Best way to define error codes strings in Java

Question

I am writing a web service in Java  and I am trying to figure out the best way to define error codes and their associated error strings  I need to have a numerical error code and an error string grouped together  Both the error code and error string will be sent to the client accessing the web service  For example  when a SQLException occurs  I might want to do the following      Example  errorCode   1               errorString    There was a problem accessing the database   throw new SomeWebServiceException errorCode  errorString     The client program might be shown the message       Error  1 has occured  There was a   problem accessing the database     My first thought was to used an Enum of the error codes and override the toString methods to return the error strings  Here is what I came up with   public enum Errors     DATABASE        Override     public String toString           return  A database error has occured                  DUPLICATE USER        Override     public String toString           return  This user already exists                     more errors follow     My question is  Is there a better way to do this  I would prefer an solution in code  rather than reading from an external file  I am using Javadoc for this project  and being able to document the error codes in-line and have them automatically update in the documentation would be helpful

User · Answer

At my last job I went a little deeper in the enum version:

public enum Messages {
    @Error
    @Text("You can''t put a {0} in a {1}")
    XYZ00001_CONTAINMENT_NOT_ALLOWED,
    ...
}

@Error, @Info, @Warning are retained in the class file and are available at runtime. (We had a couple of other annotations to help describe message delivery as well)

@Text is a compile-time annotation.

I wrote an annotation processor for this that did the following:

Verify that there are no duplicate message numbers (the part before the first underscore)
Syntax-check the message text
Generate a messages.properties file that contains the text, keyed by the enum value.

I wrote a few utility routines that helped log errors, wrap them as exceptions (if desired) and so forth.

I'm trying to get them to let me open-source it... -- Scott

User · Answer

Overloading toString   seems a bit icky -- that seems a bit of a stretch of toString   s normal use   What about   public enum Errors     DATABASE 1   A database error has occured       DUPLICATE USER 5007   This user already exists             add more cases here        private final int id    private final String message     Errors int id  String message         this id   id       this message   message         public int getId     return id      public String getMessage     return message        seems a lot cleaner to me    and less verbose

User · Answer

Using interface as message constant is generally a bad idea  It will leak into client program permanently as part of exported API  Who knows  that later client programmers might parse that error messages public  as part of their program    You will be locked forever to support this  as changes in string format will may break client program

User · Answer

There are many ways to solve this  My preferred approach is to have interfaces   public interface ICode          your preferred code type here  can be int or string or whatever   id       public interface IMessage       ICode code        Now you can define any number of enums which provide messages   public enum DatabaseMessage implements IMessage        CONNECTION FAILURE DatabaseCode CONNECTION FAILURE            Now you have several options to turn those into Strings  You can compile the strings into your code  using annotations or enum constructor parameters  or you can read them from a config property file or from a database table or a mixture  The latter is my preferred approach because you will always need some messages that you can turn into text very early  ie  while you connect to the database or read the config    I m using unit tests and reflection frameworks to find all types that implement my interfaces to make sure each code is used somewhere and that the config files contain all expected messages  etc   Using frameworks that can parse Java like https   github com javaparser javaparser or the one from Eclipse  you can even check where the enums are used and find unused ones

User · Answer

I use PropertyResourceBundle to define the error codes in an enterprise application to manage locale error code resources  This is the best way to handle error codes instead of writing code  may be hold good for few error codes  when the number of error codes are huge and structured  Look at java doc for more information on PropertyResourceBundle

User · Answer

Overloading toString   seems a bit icky -- that seems a bit of a stretch of toString   s normal use   What about   public enum Errors     DATABASE 1   A database error has occured       DUPLICATE USER 5007   This user already exists             add more cases here        private final int id    private final String message     Errors int id  String message         this id   id       this message   message         public int getId     return id      public String getMessage     return message        seems a lot cleaner to me    and less verbose

User · Answer

Please follow the below example   public enum ErrorCodes   NO File  No file found      private ErrorCodes String value         this errordesc   value         private String errordesc        public String errordesc         return errordesc    public void setValue String errordesc        this errordesc   errordesc          In your code call it like   fileResponse setErrorCode ErrorCodes NO FILE errordesc

