = pURL.getPath();
final URL resourceUrl;
if (path.startsWith(“/./”)) {
resourceUrl = new File(path.substring(1, path.length())).toURL();
} else {
throw new RuntimeException(“Unsupported url schema. currently you can ” +
“use only extfile:///./path/to/somewhere/in”);
}
return resourceUrl.openConnection();
}
}
3. i registered my protocol package through the system property -

System.setProperty(“java.protocol.handler.pkgs”, “com.ideabase.repository.core.protocols”);

now have a look on the main applicationContext.xml

if you observe closely again you could find the difference, on the normal case i have used relative path reference. so it must be from classloader or if it is loaded through file system based resource locator it will be located from the file system.

but now i can use cross context (relative file system and class loader path reference) resource file path reference. you can see i have imported “indexer-beans.xml” from the application relative path “config/index-configuration/…” where “data-access-layer-beans.xml” is loaded from the class loader.
now have a quick look on my configuration directory, to get an idea how i have improved configuration ability.

hope this will help you to solve similar problem.

within spring container i was getting problem with managing multi level configuration.
for example while i am developing i got a specific filesystem path, database configuration and so on.
this configuration are mostly get changed while i an deploying them on the test or production environment.

this type of scenario is common on most of the projects. managing different scoped configuration is one of the bothering stuff. so i was always thinking some simpler way with in spring container.

so i wrote “ext-util” namespace handler, which is locating property from multi scoped resource.
lets give you a more details use case -

in my test environment i have a property “index.directory=/Users/…/index”
in my test server i use “index.directory=/var/index”
in my production server i use “index.directory=/nfs/index”

here i have a bean which need this property.

you can see the hardcoded configuration. which is not easy to manage.
thats why here my “ext-util” goes with the simplest solution -

now my property resource is locating from “test” scope.

you might think, this “scope=’test’” is again hardcoded stuff, so i also support the following value -
scope=”sys:env”, now you have to define “-Denv=test” while you running your application, and spring bean will find the right property.

so what ever you put over your spring are no longer hardcoded as long as you locate them through “ext-util” which is stands for “extended utility”.

here is my attached source code – (i just extracted them from my on going project, thats why no build script or prebuilt package or maven artifact is bundled)

how to use -
include the source file with in your project
keep “META-INF” while you building your jar or keep them inside your classpath.
change your spring configuration -

xmlns:xsi=”http://www.w3.org/2001/XMLSchema-instance”
xmlns:lang=”http://www.springframework.org/schema/lang”
xmlns:aop=”http://www.springframework.org/schema/aop”
xmlns:ext-util=”http://dev.somewherein.net/schema/ext-util”
xsi:schemaLocation=”http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang-2.0.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd
http://dev.somewherein.net/schema/ext-util http://dev.somewherein.net/resources/schemas/ext-util-0.1.xsd“/>
basic properties of ext-util -

1. from-property – which property you are looking for.

2. or-default – define default value if no property is found from default scope (system properties) this value is returned.

3. scope – define scope name, by default whatever you set except “sys:” prefixed string, will search for “classpath:”. also you can use “sys:abc” where abc is located from system properties.

4. path-prefix – you can define scope properties path prefix, this prefix can be “file:///, classpath:”. this value also can be prefixed by “sys:abc” where abc is located from system properties.

[download source code]
[download missing xsd file]

best wishes,

hi today i found an interesting stuff..

Rod talked about new configuration option in spring (actually you can add as an addon) Define bean using Java code Wow!!!.. i was looking for this stuff for a long while… sometimes it is really meaningful to me…

here is code example for rod blog: