Jackson 自定义反序列化器字符串到列表，并删除 \r\n

Question

我收到以下 JSON 作为来自服务的响应。我正在使用 Spring RestTemplate 调用服务，该服务还将 JSON 反序列化回对象。我正在尝试将其反序列化为一个除了其他字段之外还有一个列表的对象。反序列化时出现以下错误：

Can not instantiate value of type [simple type, class com.org.EmployeeInfo] from String value; no single-String constructor/factory method.

以下是我要反序列化的 JSON：

{
    "employees": {       
        "employeeInfo": [
            "{\r\n  \"id\": \"123\",\r\n  \"group\": \"MARKETING\",\r\n  \"role\": \"MANAGER\",\r\n}",
            "{\r\n  \"id\": \"256\",\r\n  \"group\": \"IT\",\r\n  \"role\": \"DIRECTOR\",\r\n}",
            "{\r\n  \"id\": \"789\",\r\n  \"group\": \"SALES\",\r\n  \"role\": \"CEO\",\r\n}"
        ]
    },
    "status": "EMPLOYED",
    "somethingElse": {
        "something": []
    }
}

如果我尝试将响应映射到的对象中有List<EmployeeInfo>，则默认反序列化器会失败，但如果我使用List<String> 或String[]，它会起作用。这是因为 JSON 中的双引号（我说的是 "{\r\n) 使其被视为字符串

我打算编写一个自定义反序列化器，将其反序列化为具有 List 的对象，并删除作为响应的一部分的 \r\n。我怎样才能做到这一点？感谢任何回复。

这是我的 POJO：

public class Response {
    private Employees employees;
    private String status;
    private SomethingElse somethingElse; 

   // getters, setters
}

public class Employees {
    List<EmployeeInfo> employeeInfo;
    // getters, setters
}

public class EmployeeInfo
{
   private String id, group, role;
   // getters, setters 
}

谢谢

Answer 1

我通过以下方式解决了这个问题（部分逻辑需​​要优化）

public class EmployeeInfoJsonDeserializer extends JsonDeserializer<List<EmployeeInfo>> {

    @Override
    public List<EmployeeInfo> deserialize(final JsonParser jp, final DeserializationContext ctxt)
                    throws IOException, JsonProcessingException {

        final ObjectMapper mapper = (ObjectMapper) jp.getCodec();

        final JsonNode node = (JsonNode) mapper.readTree(jp);

        // TODO - Write the following logic in a better way
        String toStr = node.toString();
        toStr = StringUtils.replace(toStr, "\"{", "{");
        toStr = StringUtils.replace(toStr, "}\"", "}");
        toStr = StringUtils.remove(toStr, "\\r\\n");
        toStr = StringUtils.remove(toStr, "\\");

        final JsonNode newNode = mapper.readTree(toStr);

        final EmployeeInfo[] empInfo = mapper.convertValue(newNode, EmployeeInfo[].class);

        return Arrays.asList(empInfo);
    }
}

在 Pojo 中：

public class Employees {
       List<EmployeeInfo> employeeInfo;

       public List<EmployeeInfo> getEmployeeInfo() {
            return employeeInfo;
       }

       @JsonDeserialize(using = EmployeeInfoJsonDeserializer .class)
       public void setEmployeeInfo(final List<EmployeeInfo> employeeInfo) {
            this.employeeInfo= employeeInfo;
       }
}

Answer 2

那个 JSON 是不可解析的，因为它是无效的，即使你有一个自定义的反序列化器，你也不能反序列化它。

无论如何，一个自定义的反序列化器示例（不起作用，仅用于学习目的）

public class EmployeeInfoDeSerializer extends JsonDeserializer<List<EmployeeInfo>> {

    @Override
    public List<EmployeeInfo> deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {

        // for learning purpouses only, does not work
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);

        List<EmployeeInfo> employeeInfos = new ArrayList<>();

        while (jp.nextToken() != JsonToken.END_OBJECT) {

            if (jp.getCurrentToken() != JsonToken.END_ARRAY) {

                JsonParser jParser = mapper.getJsonFactory().createJsonParser(jp.getText());
                employeeInfos.add(jParser.readValueAs(EmployeeInfo.class));
            }
        }
        return employeeInfos;
    }
}

在您的员工类中

public class Employees {

    @JsonDeserialize(using=EmployeeInfoDeSerializer.class)
    private List<EmployeeInfo> employeeInfo;

    public List<EmployeeInfo> getEmployeeInfo() {
        return employeeInfo;
    }

    public void setEmployeeInfo(List<EmployeeInfo> employeeInfo) {
        this.employeeInfo = employeeInfo;
    }


}