Spring @Requestbody 未映射到内部类

Question

我正在使用 Spring 4.x 做 Spring Rest Api 项目

这有效:

Controller.java

@PostMapping("newTransaction")
TransactionRequestModel insertNewTransaction(@RequestBody TransactionRequestModel model){
    //do something
}

TransactionRequestModel.java

public class TransactionRequestModel {
    private int id;
    private List<KeyValue> keyValueList;
    public TransactionRequestModel(){}
    //default constructor
    //getter-setter 
}

KeyValue.java

public class KeyValue {

    String key;
    String value;
    //default constructor
    //setter-getter
}

请求正文 Json

{
  "id": 1 
  "keyValueList": [
    {
      "key": "dummy",
      "value": "dummy"
    }
  ]
}

使用 Jackson 的 Spring 消息转换器工作正常。

这不会:

当我将 TransactionRequestModel.java 更改为以下内容时(并删除 KeyValue.java)

public class TransactionRequestModel {

    public class KeyValue {     
      String key;
      String value;
      //default constructor
      //setter-getter
    }
    private int id;
    private List<KeyValue> keyValueList;
    public TransactionRequestModel(){}
    //default constructor
    //getter-setter 
}

意味着，将KeyValue作为内部类，出现以下错误。

org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: No suitable constructor found for type [simple type, class com.example.model.TransactionRequestModel$KeyValue]: can not instantiate from JSON object (missing default constructor or creator, or perhaps need to add/enable type information?)

为什么？

SO 中的所有相关帖子都提到了第一种情况。我想知道为什么这行不通。请帮忙。

Answer 1

您必须使内部类静态。

public class TransactionRequestModel {

  public static class KeyValue {     
    String key;
    String value;
    //default constructor
    //setter-getter
  }
  private int id;
  private List<KeyValue> keyValueList;
  public TransactionRequestModel(){}
  //default constructor
  //getter-setter 
}