how to read System environment variable in Spring applicationContext

Question

How to read the system environment variable in the application context   I want something like     lt util properties id  dbProperties          location  classpath config DEV db properties    gt    or   lt util properties id  dbProperties          location  classpath config QA db properties    gt    depending on the environement   Can I have something like this in my application Context     lt util properties id  dbProperties          location  classpath config   systemProperties env  db properties    gt    where the actual val is set based on the SYSTEM ENVIRONMENT VARIABLE  I m using Spring 3 0

User · Answer

Updated version  2020   Use System getEnv  quot ENV VARIABLE quot

User · Answer

You can mention your variable attributes in a property file and define environment specific property files like local properties  production propertied etc   Now based on the environment  one of these property file can be read in one the listeners invoked at startup  like the ServletContextListener   The property file will contain the the environment specific values for various keys   Sample  local propeties   db logsDataSource url jdbc mysql   localhost 3306 logs db logsDataSource username root db logsDataSource password root  db dataSource url jdbc mysql   localhost 3306 main db dataSource username root db dataSource password root   Sample  production properties   db logsDataSource url jdbc mariadb   111 111 111 111 3306 logs db logsDataSource username admin db logsDataSource password xyzqer  db dataSource url jdbc mysql   111 111 111 111 3306 carsinfo db dataSource username admin db dataSource password safasf mn   For using these properties file  you can make use of  REsource as mentioned below          PropertyPlaceholderConfigurer configurer   new PropertyPlaceholderConfigurer            ResourceLoader resourceLoader   new DefaultResourceLoader             Resource resource   resourceLoader getResource  classpath   System getenv  SERVER TYPE    DB properties            configurer setLocation resource           configurer postProcessBeanFactory beanFactory     SERVER TYPE can be defined as the environment variable with appropriate values for local and production environment     With these changes the appplicationContext xml will have the following changes   lt bean id  dataSource  class  org apache commons dbcp BasicDataSource  gt    lt property name  driverClassName  value  com mysql jdbc Driver    gt     lt property name  url  value    db dataSource url     gt     lt property name  username  value    db dataSource username     gt     lt property name  password  value    db dataSource password     gt         Hope this helps

User · Answer

Check this article  It gives you several ways to do this  via the PropertyPlaceholderConfigurer which supports external properties  via the systemPropertiesMode property

User · Answer

Thanks to  Yiling  That was a hint    lt bean id  propertyConfigurer          class  org springframework web context support ServletContextPropertyPlaceholderConfigurer  gt        lt property name  systemPropertiesModeName  value  SYSTEM PROPERTIES MODE OVERRIDE    gt       lt property name  searchSystemEnvironment  value  true    gt       lt property name  locations  gt           lt list gt               lt value gt file   systemEnvironment  FILE PATH    first properties lt  value gt               lt value gt file   systemEnvironment  FILE PATH    second properties lt  value gt               lt value gt file   systemEnvironment  FILE PATH    third properties lt  value gt           lt  list gt       lt  property gt   lt  bean gt    After this  you should have one environment variable named  FILE PATH   Make sure you restart your terminal IDE after creating that environment variable

User · Answer

Yes  you can do  lt property name  defaultLocale  value     systemProperties  user region      gt  for instance   The variable systemProperties is predefined  see 6 4 1 XML based configuration

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In your bean definition  make sure to include  searchSystemEnvironment  and set it to  true   And if you re using it to build a path to a file  specify it as a file     url   So for example  if you have a config file located in    testapp config my app config properties   then set an environment variable like so   MY ENV VAR PATH  testapp config   and your app can load the file using a bean definition like this   e g    lt bean class  org springframework web context support ServletContextPropertyPlaceholderConfigurer  gt       lt property name  systemPropertiesModeName  value  SYSTEM PROPERTIES MODE OVERRIDE    gt       lt property name  searchSystemEnvironment  value  true    gt       lt property name  searchContextAttributes  value  true    gt       lt property name  contextOverride  value  true    gt       lt property name  ignoreResourceNotFound  value  true    gt       lt property name  locations  gt           lt list gt               lt value gt file      MY ENV VAR PATH  my app config properties lt  value gt           lt  list gt       lt  property gt   lt  bean gt

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Using Spring EL you can eis example write as follows   lt bean id  myBean  class  path to my BeanClass  gt       lt  -- can be overridden with -Dtest target host http   whatever com -- gt       lt constructor-arg value    systemProperties  test target host       http   localhost 18888     gt   lt  bean gt

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For my use case  I needed to access just the system properties  but provide default values in case they are undefined   This is how you do it    lt bean id  propertyPlaceholderConfigurer         class  org springframework beans factory config PropertyPlaceholderConfigurer  gt         lt property name  systemPropertiesModeName  value  SYSTEM PROPERTIES MODE OVERRIDE    gt       lt property name  searchSystemEnvironment  value  true    gt   lt  bean gt     lt bean id  myBean  class  path to my BeanClass  gt       lt  -- can be overridden with -Dtest target host http   whatever com -- gt       lt constructor-arg value    test target host http   localhost 18888    gt   lt  bean gt

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This is how you do it    lt bean id  systemPrereqs  class  org springframework beans factory config MethodInvokingFactoryBean  scope  prototype  gt                lt property name  targetObject  value     systemProperties     gt                lt property name  targetMethod  value  putAll    gt                lt property name  arguments  gt                      lt util properties gt                          lt prop key  deployment env  gt dev lt  prop gt                      lt  util properties gt               lt  property gt       lt  bean gt    But remember spring gets loaded first and then it will load this bean MethodInvokingFactoryBean  So if you are trying to use this for your test case then make sure that you use depends-on  For e g  in this case   In case you are using it for your main class better to set this property using your pom xml as   lt systemProperty gt       lt name gt deployment env lt  name gt       lt value gt dev lt  value gt   lt  systemProperty gt

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You are close  o  Spring 3 0 adds Spring Expression Language   You can use    lt util properties id  dbProperties       location  classpath config   systemProperties  env    db properties    gt    Combined with java     -Denv QA should solve your problem   Note also a comment by  yiling      In order to access system environment variable  that is OS level   variables as amoe commented  we can simply use  systemEnvironment    instead of  systemProperties  in that EL  Like     systemEnvironment  ENV VARIABLE NAME

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Declare the property place holder as follows   lt bean id  propertyPlaceholderConfigurer             class  org springframework beans factory config PropertyPlaceholderConfigurer  gt         lt property name  systemPropertiesModeName  value  SYSTEM PROPERTIES MODE OVERRIDE    gt       lt property name  locations  gt           lt list gt               lt value gt file    path to your app config properties lt  value gt           lt  list gt       lt  property gt   lt  bean gt    Then lets say you want to read System property  java io tmpdir   for your Tomcat bean or any bean then add following in your properties file   tomcat tmp dir   java io tmpdir

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Nowadays you can put    Autowired private Environment environment    in your  Component   Bean  etc   and then access the properties through the Environment class   environment getProperty  myProp        For a single property in a  Bean   Value    my another property 123       value after     is the default Integer property      Another way are the handy  ConfigurationProperties beans    ConfigurationProperties prefix  my properties prefix   public class MyProperties        value from my properties prefix myProperty will be bound to this variable   String myProperty        and this will even throw a startup exception if the property is not found    javax validation constraints NotNull   String myRequiredProperty       getters     Component public class MyOtherBean      Autowired   MyProperties myProperties      Note  Just remember to restart eclipse after setting a new environment variable

[java] how to read System environment variable in Spring applicationContext

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