How can I specify system properties in Tomcat configuration on startup

Question

I understand that I can specify system properties to Tomcat by passing arguments with the -D parameter  for example  -Dmy prop value    I am wondering if there is a cleaner way of doing this by specifying the property values in the context xml file or some other tomcat configuration file  I would like to do this because  first  it is easier to keep track of my properties  and second  I have multiple contexts running and I don t know how I would specify context-specific properties through the -D parameter   I am using Tomcat version 5 5

User · Answer

If you want to define an environment variable in your context base on documentation you shod define them as below

<Context ...>
  ...
  <Environment name="maxExemptions" value="10"
         type="java.lang.Integer" override="false"/>
  ...
</Context>

Also use them as below:

((Context)new InitialContext().lookup("java:comp/env")).lookup("maxExemptions")

You should get 10 as output.

User · Answer

Update  If I could delete this answer I would  although since it s accepted  I can t  I m updating the description to provide better guidance and discourage folks from using the poor practice I outlined in the original answer    You can specify these parameters via context or environment parameters  such as in context xml   See the sections titled  Context Parameters  and  Environment Entries  on this page   http   tomcat apache org tomcat-5 5-doc config context html  As  netjeff points out  these values will be available via the Context lookup String  method and not as System parameters   Another way to do specify these values is to define variables inside of the web xml file of the web application you re deploying  see below   As  Roberto Lo Giacco points out  this is generally considered a poor practice since a deployed artifact should not be environment specific  However  below is the configuration snippet if you really want to do this    lt env-entry gt       lt env-entry-name gt SMTP PASSWORD lt  env-entry-name gt       lt env-entry-type gt java lang String lt  env-entry-type gt       lt env-entry-value gt abc123ftw lt  env-entry-value gt   lt  env-entry gt

User · Answer

cliff meyers s original answer that suggested using  lt env-entry gt  will not help when using only System getProperty     According to the Tomcat 6 0 docs  lt env-entry gt  is for JNDI   So that means it won t have any effect on System getProperty     With the  lt env-entry gt  from cliff meyers s example  the following code   System getProperty  SMTP PASSWORD      will return null  not the value  abc123ftw    According to the Tomcat 6 docs  to use  lt env-entry gt  you d have to write code like this to use  lt env-entry gt       Obtain our environment naming context Context initCtx   new InitialContext    Context envCtx    Context  initCtx lookup  java comp env        Look up our data source String s    String envCtx lookup  SMTP PASSWORD      Caveat   I have not actually tried the example above   But I have tried  lt env-entry gt  with System getProperty    and that definitely does not work

User · Answer

This question is addressed in the Apache wiki   Question   Can I set Java system properties differently for each webapp    Answer  No  If you can edit Tomcat s startup scripts  or better create a setenv sh file   you can add  -D  options to Java  But there is no way in Java to have different values of system properties for different classes in the same JVM   There are some other methods available  like using ServletContext getContextPath   to get the context name of your web application and locate some resources accordingly  or to define  elements in WEB-INF web xml file of your web application and then set the values for them in Tomcat context file  META-INF context xml   See http   tomcat apache org tomcat-7 0-doc config context html     http   wiki apache org tomcat HowTo Can I set Java system properties differently for each webapp 3F

User · Answer

An alternative to setting the system property on tomcat configuration is to use CATALINA OPTS environment variable

User · Answer

Generally you shouldn t rely on system properties to configure a webapp - they may be used to configure the container  e g  Tomcat  but not an application running inside tomcat   cliff meyers has already mentioned the way you should rather use for your webapplication  That s the standard way  that also fits your question of being configurable through context xml or server xml means   That said  should you really need system properties or other jvm options  like max memory settings  in tomcat  you should create a file named  bin setenv sh  or  bin setenv bat   These files do not exist in the standard archive that you download  but if they are present  the content is executed during startup  if you start tomcat via startup sh startup bat   This is a nice way to separate your own settings from the standard tomcat settings and makes updates so much easier  No need to tweak startup sh or catalina sh    If you execute tomcat as windows servive  you usually use tomcat5w exe  tomcat6w exe etc  to configure the registry settings for the service    EDIT  Also  another possibility is to go for JNDI Resources

