问题

我正在尝试反序列化一个具有以下属性的 JSON 对象：

其中第一个键名是未知的，而内部映射始终包含两个名为 "key1" 和 "key2" 的属性。

```json
{
   "operation_rand":
   {
      "key1": 1005, 
      "key2": 5
   }
}

我有以下代码：

Operation.java

public class Operation {
    private Map<String, Map<String, Integer>> operationDetails = new HashMap<>();

    @JsonAnyGetter
    public Map<String, Map<String, Integer>> getOperation() {
        return operationDetails;
    }
} 

Main

ObjectMapper mapper = new ObjectMapper();

Operation op = mapper.readValue(jsonData, Operation.class);
Map<String, Map<String, Integer>> oDetails = op.getOperation();

然而我得到了错误：
在第 1 行，第 25 列无法将 java.lang.String 的实例反序列化为 START_OBJECT 标记，这是内部映射开始的地方。

有关如何映射内部映射的任何想法吗？
如果映射只有一层深，我可以获取正确的值。

{
   "operation_rand": 100
}

并将上述映射调整为 Map<String, Integer>

<details>
<summary>英文:</summary>

I am trying to deserialize a json object with the attributes

Where the first key name is unknown, while the inner map always contains two attributes named &quot;key1&quot; and &quot;key2&quot;.

{
"operation_rand":
{
"key1": 1005,
"key2": 5
}
}

I have the code :

Operation.java

public class Operation {
private Map<String, Map<String, Integer>> operationDetails = new HashMap<>();

@JsonAnyGetter
public Map<String, Map<String, Integer>> getOperation() {
    return operationDetails;
}

}

Main

ObjectMapper mapper = new ObjectMapper();

Operation op = mapper.readValue(jsonData, Operation.class);
Map<String, Map<String, Integer>> oDetails = address.getOperation();

However I get the error:
`Can not deserialize instance of java.lang.String out of START_OBJECT token` at line: 1, column: 25, which is where the inner map starts.  

Any ideas on how I can map the inner map?
I can grab the correct value if the map was only one layer deep.

{
"operation_rand": 100
}

And adjusting the above maps to just `Map<String, Integer>`






</details>


# 答案1
**得分**: 2

你需要一个用于预期的 JSON 的对象表示，以及一个 Gson 依赖。

对象的类如下：

```java
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonRootName;

@JsonRootName("operation_rand")
public class OperationRand {
    @JsonProperty("key1")
    private int key1;
    @JsonProperty("key2")
    private int key2;

    public int getKey1() {
        return key1;
    }

    public void setKey1(int key1) {
        this.key1 = key1;
    }

    public int getKey2() {
        return key2;
    }

    public void setKey2(int key2) {
        this.key2 = key2;
    }

    public OperationRand(int key1, int key2) {
        this.key1 = key1;
        this.key2 = key2;
    }

    @Override
    public String toString() {
        return "OperationRand{" +
                "key1=" + key1 +
                ", key2=" + key2 +
                '}';
    }
}

Gson（来自 Google）的依赖如下：

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
</dependency>

然后，可以如下使用：

String json = "{'operation_rand': {'key1': 1005, 'key2': 5}}";
Gson gson = new Gson();
OperationRand res = gson.fromJson(json, OperationRand.class);
System.out.println(res);

对于更改的 operation_rand，你可以使用对象来表示不变的字段：

import lombok.*;

@Setter
@Getter
@AllArgsConstructor
@NoArgsConstructor
@ToString
public class Key {
    int key1;
    int key2;
}

在主要部分中：

Gson gson = new Gson();
Map<String, Key> rest = gson.fromJson(json, HashMap.class);
System.out.println(rest);

    import com.fasterxml.jackson.annotation.JsonProperty;
    import com.fasterxml.jackson.annotation.JsonRootName;

    @JsonRootName("operation_rand")
    public class OperationRand{
    @JsonProperty("key1")
    private int key1;
    @JsonProperty("key2")
    private int key2;

    public int getKey1() {
        return key1;
    }

    public void setKey1(int key1) {
        this.key1 = key1;
    }

    public int getKey2() {
        return key2;
    }

    public void setKey2(int key2) {
        this.key2 = key2;
    }

    public OperationRand(int key1, int key2) {
        this.key1 = key1;
        this.key2 = key2;
    }

    @Override
    public String toString() {
        return "OperationRand{" +
                "key1=" + key1 +
                ", key2=" + key2 +
                '}';
    }
    }

    <dependency>

		<groupId>com.google.code.gson</groupId>

		<artifactId>gson</artifactId>

    </dependency>

    String json ="{\n" +
				"   \"operation_rand\":\n" +
				"   {\n" +
				"      \"key1\": 1005, \n" +
				"      \"key2\": 5\n" +
				"   }\n" +
				"}";
    Gson gson = new Gson();
    OperationRand res = gson.fromJson(json, OperationRand.class);

    System.out.println(res);
	

    import lombok.*;
    
    @Setter
    @Getter
    @AllArgsConstructor
    @NoArgsConstructor
    @ToString
    public class Key {
    int key1;
    int key2;
    }

    Gson gson = new Gson();
    Map<String,Key> rest = gson.fromJson(json,HashMap.class);
    System.out.println(rest);

答案2

得分: 0

100 不是 Map<String, Integer>。

也许使用 Map<String, Object> 而不是 Map<String, Map<String, Integer>>。

通过 instanceof Integer、instanceof Map 来确定类型。

答案3

得分: 0

你只需将类简化如下：

public class Operation {
    @JsonProperty("operation_rand")
    private Map operationDetails;
    
    public Map getOperation() {
        return operationDetails;
    }
}

public class Operation {
    @JsonProperty("operation_rand")
    private Map operationDetails;
    
    public Map getOperation() {
        return operationDetails;
    }
}