java - 如何为 JsonObjects 的 JsonObject 创建 Jackson XML POJO 类

Question

我正在尝试为以下 JSON 结构创建 POJO。 Fields 节点很容易连接，但我不确定如何使用注释来连接 Description 节点。如果我为该节点定义了 JSON 结构，我会创建一个 JsonObjects 的 JsonArray，这将使 java 类变得简单，但由于我没有，所以我需要弄清楚如何序列化下面的结构:

{
    "Fields": {
        "Required": ["ftp.hostname"],
        "Optional": ["ftp.rootDirectory"]
    },
    "Description": {
        "ftp.hostname": {
            "label": "SFTP Hostname",
            "description": "SFTP server hostname or IP address"
        },
        "ftp.rootDirectory": {
            "label": "Root Directory",
            "description": "The root path on the Data Store accessible by this connector"
        }
    }
}

请注意，Description 对象中的节点具有与 Fields 节点中定义的值相关的名称，这意味着它们的节点名称可能因负载而异。

Fields 节点的类:

public class FieldDetails {

    public static final String REQUIRED = "Required";
    public static final String OPTIONAL = "Optional";

    @JsonProperty(value = REQUIRED, required = true)
    private List<String> required;

    @JsonProperty(value = OPTIONAL, required = true)
    private List<String> optional;
}

到目前为止我对整个对象的了解:

public class FieldDefinitions {

    public static final String FIELDS = "Fields";
    public static final String DESCRIPTION = "Description";

    @JsonProperty(value = FIELDS, required = true)
    private FieldDetails fields;

    @JsonProperty(value = DESCRIPTION , required = true)
    private ??? descriptions;
}

Answer 1

一般来说，您始终可以映射任何 JSON反对 Map<String, Object> 。如果JSON由于许多嵌套对象而变得复杂，Jackson将自动选择正确的类型:Map对于物体和List对于数组。

您还可以像下面这样为 Description 声明类特性。

class Description {
    private String label;
    private String description;
    // getters, setters, toString
}

整体Description是个大JSON您可以将其映射到 Map<String, Description> 。因此，它可能如下所示:

class FieldDefinitions {

    public static final String FIELDS = "Fields";
    public static final String DESCRIPTION = "Description";

    @JsonProperty(value = FIELDS, required = true)
    private FieldDetails fields;

    @JsonProperty(value = DESCRIPTION, required = true)
    private Map<String, Description> descriptions;

    // getters, setters, toString
}

休息是一样的。示例应用程序:

import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.File;
import java.util.List;
import java.util.Map;

public class JsonApp {

    public static void main(String[] args) throws Exception {
        File json = new File("./resource/test.json").getAbsoluteFile();

        ObjectMapper mapper = new ObjectMapper();

        FieldDefinitions fields = mapper.readValue(json, FieldDefinitions.class);
        System.out.println("Required");
        fields.getFields().getRequired().forEach(r ->
                System.out.println(r + " = " + fields.getDescriptions().get(r)));
        System.out.println("Optional");
        fields.getFields().getOptional().forEach(r ->
                System.out.println(r + " = " + fields.getDescriptions().get(r)));
    }
}

对于给定的JSON payload打印:

Required
ftp.hostname = Description{label='SFTP Hostname', description='SFTP server hostname or IP address'}
Optional
ftp.rootDirectory = Description{label='Root Directory', description='The root path on the Data Store accessible by this connector'}