User · Answer

Update  If I could delete this answer I would  although since it s accepted  I can t  I m updating the description to provide better guidance and discourage folks from using the poor practice I outlined in the original answer    You can specify these parameters via context or environment parameters  such as in context xml   See the sections titled  Context Parameters  and  Environment Entries  on this page   http   tomcat apache org tomcat-5 5-doc config context html  As  netjeff points out  these values will be available via the Context lookup String  method and not as System parameters   Another way to do specify these values is to define variables inside of the web xml file of the web application you re deploying  see below   As  Roberto Lo Giacco points out  this is generally considered a poor practice since a deployed artifact should not be environment specific  However  below is the configuration snippet if you really want to do this    lt env-entry gt       lt env-entry-name gt SMTP PASSWORD lt  env-entry-name gt       lt env-entry-type gt java lang String lt  env-entry-type gt       lt env-entry-value gt abc123ftw lt  env-entry-value gt   lt  env-entry gt

User · Answer

It s also possible letting a ServletContextListener set the System properties   import java util Enumeration  import javax servlet     public class SystemPropertiesHelper implements         javax servlet ServletContextListener       private ServletContext context   null       public void contextInitialized ServletContextEvent event            context   event getServletContext            Enumeration lt String gt  params   context getInitParameterNames             while  params hasMoreElements                String param    String  params nextElement              String value                context getInitParameter param             if  param startsWith  customPrefix                     System setProperty param  value                                    public void contextDestroyed ServletContextEvent event              And then put this into your web xml  should be possible for context xml too    lt context-param gt           lt param-name gt customPrefix property lt  param-name gt           lt param-value gt value lt  param-value gt           lt param-type gt java lang String lt  param-type gt   lt  context-param gt    lt listener gt       lt listener-class gt servletUtils SystemPropertiesHelper lt  listener-class gt       lt  listener gt    It worked for me

User · Answer

Generally you shouldn t rely on system properties to configure a webapp - they may be used to configure the container  e g  Tomcat  but not an application running inside tomcat   cliff meyers has already mentioned the way you should rather use for your webapplication  That s the standard way  that also fits your question of being configurable through context xml or server xml means   That said  should you really need system properties or other jvm options  like max memory settings  in tomcat  you should create a file named  bin setenv sh  or  bin setenv bat   These files do not exist in the standard archive that you download  but if they are present  the content is executed during startup  if you start tomcat via startup sh startup bat   This is a nice way to separate your own settings from the standard tomcat settings and makes updates so much easier  No need to tweak startup sh or catalina sh    If you execute tomcat as windows servive  you usually use tomcat5w exe  tomcat6w exe etc  to configure the registry settings for the service    EDIT  Also  another possibility is to go for JNDI Resources

User · Answer

It s also possible letting a ServletContextListener set the System properties   import java util Enumeration  import javax servlet     public class SystemPropertiesHelper implements         javax servlet ServletContextListener       private ServletContext context   null       public void contextInitialized ServletContextEvent event            context   event getServletContext            Enumeration lt String gt  params   context getInitParameterNames             while  params hasMoreElements                String param    String  params nextElement              String value                context getInitParameter param             if  param startsWith  customPrefix                     System setProperty param  value                                    public void contextDestroyed ServletContextEvent event              And then put this into your web xml  should be possible for context xml too    lt context-param gt           lt param-name gt customPrefix property lt  param-name gt           lt param-value gt value lt  param-value gt           lt param-type gt java lang String lt  param-type gt   lt  context-param gt    lt listener gt       lt listener-class gt servletUtils SystemPropertiesHelper lt  listener-class gt       lt  listener gt    It worked for me

