Question

我使用的是API，我试图用Jackson反序列化结果，但我总是犯同样的错误。

我猜我的POJO不对，但我找不到错误。

错误在于libs

我试图声明为String或List而没有任何成功。有什么想法吗？

{
"libs": {},
"items": [
    {
        "id": "001",
        "cars": [
            "cd1042af-856d-4649-a170-032d15a4119b",
            "00ed61a4-3aab-4722-90c2-7f4cca4cbded",
            "8fa3aa8b-3f22-4413-a41d-e78de9051de2"
        ],
        "name": "James"


    },
    {

        "id": "002",
        "cars": [
            "cd1043af-856d-4649-a170-032d15a4119b",
            "00ed61a4-3aab-4722-90c2-7f4cca4cbded",
            "8fa3aa8b-3f22-4413-a41d-e78de9051de2"
        ],
        "name": "James"

    }]

}

public class Page<Car> {


    private List<String> libs;

    private List<Car>items;



    public List<Car> getItems() {
        return items;
    }

    public void setItems(List<Car> items) {
        this.items = items;
    }

    public List<String> getLibs() {
        return libs;
    }

    public void setLibs(List<String> libs) {
        this.libs = libs;
    }



}

Answer 1

您将libs声明为列表，但使用了maps / objects括号。

应为"libs": []

在name属性在每个列表元素中结束后，您有额外的逗号。

Answer 2

更正的json如下：

// Server setup from node.js website
const http = require('http');
const hostname = '127.0.0.1';
const port = 3000;

const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.end('Hello World\n');
});

server.listen(port, hostname, () => {
  console.log(`Server running at http://${hostname}:${port}/`);
});


// Trying to listen for data from React app to feed into JSON (broken)
var express = require("express");
var myParser = require("body-parser");
var app = express();

app.use(myParser.urlencoded({extended : true}));
app.post("/scene-setup.json", function(request, response) {
    console.log(request.body); //This prints the JSON document received (if it is a JSON document)
});
app.listen(3001);


// Updating JSON file with "obj" (working)
var jsonfile = require('jsonfile')

var file = './scene-setup.json'
var obj = {name: 'JP'}

jsonfile.writeFile(file, obj, function (err) {
  console.error(err)
})

Answer 3

使用Jackson库解决了此问题，这是我的代码段。

  **Main Class:**
       public class MainClass {

    public static void main(String[] args) throws JsonParseException, 
      JsonMappingException, IOException {

    String jsonStr = "{\r\n" + "    \"libs\": [\"ram\", \"shyam\"],\r\n" + "    \"items\": [{\r\n"
            + "         \"id\": \"001\",\r\n" + "           \"cars\": [\r\n"
            + "             \"cd1042af-856d-4649-a170-032d15a4119b\",\r\n"
            + "             \"00ed61a4-3aab-4722-90c2-7f4cca4cbded\",\r\n"
            + "             \"8fa3aa8b-3f22-4413-a41d-e78de9051de2\"\r\n" + "           ],\r\n"
            + "         \"name\": \"James\"\r\n" + "        },\r\n" + "     {\r\n"
            + "         \"id\": \"002\",\r\n" + "           \"cars\": [\r\n"
            + "             \"cd1043af-856d-4649-a170-032d15a4119b\",\r\n"
            + "             \"00ed61a4-3aab-4722-90c2-7f4cca4cbded\",\r\n"
            + "             \"8fa3aa8b-3f22-4413-a41d-e78de9051de2\"\r\n" + "           ],\r\n"
            + "         \"name\": \"James\"\r\n" + "        }\r\n" + "  ]\r\n" + "}";

    ObjectMapper mapper = new ObjectMapper();

    MyPojo details = mapper.readValue(jsonStr, MyPojo.class);

    for (String itrs : details.getLibs()) {

        System.out.println("Value for getLibs is: " + itrs);
    }

    for (Items itr : details.getItems()) {

        System.out.println("Value for getId is: " + itr.getId());
        System.out.println("Value for getName is: " + itr.getName() + "\n");

        for (String carItr : itr.getCars()) {
            System.out.println("Value for getCars is: " + carItr);
        }       }   }}

   **MyPojo** 

             import java.util.ArrayList;

     public class MyPojo {
    private ArrayList<Items> items;

private String[] libs;

public ArrayList<Items> getItems() {
    return items;
}

public void setItems(ArrayList<Items> items) {
    this.items = items;
}

public String[] getLibs() {
    return libs;
}

public void setLibs(String[] libs) {
    this.libs = libs;
  }     }

   **Items**

       public class Items {
       private String id;

       private String[] cars;

       private String name;

public String getId() {
    return id;
}

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

public String[] getCars() {
    return cars;
}

public void setCars(String[] cars) {
    this.cars = cars;
}

public String getName() {
    return name;
}

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

   **RESULTS:**

  Value for getLibs is: ram
  Value for getLibs is: shyam
  Value for getId is: 001
  Value for getName is: James

   Value for getCars is: cd1042af-856d-4649-a170-032d15a4119b
   Value for getCars is: 00ed61a4-3aab-4722-90c2-7f4cca4cbded
   Value for getCars is: 8fa3aa8b-3f22-4413-a41d-e78de9051de2
   Value for getId is: 002
   Value for getName is: James

  Value for getCars is: cd1043af-856d-4649-a170-032d15a4119b
  Value for getCars is: 00ed61a4-3aab-4722-90c2-7f4cca4cbded
  Value for getCars is: 8fa3aa8b-3f22-4413-a41d-e78de9051de2

**注意：我已经修改了库以添加一些字符串值，以查看我们的状况。

Jackson JSon：无法从START_OBJECT标记中反序列化java.lang.String的实例

3 个答案: