Groovy调用脚本基类中意外的“ get（String）”方法

Question

I have a small program that lets its user execute arbitrary Groovy code. I use a base groovy.lang.Script class that provides a number of methods, of which one is named get . All this code is written in Java.

Base class:

import groovy.lang.Script;
public class ScriptClass extends Script {

    @Override
    public Object run() {
        return null;
    }

    //many other methods

    public String get(String uri) {
        System.out.println("get called with '" + uri + "'");
        return uri;
    }
}

The get(String) method above is intended to be an alias for http(method=GET) .

Groovy shell invocation:

public static void main(String[] args) throws Exception {
    CompilerConfiguration compilerConfiguration = new CompilerConfiguration();
    compilerConfiguration.setScriptBaseClass(ScriptClass.class.getName());

    GroovyShell groovyShell = new GroovyShell(compilerConfiguration);

    Map<String, Object> map = new HashMap<>();
    map.put("no", "NO");

    String template = "yes";
    Script script = groovyShell.parse(template);
    script.setBinding(new Binding(map));

    Object res = script.run();
    System.out.println(res);
}

And that outpus:

get called with 'yes'
yes

The method is not called when I change the input code:

String template = "no";

I couldn't find any explanation to why this method is being called, maybe I missed some documentation paragraph.

The questions :

• Why is Groovy calling ScriptClass.get(String) when the script references a variable not defined in the binding?
• If this behavior is standard/correct, is there a way to prevent the resolution of undefined variables from being routed to ScriptClass.get(String) ?

Answer 1

Actually your get method disturbs the metaprogramming abilities of groovy. See Groovy - difference between get and propertyMissing? . Quote: When you overloaded get, you lost the propertyMissing functionality.

In your example the template is always evaluated. With the template being no the script returns NO , which is defined in the binding. With the template being yes the unbound variable yes is evaluated, which, being unbound, usually always results in calling get and propertyMissing but breaks because get is overridden in your script.

You will have to resort to a different method name for get in your script.