升级到Java8和端点V2后，AppEngine错误

Question

Following an upgrade to Java 8 and endpoint upgrade to V2 I kept on getting server error and getting the following errors in my appengine logs:

com.google.apphosting.runtime.jetty9.JettyLogger warn: Error xxxxxxxxx (JettyLogger.java:29)
    java.lang.NoClassDefFoundError: com/google/appengine/repackaged/com/google/gson/JsonElement
        at java.lang.Class.getDeclaredConstructors0(Native Method)
        at java.lang.Class.privateGetDeclaredConstructors(Class.java:2673)
        at java.lang.Class.getConstructor0(Class.java:3077)
        at java.lang.Class.newInstance(Class.java:413)

Answer 1

Turns out it's because as part of the app engine upgrade the following statements are no longer valid

import com.google.appengine.repackaged.com.google.gson.Gson;
import com.google.appengine.repackaged.com.google.gson.GsonBuilder;
...
Gson gson = new GsonBuilder().create();

you need to use the new Json library instead:

1) add new dependency to your gradle file:

compile 'com.google.code.gson:gson:2.8.1' 

2) replace

import com.google.appengine.repackaged.com.google.gson.Gson;
import com.google.appengine.repackaged.com.google.gson.GsonBuilder;

with

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;