Matcher, find and replace placeholders with values - regex

Question

I have an input String which is something like a query with placeholders, like this
#input String queryText, test, test2
//queryText is something like " SELECT stuff FROM stufftable WHERE oid_2 = $$test$$ || oid_2 = $$test2$$
Now my task is to replace those placeholders with the content of the inputs, the input variables have the same name of the placeholders, so variable test should replace placeholder $$test$$ and variable test2 should replace placeholder $$test2$$
Here's what I've written down as a test
final List<String> list = new LinkedList<String>();
Pattern pattern = Pattern.compile(/\$\$(.*?)\$\$/)
Matcher matcher = pattern.matcher(queryText)
log.debug(pattern)
while (matcher.find()) {
list.add(matcher.group(1));
String text = matcher.group(1)
log.debug(list)
log.debug(text)
}
And the output I have from the logs is the following:
\$\$(.*?)\$\$
[test]
test
[test, test2]
test2
So the placeholders are found correctly in groups, the part i miss is how to replace the values into them. I've tried .replaceFirst but it loops in the while, I've tried .replaceAll but it replaces all the placeholders at the first time so the others are not even found.
I hope it's clear, it's hard to explain. I'm here for any explanation.

Answer 1

The idea is to put the variables names and their values to a Map, and then use Matcher#appendReplacement to find the variable data in the map by the variable name. The code below is a combination of what the previous answers are about:
// Input:
String queryText = " SELECT stuff FROM stufftable WHERE oid_2 = $$test$$ || oid_2 = $$test2$$";
String test = "1";
String test2 = "2";
Map<String, String> map = new HashMap<>();
map.put("test", test);
map.put("test2", test2);
StringBuffer result = new StringBuffer();
Matcher m = Pattern.compile("\\${2}(.*?)\\${2}").matcher(queryText);
while (m.find()) {
if (!m.group(1).isEmpty()) {
m.appendReplacement(result, map.get(m.group(1)));
}
else {
m.appendReplacement(result, m.group(0));
}
}
m.appendTail(result);
System.out.println(result.toString());
// => SELECT stuff FROM stufftable WHERE oid_2 = 1 || oid_2 = 2
See the Java demo
In Groovy, it is as simple as
String test = "1";
String test2 = "2";
Map map = ["test":test, "test2":test2];
String txt = 'WHERE oid_2 = $$test$$ || oid_2 = $$test2$$';
print txt.replaceAll(/\$\$(.*?)\$\$/) { k -> map[k[1]] ?: k[0] }
See the Groovy demo

Answer 2

String queryText = "SELECT stuff FROM stufftable WHERE oid_2 = $$test$$ || oid_2 = $$test2$$";
String regex="\\$+(.*?)\\$+";
Matcher m=Pattern.compile(regex).matcher(queryText);
StringBuffer sql=new StringBuffer();
while (m.find()) {
m.appendReplacement(sql, "$1");
}
m.appendTail(sql);
System.out.println(sql);
you can try this .