Properties file with a list as the value for an individual key

Question

For my program I want to read a key from a properties file and an associated List of values for the key  Recently I was trying like that  public static Map lt String List lt String gt  gt categoryMap   new Hashtable lt String  List lt String gt  gt           Properties prop   new Properties          try            prop2 load new FileInputStream  displayCategerization properties            Set lt Object gt  keys   prop keySet            List lt String gt  categoryList   new ArrayList lt String gt             for  Object key   keys                categoryList add  String prop2 get key                LogDisplayService categoryMap put  String key categoryList                     System out println categoryList           System out println  Category Map    LogDisplayService categoryMap            keys   null          prop   null         catch  Throwable e            e printStackTrace            and my properties file is like below -   A APPLE A ALPHABET A ANT B BAT B BALL B BUS   I want for key A there should be a list which contain  APPLE  ALPHABET ANT  and B contain  BAT BALL BUS   So Map should be like this  A  APPLE  ALPHABET ANT   B  BAT BALL BUS   but I get        A  ANT   B  BUS   I searched on the internet for such a way but found nothing  I wish there should be a way  Any help

User · Answer

If this is for some configuration file processing, consider using Apache configuration. https://commons.apache.org/proper/commons-configuration/javadocs/v1.10/apidocs/index.html?org/apache/commons/configuration/PropertiesConfiguration.html It has way to multiple values to single key- The format is bit different though

key=value1,value2,valu3 gives three values against same key.

User · Answer

Try writing the properties as a comma separated list  then split the value after the properties file is loaded  For example  a one two three b nine ten fourteen   You can also use org apache commons configuration and change the value delimiter using the AbstractConfiguration setListDelimiter char  method if you re using comma in your values

User · Answer

There s probably a another way or better  But this is how I do this in Spring Boot   My property file contains the following lines      is the delimiter in each line   mml pots STDEP DETY LI3  STDEP DETY LIMA  mml isdn grunntengingar STDEP DETY LIBAE  STDEP DETY LIBAMA  mml isdn stofntengingar STDEP DETY LIPRAE  STDEP DETY LIPRAM  STDEP DETY LIPRAGS  STDEP DETY LIPRVGS    My server config   Configuration public class ServerConfig         Inject     private Environment env        Bean     public MMLProperties mmlProperties             MMLProperties properties   new MMLProperties            properties setMmmlPots env getProperty  mml pots             properties setMmmlPots env getProperty  mml isdn grunntengingar             properties setMmmlPots env getProperty  mml isdn stofntengingar             return properties            MMLProperties class   public class MMLProperties       private String mmlPots      private String mmlIsdnGrunntengingar      private String mmlIsdnStofntengingar       public MMLProperties             super               public void setMmmlPots String mmlPots            this mmlPots   mmlPots             public void setMmlIsdnGrunntengingar String mmlIsdnGrunntengingar            this mmlIsdnGrunntengingar   mmlIsdnGrunntengingar             public void setMmlIsdnStofntengingar String mmlIsdnStofntengingar            this mmlIsdnStofntengingar   mmlIsdnStofntengingar                These three public getXXX functions then take care of spliting the properties into List     public List lt String gt  getMmmlCommandForPotsAsList             return getPropertieAsList mmlPots              public List lt String gt  getMmlCommandsForIsdnGrunntengingarAsList             return getPropertieAsList mmlIsdnGrunntengingar              public List lt String gt  getMmlCommandsForIsdnStofntengingarAsList             return getPropertieAsList mmlIsdnStofntengingar              private List lt String gt  getPropertieAsList String propertie            return   propertie    null      propertie length    gt  0             Arrays asList propertie split    s    s               Collections emptyList              Then in my Runner class I Autowire MMLProperties   Component public class Runner implements CommandLineRunner         Autowired     MMLProperties mmlProperties        Override     public void run String    arg0  throws Exception              Now I can call my getXXX function to retrieve the properties as List         for  String command   mmlProperties getMmmlCommandForPotsAsList                  System out println command                       Hope this helps

User · Answer

Create a wrapper around properties and assume your A value has keys A 1  A 2  etc  Then when asked for A your wrapper will read all the A   items and build the list  HTH

User · Answer

Your logic is flawed    basically  you need to    get the list for the key if the list is null  create a new list and put it in the map add the word to the list   You re not doing step 2   Here s the code you want   Properties prop   new Properties    prop load new FileInputStream   displayCategerization properties     for  Map Entry lt Object  Object gt  entry   prop entrySet          List lt String gt  categoryList   categoryMap get  String  entry getKey         if  categoryList    null                categoryList   new ArrayList lt String gt             LogDisplayService categoryMap put  String  entry getKey    categoryList             categoryList add  String  entry getValue         Note also the  correct  way to iterate over the entries of a map properties - via its entrySet

User · Answer

The comma separated list option is the easiest but becomes challenging if the values could include commas   Here is an example of the a 1  a 2      approach   for  String value   getPropertyList prop   a          System out println value      public static List lt String gt  getPropertyList Properties properties  String name         List lt String gt  result   new ArrayList lt String gt         for  Map Entry lt Object  Object gt  entry   properties entrySet                  if    String entry getKey    matches       Pattern quote name          d                            result add  String  entry getValue                         return result

[java] Properties file with a list as the value for an individual key

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