使用MOXy将JSON字符串解封到某个“对象”

Question

我正在尝试使用MOXY编写一个方法来打印JSON字符串。所以我想要的是有一个像这样的方法

public String formatJson(String input) { ... }

我认为应该将字符串解析为一个通用对象（类似于SAX-Document，或类似的对象），然后使用一些格式化属性将该对象封送回JSON（这不是问题所在：-））。

[编辑]GSON和Jackson的例子被删除，因为只有MOXy才是问题所在。

我试过这个：

public static String toFormattedJson(final String jsonString) {
    String formatted;
    try {
        JAXBContext jaxbContext = JAXBContextFactory.createContext(new Class[] { JAXBElement.class }, null);
        Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
        unmarshaller.setProperty(MEDIA_TYPE, MediaType.APPLICATION_JSON);
        unmarshaller.setProperty(JSON_INCLUDE_ROOT, true);
        StringReader reader = new StringReader(jsonString);
        Object element = unmarshaller.unmarshal(reader); // Exception is thrown here
        formatted = toFormattedJson(element);
    } catch (final JAXBException e) {
        formatted = jsonString;
    }
    return formatted;
}

但我有个例外

private static String toFormattedJson(Object obj) {
    String result;
    try (StringWriter writer = new StringWriter()) {
        final JAXBContext jaxbContext = JAXBContextFactory.createContext(new Class[] { obj.getClass() }, null);
        final Marshaller marshaller = jaxbContext.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.setProperty(JAXBContextProperties.MEDIA_TYPE, MediaType.APPLICATION_JSON);
        marshaller.setProperty(MarshallerProperties.JSON_REDUCE_ANY_ARRAYS, false);
        marshaller.setProperty(MarshallerProperties.JSON_MARSHAL_EMPTY_COLLECTIONS, false);
        marshaller.setProperty(JAXBContextProperties.JSON_WRAPPER_AS_ARRAY_NAME, false);
        marshaller.setProperty(JAXBContextProperties.JSON_INCLUDE_ROOT, true);
        marshaller.marshal(obj, writer);
        writer.flush();
        result = writer.toString();
    } catch (JAXBException | IOException e) {
        result = obj.toString();
    }
    return result;
}

String jsonString = "{\"p\" : [ 1, 2, 3]}";

{
   "p" : "1"
}

Answer 1

可以将String指定为反封送目标：

public static void main(String[] args) {
        System.out.println(toFormattedJson("[{\"test\":true}, \"ok\", [\"inner\",1]]"));
}

public static String toFormattedJson(final String jsonString) {
    String formatted;
    try {
        JAXBContext jaxbContext = JAXBContextFactory.createContext(new Class[] { JAXBElement.class }, null);
        System.out.println("jaxbContext="+jaxbContext);
        Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
        unmarshaller.setProperty(JAXBContextProperties.MEDIA_TYPE, MediaType.APPLICATION_JSON);
        unmarshaller.setProperty(JAXBContextProperties.JSON_INCLUDE_ROOT, true);
        StringReader reader = new StringReader(jsonString);
        Object element = unmarshaller.unmarshal(new StreamSource(reader), String.class);
        formatted = toFormattedJsonElement(element);
    } catch (final JAXBException e) {
        e.printStackTrace();
        formatted = jsonString;
    }
    return formatted;
}

private static String toFormattedJsonElement(Object element) {
    return "formatted: " + element;
}