User · Answer

You could add necessary properties to catalina properties file in  lt tomcat installation directory gt  conf directory   Reference  https   tomcat apache org tomcat-8 0-doc config index html     All system properties are available including those set using the -D   syntax  those automatically made available by the JVM and those   configured in the  CATALINA BASE conf catalina properties file

User · Answer

Generally you shouldn t rely on system properties to configure a webapp - they may be used to configure the container  e g  Tomcat  but not an application running inside tomcat   cliff meyers has already mentioned the way you should rather use for your webapplication  That s the standard way  that also fits your question of being configurable through context xml or server xml means   That said  should you really need system properties or other jvm options  like max memory settings  in tomcat  you should create a file named  bin setenv sh  or  bin setenv bat   These files do not exist in the standard archive that you download  but if they are present  the content is executed during startup  if you start tomcat via startup sh startup bat   This is a nice way to separate your own settings from the standard tomcat settings and makes updates so much easier  No need to tweak startup sh or catalina sh    If you execute tomcat as windows servive  you usually use tomcat5w exe  tomcat6w exe etc  to configure the registry settings for the service    EDIT  Also  another possibility is to go for JNDI Resources

User · Answer

If you want to define an environment variable in your context base on documentation you shod define them as below

<Context ...>
  ...
  <Environment name="maxExemptions" value="10"
         type="java.lang.Integer" override="false"/>
  ...
</Context>

Also use them as below:

((Context)new InitialContext().lookup("java:comp/env")).lookup("maxExemptions")

You should get 10 as output.

User · Answer

cliff meyers s original answer that suggested using  lt env-entry gt  will not help when using only System getProperty     According to the Tomcat 6 0 docs  lt env-entry gt  is for JNDI   So that means it won t have any effect on System getProperty     With the  lt env-entry gt  from cliff meyers s example  the following code   System getProperty  SMTP PASSWORD      will return null  not the value  abc123ftw    According to the Tomcat 6 docs  to use  lt env-entry gt  you d have to write code like this to use  lt env-entry gt       Obtain our environment naming context Context initCtx   new InitialContext    Context envCtx    Context  initCtx lookup  java comp env        Look up our data source String s    String envCtx lookup  SMTP PASSWORD      Caveat   I have not actually tried the example above   But I have tried  lt env-entry gt  with System getProperty    and that definitely does not work

User · Answer

An alternative to setting the system property on tomcat configuration is to use CATALINA OPTS environment variable

User · Answer

This question is addressed in the Apache wiki   Question   Can I set Java system properties differently for each webapp    Answer  No  If you can edit Tomcat s startup scripts  or better create a setenv sh file   you can add  -D  options to Java  But there is no way in Java to have different values of system properties for different classes in the same JVM   There are some other methods available  like using ServletContext getContextPath   to get the context name of your web application and locate some resources accordingly  or to define  elements in WEB-INF web xml file of your web application and then set the values for them in Tomcat context file  META-INF context xml   See http   tomcat apache org tomcat-7 0-doc config context html     http   wiki apache org tomcat HowTo Can I set Java system properties differently for each webapp 3F

User · Answer

Update  If I could delete this answer I would  although since it s accepted  I can t  I m updating the description to provide better guidance and discourage folks from using the poor practice I outlined in the original answer    You can specify these parameters via context or environment parameters  such as in context xml   See the sections titled  Context Parameters  and  Environment Entries  on this page   http   tomcat apache org tomcat-5 5-doc config context html  As  netjeff points out  these values will be available via the Context lookup String  method and not as System parameters   Another way to do specify these values is to define variables inside of the web xml file of the web application you re deploying  see below   As  Roberto Lo Giacco points out  this is generally considered a poor practice since a deployed artifact should not be environment specific  However  below is the configuration snippet if you really want to do this    lt env-entry gt       lt env-entry-name gt SMTP PASSWORD lt  env-entry-name gt       lt env-entry-type gt java lang String lt  env-entry-type gt       lt env-entry-value gt abc123ftw lt  env-entry-value gt   lt  env-entry gt

