发生此异常的原因是您正在接收的json响应-

{
    "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”字段是空字符串
因此，您需要验证您的json并相应地Map您的pojo。

这个代码起作用了。
尝试使用这些对象调用API。
我认为你在多媒体或类似的东西命名问题。

class Multimedia{
    public String url;
    public String format;
    public int height;
    public int width;
    public String type;
    public String subtype;
    public String caption;
    public String copyright;

    @Override
    public String toString() {
        return String.format(
                "Multimedia (url=%s, format=%s, height=%s, width=%s, type=%s, subtype=%s, caption=%s, copyright=%s)", this.url, this.format, this.height, this.width, this.type, this.subtype, this.caption, this.copyright);
    }
}

class Result{
    public String section;
    public String subsection;
    public String title;
    @JsonProperty("abstract")
    public String abstract2;
    public String url;
    public String byline;
    public String item_type;
    public Date updated_date;
    public Date created_date;
    public Date published_date;
    public String material_type_facet;
    public String kicker;
    public List<Object> des_facet;
    public List<Object> org_facet;
    public List<Object> per_facet;
    public List<Object> geo_facet;
    public List<Multimedia> multimedia;
    public String short_url;

    @Override
    public String toString() {
        return String.format(
                "Result (section=%s, subsection=%s, title=%s, abstract2=%s, url=%s, byline=%s, item_type=%s, updated_date=%s, created_date=%s, published_date=%s, material_type_facet=%s, kicker=%s, des_facet=%s, org_facet=%s, per_facet=%s, geo_facet=%s, multimedia=%s, short_url=%s)", this.section, this.subsection, this.title, this.abstract2, this.url, this.byline, this.item_type, this.updated_date, this.created_date, this.published_date, this.material_type_facet, this.kicker, this.des_facet, this.org_facet, this.per_facet, this.geo_facet, this.multimedia, this.short_url);
    }
}

class Root{
    public String status;
    public String copyright;
    public String section;
    public Date last_updated;
    public int num_results;
    public List<Result> results;

    @Override
    public String toString() {
        return String.format(
                "Root (status=%s, copyright=%s, section=%s, last_updated=%s, num_results=%s, results=%s)", this.status, this.copyright, this.section, this.last_updated, this.num_results, this.results);
    }
}

public class IAE {
    public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper objectMapper = new ObjectMapper();
        String json = "{\n" +
                "    \"status\": \"OK\",\n" +
                "    \"copyright\": \"Copyright (c) 2016 The New York Times Company. All Rights Reserved.\",\n" +
                "    \"section\": \"home\",\n" +
                "    \"last_updated\": \"2016-10-20T19:57:45-04:00\",\n" +
                "    \"num_results\": 30,\n" +
                "    \"results\": [{\n" +
                "            \"section\": \"Briefing\",\n" +
                "            \"subsection\": \"\",\n" +
                "            \"title\": \"Election, Dodgers, Duterte: Your Thursday Evening Briefing\",\n" +
                "            \"abstract\": \"Here’s what you need to know at the end of the day.\",\n" +
                "            \"url\": \"abc.co\",\n" +
                "            \"byline\": \"By KAREN ZRAICK and MERRILL D. OLIVER\",\n" +
                "            \"item_type\": \"Article\",\n" +
                "            \"updated_date\": \"2016-10-20T18:32:41-04:00\",\n" +
                "            \"created_date\": \"2016-10-20T17:58:30-04:00\",\n" +
                "            \"published_date\": \"2016-10-20T17:58:30-04:00\",\n" +
                "            \"material_type_facet\": \"\",\n" +
                "            \"kicker\": \"\",\n" +
                "            \"des_facet\": [],\n" +
                "            \"org_facet\": [],\n" +
                "            \"per_facet\": [],\n" +
                "            \"geo_facet\": [],\n" +
                "            \"multimedia\": [{\n" +
                "                \"url\": \"abc.co\",\n" +
                "                \"format\": \"Standard Thumbnail\",\n" +
                "                \"height\": 75,\n" +
                "                \"width\": 75,\n" +
                "                \"type\": \"image\",\n" +
                "                \"subtype\": \"photo\",\n" +
                "                \"caption\": \"\",\n" +
                "                \"copyright\": \"Damon Winter/The New York Times\"\n" +
                "            }, {\n" +
                "                \"url\": \"abc.co\",\n" +
                "                \"format\": \"thumbLarge\",\n" +
                "                \"height\": 150,\n" +
                "                \"width\": 150,\n" +
                "                \"type\": \"image\",\n" +
                "                \"subtype\": \"photo\",\n" +
                "                \"caption\": \"\",\n" +
                "                \"copyright\": \"Damon Winter/The New York Times\"\n" +
                "            }, {\n" +
                "                \"url\": \"abc.co\",\n" +
                "                \"format\": \"Normal\",\n" +
                "                \"height\": 127,\n" +
                "                \"width\": 190,\n" +
                "                \"type\": \"image\",\n" +
                "                \"subtype\": \"photo\",\n" +
                "                \"caption\": \"\",\n" +
                "                \"copyright\": \"Damon Winter/The New York Times\"\n" +
                "            }, {\n" +
                "                \"url\": \"abc.co\",\n" +
                "                \"format\": \"mediumThreeByTwo210\",\n" +
                "                \"height\": 140,\n" +
                "                \"width\": 210,\n" +
                "                \"type\": \"image\",\n" +
                "                \"subtype\": \"photo\",\n" +
                "                \"caption\": \"\",\n" +
                "                \"copyright\": \"Damon Winter/The New York Times\"\n" +
                "            }, {\n" +
                "                \"url\": \"abc.co\",\n" +
                "                \"format\": \"superJumbo\",\n" +
                "                \"height\": 1365,\n" +
                "                \"width\": 2048,\n" +
                "                \"type\": \"image\",\n" +
                "                \"subtype\": \"photo\",\n" +
                "                \"caption\": \"\",\n" +
                "                \"copyright\": \"Damon Winter/The New York Times\"\n" +
                "            }],\n" +
                "            \"short_url\": \"http://abc.co\"\n" +
                "        }\n" +
                "\n" +
                "    ]\n" +
                "}";

        System.out.println(objectMapper.readValue(json,Root.class));
    }

}

输出量：

Root (status=OK, copyright=Copyright (c) 2016 The New York Times Company. All Rights Reserved., section=home, last_updated=Fri Oct 21 02:57:45 IDT 2016, num_results=30, results=[Result (section=Briefing, subsection=, title=Election, Dodgers, Duterte: Your Thursday Evening Briefing, abstract2=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=Fri Oct 21 01:32:41 IDT 2016, created_date=Fri Oct 21 00:58:30 IDT 2016, published_date=Fri Oct 21 00:58:30 IDT 2016, material_type_facet=, kicker=, des_facet=[], org_facet=[], per_facet=[], geo_facet=[], multimedia=[Multimedia (url=abc.co, format=Standard Thumbnail, height=75, width=75, type=image, subtype=photo, caption=, copyright=Damon Winter/The New York Times), Multimedia (url=abc.co, format=thumbLarge, height=150, width=150, type=image, subtype=photo, caption=, copyright=Damon Winter/The New York Times), Multimedia (url=abc.co, format=Normal, height=127, width=190, type=image, subtype=photo, caption=, copyright=Damon Winter/The New York Times), Multimedia (url=abc.co, format=mediumThreeByTwo210, height=140, width=210, type=image, subtype=photo, caption=, copyright=Damon Winter/The New York Times), Multimedia (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)])