java - json 到 java 对象(使用映射)？

Question

 ObjectMapper mapper=new ObjectMapper();
 String response1=client.execute(request1, responseHandler);
 Map jsonObject=mapper.readValue(response1, Map.class);
 jsonObject.get("docs");

我从字符串名称response1中的url获取json字符串并尝试映射它。我的response1字符串如下所示。

{"response":
 {"numFound":5,
  "start":0,
  "docs":[
   {"id":1},
   {"id":2},
   {"id":3},
   {"id":4},
   {"id":5}
   ]
  }
 }

我想从这个字符串中创建所有 id 的数组。我怎样才能做到这一点？我正在努力做jsonObject.get("docs") 但它没有做任何事情，它说(没有明确的返回值)

Answer 1

编辑
使用我的 GSON 示例中的数据模型。现在您可以通过以下方式做到这一点:

String response = "{\"response\":{\"numFound\":5,\"start\":0,\"docs\":[{\"id\":1},{\"id\":2},{\"id\":3},{\"id\":4},{\"id\":5}]}}";
ObjectMapper mapper = new ObjectMapper();
ObjectReader objectReader = mapper.reader(Body.class);
Body body = (Body) objectReader.readValue(response);
System.out.println(body.getResponse().getDocs());

GSON 示例
您应该使用 GSON到 JSON 解析。创建数据模型，帮助您处理“响应”字符串。看我的例子:

import java.util.Arrays;
import java.util.List;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

public class SourceCodeProgram {

    public static void main(String[] args) throws Exception {
        String response = "{\"response\":{\"numFound\":5,\"start\":0,\"docs\":[{\"id\":1},{\"id\":2},{\"id\":3},{\"id\":4},{\"id\":5}]}}";
        Gson gson = new GsonBuilder().serializeNulls().create();

        System.out.println("To JSON");
        System.out.println(gson.toJson(createTestBody()));
        System.out.println("From JSON");
        System.out.println(gson.fromJson(response, Body.class));
    }

    private static Body createTestBody() {
        Response response = new Response();
        response.setNumFound(5);
        response.setStart(0);
        response.setDocs(Arrays.asList(new Doc(1), new Doc(2), new Doc(3),
                new Doc(4), new Doc(5)));

        Body body = new Body();
        body.setResponse(response);
        return body;
    }
}

class Body {

    private Response response;

    public Response getResponse() {
        return response;
    }

    public void setResponse(Response response) {
        this.response = response;
    }

    @Override
    public String toString() {
        return "Body [response=" + response + "]";
    }
}

class Response {

    private int numFound;
    private int start;
    private List<Doc> docs;

    public int getNumFound() {
        return numFound;
    }

    public void setNumFound(int numFound) {
        this.numFound = numFound;
    }

    public int getStart() {
        return start;
    }

    public void setStart(int start) {
        this.start = start;
    }

    public List<Doc> getDocs() {
        return docs;
    }

    public void setDocs(List<Doc> docs) {
        this.docs = docs;
    }

    @Override
    public String toString() {
        return "Response [numFound=" + numFound + ", start=" + start
                + ", docs=" + docs + "]";
    }
}

class Doc {

    private int id;

    public Doc() {
    }

    public Doc(int id) {
        this.id = id;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Override
    public String toString() {
        return Integer.toString(id);
    }
}

输出:

To JSON
{"response":{"numFound":5,"start":0,"docs":[{"id":1},{"id":2},{"id":3},{"id":4},{"id":5}]}}
From JSON
Body [response=Response [numFound=5, start=0, docs=[1, 2, 3, 4, 5]]]

您可以通过以下方式检索“文档”:

Body body = gson.fromJson(response, Body.class);
System.out.println(body.getResponse().getDocs());