java - 如何使用 jackson 解析这个 JSON 文件？

Question

我有这个 JSON 文件

{
  "personal": {
    "name": "John Doe",
    "age": "28",
    "gender": "male",
  }
}

这是我要解析的 POJO

public class customerInfo{
   private String infoType;
   private Map<String, String>;
}

我之所以要用这个POJO是因为JSON文件也可以

{
  "address": {
    "street": "123 main st",
    "state": "md",
    "zipcode": "21228"
  }
}

这是我试过的，但是没有用

customerInfo customer = mapper.readValue(new File("jsonTestFile.json"), customerInfo.class);

有什么帮助吗？谢谢!

编辑:所以我希望 infoType 映射到个人或地址。而Map应该是，等等

Answer 1

您可以使用自定义反序列化器和序列化器来完成此操作。

反序列化器看起来像

public class CustomerInfoDeserializer extends JsonDeserializer<CustomerInfo> {

    private final Set<String> allowedFields;

    public CustomerInfoDeserializer(String... allowedFields) {
        Set<String> allowed = new HashSet<>(Arrays.asList(allowedFields));
        this.allowedFields = Collections.unmodifiableSet(allowed);
    }

    @Override
    public CustomerInfo deserialize(JsonParser jp, DeserializationContext dc) 
            throws IOException, JsonProcessingException {
        JsonNode node = jp.getCodec().readTree(jp);
        String field = node.fieldNames().next();
        if (!allowedFields.contains(field)) {
            throw new JsonMappingException("Field '" + field + "' not allowed");
        }

        CustomerInfo info = new CustomerInfo();
        info.setInfoType(field);
        JsonNode dataNode = node.get(field);
        for (Iterator<String> it = dataNode.fieldNames(); it.hasNext();) {
            String name = it.next();
            info.addProperty(name, dataNode.get(name).asText());
        }

        return info;
    }  
}

序列化器就是

public class CustomerInfoSerializer extends JsonSerializer<CustomerInfo> {

    @Override
    public void serialize(CustomerInfo c, JsonGenerator jg, SerializerProvider sp) 
            throws IOException, JsonProcessingException {
        jg.writeStartObject();
        jg.writeObjectField(c.getInfoType(), c.getProperties());
        jg.writeEndObject();
    } 
}

和CustomerInfo类

public class CustomerInfo {

    private String infoType;
    private final Map<String, String> properties = new HashMap<>();

    public void addProperty(String name, String value) {
        properties.put(name, value);
    }

    public Map<String, String> getProperties() {
        return properties;
    }

    public String getInfoType() {
        return infoType;
    }

    public void setInfoType(String infoType) {
        this.infoType = infoType;
    }
}

测试

public static void main(String[] args) throws Exception {
    final String personal
            = "{"
            + "  \"personal\": {"
            + "    \"name\": \"John Doe\","
            + "    \"age\": \"28\","
            + "    \"gender\": \"male\""
            + "  }"
            + "}";
    final String address 
            = "{"
            + "  \"address\": {"
            + "    \"street\": \"123 main st\","
            + "    \"state\": \"md\","
            + "    \"zipcode\": \"21228\""
            + "  }"
            + "}";

    ObjectMapper mapper = new ObjectMapper();
    SimpleModule module = new SimpleModule();
    module.addDeserializer(
            CustomerInfo.class, 
            new CustomerInfoDeserializer("personal", "address")
    );
    module.addSerializer(CustomerInfo.class, new CustomerInfoSerializer());
    mapper.registerModule(module);

    CustomerInfo info = mapper.readValue(personal, CustomerInfo.class);
    System.out.println(mapper.writeValueAsString(info));

    info = mapper.readValue(address, CustomerInfo.class);
    System.out.println(mapper.writeValueAsString(info));
}

查看更多:

• Jackson – Custom Deserializer
• Jackson - Custom Serializer