如何用Gson序列化java.nio.file.Path？

我在尝试序列化包含java.nio.file.Path的Object时得到java.lang.StackOverflowError
甚至当我写道：

public class PathConverter implements JsonDeserializer<Path>, JsonSerializer<Path> {
    @Override
    public Path deserialize(JsonElement jsonElement, Type type, JsonDeserializationContext jsonDeserializationContext) throws JsonParseException {
        return Paths.get(jsonElement.getAsString());
    }

    @Override
    public JsonElement serialize(Path path, Type type, JsonSerializationContext jsonSerializationContext) {
        return new JsonPrimitive(path.toString());
    }
}

并应用它：

String json = new GsonBuilder()
            .registerTypeAdapter(Path.class, new PathConverter())
            .create()
            .toJson(constructorSetup, new TypeToken<ConstructorSetup>() {}.getType());

我仍然不能序列化这个类：

public class ConstructorSetup {

    private Path appIconMimmapDirPathOnPc;

}

Stacktrace：（在pastebin上完整）

Exception in thread "main" java.lang.StackOverflowError
    at com.google.gson.internal.$Gson$Types.resolve($Gson$Types.java:380)
    at com.google.gson.internal.$Gson$Types.resolve($Gson$Types.java:375)
    at com.google.gson.internal.$Gson$Types.resolve($Gson$Types.java:380)
        ...
    at com.google.gson.internal.$Gson$Types.resolve($Gson$Types.java:380)
    at com.google.gson.internal.$Gson$Types.resolve($Gson$Types.java:355)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.getBoundFields(ReflectiveTypeAdapterFactory.java:117)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.create(ReflectiveTypeAdapterFactory.java:72)
    at com.google.gson.Gson.getAdapter(Gson.java:356)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.<init>(ReflectiveTypeAdapterFactory.java:82)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.createBoundField(ReflectiveTypeAdapterFactory.java:81)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.getBoundFields(ReflectiveTypeAdapterFactory.java:118)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.create(ReflectiveTypeAdapterFactory.java:72)
    at com.google.gson.Gson.getAdapter(Gson.java:356)
        ...
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.<init>(ReflectiveTypeAdapterFactory.java:82)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.createBoundField(ReflectiveTypeAdapterFactory.java:81)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.getBoundFields(ReflectiveTypeAdapterFactory.java:118)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.create(ReflectiveTypeAdapterFactory.java:72)
    at com.google.gson.Gson.getAdapter(Gson.java:356)

有什么办法吗？

你的问题是Path是一个interface。假设你使用了Paths.get("/")，它将在我的Windows PC上创建类似WindowsPath的示例。现在，你必须告诉GSON如何实现这种类型：

ConstructorSetup setup = new ConstructorSetup();
setup.setAppIconMimmapDirPathOnPc(Paths.get("/"));

// here we get actual class type of our Path object
Class classT = setup.getAppIconMimmapDirPathOnPc().getClass();

Gson gson = new GsonBuilder().registerTypeAdapter(classT, new MyPathConverter())

另一种可以使用的方法是registerTypeHierarchyAdapter：

.registerTypeHierarchyAdapter(Path.class, new MyPathConverter())

typeHierarchyAdapter的目的是覆盖当你想要一个类型的所有子类型的相同表示时的情况，这正是你使用Path的情况。

如何用Gson序列化java.nio.file.Path？

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