java 使用 GSON 解析 JSON 对象列表

Parse List of JSON objects using GSON

提问by ITisha

I have a JSON object like this:

我有一个像这样的 JSON 对象：

{
  "user1": {
    "timeSpent": "20.533333333333335h",
    "worklog": [
      {
        "date": "06/26/2013",
        "issues": [
          {
            "issueCode": "COC-2",
            "comment": "\ncccccc",
            "timeSpent": "20.533333333333335h"
          }
        ],
        "dayTotal": "20.533333333333335h"
      }
    ]
  },
  "admin": {
    "timeSpent": "601.1h",
    "worklog": [
      {
        "date": "06/25/2013",
        "issues": [
          {
            "issueCode": "COC-1",
            "comment": "",
            "timeSpent": "113.1h"
          }
        ],
        "dayTotal": "113.1h"
      },
      {
        "date": "06/26/2013",
        "issues": [
          {
            "issueCode": "COC-1",
            "comment": "",
            "timeSpent": "8h"
          },
          {
            "issueCode": "COC-2",
            "comment": "",
            "timeSpent": "480h"
          }
        ],
        "dayTotal": "488h"
      }
    ]
  }
}

and trying to parse it with Gson:

并尝试用 Gson 解析它：

Gson gson = new Gson();
Book responseBean = gson.fromJson(jsonString, Book.class);

But the 'responceBean' is always 'null'

但是“responceBean”始终为“null”

Here are all the other classes:

以下是所有其他类：

public class Book {

    private List<User> user = new LinkedList<User>();

    public List<User> getUser() {
        return user;
    }

    public void setUser(List<User> user) {
        this.user = user;
    }
}

public class User {
    private String timeSpent;
    private List<WorkLog> worklogs = new LinkedList<WorkLog>();;

    public List<WorkLog> getWorklogs() {
        return worklogs;
    }

    public void setWorklogs(List<WorkLog> worklogs) {
        this.worklogs = worklogs;
    }

    public String getTimeSpent() {
        return timeSpent;
    }

    public void setTimeSpent(String timeSpent) {
        this.timeSpent = timeSpent;
    }
}

public class WorkLog{
    private String date;
    private String dayTotal;
    private List<Issues> issues;

    public String getDate(){
        return this.date;
    }
    public void setDate(String date){
        this.date = date;
    }
    public String getDayTotal(){
        return this.dayTotal;
    }
    public void setDayTotal(String dayTotal){
        this.dayTotal = dayTotal;
    }
    public List<Issues> getIssues(){
        return this.issues;
    }
    public void setIssues(List<Issues> issues){
        this.issues = issues;
    }
}

public class Issues{
    private String comment;
    private String issueCode;
    private String timeSpent;

    public String getComment(){
        return this.comment;
    }
    public void setComment(String comment){
        this.comment = comment;
    }
    public String getIssueCode(){
        return this.issueCode;
    }
    public void setIssueCode(String issueCode){
        this.issueCode = issueCode;
    }
    public String getTimeSpent(){
        return this.timeSpent;
    }
    public void setTimeSpent(String timeSpent){
        this.timeSpent = timeSpent;
    }
}

This is my latest attempt. Somehow I cannot figure out the right way. Will be very appreciative for any help.

这是我最近的尝试。不知何故，我无法找出正确的方法。将非常感谢任何帮助。

回答by Pragmateek

Your JSON model does not match your object model.

您的JSON 模型与您的对象模型不匹配。

You need an intermediate layer to fill the gap: a TypeAdapter.

您需要一个中间层来填补空白：一个TypeAdapter。

Moreover there is no naming information for the user.

此外，没有用户的命名信息。

And finally there is a name mismatch: "worklog" in JSON, "worklogs" in Java.

