Java.net(RestFul服务JSON响应解析问题) 如何将JSON响应字符串中的相同项目列表转换为Java对象？

Question

我正在使用以下代码调用 Restful 服务:(Java.net 实现)

StringBuilder responseStrBuilder = new StringBuilder();

try 
{
    URL url = new URL(restUrl);
    conn = (HttpURLConnection) url.openConnection();
    conn.setRequestMethod(httpRequestMethod);
    conn.setRequestProperty("Accept-Language", "en-US,en;q=0.5");
    conn.setRequestProperty("Content-Type", "application/json");

    if (requestHeaders != null) 
    {
        for (Map.Entry<String, String> entry :  requestHeaders.entrySet()) 
        {
            conn.setRequestProperty(entry.getKey(), entry.getValue());
        }
    }

    conn.setDoInput(true);
    conn.setDoOutput(true);

    OutputStream os = conn.getOutputStream();
    os.write(urlParameters.getBytes());
    os.flush();
    os.close();

    if (conn.getResponseCode() != 200) {//do something}
    br = new BufferedReader(new InputStreamReader((conn.getInputStream())));

    while ((output = br.readLine()) != null)
       responseStrBuilder.append(output);

方法 1:我有以下字符串(JSON String)作为我的 Restful 服务响应，如何将其转换为 Java 对象。由于如果我使用 org.codehaus.jettison.json.JSONObject myObject = new org.codehaus.jettison.json.JSONObject(responseStrBuilder.toString()); ，则相同(Itm)对象会重复多次它只读取第一个 Itm 对象，不带所有 item 对象的列表。

服务的 JSON 字符串输出:

{"Response":{"RID":"04'34'",
"Itm":{"id":{"ab":"1","cd":"12"},"qw":"JK","name":"abcd "},
"Itm":{"id":{"ab":"2","cd":"34},"qw":"JK","name":"asdf "},
"Itm":{"id":{"ab":"3","cd":"12"},"qw":"JK","name":"fghj "}
}}

方法 2:我还尝试了下面的代码片段，其中包含带有 setter 和 getter 的正确 Java 对象

ObjectMapper objectMapper = new ObjectMapper();
mapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
MyJavaReponseObject javaObj = mapper.readValue(json, MyJavaReponseObject.class);

这种方法也只读取 Itm 的一个对象，而不是所有对象，因为它不是 JSON 字符串中的数组格式。有没有更好的方法将所有对象(Itm)映射到 java pojo 中的单个对象列表？

Answer 1

如果您应该解析该 json 字符串本身，则可以在响应对象中使用 List 类。

我有一个 ReponseJSON 类，其中包含 json 对象、一个 Response 和三个 Itms

static class ReponseJSON {
    private Response Response;

    @JsonProperty("Response")
    public Response getResponse() {
        return Response;
    }

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

    static class Response {
        private String rid;
        private Itm Itm;
        private List<Itm> listItm = new ArrayList<Itm>();

        public Itm getItm() {
            return Itm;
        }

        @JsonProperty("Itm")
        public void setItm(Itm Itm) {
            this.Itm = Itm;
            listItm.add(Itm);
        }

        public String getRID() {
            return rid;
        }

        public List<Itm> getItms() {
            return listItm;
        }

        @JsonProperty("RID")
        public void setRID(String rid) {
            this.rid = rid;
        }

        static class Itm {
            private Id id;

            private String qw, name;

            public String getQw() {
                return qw;
            }

            public void setQw(String qw) {
                this.qw = qw;
            }

            public String getName() {
                return name;
            }

            public void setName(String name) {
                this.name = name;
            }

            public Id getId() {
                return id;
            }

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

            static class Id {
                private String ab, cd;

                public String getCd() {
                    return cd;
                }

                public void setCd(String cd) {
                    this.cd = cd;
                }

                public String getAb() {
                    return ab;
                }

                public void setAb(String ab) {
                    this.ab = ab;
                }
            }
        }
    }
}

在 Response 类中，我有一个列表类，并在对象映射器调用此类时保存 Itm 对象。

static class Response {
    ... skip ..
    private List<Itm> listItm = new ArrayList<Itm>();
    ... skip ..
    @JsonProperty("Itm")
    public void setItm(Itm Itm) {
        this.Itm = Itm;
        listItm.add(Itm);
    }
}

查看完整源代码如下。

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JacksonParserTest {

    static class ReponseJSON {
        private Response Response;

        @JsonProperty("Response")
        public Response getResponse() {
            return Response;
        }

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

        static class Response {
            private String rid;
            private Itm Itm;
            private List<Itm> listItm = new ArrayList<Itm>();

            public Itm getItm() {
                return Itm;
            }

            @JsonProperty("Itm")
            public void setItm(Itm Itm) {
                this.Itm = Itm;
                listItm.add(Itm);
            }

            public String getRID() {
                return rid;
            }

            public List<Itm> getItms() {
                return listItm;
            }

            @JsonProperty("RID")
            public void setRID(String rid) {
                this.rid = rid;
            }

            static class Itm {
                private Id id;

                private String qw, name;

                public String getQw() {
                    return qw;
                }

                public void setQw(String qw) {
                    this.qw = qw;
                }

                public String getName() {
                    return name;
                }

                public void setName(String name) {
                    this.name = name;
                }

                public Id getId() {
                    return id;
                }

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

                static class Id {
                    private String ab, cd;

                    public String getCd() {
                        return cd;
                    }

                    public void setCd(String cd) {
                        this.cd = cd;
                    }

                    public String getAb() {
                        return ab;
                    }

                    public void setAb(String ab) {
                        this.ab = ab;
                    }
                }
            }
        }
    }

    public static void main(String[] args) {

        String responseJson = 
        "{\"Response\":{\"RID\":\"04'34'\","
                + "\"Itm\":{\"id\":{\"ab\":\"1\",\"cd\":\"12\"},\"qw\":\"JK\",\"name\":\"abcd\"}"
                + ",\"Itm\":{\"id\":{\"ab\":\"2\",\"cd\":\"34\"},\"qw\":\"JK\",\"name\":\"asdf\"}"
                + ",\"Itm\":{\"id\":{\"ab\":\"3\",\"cd\":\"12\"},\"qw\":\"JK\",\"name\":\"fghj\"}"
                + "}} ";

        ObjectMapper mapper = new ObjectMapper();

        ReponseJSON responseObj = null;

        try {
            responseObj = mapper.readValue(responseJson, ReponseJSON.class);
            ReponseJSON.Response response = responseObj.getResponse();

            for(int i = 0; i < response.getItms().size(); i++)
            {
                ReponseJSON.Response.Itm item = response.getItms().get(i);

                System.out.println(item.getId().getAb());
            }

        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

我的 Jackson Mapper 的版本是 2.9.1。

你检查源码的main方法，因为你准备的JSON字符串是无效的，正如coddemonkey提到的。

祝你有美好的一天。