User · Answer

Just to keep flogging this particular dead horse- we ve had good use of numeric error codes when errors are shown to end-customers  since they frequently forget or misread the actual error message but may sometimes retain and report a numeric value that can give you a clue to what actually happened

User · Answer

I  and the rest of our team in my company  prefer to raise exceptions instead of returning error codes  Error codes have to be checked everywhere  passed around  and tend to make the code unreadable when the amount of code becomes bigger   The error class would then define the message   PS  and actually also care for internationalization   PPS  you could also redefine the raise-method and add logging  filtering etc  if required  at leastin environments  where the Exception classes and friends are extendable changeable

User · Answer

Just to keep flogging this particular dead horse- we ve had good use of numeric error codes when errors are shown to end-customers  since they frequently forget or misread the actual error message but may sometimes retain and report a numeric value that can give you a clue to what actually happened

User · Answer

As far as I am concerned  I prefer to externalize the error messages in a properties files  This will be really helpful in case of internationalization of your application  one properties file per language   It is also easier to modify an error message  and it won t need any re-compilation of the Java sources   On my projects  generally I have an interface that contains errors codes  String or integer  it doesn t care much   which contains the key in the properties files for this error   public interface ErrorCodes       String DATABASE ERROR    DATABASE ERROR       String DUPLICATE USER    DUPLICATE USER               in the properties file   DATABASE ERROR An error occurred in the database  DUPLICATE USER The user already exists        Another problem with your solution is the maintenability  you have only 2 errors  and already 12 lines of code  So imagine your Enumeration file when you will have hundreds of errors to manage

User · Answer

I d recommend that you take a look at java util ResourceBundle   You should care about I18N  but it s worth it even if you don t   Externalizing the messages is a very good idea   I ve found that it was useful to be able to give a spreadsheet to business folks that allowed them to put in the exact language they wanted to see   We wrote an Ant task to generate the  properties files at compile time   It makes I18N trivial     If you re also using Spring  so much the better   Their MessageSource class is useful for these sorts of things

User · Answer

Overloading toString   seems a bit icky -- that seems a bit of a stretch of toString   s normal use   What about   public enum Errors     DATABASE 1   A database error has occured       DUPLICATE USER 5007   This user already exists             add more cases here        private final int id    private final String message     Errors int id  String message         this id   id       this message   message         public int getId     return id      public String getMessage     return message        seems a lot cleaner to me    and less verbose

User · Answer

Overloading toString   seems a bit icky -- that seems a bit of a stretch of toString   s normal use   What about   public enum Errors     DATABASE 1   A database error has occured       DUPLICATE USER 5007   This user already exists             add more cases here        private final int id    private final String message     Errors int id  String message         this id   id       this message   message         public int getId     return id      public String getMessage     return message        seems a lot cleaner to me    and less verbose

User · Answer

As far as I am concerned  I prefer to externalize the error messages in a properties files  This will be really helpful in case of internationalization of your application  one properties file per language   It is also easier to modify an error message  and it won t need any re-compilation of the Java sources   On my projects  generally I have an interface that contains errors codes  String or integer  it doesn t care much   which contains the key in the properties files for this error   public interface ErrorCodes       String DATABASE ERROR    DATABASE ERROR       String DUPLICATE USER    DUPLICATE USER               in the properties file   DATABASE ERROR An error occurred in the database  DUPLICATE USER The user already exists        Another problem with your solution is the maintenability  you have only 2 errors  and already 12 lines of code  So imagine your Enumeration file when you will have hundreds of errors to manage

User · Answer

Well there s certainly a better implementation of the enum solution  which is generally quite nice   public enum Error     DATABASE 0   quot A database error has occurred  quot      DUPLICATE USER 1   quot This user already exists  quot       private final int code    private final String description     private Error int code  String description        this code   code      this description   description         public String getDescription          return description         public int getCode          return code          Override   public String toString         return code    quot    quot    description         You may want to override toString   to just return the description instead - not sure  Anyway  the main point is that you don t need to override separately for each error code  Also note that I ve explicitly specified the code instead of using the ordinal value - this makes it easier to change the order and add remove errors later  Don t forget that this isn t internationalised at all - but unless your web service client sends you a locale description  you can t easily internationalise it yourself anyway  At least they ll have the error code to use for i18n at the client side

