Question

I have text with multiple #{key} phrases. For example:

Lorem ipsum dolor sit amet, consectetur adipisicing #{key1}. Proin nibh 
augue, suscipit a, scelerisque #{key1}, lacinia in, mi. Cras vel #{key2}. 
Etiam pellentesque aliquet tellus. Phasellus pharetra nulla ac diam. 
Quisque semper #{key3} at risus.

I need to replace all #{key} values with corresponding messageSource.getMessage(key, null, locale) (messageSource is org.springframework.context.MessageSource), but i’m not good at regex. How to build right regular expression ?

Examples:

#{texts.appName} need to replace with messageSource.getMessage("texts.appName", null, locale);
#{my.company} need to replace with messageSource.getMessage("my.company", null, locale);

Answer 1

Assuming key is just a placeholder for any name your regex would be something like this: #\{([\w\.]+)\}

This means: any sequence of word characters or dots (\w\., which is equivalent to a-zA-Z0-9_\.) between #{ and } is returned as group 1.

Now you need to create a matcher and iterate over the matches, extract the key and replace the match with your message:

String input = "Lorem ipsum dolor sit amet, consectetur adipisicing #{key1}. " +
   "Proin nibh augue, suscipit a, scelerisque #{key1}," + 
   "lacinia in, mi. Cras vel #{key2}. Etiam pellentesque aliquet tellus." + 
   " Phasellus pharetra nulla ac diam. Quisque semper #{key3} at risus.";
StringBuffer result = new StringBuffer();

Pattern p = Pattern.compile( "#\\{([\\w\\.]+)\\}" );
Matcher m = p.matcher( input );

while( m.find() ) {      
  //extract the message for key = m.group( 1 ) here
  //i'll just mark the found keys 
  m.appendReplacement( result,  "##" + m.group( 1 ) + "##" );      
}
m.appendTail( result );

System.out.println(result); //output: ... consectetur adipisicing ##key1## ...  etc.