Java gson，解码到 Map 时出现 ClassCastException

我想解码 json 字符串，例如{"username":["emmet"]} to a Map<String,String[]> object.

使用以下代码：

    String json = "{\"username\":[\"emmet\"]}";
    Gson gson = new GsonBuilder().create();
    Map<String,String[]> map = new HashMap<>();
    map  = (Map<String,String[]>)gson.fromJson(json, map.getClass());
    String[] val = map.get("username");
    System.out.println(val);

出现此异常：

Exception in thread "main" java.lang.ClassCastException: java.util.ArrayList cannot be cast to [Ljava.lang.String;
    at com.company.Main.main(Main.java:16)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

Gson 已将我的对象解码为Map<String, ArrayList<String>>对象而不是Map<String,String[]>目的。我如何强制 gson 将我的对象解码为Array not ArrayList?

我在用着gson-2.8.1.

Gson皈依者json数组到javaList，所以当你尝试获取用户名时String[]你得到一个ClassCastException

如果你想把它作为String[]那样使用它：

    String json = "{\"username\":[\"emmet\"]}";
    Gson gson = new GsonBuilder().create();
    Map<String,List<String>> map = new HashMap<>();
    map  = (Map<String,List<String>>)gson.fromJson(json, map.getClass());
    List<String> usernames = map.get("username");
    String[] val = usernames.toArray(new String[0]);
    System.out.println(val);

这对你有用