Java Jackson，使用 Map 编码类，无需访问类代码库

Question

我正在尝试使用 Jackson 映射器编码(序列化)类。类具有 Map 属性。属性必须具有某种序列化...我得到的一切都是序列化的字节流或错误序列化的map.toString()。

我尝试过使用 mixins 或设置 Jackson 映射器...没有任何帮助。

com.fasterxml.jackson 2.8.11com.rabbitmq.client 5.4.3

我的代码:

private RawMessage parseMetadata(RawMessage rawMessage, Envelope envelope, AMQP.BasicProperties properties) throws JsonProcessingException {
    ObjectMapper mapper = new ObjectMapper();
    mapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
    mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);


    JsonNode rootNode = mapper.createObjectNode();

    JsonNode message = mapper.valueToTree(new String(rawMessage.getPayload()));
    ((ObjectNode) rootNode).set("message", message);

    JsonNode envelopeNode = mapper.valueToTree(envelope);
    ((ObjectNode) rootNode).set("envelope", envelopeNode);

    JsonNode propertiesNode = mapper.valueToTree(properties);
    ((ObjectNode) rootNode).set("properties", propertiesNode);

    return new RawMessage(mapper.writerWithDefaultPrettyPrinter().writeValueAsBytes(rootNode));
}

结果:

{
  "properties": {
    "bodySize": 0,
    "headers": {
      "connection_name": {
        "bytes": "MTcyLjE5LjAuMTo0NTgzNiAtPiAxNzIuMTkuMC40OjU2NzI=",
        "stream": {
          "in": { "buf": "MTcyLjE5LjAuMTo0NTgzNiAtPiAxNzIuMTkuMC40OjU2NzI=", "pos": 0, "mark": 0, "count": 35 },
          "bytearr": "A...",
          "chararr": "\u0000...",
          "readBuffer": "AAAAAAAAAAA="
        }
      },
      "timestamp_in_ms": 1565957758662,
      "protocol": {
        "bytes": "ezAsOSwxfQ==",
        "stream": {
          "in": { "buf": "ezAsOSwxfQ==", "pos": 0, "mark": 0, "count": 7 },
          "bytearr": "AAA...",
          "chararr": "\u0000\u0000\...",
          "readBuffer": "AAAAAAAAAAA="
        }
      },...
      },
      "ssl": false
    },
    "deliveryMode": 2,
    "timestamp": 1565957758000,
    "classId": 60,
    "className": "basic"
  }
}

class BasicProperties extends com.rabbitmq.client.impl.AMQBasicProperties {
        private String contentType;
        private String contentEncoding;
        private Map<String,Object> headers; <--- 
        private Integer deliveryMode;
        private Integer priority;
        private String correlationId;
        private String replyTo;
        private String expiration;
        private String messageId;
        private Date timestamp;
        private String type;
        private String userId;
        private String appId;
        private String clusterId;
...}

复制:

import com.rabbitmq.client.AMQP;

Map<String, Object> map = new HashMap<>();
byte[] test =  "test".getBytes();
map.put("test", test);
AMQP.BasicProperties prop = new AMQP.BasicProperties(null, null, map,null,null,null,null,null,null,null,null,null,null,null);

ObjectMapper objectMapper = new ObjectMapper();
objectMapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);

JsonNode root = objectMapper.createObjectNode();

JsonNode propertiesN = objectMapper.valueToTree(prop);
((ObjectNode) root).set("properties", propertiesN);

LOG.info(root.toString());

结果:

{
  "properties": {
    "bodySize": 0,
    "headers": { "test": "dGVzdA==" },
    "classId": 60,
    "className": "basic"
  }
}

三个点意味着还有更多。它太长了。字节流太多。

我希望 map 的输出是 -> key: String

我想输出看起来像他的 ->properties.headers.test: "test"

没有 AMQP.BasicProperties 类的任何注释。

我认为 Jacksons Mixins 应该是实现这一目标的方法。

Answer 1

回答这个问题: - 让你拥有 Jackson Mixin，用自定义 JsonSerialize 类注释你的类 - 创建您自己的 Serialize 类来扩展 JsonSerializer 类 - 使用 addMixIn(DataClass.class, Mixin.class) 方法将 Mixin 注册到映射器

示例:

创建混音

abstract class MixIn {
  @JsonSerialize(using = MyPairSerializer.class)
  abstract Map<String, Object> get_map();
}

创建MapSerializer

class MyPairSerializer extends JsonSerializer<Map<String, Object>> {
  public void serialize(Map<String, Object> map, JsonGenerator gen, SerializerProvider serializerProvider) throws IOException {
    for (Map.Entry<String, Object> entry : map.entrySet()) {
      gen.writeStringField(entry.getKey(), entry.getValue().toString());
    }
  }
}

注册序列化器和映射对象

// API call
Data data = getData();

ObjectMapper objectMapper = new ObjectMapper();
JsonNode node = objectMapper.valueToTree(data);
System.out.println("node = " + node);

之前:{“数据”:“测试”，“ map ”:{“测试”:“dGVzdA ==”}}

之后:{“数据”:“测试”，“ map ”:{“测试”:“测试”}}

TLDR 答案是 Mixins 与自定义序列化器...