java使用gson从json格式解析来映射问题答案

【问题标题】：java uses gson to parse from json format to map issuesjava使用gson从json格式解析来映射问题
【发布时间】：2016-07-04 07:44:40
【问题描述】：

我想使用google的gson从json测试解析到map，这是我的代码但是得到了一个异常：

Gson gson = new GsonBuilder().serializeNulls().setLenient().setPrettyPrinting().create();
Map<String, List<String>> map = new LinkedHashMap<>();
map = gson.fromJson("The json text", new TypeToken<Map<String, List<String>>>(){}.getType());

json 文本为：

{
    "Worker": {
        "127.0.0.1:9001",
        "127.0.0.1:9002",
        "127.0.0.1:9003",
        "127.0.0.1:9004",
        "127.0.0.1:9005",
        "127.0.0.1:9006",
        "127.0.0.1:9007"
    }
}

错误信息是：

Exception in thread "main" com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 2 column 16 path $.
        at com.google.gson.Gson.fromJson(Gson.java:891)
        at com.google.gson.Gson.fromJson(Gson.java:844)
        at com.google.gson.Gson.fromJson(Gson.java:793)
        at TestBasic.TestBasic.main(TestBasic.java:140)
Caused by: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 2 column 16 path $.
        at com.google.gson.stream.JsonReader.beginArray(JsonReader.java:351)
        at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:80)
        at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:61)
        at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:40)
        at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:187)
        at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:145)
        at com.google.gson.Gson.fromJson(Gson.java:879)
        ... 3 more

【问题讨论】：

标签： java json dictionary gson linkedhashmap

【解决方案1】：

您的 json 文本无效。 Worker 内部的字符串标记应该用 json 数组 [] 括起来

"Worker": [
    "127.0.0.1:9001",
    "127.0.0.1:9002",
    "127.0.0.1:9003",
    "127.0.0.1:9004",
    "127.0.0.1:9005",
    "127.0.0.1:9006",
    "127.0.0.1:9007"
]

【讨论】：