MVEL'in'运算符不适用于java中的集合

Question

I'm trying to use MVEL 'in' operator in my code to evaluate an expression

List<String> countriesAvailable = new ArrayList<String>();
countriesAvailable.add("Australia");
countriesAvailable.add("France");
List<String> countriesVisited = new ArrayList<String>();
countriesVisited.add("Austria");
countriesVisited.add("France");
Map<String, List<String>> vars = new HashMap<String, List<String>>();
vars.put("countriesAvailable", countriesAvailable);
vars.put("countriesVisited", countriesVisited);
Boolean s = (Boolean) MVEL.eval("countriesVisited in countriesAvailable", vars);
System.out.println(s);

Gives Error: syntax error or incompatible types

Answer 1

Here is the solution. You need to use containsAll

Also note that you misspelled Australia in the second list. I'm not sure if that was on purpose to check the evaluation.

    List<String> countriesAvailable = new ArrayList<String>();
    countriesAvailable.add("Australia");
    countriesAvailable.add("France");

    List<String> countriesVisited = new ArrayList<String>();
    countriesVisited.add("Austria");
    countriesVisited.add("France");

    Map<String, List<String>> vars = new HashMap<String, List<String>>();
    vars.put("countriesAvailable", countriesAvailable);
    vars.put("countriesVisited", countriesVisited);

    Boolean s = (Boolean) MVEL.eval(
            "countriesAvailable.containsAll(countriesVisited)", vars);

    System.out.println("Result = " + s);

Result = false

You can also use the java.util.Collections to perform a disjoint. And take the negative of that.

Boolean s = 
   (Boolean) MVEL.eval(
         "!java.util.Collections.disjoint(countriesAvailable,countriesVisited)",
         vars);

Result = true