package us.monoid.web;
import java.io.IOException;
import java.io.StringReader;
import us.monoid.json.JSONException;
import us.monoid.json.JSONObject;
import us.monoid.web.jp.javacc.JSONPathCompiler;
import us.monoid.web.jp.javacc.ParseException;
/** Create a path query for a JSON object. Usualy this is done by calling Resty.path(...)
*
* A JSONPathQuery is similar to JsonPath or XPath in that you can create access paths into an JSON object.
* It uses dot '.' as a path separator and [] to access arrays.
* The array index is either a number or an expression to evaluate for each object in the array. The first matching object is returned.
* I.e. <p>
* <code>store.book[price>7 && price<12.999].author</code>
* <p>
* In the example above the JSON object with a prive value between 7 and 12.999 is selected and the author returned.
* Boolean expressions are supported with && (and), || (or), ! (not). Values can be compared with =,<,>.
*
*
* @author beders
*
*/
public class JSONPathQuery extends PathQuery<JSONResource, Object> {
private JSONPathCompiler compiler;
private String expr;
public JSONPathQuery(String anExpression) {
expr = anExpression;
}
@Override
Object eval(JSONResource resource) throws JSONException, ParseException, IOException {
JSONObject json = resource.object();
Object result = getCompiler().expr().eval(json);
return result;
}
protected JSONPathCompiler getCompiler() throws ParseException {
if (null == compiler) {
compiler = new JSONPathCompiler(new StringReader(expr));
}
return compiler;
}
}