最后还有一个名称不匹配：JSON 中的“worklog”，Java 中的“worklogs”。

Here is a fixed version:

这是一个固定版本：

Java model:

Java模型：

class User {
    private String timeSpent;
    @SerializedName("worklog")
    private List<WorkLog> worklogs = new LinkedList<WorkLog>();
    private String name;

    public List<WorkLog> getWorklogs() {
        return worklogs;
    }

    public void setWorklog(List<WorkLog> worklogs) {
        this.worklogs = worklogs;
    }

    public String getTimeSpent() {
        return timeSpent;
    }

    public void setTimeSpent(String timeSpent) {
        this.timeSpent = timeSpent;
    }

    public String getName() {
        return name;
    }

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

The plumbing to fill the gap:

填补空白的管道：

class BookTypeAdapter implements JsonSerializer<Book>, JsonDeserializer<Book>
{
      Gson gson = new Gson();

      public JsonElement serialize(Book book, Type typeOfT, JsonSerializationContext context)
      {
          JsonObject json = new JsonObject();

          for (User user : book.getUser())
          {
              json.addProperty(user.getName(), gson.toJson(user));
          }

          return json;
      }

      public Book deserialize(JsonElement element, Type typeOfT, JsonDeserializationContext context) throws JsonParseException
      {
          JsonObject json = element.getAsJsonObject();

          Book book = new Book();

          for (Entry<String, JsonElement> entry : json.entrySet())
          {
              String name = entry.getKey();
              User user = gson.fromJson(entry.getValue(), User.class);
              user.setName(name);

              book.getUser().add(user); 
          }

          return book;
      }
}

And a roundtrip:

和往返：

GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(Book.class, new BookTypeAdapter());

Gson gson = builder.create();

Book book = gson.fromJson("{" +
        " \"user1\": {" +
        "   \"timeSpent\": \"20.533333333333335h\"," +
        "   \"worklog\": [" +
        "     {" +
        "       \"date\": \"06/26/2013\"," +
        "       \"issues\": [" +
        "         {" +
        "           \"issueCode\": \"COC-2\"," +
        "           \"comment\": \"\ncccccc\"," +
        "           \"timeSpent\": \"20.533333333333335h\"" +
        "         }" +
        "       ]," +
        "       \"dayTotal\": \"20.533333333333335h\"" +
        "     }" +
        "   ]" +
        " }," +
        " \"admin\": {" +
        "   \"timeSpent\": \"601.1h\"," +
        "   \"worklog\": [" +
        "     {" +
        "       \"date\": \"06/25/2013\"," +
        "       \"issues\": [" +
        "         {" +
        "           \"issueCode\": \"COC-1\"," +
        "           \"comment\": \"\"," +
        "           \"timeSpent\": \"113.1h\"" +
        "         }" +
        "       ]," +
        "       \"dayTotal\": \"113.1h\"" +
        "     }," +
        "     {" +
        "       \"date\": \"06/26/2013\"," +
        "       \"issues\": [" +
        "         {" +
        "           \"issueCode\": \"COC-1\"," +
        "           \"comment\": \"\"," +
        "           \"timeSpent\": \"8h\"" +
        "         }," +
        "         {" +
        "           \"issueCode\": \"COC-2\"," +
        "           \"comment\": \"\"," +
        "           \"timeSpent\": \"480h\"" +
        "         }" +
        "       ]," +
        "       \"dayTotal\": \"488h\"" +
        "     }" +
        "   ]" +
        " }" +
        "}", Book.class);

String json = gson.toJson(book);

Have a look at my tutorial to get an idea of what is possible with Gson: Java/JSON mapping with Gson

查看我的教程以了解 Gson 的可能性：Java/JSON mapping with Gson

Enjoy! :)

享受！:)

回答by Kamen Stoykov

I had some problem before a month. As far as I remember it was because, same as you, I forgot to make "new" to objects. I mean that it should look:

一个月前我遇到了一些问题。据我所知，这是因为，和你一样，我忘记了对对象进行“新”处理。我的意思是它应该看起来：

public class User {
    private String timeSpent;
    private List<WorkLog> worklogs = new List < WorkLog >();
}

Try this and I hope that it will help.

试试这个，我希望它会有所帮助。

P.S. Also as Erik Pragt said you have array of Users, not just single one. So you will have to make 1 more class that contains a List < Users >.

PS 同样，正如 Erik Pragt 所说，您有一系列用户，而不仅仅是一个。因此，您将不得不再创建 1 个包含 List < Users > 的类。