Reading a List from properties file and load with spring annotation Value

Question

I want to have a list of values in a  properties file  ie   my list of strings ABC CDE EFG   And to load it in my class directly  ie    Value    my list of strings    private List lt String gt  myList    As I understand  an alternative of doing this is to have it in the spring config file  and load it as a bean reference  correct me if I m wrong   ie   lt bean name  list  gt    lt list gt     lt value gt ABC lt  value gt     lt value gt CDE lt  value gt     lt value gt EFG lt  value gt    lt  list gt   lt  bean gt    But is there any way of doing this  using a  properties file   ps  I would like to do this with out any custom code if possible

User · Answer

Have you considered  Autowireding the constructor or a setter and String split  ing in the body   class MyClass       private List lt String gt  myList        Autowired     public MyClass  Value    my list of strings    final String strs            myList   Arrays asList strs split                     or       Autowired     public void setMyList  Value    my list of strings    final String strs            myList   Arrays asList strs split                  I tend to prefer doing my autowiring in one of these ways to enhance the testability of my code

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If you are using latest Spring framework version Spring 3 1  I believe   you don t need to those string split stuff in SpringEL   Simply add PropertySourcesPlaceholderConfigurer and DefaultConversionService in your Spring s Configuration class   the one with annotated with Configuration   e g     Configuration public class AppConfiguration         Bean     public static PropertySourcesPlaceholderConfigurer propertyPlaceholderConfigurer             return new PropertySourcesPlaceholderConfigurer                Bean public ConversionService conversionService             return new DefaultConversionService              and in your class    Value    list    private List lt String gt  list    and in the properties file  list A B C D E   Without DefaultConversionService  you can only take comma separated String into String array when you inject the value into your field  but DefaultConversionService does a few convenient magic for you and will add those into Collection  Array  etc    check the implementation if you d like to know more about it    With these two  it even handles all the redundant whitespaces including newline  so you don t need to add additional logics to trim them

User · Answer

All the above answers are correct  But you can achieve this in just one line  Please try following declaration and you will get all the comma separated values in a String list   private  Value    T java util Arrays  asList projectProperties  my list of strings       List lt String gt  myList    And also you need to have the following line defined in your xml configuration    lt util properties id  projectProperties  location   project properties   gt    just replace the path and file name of your properties file  And you are good to go      Hope this helps you  Cheers

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I think this is simpler for grabbing the array and stripping spaces    Value       my array   replace          split         private List lt String gt  array

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If you are reading this and you are using Spring Boot  you have 1 more option for this feature  Usually comma separated list are very clumsy for real world use case   And sometime not even feasible  if you want to use commas in your config    email sendTo somebody example com somebody2 example com somebody3 example com         With Spring Boot  you can write it like these  Index start at 0    email sendTo 0  somebody example com email sendTo 1  somebody2 example com email sendTo 2  somebody3 example com   And use it like these    Component  ConfigurationProperties  email   public class EmailProperties        private List lt String gt  sendTo       public List lt String gt  getSendTo             return sendTo             public void setSendTo List lt String gt  sendTo            this sendTo   sendTo              Component public class EmailModel       Autowired   private EmailProperties emailProperties       Use the sendTo List by      emailProperties getSendTo          Configuration public class YourConfiguration        Bean   public EmailProperties emailProperties            return new EmailProperties              Put this in src main resource META-INF spring factories   org springframework boot autoconfigure EnableAutoConfiguration example compackage YourConfiguration

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If you are using Spring Boot 2  it works as is  without any additional configuration   my list of strings ABC CDE EFG   Value    my list of strings    private List lt String gt  myList

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My preferred way  for strings  in particular   is the following one   admin user   Doe  John   Headroom  Max   Mouse  Micky     and use    Value      admin user     private List lt String gt  userList    In this way  you can include also commas in your parameter  It works also for Sets

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By specifying the the my list of strings ABC CDE EFG in  properties file and using    Value    my list of strings    private String   myString   You can get the arrays of strings  And using CollectionUtils addAll myList  myString   you can get the list of strings

