Question

我正在获取一个大的json文档，我想只将它的一部分解析为我的java类。我正在考虑使用类似jsonpath的东西从中提取部分数据，而不是创建整个java类的层次结构。

Jackson或Gson是否以任何方式支持jsonpath？如果是，您可以为我提供一些示例或指向另一个标准库吗？

例如，假设我有一个下面的文档，我想在我的java类中仅提取它下面的数据：

$。store.book [0] - 只有第一本书 $ .store.bicycle.price - 自行车价格

{
    "store": {
        "book": [
            {
                "category": "reference",
                "author": "Nigel Rees",
                "title": "Sayings of the Century",
                "price": 8.95
            },
            {
                "category": "fiction",
                "author": "Evelyn Waugh",
                "title": "Sword of Honour",
                "price": 12.99
            },
            {
                "category": "fiction",
                "author": "Herman Melville",
                "title": "Moby Dick",
                "isbn": "0-553-21311-3",
                "price": 8.99
            },
            {
                "category": "fiction",
                "author": "J. R. R. Tolkien",
                "title": "The Lord of the Rings",
                "isbn": "0-395-19395-8",
                "price": 22.99
            }
        ],
        "bicycle": {
            "color": "red",
            "price": 19.95
        }
    },
    "expensive": 10
}

Answer 1

Jayway JsonPath库支持使用JSON路径读取值。

例如：

String json = "...";

Map<String, Object> book = JsonPath.read(json, "$.store.book[0]");
System.out.println(book);  // prints {category=reference, author=Nigel Rees, title=Sayings of the Century, price=8.95}

Double price = JsonPath.read(json, "$.store.bicycle.price");
System.out.println(price);  // prints 19.95

您还可以将JSON对象直接映射到类，例如GSON或Jackson：

Book book = JsonPath.parse(json).read("$.store.book[0]", Book.class);
System.out.println(book);  // prints Book{category='reference', author='Nigel Rees', title='Sayings of the Century', price=8.95}

如果您想专门使用GSON或Jackson进行反序列化（默认是使用json-smart），您也可以配置：

Configuration.setDefaults(new Configuration.Defaults() {
    private final JsonProvider jsonProvider = new JacksonJsonProvider();
    private final MappingProvider mappingProvider = new JacksonMappingProvider();

    @Override
    public JsonProvider jsonProvider() {
        return jsonProvider;
    }

    @Override
    public MappingProvider mappingProvider() {
        return mappingProvider;
    }

    @Override
    public Set<Option> options() {
        return EnumSet.noneOf(Option.class);
    }
});

有关详细信息，请参阅the documentation。

Answer 2

String json = "{\"firstName\":\"John\",\"lastName\":\"Doe\",\"address\":{\"street\":"
            + "\"21 2nd Street\",\"city\":\"New York\",\"postalCode\":\"10021-3100\","
            + "\"coordinates\":{\"latitude\":40.7250387,\"longitude\":-73.9932568}}}";

ObjectMapper mapper = new ObjectMapper();
JsonNode node = mapper.readTree(json);
JsonNode coordinatesNode = node.at("/address/coordinates");

这是一种JSON Pointer方法，我在这里找到：https://cassiomolin.com/2016/07/13/using-jackson-and-json-pointer-to-query-and-parse-an-arbitrary-json-node/

Jsonpath与Jackson或Gson

2 个答案: