Java - Groovy : regex parse text block

Question

I know that this is a common question and I've been through a lot of forums to figure out whats the problem in my code.

I have to read a text file with several blocks in the following format:

import com.myCompanyExample.gui.Layout

/*some comments here*/

@Layout
LayoutModel currentState() {
   MyBuilder builder = new MyBuilder()
   form example
     title form{
        row_1
        row_1 
        row_n
      }
   return build.get()
}

@Layout
LayoutModel otherState() {
   ....
   ....
   return build.get()
}

I have this code to read all the file and I'd like to extract each block between the keyword "@Layout" and the keyword "return". I need also to catch all newline so later I'll be able to split each matched block into a list

private void myReadFile(File fileLayout){
    String line = null;
    StringBuilder allText = new StringBuilder();
    try{
        FileReader fileReader = new FileReader(fileLayout);
        BufferedReader bufferedReader = new BufferedReader(fileReader);
        while((line = bufferedReader.readLine()) != null) {
            allText.append(line)
        }
        bufferedReader.close();
    }
    catch(FileNotFoundException ex) {
        System.out.println("Unable to open file");
    }
    catch(IOException ex) {
        System.out.println("Error reading file");
    }
    Pattern pattern = Pattern.compile("(?s)@Layout.*?return",Pattern.DOTALL);
    Matcher matcher = pattern.matcher(allText);
    while(matcher.find()){
       String [] layoutBlock = (matcher.group()).split("\\r?\\n")
      for(index in layoutBlock){
           //check each line of the current block
      }
}

layoutBlock returns size=1

Are you sure that layoutBlock length is 1? I have run the same code and it works (layoutBlock contains matched lines) — cybersoft
– cybersoft, Commented Dec 13, 2015 at 16:20
Why not try to parse the script and interrogate the class normally, rather than trying to write a regular expression to read groovy scripts? — tim_yates
– tim_yates, Commented Dec 13, 2015 at 16:27
@cybersoft I think that layoutBlock has just one element which is the entire block returned from the matcher find, and that's fine. Now I not able to split that string on each newline — 4mac07
– 4mac07, Commented Dec 13, 2015 at 17:57

Giuseppe Ricupero · Accepted Answer · 2015-12-13 18:17:30Z

1

I think this can potentially be a so called XY problem anyway...if the groovy source is composed only by @Layout annotated blocks of code you can use a tempered greedy token to select till the next annotation (view online demo).

Change the pattern loc as this:

Pattern pattern = Pattern.compile( "@Layout(?:(?!@Layout).)*", Pattern.DOTALL );

PS: the dotall flag (?s) inside the regex and the parameter Pattern.DOTALL do the same thing (enable the so called multiline mode), use only one of them indifferently.

UPDATE

I tried your code, the problem (preserving newline) is in the method you use to slurp the file (bufferedReader.readline() remove the newline at the end of the string).

Simply readd a newline when append to allText:

String ln = System.lineSeparator();
while((line = bufferedReader.readLine()) != null) {
    allText.append(line + ln);
}

Or you can replace all the code to slurp the file with this:

import java.nio.file.Files;
import java.nio.file.Paths;

//can throw an IOException
String filePath = "/path/to/layout.groovy";
String allText = new String(Files.readAllBytes(Paths.get(filePath)),StandardCharsets.UTF_8);

edited Dec 13, 2015 at 18:17

answered Dec 13, 2015 at 17:05

Giuseppe Ricupero

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1 Comment

4mac07 Over a year ago

You're right, readLine() was removing newline. Thank you for your help

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