User · Answer

At my last job I went a little deeper in the enum version:

public enum Messages {
    @Error
    @Text("You can''t put a {0} in a {1}")
    XYZ00001_CONTAINMENT_NOT_ALLOWED,
    ...
}

@Error, @Info, @Warning are retained in the class file and are available at runtime. (We had a couple of other annotations to help describe message delivery as well)

@Text is a compile-time annotation.

I wrote an annotation processor for this that did the following:

Verify that there are no duplicate message numbers (the part before the first underscore)
Syntax-check the message text
Generate a messages.properties file that contains the text, keyed by the enum value.

I wrote a few utility routines that helped log errors, wrap them as exceptions (if desired) and so forth.

I'm trying to get them to let me open-source it... -- Scott

User · Answer

enum for error code message definition is still a nice solution though it has a i18n concerns  Actually we may have two situations  the code message is displayed to the end user or to the system integrator  For the later case  I18N is not necessary  I think the web services is most likely the later case

User · Answer

Well there s certainly a better implementation of the enum solution  which is generally quite nice   public enum Error     DATABASE 0   quot A database error has occurred  quot      DUPLICATE USER 1   quot This user already exists  quot       private final int code    private final String description     private Error int code  String description        this code   code      this description   description         public String getDescription          return description         public int getCode          return code          Override   public String toString         return code    quot    quot    description         You may want to override toString   to just return the description instead - not sure  Anyway  the main point is that you don t need to override separately for each error code  Also note that I ve explicitly specified the code instead of using the ordinal value - this makes it easier to change the order and add remove errors later  Don t forget that this isn t internationalised at all - but unless your web service client sends you a locale description  you can t easily internationalise it yourself anyway  At least they ll have the error code to use for i18n at the client side

User · Answer

I  and the rest of our team in my company  prefer to raise exceptions instead of returning error codes  Error codes have to be checked everywhere  passed around  and tend to make the code unreadable when the amount of code becomes bigger   The error class would then define the message   PS  and actually also care for internationalization   PPS  you could also redefine the raise-method and add logging  filtering etc  if required  at leastin environments  where the Exception classes and friends are extendable changeable

User · Answer

enum for error code message definition is still a nice solution though it has a i18n concerns  Actually we may have two situations  the code message is displayed to the end user or to the system integrator  For the later case  I18N is not necessary  I think the web services is most likely the later case

User · Answer

I use PropertyResourceBundle to define the error codes in an enterprise application to manage locale error code resources  This is the best way to handle error codes instead of writing code  may be hold good for few error codes  when the number of error codes are huge and structured  Look at java doc for more information on PropertyResourceBundle

User · Answer

A little late but  I was just looking for a pretty solution for myself  If you have different kind of message error you can add simple  custom message factory so that you can specify more details and format that you d like later   public enum Error       DATABASE 0   A database error has occured           DUPLICATE USER 1   User already exists                   private String description           public Error changeDescription String description            this description   description          return this                    Error genericError   Error DATABASE  Error specific   Error DUPLICATE USER changeDescription   Call Admin       EDIT  ok  using enum here is a little dangerous since you alter particular enum permanently  I guess better would be to change to class and use static fields  but than you cannot use      anymore  So I guess it s a good example what not to do   or do it only during initialization

User · Answer

I  and the rest of our team in my company  prefer to raise exceptions instead of returning error codes  Error codes have to be checked everywhere  passed around  and tend to make the code unreadable when the amount of code becomes bigger   The error class would then define the message   PS  and actually also care for internationalization   PPS  you could also redefine the raise-method and add logging  filtering etc  if required  at leastin environments  where the Exception classes and friends are extendable changeable

User · Answer

At my last job I went a little deeper in the enum version:

public enum Messages {
    @Error
    @Text("You can''t put a {0} in a {1}")
    XYZ00001_CONTAINMENT_NOT_ALLOWED,
    ...
}

@Error, @Info, @Warning are retained in the class file and are available at runtime. (We had a couple of other annotations to help describe message delivery as well)

@Text is a compile-time annotation.

