ScriptObjectMirrorTest.java 文件源码

@Test
public void mapScriptObjectMirrorCallsiteTest() throws ScriptException {
    final ScriptEngineManager m = new ScriptEngineManager();
    final ScriptEngine engine = m.getEngineByName("nashorn");
    final String TEST_SCRIPT = "typeof obj.foo";

    final Bindings global = engine.getContext().getBindings(ScriptContext.ENGINE_SCOPE);
    engine.eval("var obj = java.util.Collections.emptyMap()");
    // this will drive callsite "obj.foo" of TEST_SCRIPT
    // to use "obj instanceof Map" as it's guard
    engine.eval(TEST_SCRIPT, global);
    // redefine 'obj' to be a script object
    engine.eval("obj = {}");

    final Bindings newGlobal = engine.createBindings();
    // transfer 'obj' from default global to new global
    // new global will get a ScriptObjectMirror wrapping 'obj'
    newGlobal.put("obj", global.get("obj"));

    // Every ScriptObjectMirror is a Map! If callsite "obj.foo"
    // does not see the new 'obj' is a ScriptObjectMirror, it'll
    // continue to use Map's get("obj.foo") instead of ScriptObjectMirror's
    // getMember("obj.foo") - thereby getting null instead of undefined
    assertEquals("undefined", engine.eval(TEST_SCRIPT, newGlobal));
}