使用Jackson将文件类型从Angular反序列化为Java [英] Deserialization of File type from Angular to Java using Jackson

问题描述

在我使用SpringBoot和Angular开发的REST应用程序中，我需要向SpringBoot后端发送REST请求，以便将对象保存到数据库中。

In my REST application developed using SpringBoot and Angular, I need to send a REST request to SpringBoot back end in order to save a object into the database.

在前端，用户填写表格并提交。以下是从中创建对象以将其作为REST调用发送到后端的接口。

In the front end, user fills up a form and submits. Following is the interface from which a object is created in order to be sent to the backend as a REST call.

export interface TenderToPost{

    id: number;
    name: string;
    description: string;
    images: File[];
    referenceNumber: string;

}

后端应将以上对象反序列化为Follow对象

The backend should deserialize the above object to a object of Following class in Java.

public class TenderDTO implements Serializable{

    private long id;

    private String name;

    private String description;

    private List<MultipartFile> images;

    private String referenceNumber;

    // default constructor

    // geters and setters

}

如上所述，我需要接受前端发送的文件作为 MultipartFile 。

As shown above, I need to accept the File sent from frontend as a MultipartFile.

但是，当从前端发送请求时，杰克逊给了我错误

However, when the request is sent from the front end, Jackson gives me the error

无法构造
的实例org.springframework.web.multipart.MultipartFile：抽象类型
需要映射为具体类型，具有自定义反序列化器，或者
包含其他类型信息

Can not construct instance of org.springframework.web.multipart.MultipartFile: abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information

我知道此错误来自我使用过 MultipartFile 界面作为我的图片列表的类型。

I am aware that that this error comes since I have used MultipartFile interface as the type of my images list.

我想到的解决方案是，让Jackson知道应使用反注释将列表反序列化为哪种类型。因此，我使用了以下

What I thought of as the solution for this, is letting Jackson know to what type the list should be deserialized into using an annotation. So, I used following

@JsonDeserialize(contentAs = CommonsMultipartFile.class)
private List<MultipartFile> images;

CommonsMultipartFile是 MultipartFile 的实现。这就是为什么我使用它。

CommonsMultipartFile is an implementation of MultipartFile. That is why I used it.

现在，我收到以下错误。

Now I get the following error.

无法构造
的实例org.springframework.web.multipart.commons.CommonsMultipartFile：找不到
合适的构造函数，无法从对象值
反序列化（缺少默认构造函数或创建者，或者也许是否需要添加/启用
类型信息？）

Can not construct instance of org.springframework.web.multipart.commons.CommonsMultipartFile: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?)

我是否需要更改图像列表的设置器？还是我的整体方法不正确？

Do I need to change the setter for the images list? Or is my whole approach incorrect?

请告诉我如何纠正此问题。

Kindly show me the way how I should correct this.

推荐答案

尝试使用 @JsonPropertyDescription 构造对象。
@JsonPropertyDescription示例

Try to use @JsonPropertyDescription to construct object. @JsonPropertyDescription example

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