I wrote an annotation processor for this that did the following:

Verify that there are no duplicate message numbers (the part before the first underscore)
Syntax-check the message text
Generate a messages.properties file that contains the text, keyed by the enum value.

I wrote a few utility routines that helped log errors, wrap them as exceptions (if desired) and so forth.

I'm trying to get them to let me open-source it... -- Scott

User · Answer

As far as I am concerned  I prefer to externalize the error messages in a properties files  This will be really helpful in case of internationalization of your application  one properties file per language   It is also easier to modify an error message  and it won t need any re-compilation of the Java sources   On my projects  generally I have an interface that contains errors codes  String or integer  it doesn t care much   which contains the key in the properties files for this error   public interface ErrorCodes       String DATABASE ERROR    DATABASE ERROR       String DUPLICATE USER    DUPLICATE USER               in the properties file   DATABASE ERROR An error occurred in the database  DUPLICATE USER The user already exists        Another problem with your solution is the maintenability  you have only 2 errors  and already 12 lines of code  So imagine your Enumeration file when you will have hundreds of errors to manage

User · Answer

I d recommend that you take a look at java util ResourceBundle   You should care about I18N  but it s worth it even if you don t   Externalizing the messages is a very good idea   I ve found that it was useful to be able to give a spreadsheet to business folks that allowed them to put in the exact language they wanted to see   We wrote an Ant task to generate the  properties files at compile time   It makes I18N trivial     If you re also using Spring  so much the better   Their MessageSource class is useful for these sorts of things

User · Answer

I d recommend that you take a look at java util ResourceBundle   You should care about I18N  but it s worth it even if you don t   Externalizing the messages is a very good idea   I ve found that it was useful to be able to give a spreadsheet to business folks that allowed them to put in the exact language they wanted to see   We wrote an Ant task to generate the  properties files at compile time   It makes I18N trivial     If you re also using Spring  so much the better   Their MessageSource class is useful for these sorts of things

User · Answer

Well there s certainly a better implementation of the enum solution  which is generally quite nice   public enum Error     DATABASE 0   quot A database error has occurred  quot      DUPLICATE USER 1   quot This user already exists  quot       private final int code    private final String description     private Error int code  String description        this code   code      this description   description         public String getDescription          return description         public int getCode          return code          Override   public String toString         return code    quot    quot    description         You may want to override toString   to just return the description instead - not sure  Anyway  the main point is that you don t need to override separately for each error code  Also note that I ve explicitly specified the code instead of using the ordinal value - this makes it easier to change the order and add remove errors later  Don t forget that this isn t internationalised at all - but unless your web service client sends you a locale description  you can t easily internationalise it yourself anyway  At least they ll have the error code to use for i18n at the client side

User · Answer

As far as I am concerned  I prefer to externalize the error messages in a properties files  This will be really helpful in case of internationalization of your application  one properties file per language   It is also easier to modify an error message  and it won t need any re-compilation of the Java sources   On my projects  generally I have an interface that contains errors codes  String or integer  it doesn t care much   which contains the key in the properties files for this error   public interface ErrorCodes       String DATABASE ERROR    DATABASE ERROR       String DUPLICATE USER    DUPLICATE USER               in the properties file   DATABASE ERROR An error occurred in the database  DUPLICATE USER The user already exists        Another problem with your solution is the maintenability  you have only 2 errors  and already 12 lines of code  So imagine your Enumeration file when you will have hundreds of errors to manage

User · Answer

At my last job I went a little deeper in the enum version:

public enum Messages {
    @Error
    @Text("You can''t put a {0} in a {1}")
    XYZ00001_CONTAINMENT_NOT_ALLOWED,
    ...
}

@Error, @Info, @Warning are retained in the class file and are available at runtime. (We had a couple of other annotations to help describe message delivery as well)

@Text is a compile-time annotation.

