Where to place and how to read configuration resource files in servlet based application

Question

In my web application I have to send email to set of predefined users like finance xyz com  so I wish to add that to a  properties file and access it when required  Is this a correct procedure  if so then where should I place this file  I am using Netbeans IDE which is having two separate folders for source and JSP files

User · Answer

Assume your code is looking for the file say app.properties. Copy this file to any dir and add this dir to classpath, by creating a setenv.sh in the bin dir of tomcat.

In your setenv.sh of tomcat( if this file is not existing, create one , tomcat will load this setenv.sh file. #!/bin/sh CLASSPATH="$CLASSPATH:/home/user/config_my_prod/"

You should not have your properties files in ./webapps//WEB-INF/classes/app.properties

Tomcat class loader will override the with the one from WEB-INF/classes/

A good read: https://tomcat.apache.org/tomcat-8.0-doc/class-loader-howto.html

User · Answer

It s your choice  There are basically three ways in a Java web application archive  WAR    1  Put it in classpath So that you can load it by ClassLoader getResourceAsStream   with a classpath-relative path  ClassLoader classLoader   Thread currentThread   getContextClassLoader    InputStream input   classLoader getResourceAsStream  quot foo properties quot           Properties properties   new Properties    properties load input    Here foo properties is supposed to be placed in one of the roots which are covered by the default classpath of a webapp  e g  webapp s  WEB-INF lib and  WEB-INF classes  server s  lib  or JDK JRE s  lib  If the propertiesfile is webapp-specific  best is to place it in  WEB-INF classes  If you re developing a standard WAR project in an IDE  drop it in src folder  the project s source folder   If you re using a Maven project  drop it in  main resources folder  You can alternatively also put it somewhere outside the default classpath and add its path to the classpath of the appserver  In for example Tomcat you can configure it as shared loader property of Tomcat conf catalina properties  If you have placed the foo properties it in a Java package structure like com example  then you need to load it as below ClassLoader classLoader   Thread currentThread   getContextClassLoader    InputStream input   classLoader getResourceAsStream  quot com example foo properties quot            Note that this path of a context class loader should not start with a    Only when you re using a  quot relative quot  class loader such as SomeClass class getClassLoader    then you indeed need to start it with a    ClassLoader classLoader   getClass   getClassLoader    InputStream input   classLoader getResourceAsStream  quot  com example foo properties quot            However  the visibility of the properties file depends then on the class loader in question  It s only visible to the same class loader as the one which loaded the class  So  if the class is loaded by e g  server common classloader instead of webapp classloader  and the properties file is inside webapp itself  then it s invisible  The context class loader is your safest bet so you can place the properties file  quot everywhere quot  in the classpath and or you intend to be able to override a server-provided one from the webapp on   2  Put it in webcontent So that you can load it by ServletContext getResourceAsStream   with a webcontent-relative path  InputStream input   getServletContext   getResourceAsStream  quot  WEB-INF foo properties quot            Note that I have demonstrated to place the file in  WEB-INF folder  otherwise it would have been public accessible by any webbrowser  Also note that the ServletContext is in any HttpServlet class just accessible by the inherited GenericServlet getServletContext   and in Filter by FilterConfig getServletContext    In case you re not in a servlet class  it s usually just injectable via  Inject   3  Put it in local disk file system So that you can load it the usual java io way with an absolute local disk file system path  InputStream input   new FileInputStream  quot  absolute path to foo properties quot            Note the importance of using an absolute path  Relative local disk file system paths are an absolute no-go in a Java EE web application  See also the first  quot See also quot  link below   Which to choose  Just weigh the advantages disadvantages in your own opinion of maintainability  If the properties files are  quot static quot  and never needs to change during runtime  then you could keep them in the WAR  If you prefer being able to edit properties files from outside the web application without the need to rebuild and redeploy the WAR every time  then put it in the classpath outside the project  if necessary add the directory to the classpath   If you prefer being able to edit properties files programmatically from inside the web application using Properties store   method  put it outside the web application  As the Properties store   requires a Writer  you can t go around using a disk file system path  That path can in turn be passed to the web application as a VM argument or system property  As a precaution  never use getRealPath    All changes in deploy folder will get lost on a redeploy for the simple reason that the changes are not reflected back in original WAR file  See also   getResourceAsStream   vs FileInputStream Adding a directory to tomcat classpath Accessing properties file in a JSF application programmatically

User · Answer

It just needs to be in the classpath  aka make sure it ends up under  WEB-INF classes in the  war as part of the build

User · Answer

You can you with your source folder so whenever you build  those files are automatically copied to the classes directory   Instead of using properties file  use XML file   If the data is too small  you can even use web xml for accessing the properties   Please note that any of these approach will require app server restart for changes to be reflected

User · Answer

Ex  In web xml file the tag   lt context-param gt           lt param-name gt chatpropertyfile lt  param-name gt           lt  --  Name of the chat properties file  It contains the name and description                   of rooms -- gt                lt param-value gt chat properties lt  param-value gt       lt  context-param gt    And chat properties you can declare your properties like this   For Ex    Jsp   Discussion about JSP can be made here  Java   Talk about java and related technologies like J2EE  ASP   Discuss about Active Server Pages related technologies like VBScript and JScript etc  Web Designing   Any discussion related to HTML  JavaScript  DHTML etc  StartUp   Startup chat room  Chatter is added to this after he logs in

User · Answer

Word of warning  if you put config files in your WEB-INF classes folder  and your IDE  say Eclipse  does a clean rebuild  it will nuke your conf files unless they were in the Java source directory  BalusC s great answer alludes to that in option 1 but I wanted to add emphasis   I learned the hard way that if you  copy  a web project in Eclipse  it does a clean rebuild from any source folders  In my case I had added a  linked source dir  from our POJO java library  it would compile to the WEB-INF classes folder  Doing a clean rebuild in that project  not the web app project  caused the same problem    I thought about putting my confs in the POJO src folder  but these confs are all for 3rd party libs  like Quartz or URLRewrite  that are in the WEB-INF lib folder  so that didn t make sense  I plan to test putting it in the web projects  src  folder when i get around to it  but that folder is currently empty and having conf files in it seems inelegant   So I vote for putting conf files in WEB-INF commonConfFolder filename properties  next to the classes folder  which is Balus option 2

[servlets] Where to place and how to read configuration resource files in servlet based application?

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