javax.script.ScriptException: ReferenceError: "xxx" is not defined in

大家好，我是烤鸭：
今天使用 javax.script.ScriptEngine 遇到一个奇怪的问题，无法识别js方法。

1. 报错内容：

javax.script.ScriptException: ReferenceError: "a" is not defined in <eval> at line number 1057
    at jdk.nashorn.api.scripting.NashornScriptEngine.throwAsScriptException(NashornScriptEngine.java:470) ~[nashorn.jar:na]
    at jdk.nashorn.api.scripting.NashornScriptEngine.invokeImpl(NashornScriptEngine.java:392) ~[nashorn.jar:na]
    at jdk.nashorn.api.scripting.NashornScriptEngine.invokeFunction(NashornScriptEngine.java:190) ~[nashorn.jar:na]
    at com.mys.my.wechat.utils.aes.JSSecret.getDatas(JSSecret.java:50) ~[classes!/:1.0.0-SNAPSHOT]
    at com.mys.my.wechat.WxMpDemoApplication.main(WxMpDemoApplication.java:26) [classes!/:1.0.0-SNAPSHOT]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_201]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_201]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_201]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_201]
    at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:48) [wxChat.jar:1.0.0-SNAPSHOT]
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:87) [wxChat.jar:1.0.0-SNAPSHOT]
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:50) [wxChat.jar:1.0.0-SNAPSHOT]
    at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:51) [wxChat.jar:1.0.0-SNAPSHOT]
Caused by: jdk.nashorn.internal.runtime.ECMAException: ReferenceError: "a" is not defined
    at jdk.nashorn.internal.runtime.ECMAErrors.error(ECMAErrors.java:57) ~[nashorn.jar:na]
    at jdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:319) ~[nashorn.jar:na]
    at jdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:291) ~[nashorn.jar:na]
    at jdk.nashorn.internal.objects.Global.__noSuchProperty__(Global.java:1442) ~[nashorn.jar:na]
    at jdk.nashorn.internal.scripts.Script$Recompilation$17$41307AAAA$\^eval\_.d(<eval>:1057) ~[na:na]
    at jdk.nashorn.internal.scripts.Script$Recompilation$16$41694A$\^eval\_.myFunc(<eval>:1069) ~[na:na]
    at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:639) ~[nashorn.jar:na]
    at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:494) ~[nashorn.jar:na]
    at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:393) ~[nashorn.jar:na]
    at jdk.nashorn.api.scripting.ScriptObjectMirror.callMember(ScriptObjectMirror.java:199) ~[nashorn.jar:na]
    at jdk.nashorn.api.scripting.NashornScriptEngine.invokeImpl(NashornScriptEngine.java:386) ~[nashorn.jar:na]
    ... 11 common frames omitted