I wrote an annotation processor for this that did the following:

Verify that there are no duplicate message numbers (the part before the first underscore)
Syntax-check the message text
Generate a messages.properties file that contains the text, keyed by the enum value.

I wrote a few utility routines that helped log errors, wrap them as exceptions (if desired) and so forth.

I'm trying to get them to let me open-source it... -- Scott

User · Answer

Well there s certainly a better implementation of the enum solution  which is generally quite nice   public enum Error     DATABASE 0   quot A database error has occurred  quot      DUPLICATE USER 1   quot This user already exists  quot       private final int code    private final String description     private Error int code  String description        this code   code      this description   description         public String getDescription          return description         public int getCode          return code          Override   public String toString         return code    quot    quot    description         You may want to override toString   to just return the description instead - not sure  Anyway  the main point is that you don t need to override separately for each error code  Also note that I ve explicitly specified the code instead of using the ordinal value - this makes it easier to change the order and add remove errors later  Don t forget that this isn t internationalised at all - but unless your web service client sends you a locale description  you can t easily internationalise it yourself anyway  At least they ll have the error code to use for i18n at the client side

User · Answer

There are many ways to solve this  My preferred approach is to have interfaces   public interface ICode          your preferred code type here  can be int or string or whatever   id       public interface IMessage       ICode code        Now you can define any number of enums which provide messages   public enum DatabaseMessage implements IMessage        CONNECTION FAILURE DatabaseCode CONNECTION FAILURE            Now you have several options to turn those into Strings  You can compile the strings into your code  using annotations or enum constructor parameters  or you can read them from a config property file or from a database table or a mixture  The latter is my preferred approach because you will always need some messages that you can turn into text very early  ie  while you connect to the database or read the config    I m using unit tests and reflection frameworks to find all types that implement my interfaces to make sure each code is used somewhere and that the config files contain all expected messages  etc   Using frameworks that can parse Java like https   github com javaparser javaparser or the one from Eclipse  you can even check where the enums are used and find unused ones

User · Answer

I d recommend that you take a look at java util ResourceBundle   You should care about I18N  but it s worth it even if you don t   Externalizing the messages is a very good idea   I ve found that it was useful to be able to give a spreadsheet to business folks that allowed them to put in the exact language they wanted to see   We wrote an Ant task to generate the  properties files at compile time   It makes I18N trivial     If you re also using Spring  so much the better   Their MessageSource class is useful for these sorts of things

User · Answer

I  and the rest of our team in my company  prefer to raise exceptions instead of returning error codes  Error codes have to be checked everywhere  passed around  and tend to make the code unreadable when the amount of code becomes bigger   The error class would then define the message   PS  and actually also care for internationalization   PPS  you could also redefine the raise-method and add logging  filtering etc  if required  at leastin environments  where the Exception classes and friends are extendable changeable

User · Answer

Using interface as message constant is generally a bad idea  It will leak into client program permanently as part of exported API  Who knows  that later client programmers might parse that error messages public  as part of their program    You will be locked forever to support this  as changes in string format will may break client program

User · Answer

A little late but  I was just looking for a pretty solution for myself  If you have different kind of message error you can add simple  custom message factory so that you can specify more details and format that you d like later   public enum Error       DATABASE 0   A database error has occured           DUPLICATE USER 1   User already exists                   private String description           public Error changeDescription String description            this description   description          return this                    Error genericError   Error DATABASE  Error specific   Error DUPLICATE USER changeDescription   Call Admin       EDIT  ok  using enum here is a little dangerous since you alter particular enum permanently  I guess better would be to change to class and use static fields  but than you cannot use      anymore  So I guess it s a good example what not to do   or do it only during initialization

User · Answer

Please follow the below example   public enum ErrorCodes   NO File  No file found      private ErrorCodes String value         this errordesc   value         private String errordesc        public String errordesc         return errordesc    public void setValue String errordesc        this errordesc   errordesc          In your code call it like   fileResponse setErrorCode ErrorCodes NO FILE errordesc

[java] Best way to define error codes/strings in Java?

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