如何将 JSON 字符串反序列化为枚举

Question

我有 JSON 如下所示：

{
  "name": "john",
  "options": {
    "test": 1,
    "operation": "op1",     // I need to deserialize this option to enum.
    ...
    // any number of options
  }
}

我的 class 如下所示：

public class Info {
    public String name;
    @JsonTypeInfo(use = JsonTypeInfo.Id.NONE)
    public Map<String, Object> options;
}

public enum OperationEnum {OP1, OP2, OP3}

我如何反序列化到 options 将 operation 像 enum 和 test 映射到 Integer

Answer 1

为什么不这样做：


public class Info {
    public static class Options {
      public int test;
      public OperationEnum operation;
    }

    public String name;
    public Options options;
}

public enum OperationEnum {OP1, OP2, OP3}

那就应该JustWork了！

Answer 2

JSON 结构，其中存储所有选项（不同种类），如 Map<String, Object> options; 强制执行额外的解析，因为值类型是根据标签识别的（如 "operation" 和 OperationEnum class) 这是 ObjectMapper.readValue 和 Enum.valueOf

的 2 种方法

如果可能，请考虑更灵活的解决方案，例如@Matthew

class Demo {
    public static void main(String[] args) throws Exception {
        ObjectMapper om = new ObjectMapper();
        Info info = om.readValue(jsonValue, Info.class);
        OperationEnum operationM = om.readValue("\"" + info.options.get("operation") + "\"", OperationEnum.class);
        System.out.println(operationM);

        OperationEnum operationE = OperationEnum.valueOf(info.options.get("operation").toString());
        System.out.println(operationE);
    }

    static String jsonValue = "{\n" +
            "  \"name\": \"john\",\n" +
            "  \"options\": {\n" +
            "    \"test\": 1,\n" +
            "    \"operation\": \"OP1\" \n" +
            "  }\n" +
            "}";
}

Answer 3

您应该可以使用 @JsonAnySetter 来帮助您：

public class Info {
    public static class Options {
      public int test;
      public OperationEnum operation;
    }

    public String name;
    public Options options;
    private final Map<String, Object> properties = new HashMap<>();

    @JsonAnySetter
    public void add(String key, String value) {
        properties.put(key, value);
    }

}

public enum OperationEnum {OP1, OP2, OP3}

这里有一篇很好的文章：https://www.concretepage.com/jackson-api/jackson-jsonanygetter-and-jsonanysetter-example

Answer 4

简单的解决方案是用 class 包装 Map 实例，并为每个非常规属性实现额外的方法。您可以使用 @JsonAnySetter 注释来存储所有 key-value 对。

见下例：

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

import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.Map;

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

        ObjectMapper mapper = new ObjectMapper();
        Info info = mapper.readValue(jsonFile, Info.class);
        Options options = info.getOptions();
        System.out.println(options.toMap());
        System.out.println(options.getOperation());
    }
}

class Info {
    private String name;
    private Options options;

    //getters, setters
}

class Options {
    private Map<String, Object> values = new LinkedHashMap<>();

    @JsonAnySetter
    private void setValues(String key, Object value) {
        values.put(key, value);
    }

    public OperationEnum getOperation() {
        Object operation = values.get("operation");
        if (operation == null) {
            return null;
        }
        return Arrays.stream(OperationEnum.values())
            .filter(op -> op.name().equalsIgnoreCase(operation.toString()))
            .findFirst()
            .orElse(null);
    }

    public Map<String, Object> toMap() {
        return values;
    }
}

enum OperationEnum {OP1, OP2, OP3}

以上代码打印：

{test=1, operation=op1}
OP1

如何将 JSON 字符串反序列化为枚举

How to deserialize JSON string to enum

java

jackson

jackson-databind