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you can do this with annotations like this    Value    T java util Arrays  asList    my list of strings a b c            private List lt String gt  mylist    here my list of strings will be picked from the properties file  if its not there  then the defaults a b c will be used  and in your properties file  you can have something like this  my list of strings d e f

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if using property placeholders then ser1702544 example would become    Value    myConfigProperties  myproperty   trim   replaceAll     s          lt      s           split            With placeholder xml    lt bean class  org springframework beans factory config PropertyPlaceholderConfigurer  gt          lt property name  properties  ref  myConfigProperties    gt       lt property name  placeholderPrefix  gt  lt value gt  myConfigProperties  lt  value gt  lt  property gt   lt  bean gt        lt bean id  myConfigProperties  class  org springframework beans factory config PropertiesFactoryBean  gt        lt property name  locations  gt            lt list gt                   lt value gt classpath myprops properties lt  value gt            lt  list gt        lt  property gt   lt  bean gt

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Beware of spaces in the values  I could be wrong  but I think spaces in the comma-separated list are not truncated using  Value and Spel  The list  foobar a  b  c   would be read in as a list of strings   a     b     c    In most cases you would probably not want the spaces   The expression   Value       foobar   trim   replaceAll     s          lt      s           split         private List lt String gt  foobarList    would give you a list of strings    a    b    c     The regular expression removes all spaces just before and just after a comma  Spaces inside of the values are not removed  So  foobar   AA  B B  CCC   should result in values   AA    B B    CCC

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I am using Spring Boot 2 2 6  My property file   usa big banks  JP Morgan  Wells Fargo  Citigroup  Morgan Stanley  Goldman Sachs   My code    Value    usa big banks        private List lt String gt  bigBanks    RequestMapping   bigbanks       public String getBanks             System out println  bigBanks       bigBanks           return bigBanks toString            It works fine

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Since Spring 3 0  you can add a line like   lt bean id  conversionService       class  org springframework context support ConversionServiceFactoryBean    gt    to your applicationContext xml  or where you configure things   As Dmitry Chornyi points out in a comment  Java based configuration looks like    Bean public ConversionService conversionService         return new DefaultConversionService        This activates the new configuration service which supports converting String to Collection types  If you do not activate this configuration service  Spring falls back on its legacy property editors as configuration services  which do not support this kind of conversion   Converting to collections of other types works  too    Value    my list of ints    private List lt Integer gt  myList   will work with a line like   my list of ints  1  2  3  4   No problems with whitespace there  the ConversionServiceFactoryBean takes care of it   See http   docs spring io spring docs current spring-framework-reference htmlsingle  core-convert-Spring-config     In a Spring application  you typically configure a ConversionService instance per Spring container  or ApplicationContext   That ConversionService will be picked up by Spring and then used whenever a type conversion needs to be performed by the framework            If no ConversionService is registered with Spring  the original PropertyEditor-based system is used

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In my case of a list of integers works this    Value      my list of integers     private List lt Integer gt  listOfIntegers    Property file   my list of integers  100 200 300 400 999

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Consider using Commons Configuration  It have built in feature to break an entry in properties file to array list  Combing with SpEL and  Value should give what you want    As requested  here is what you need  Haven t really tried the code  may got some typoes  please bear with me    In Apache Commons Configuration  there is PropertiesConfiguration   It supports the feature of converting delimited string to array list   For example  if you have a properties file   Foo properties foo bar1  bar2  bar3   With the below code   PropertiesConfiguration config   new PropertiesConfiguration  Foo properties    String   values   config getStringArray  foo      will give you a string array of   bar1    bar2    bar3    To use with Spring  have this in your app context xml    lt bean id  fooConfig  class  org apache commons configuration PropertiesConfiguration  gt       lt constructor-arg type  java lang String  value  classpath  Foo properties   gt   lt  bean gt    and have this in your spring bean   public class SomeBean         Value  fooConfig getStringArray  foo         private String   fooArray      I believe this should work   P

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Using Spring EL    Value       my list of strings   split          private List lt String gt  myList    Assuming your properties file is loaded correctly with the following   my list of strings ABC CDE EFG

[java] Reading a List from properties file and load with spring annotation @Value

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