如何使用Gson序列化java.nio.file.Path？

Question

我java.lang.StackOverflowError在尝试序列化Object包含java.nio.file.Path

即使我写了：

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：

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

我仍然无法序列化此类：

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？

Answer 1

您的问题是那Path是一个interface。假设您使用Paths.get("/")它将WindowsPath在Windows
PC上创建类似的实例。现在，您必须告诉GSON如何反序列化此类型：

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())

您可以使用的另一种方法是registerTypeHierarchyAdapter：

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

typeHierarchyAdapter的目的是在您希望为类型的所有子类型使用相同的表示形式时涵盖这种情况，而这正是您使用的情况Path。