User · Answer

You could add necessary properties to catalina properties file in  lt tomcat installation directory gt  conf directory   Reference  https   tomcat apache org tomcat-8 0-doc config index html     All system properties are available including those set using the -D   syntax  those automatically made available by the JVM and those   configured in the  CATALINA BASE conf catalina properties file

User · Answer

cliff meyers s original answer that suggested using  lt env-entry gt  will not help when using only System getProperty     According to the Tomcat 6 0 docs  lt env-entry gt  is for JNDI   So that means it won t have any effect on System getProperty     With the  lt env-entry gt  from cliff meyers s example  the following code   System getProperty  SMTP PASSWORD      will return null  not the value  abc123ftw    According to the Tomcat 6 docs  to use  lt env-entry gt  you d have to write code like this to use  lt env-entry gt       Obtain our environment naming context Context initCtx   new InitialContext    Context envCtx    Context  initCtx lookup  java comp env        Look up our data source String s    String envCtx lookup  SMTP PASSWORD      Caveat   I have not actually tried the example above   But I have tried  lt env-entry gt  with System getProperty    and that definitely does not work

User · Answer

cliff meyers s original answer that suggested using  lt env-entry gt  will not help when using only System getProperty     According to the Tomcat 6 0 docs  lt env-entry gt  is for JNDI   So that means it won t have any effect on System getProperty     With the  lt env-entry gt  from cliff meyers s example  the following code   System getProperty  SMTP PASSWORD      will return null  not the value  abc123ftw    According to the Tomcat 6 docs  to use  lt env-entry gt  you d have to write code like this to use  lt env-entry gt       Obtain our environment naming context Context initCtx   new InitialContext    Context envCtx    Context  initCtx lookup  java comp env        Look up our data source String s    String envCtx lookup  SMTP PASSWORD      Caveat   I have not actually tried the example above   But I have tried  lt env-entry gt  with System getProperty    and that definitely does not work

User · Answer

Update  If I could delete this answer I would  although since it s accepted  I can t  I m updating the description to provide better guidance and discourage folks from using the poor practice I outlined in the original answer    You can specify these parameters via context or environment parameters  such as in context xml   See the sections titled  Context Parameters  and  Environment Entries  on this page   http   tomcat apache org tomcat-5 5-doc config context html  As  netjeff points out  these values will be available via the Context lookup String  method and not as System parameters   Another way to do specify these values is to define variables inside of the web xml file of the web application you re deploying  see below   As  Roberto Lo Giacco points out  this is generally considered a poor practice since a deployed artifact should not be environment specific  However  below is the configuration snippet if you really want to do this    lt env-entry gt       lt env-entry-name gt SMTP PASSWORD lt  env-entry-name gt       lt env-entry-type gt java lang String lt  env-entry-type gt       lt env-entry-value gt abc123ftw lt  env-entry-value gt   lt  env-entry gt

User · Answer

Generally you shouldn t rely on system properties to configure a webapp - they may be used to configure the container  e g  Tomcat  but not an application running inside tomcat   cliff meyers has already mentioned the way you should rather use for your webapplication  That s the standard way  that also fits your question of being configurable through context xml or server xml means   That said  should you really need system properties or other jvm options  like max memory settings  in tomcat  you should create a file named  bin setenv sh  or  bin setenv bat   These files do not exist in the standard archive that you download  but if they are present  the content is executed during startup  if you start tomcat via startup sh startup bat   This is a nice way to separate your own settings from the standard tomcat settings and makes updates so much easier  No need to tweak startup sh or catalina sh    If you execute tomcat as windows servive  you usually use tomcat5w exe  tomcat6w exe etc  to configure the registry settings for the service    EDIT  Also  another possibility is to go for JNDI Resources

[tomcat] How can I specify system properties in Tomcat configuration on startup?

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