【已解决】Exception in thread "main" java.lang.ClassCastException: com.google.gson.internal.LinkedTreeMap cannot be cast to

GSON TypeToken 动态泛型

一、错误描述

Exception in thread "main" java.lang.ClassCastException: com.google.gson.internal.LinkedTreeMap cannot be cast to com.xxx

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二、代码

自定义class RecReasonConf

@Data
    @Builder
    public static class RecReasonConf {
        /**
         * 推荐理由编号
         */
        private String reasonCode;

        /**
         * 推荐理由类型
         */
        private String reasontype;
    }

泛型反序列化

public static <T> Map<String, T> gsonToMaps(String gsonString) {
        Map<String, T> map = null;
        if (gson != null) {
            map = gson.fromJson(gsonString, new TypeToken<Map<String, T>>() {
            }.getType());
        }
        return map;
    }

运行编译

public static void main(String[] args) {
        String str = "{\"A1\":{\"reasonCode\":\"A1\",\"reasontype\":\"FAVOR\"},\"A2\":{\"reasonCode\":\"A2\",\"reasontype\":\"FAVOR\"},\"A3\":{\"reasonCode\":\"A3\",\"reasontype\":\"FAVOR\"},\"B1\":{\"reasonCode\":\"B1\",\"reasontype\":\"CLICK\"},\"B2\":{\"reasonCode\":\"B2\",\"reasontype\":\"CLICK\"},\"B3\":{\"reasonCode\":\"B3\",\"reasontype\":\"CLICK\"},\"C\":{\"codePrefix\":\"C\",\"reasontype\":\"CLICK\"},\"D1\":{\"reasonCode\":\"D1\",\"reasontype\":\"EXPOSE\"},\"D2\":{\"reasonCode\":\"D2\",\"reasontype\":\"EXPOSE\"},\"D3\":{\"reasonCode\":\"D3\",\"reasontype\":\"EXPOSE\"},\"E\":{\"codePrefix\":\"E\",\"reasontype\":\"NEWEST\"}}";
        Map<String,RecReasonConf> map = GsonUtil.gsonToMaps(str);
        map.values().stream().findFirst().ifPresent(obj-> System.out.println(obj.getClass().getSimpleName()));
    }

debug查看反序列结果

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三、原因

带泛型的map被转成gson后，对象被擦除，变为LinkedTreeMap。所以无法被还原

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四、改进方案

public static <T> Map<String, T> gsonToMaps(String gsonString,Class<T> clazz) {
        Map<String, T> map = null;
        if (gson != null) {
            Type type = TypeToken.getParameterized(Map.class,String.class,clazz).getType();
            map = gson.fromJson(gsonString, type);
        }
        return map;
    }