如何将Apache、OkHttp的HttpClient响应对象序列化与反序列化为字节数组

需要对Apache HttpClient、OkHttp的HTTP响应对象进行序列化和反序列化操作，但尝试以下方法均失败：

• Java Serializable接口：这两个客户端的响应对象都未实现Serializable接口，无法直接序列化。
• Jackson：响应对象没有无参构造函数，反序列化时抛出错误：

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `org.example.Student` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator)

• Gson：序列化时出现内存溢出（以Apache HttpClient为例）：
  序列化代码：

  Gson gson = new GsonBuilder().setPrettyPrinting().create();
  ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
  OutputStreamWriter writer = new OutputStreamWriter(outputStream);
  gson.toJson(httpResponse, writer);
  writer.flush();
  

  反序列化代码：

  byte[] data = outputStream.toByteArray();
  ByteArrayInputStream inputStream = new ByteArrayInputStream(data);
  InputStreamReader reader = new InputStreamReader(inputStream);
  HttpResponse res = gson.fromJson(reader, HttpResponse.class);
  System.out.println("HttpResponse-> " + EntityUtils.toString(res.getEntity()));
  

  错误信息：

  Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
      at java.util.Arrays.copyOf(Arrays.java:3332)
      at java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:124)
      at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:448)
      at java.lang.StringBuffer.append(StringBuffer.java:276)
      at java.io.StringWriter.write(StringWriter.java:101)
      at com.google.gson.stream.JsonWriter.newline(JsonWriter.java:602)
      at com.google.gson.stream.JsonWriter.beforeValue(JsonWriter.java:646)
      at com.google.gson.stream.JsonWriter.value(JsonWriter.java:532)
      at com.google.gson.internal.bind.TypeAdapters$5.write(TypeAdapters.java:189)
      at com.google.gson.internal.bind.TypeAdapters$5.write(TypeAdapters.java:173)
      at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:69)
      at com.google.gson.internal.bind.ArrayTypeAdapter.write(ArrayTypeAdapter.java:95)
      at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:69)
      at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:127)
      at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:245)
      at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:69)
      at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:127)
      at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:245)
      at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:69)
      at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:127)
      at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:245)
      at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:69)
      at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:127)
      at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:245)
      at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:69)
      at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:97)
      at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:61)
      at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:69)
      at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:127)
      at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:245)
      at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:69)
      at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:127)
  

直接序列化Apache/OkHttp的原始响应对象之所以出问题，核心是这些对象内部包含复杂引用链（比如连接池、输入流、回调引用等），既不适合序列化，也没做序列化设计。正确做法是自定义数据传输对象（DTO），只保留需要的响应数据，再对DTO进行序列化/反序列化。

步骤1：定义响应DTO #

以Apache HttpClient的HttpResponse为例，提取关键字段：

public class HttpResponseDTO {
    private int statusCode;
    private String statusText;
    private Map<String, List<String>> headers;
    private String body;

    // 无参构造函数
    public HttpResponseDTO() {}

    // 全参构造函数
    public HttpResponseDTO(int statusCode, String statusText, Map<String, List<String>> headers, String body) {
        this.statusCode = statusCode;
        this.statusText = statusText;
        this.headers = headers;
        this.body = body;
    }

    // 自行补充getter、setter方法
}

步骤2：将原始响应转换为DTO #

// Apache HttpResponse转DTO
public static HttpResponseDTO convertToDto(HttpResponse httpResponse) throws IOException {
    int statusCode = httpResponse.getStatusLine().getStatusCode();
    String statusText = httpResponse.getStatusLine().getReasonPhrase();
    
    // 提取响应头
    Map<String, List<String>> headers = new HashMap<>();
    Header[] allHeaders = httpResponse.getAllHeaders();
    for (Header header : allHeaders) {
        headers.computeIfAbsent(header.getName(), k -> new ArrayList<>()).add(header.getValue());
    }
    
    // 提取响应体（大文件场景建议用流式处理，避免OOM）
    String body = EntityUtils.toString(httpResponse.getEntity(), StandardCharsets.UTF_8);
    
    return new HttpResponseDTO(statusCode, statusText, headers, body);
}

// OkHttp Response转DTO
public static HttpResponseDTO convertToDto(okhttp3.Response okHttpResponse) throws IOException {
    int statusCode = okHttpResponse.code();
    String statusText = okHttpResponse.message();
    
    // 提取响应头
    Map<String, List<String>> headers = new HashMap<>();
    okHttpResponse.headers().names().forEach(name -> {
        headers.put(name, okHttpResponse.headers().values(name));
    });
    
    // 提取响应体
    String body = okHttpResponse.body().string();
    
    return new HttpResponseDTO(statusCode, statusText, headers, body);
}

步骤3：对DTO进行序列化/反序列化 #

使用Jackson #

DTO有无参构造函数，Jackson可直接处理：

ObjectMapper objectMapper = new ObjectMapper();

// 序列化
HttpResponseDTO dto = convertToDto(httpResponse);
String json = objectMapper.writeValueAsString(dto);

// 反序列化
HttpResponseDTO deserializedDto = objectMapper.readValue(json, HttpResponseDTO.class);

使用Gson #

DTO结构简单无循环引用，不会出现OOM：

Gson gson = new GsonBuilder().setPrettyPrinting().create();

// 序列化
HttpResponseDTO dto = convertToDto(httpResponse);
String json = gson.toJson(dto);

// 反序列化
HttpResponseDTO deserializedDto = gson.fromJson(json, HttpResponseDTO.class);

步骤4：（可选）从DTO还原为原始响应对象 #

若需要将DTO转回客户端响应对象，可通过客户端Builder创建，以Apache HttpClient为例：

public static HttpResponse convertToOriginal(HttpResponseDTO dto) {
    BasicHttpResponse response = new BasicHttpResponse(new ProtocolVersion("HTTP", 1, 1), dto.getStatusCode(), dto.getStatusText());
    
    // 设置响应头
    dto.getHeaders().forEach((name, values) -> {
        values.forEach(value -> response.addHeader(name, value));
    });
    
    // 设置响应体
    response.setEntity(new StringEntity(dto.getBody(), StandardCharsets.UTF_8));
    
    return response;
}

内容的提问来源于stack exchange，提问作者GOURAV KUMAR