Java String Substitute substituteProperty(String value, Properties coreProperties)

Description

substitute Property

License

Apache License

Declaration

public static String substituteProperty(String value, Properties coreProperties) 

Method Source Code

//package com.java2s;
//License from project: Apache License 

import java.util.ArrayList;

import java.util.Iterator;
import java.util.List;

import java.util.Properties;

public class Main {
    public static String substituteProperty(String value, Properties coreProperties) {
        if (value == null || value.indexOf('$') == -1) {
            return value;
        }/* ww  w.  ja  va 2s . c  o m*/

        List<String> fragments = new ArrayList<String>();
        List<String> propertyRefs = new ArrayList<String>();
        parsePropertyString(value, fragments, propertyRefs);

        StringBuilder sb = new StringBuilder();
        Iterator<String> i = fragments.iterator();
        Iterator<String> j = propertyRefs.iterator();

        while (i.hasNext()) {
            String fragment = i.next();
            if (fragment == null) {
                String propertyName = j.next();
                String defaultValue = null;
                int colon_index = propertyName.indexOf(':');
                if (colon_index > -1) {
                    defaultValue = propertyName.substring(colon_index + 1);
                    propertyName = propertyName.substring(0, colon_index);
                }
                if (coreProperties != null) {
                    fragment = coreProperties.getProperty(propertyName);
                }
                if (fragment == null) {
                    fragment = System.getProperty(propertyName, defaultValue);
                }
                if (fragment == null) {
                    throw new RuntimeException("No system property or default value specified for " + propertyName
                            + " value:" + value);
                }
            }
            sb.append(fragment);
        }
        return sb.toString();
    }

    private static void parsePropertyString(String value, List<String> fragments, List<String> propertyRefs) {
        int prev = 0;
        int pos;
        //search for the next instance of $ from the 'prev' position
        while ((pos = value.indexOf("$", prev)) >= 0) {

            //if there was any text before this, add it as a fragment
            //TODO, this check could be modified to go if pos>prev;
            //seems like this current version could stick empty strings
            //into the list
            if (pos > 0) {
                fragments.add(value.substring(prev, pos));
            }
            //if we are at the end of the string, we tack on a $
            //then move past it
            if (pos == (value.length() - 1)) {
                fragments.add("$");
                prev = pos + 1;
            } else if (value.charAt(pos + 1) != '{') {
                //peek ahead to see if the next char is a property or not
                //not a property: insert the char as a literal
                /*
                fragments.addElement(value.substring(pos + 1, pos + 2));
                prev = pos + 2;
                */
                if (value.charAt(pos + 1) == '$') {
                    //backwards compatibility two $ map to one mode
                    fragments.add("$");
                    prev = pos + 2;
                } else {
                    //new behaviour: $X maps to $X for all values of X!='$'
                    fragments.add(value.substring(pos, pos + 2));
                    prev = pos + 2;
                }

            } else {
                //property found, extract its name or bail on a typo
                int endName = value.indexOf('}', pos);
                if (endName < 0) {
                    throw new RuntimeException("Syntax error in property: " + value);
                }
                String propertyName = value.substring(pos + 2, endName);
                fragments.add(null);
                propertyRefs.add(propertyName);
                prev = endName + 1;
            }
        }
        //no more $ signs found
        //if there is any tail to the string, append it
        if (prev < value.length()) {
            fragments.add(value.substring(prev));
        }
    }
}

Related

1. stringSubstitution(String argStr, Hashtable vars)
2. substitute(String original, String match, String subst)
3. substitute(String str, Hashtable vars, String delimiter)