Java 没有从字符串值反序列化的字符串参数构造函数/工厂方法
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时间：2020-08-11 22:28:10 来源:igfitidea点击:
no String-argument constructor/factory method to deserialize from String value
提问by Harry Gohil
I am trying to make use of an external NYtimes API. Here is an sample example data output :
我正在尝试使用外部 NYtimes API。这是一个示例数据输出示例：
{
"status": "OK",
"copyright": "Copyright (c) 2016 The New York Times Company. All Rights Reserved.",
"section": "home",
"last_updated": "2016-10-20T19:57:45-04:00",
"num_results": 30,
"results": [{
"section": "Briefing",
"subsection": "",
"title": "Election, Dodgers, Duterte: Your Thursday Evening Briefing",
"abstract": "Here's what you need to know at the end of the day.",
"url": "abc.co",
"byline": "By KAREN ZRAICK and MERRILL D. OLIVER",
"item_type": "Article",
"updated_date": "2016-10-20T18:32:41-04:00",
"created_date": "2016-10-20T17:58:30-04:00",
"published_date": "2016-10-20T17:58:30-04:00",
"material_type_facet": "",
"kicker": "",
"des_facet": [],
"org_facet": [],
"per_facet": [],
"geo_facet": [],
"multimedia": [{
"url": "abc.co",
"format": "Standard Thumbnail",
"height": 75,
"width": 75,
"type": "image",
"subtype": "photo",
"caption": "",
"copyright": "Damon Winter/The New York Times"
}, {
"url": "abc.co",
"format": "thumbLarge",
"height": 150,
"width": 150,
"type": "image",
"subtype": "photo",
"caption": "",
"copyright": "Damon Winter/The New York Times"
}, {
"url": "abc.co",
"format": "Normal",
"height": 127,
"width": 190,
"type": "image",
"subtype": "photo",
"caption": "",
"copyright": "Damon Winter/The New York Times"
}, {
"url": "abc.co",
"format": "mediumThreeByTwo210",
"height": 140,
"width": 210,
"type": "image",
"subtype": "photo",
"caption": "",
"copyright": "Damon Winter/The New York Times"
}, {
"url": "abc.co",
"format": "superJumbo",
"height": 1365,
"width": 2048,
"type": "image",
"subtype": "photo",
"caption": "",
"copyright": "Damon Winter/The New York Times"
}],
"short_url": "http://abc.co"
}
]
}
Here is the bean definition
这是bean定义
//Headline.class
public class Headline {
@JsonProperty("status")
String status;
@JsonProperty("copyright")
String copyright;
@JsonProperty("section")
String section;
@JsonProperty("last_updated")
String last_updated;
@JsonProperty("num_results")
int num_results;
@JsonProperty("results")
List<Story> results;
`
`
//Story.class
@JsonProperty("section")
String section;
@JsonProperty("subsection")
String subsection;
@JsonProperty("title")
String title;
@JsonProperty("abstract")
String storyAbstract;
@JsonProperty("url")
String url;
@JsonProperty("byline")
String byline;
@JsonProperty("item_type")
String item_type;
@JsonProperty("updated_date")
String updated_date;
@JsonProperty("created_date")
String created_date;
@JsonProperty("published_date")
String published_date;
@JsonProperty("material_type_facet")
String material_type_facet;
@JsonProperty("kicker")
String kicker;
/*@JsonProperty("des_facet")
List des_facet;
@JsonProperty("org_facet")
List org_facet;
@JsonProperty("per_facet")
List per_facet;
@JsonProperty("geo_facet")
List geo_facet;*/
@JsonProperty("multimedia")
List<Media> multimedia;
@JsonProperty("short_url")
String short_url;
//Media.class
@JsonProperty("url")
String url;
@JsonProperty("format")
String format;
@JsonProperty("height")
int height;
@JsonProperty("width")
int width;
@JsonProperty("type")
String type;
@JsonProperty("subtype")
String subtype;
@JsonProperty("caption")
String caption;
@JsonProperty("copyright")
String copyright;
Here is my caller :
这是我的来电者：
RestTemplate restTemplate = new RestTemplate();
MappingHymanson2HttpMessageConverter jsonConverter = new MappingHymanson2HttpMessageConverter();
jsonConverter.setSupportedMediaTypes(Arrays.asList(new MediaType("text","json",MappingHymanson2HttpMessageConverter.DEFAULT_CHARSET)));
restTemplate.getMessageConverters().add(jsonConverter);
Headline headline = restTemplate.getForObject("http://abc/svc/topstories/v1/home.json?api-key=key",Headline.class);
logger.info("Headline"+headline.toString());
The exception now that I get when I make the call is :
现在我打电话时得到的例外是：
Exception in thread "main" org.springframework.http.converter.HttpMessageNotReadableException: Could not read JSON: Can not construct instance of java.util.ArrayList: no String-argument constructor/factory method to deserialize from String value ('')
at [Source: java.io.PushbackInputStream@22d9d; line: 1, column: 1185] (through reference chain: NYTimes.Payload.Headline["results"]->java.util.ArrayList[0]->NYTimes.Story.Story["multimedia"]); nested exception is com.fasterxml.Hymanson.databind.JsonMappingException: Can not construct instance of java.util.ArrayList: no String-argument constructor/factory method to deserialize from String value ('')
at [Source: java.io.PushbackInputStream@22d9d; line: 1, column: 1185] (through reference chain: NYTimes.Payload.Headline["results"]->java.util.ArrayList[0]->NYTimes.Story.Story["multimedia"])
I've been trying to understand why it doesn't de-serialize. if the string value is empty - then it should result in an null list?
我一直在试图理解为什么它不会反序列化。如果字符串值为空 - 那么它应该导致一个空列表？
回答by Freelancer
This exception is occurring because of the json response you are receiving -
由于您收到的 json 响应而发生此异常 -
{
"status": "OK",
"copyright": "Copyright (c) 2016 The New York Times Company. All Rights Reserved.",
"section": "home",
"last_updated": "2016-10-20T19:57:45-04:00",
"num_results": 30,
"results": [{
"section": "Briefing",
"subsection": "",
"title": "Election, Dodgers, Duterte: Your Thursday Evening Briefing",
"abstract": "Here's what you need to know at the end of the day.",
"url": "abc.co",
"byline": "By KAREN ZRAICK and MERRILL D. OLIVER",
"item_type": "Article",
"updated_date": "2016-10-20T18:32:41-04:00",
"created_date": "2016-10-20T17:58:30-04:00",
"published_date": "2016-10-20T17:58:30-04:00",
"material_type_facet": "",
"kicker": "",
"des_facet": [],
"org_facet": [],
"per_facet": [],
"geo_facet": [],
"multimedia": "",
"short_url": "http://abc.co"
}
]
}
"multimedia" field is an empty string
“多媒体”字段是一个空字符串
So you need to verify your json and map you pojo accordingly.
因此，您需要验证您的 json 并相应地映射您的 pojo。
