String replacement in java similar to a velocity template

Question

Is there any String replacement mechanism in Java  where I can pass objects with a text  and it replaces the string as it occurs  For example  the text is    Hello   user name       Welcome to   site name      The objects I have are  user  and  site   I want to replace the strings given inside     with its equivalent values from the objects  This is same as we replace objects in a velocity template

User · Answer

There are a couple of Expression Language implementations out there that does this for you, could be preferable to using your own implementation as or if your requirments grow, see for example JUEL and MVEL

I like and have successfully used MVEL in at least one project.

Also see the Stackflow post JSTL/JSP EL (Expression Language) in a non JSP (standalone) context

User · Answer

Use StringSubstitutor from Apache Commons Text   https   commons apache org proper commons-text   It will do it for you  and its open source       Map lt String  String gt  valuesMap   new HashMap lt String  String gt      valuesMap put  animal    quick brown fox     valuesMap put  target    lazy dog     String templateString    The   animal  jumped over the   target      StringSubstitutor sub   new StringSubstitutor valuesMap    String resolvedString   sub replace templateString

User · Answer

I threw together a small test implementation of this   The basic idea is to call format and pass in the format string  and a map of objects  and the names that they have locally   The output of the following is      My dog is named fido  and Jane Doe owns him    public class StringFormatter        private static final String fieldStart                 private static final String fieldEnd               private static final String regex   fieldStart               fieldEnd      private static final Pattern pattern   Pattern compile regex        public static String format String format  Map lt String  Object gt  objects            Matcher m   pattern matcher format           String result   format          while  m find                  String   found   m group 1  split                     Object o   objects get found 0                Field f   o getClass   getField found 1                String newVal   f get o  toString                result   result replaceFirst regex  newVal                     return result             static class Dog           public String name          public String owner          public String gender             public static void main String   args            Dog d   new Dog            d name    fido           d owner    Jane Doe           d gender    him           Map lt String  Object gt  map   new HashMap lt String  Object gt             map put  d   d           System out println             StringFormatter format                   My dog is named   d name   and   d owner  owns   d gender                      map              Note  This doesn t compile due to unhandled exceptions   But it makes the code much easier to read   Also  I don t like that you have to construct the map yourself in the code  but I don t know how to get the names of the local variables programatically   The best way to do it  is to remember to put the object in the map as soon as you create it   The following example produces the results that you want from your example   public static void main String   args        Map lt String  Object gt  map   new HashMap lt String  Object gt         Site site   new Site        map put  site   site       site name    StackOverflow com       User user   new User        map put  user   user       user name    jjnguy       System out println           format  Hello   user name   n tWelcome to   site name      map        I should also mention that I have no idea what Velocity is  so I hope this answer is relevant

User · Answer

I use GroovyShell in java to parse template with Groovy GString   Binding binding   new Binding    GroovyShell gs   new GroovyShell binding      this JSONObject can also be replaced by any Java Object JSONObject obj   new JSONObject    obj put  key    value    binding setProperty  obj   obj  String str      obj key    String exp   String format     s   toString     str   String res    String  gs evaluate exp      value System out println str

User · Answer

There is nothing out of the box that is comparable to velocity since velocity was written to solve exactly that problem   The closest thing you can try is looking into the Formatter  http   cupi2 uniandes edu co site images recursos javadoc j2se 1 5 0 docs api java util Formatter html  However the formatter as far as I know was created to provide C like formatting options in Java so it may not scratch exactly your itch but you are welcome to try

User · Answer

Here s an outline of how you could go about doing this  It should be relatively straightforward to implement it as actual code    Create a map of all the objects that will be referenced in the template  Use a regular expression to find variable references in the template and replace them with their values  see step 3   The Matcher class will come in handy for find-and-replace  Split the variable name at the dot  user name would become user and name  Look up user in your map to get the object and use reflection to obtain the value of name from the object  Assuming your objects have standard getters  you will look for a method getName and invoke it

User · Answer

My preferred way is String format   because its a oneliner and doesn t require third party libraries   String message   String format  Hello  My name is  s  I m  s    name  age      I use this regularly  e g  in exception messages like   throw new Exception String format  Unable to login with email   s   email      Hint  You can put in as many variables as you like because format   uses Varargs

User · Answer

Take a look at the java text MessageFormat class  MessageFormat takes a set of objects  formats them  then inserts the formatted strings into the pattern at the appropriate places    Object   params   new Object    hello         String msg   MessageFormat format   0  world  1    params

[java] String replacement in java, similar to a velocity template

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