Java 将OutputStream与InputStream连接

我正在试验一个小的web框架，偶然发现了一个关于streams的问题。有一些处理程序方法，如

Response-get（HttpServletRequest）

。从框架的角度来看，响应应该为响应主体提供一个输入流。框架读取该流并将数据写入ServletAPI的底层OutputStream。但是从用户的角度来看，需要写入一个OutputStream

框架的观点：

public interface Response {
  InputStream getInputStream();
}

public interface Response {
  InputStream getOutputStream();
}

用户视角：

public interface Response {
  InputStream getInputStream();
}

public interface Response {
  InputStream getOutputStream();
}

应该这样使用：

public void get(HttpServletRequest request) {
  Response response = new Response(OK);
  response.getOutputStream().write(...);
  return response;
}

public class RequestImpl implements Request {
    private HttpServletRequest request;
    private HttpServletResponse response;

    public RequestImpl(HttpServletRequest request, HttpServletResponse response) {
        this.request = request;
        this.response = response;
    }

    public Response newResponse(Status status) {
        return new ResponseImpl(response, status);
        // Add a boolean responseCreated to avoid creation of multiple responses? Illegal state!
    }

    public String getParameter(String name) { // Just another example of decorated method.
        return request.getParameter(name);
    }

    // ...
}

public class ResponseImpl implements Response {
    private HttpServletResponse response;

    public ResponseImpl(HttpServletResponse response, Status status) {
        this.response = response;
        this.response.setStatus(status.getCode());
    }

    public OutputStream getOutputStream() {
        return response.getOutputStream();
    }

    // ...
}

问题是我无法创建没有输出目标的outputstream（并且不想写入ByteArray缓冲区）

---

你知道如何给用户一个OutputStream而不像ServletAPI那样传入一个吗？我希望避免使用输出参数。

当您给客户端一个OutputStream时，它必须连接到某个东西，缓冲区、套接字、文件或其他可以处理写入它的数据的东西

---

一个选项可能是将其设置为连接到处理数据的另一个线程中的PipedInputStream的PipedOutStream。但是，如果处理线程不能跟上客户端线程的速度，这将遇到问题。

正如Jim Garrison所说，

输出流必须连接到某个东西。。。写入其中的字节必须转移到某个地方，否则将被丢弃

在我看来，您需要做的是让
Response
直接包装
InputStream
。在
响应
上可能有如下方法：

void setContent(InputStream content);

然后，用户可以提供他们想要的任何类型的
InputStream
，而不是写入您提供的
OutputStream
，您的框架只需将其复制到servlet
OutputStream

您还可以允许他们提供一些实现类似以下接口的东西：

interface OutputProducer {
   void writeTo(OutputStream out) throws IOException;
}

在这两种情况下，您基本上都允许用户提供一个用于写入
OutputStream
的回调，这样您就不需要传入它

为了避免使用输出参数，我真的不知道这些是否值得，但这些都是选项。
也提取/修饰
请求，并从中获取
响应

例如，在前端控制器servlet中：

protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
    Request request = new RequestImpl(req, res);
    Action action = ActionFactory.getAction(req); // Do whatever way you do to locate the `Action`.
    Response = action.get(request);
    // ...
}

其中，
RequestImpl
如下所示：

public void get(HttpServletRequest request) {
  Response response = new Response(OK);
  response.getOutputStream().write(...);
  return response;
}

public class RequestImpl implements Request {
    private HttpServletRequest request;
    private HttpServletResponse response;

    public RequestImpl(HttpServletRequest request, HttpServletResponse response) {
        this.request = request;
        this.response = response;
    }

    public Response newResponse(Status status) {
        return new ResponseImpl(response, status);
        // Add a boolean responseCreated to avoid creation of multiple responses? Illegal state!
    }

    public String getParameter(String name) { // Just another example of decorated method.
        return request.getParameter(name);
    }

    // ...
}

public class ResponseImpl implements Response {
    private HttpServletResponse response;

    public ResponseImpl(HttpServletResponse response, Status status) {
        this.response = response;
        this.response.setStatus(status.getCode());
    }

    public OutputStream getOutputStream() {
        return response.getOutputStream();
    }

    // ...
}

而
ResponseImpl
如下所示：

public void get(HttpServletRequest request) {
  Response response = new Response(OK);
  response.getOutputStream().write(...);
  return response;
}

public class RequestImpl implements Request {
    private HttpServletRequest request;
    private HttpServletResponse response;

    public RequestImpl(HttpServletRequest request, HttpServletResponse response) {
        this.request = request;
        this.response = response;
    }

    public Response newResponse(Status status) {
        return new ResponseImpl(response, status);
        // Add a boolean responseCreated to avoid creation of multiple responses? Illegal state!
    }

    public String getParameter(String name) { // Just another example of decorated method.
        return request.getParameter(name);
    }

    // ...
}

public class ResponseImpl implements Response {
    private HttpServletResponse response;

    public ResponseImpl(HttpServletResponse response, Status status) {
        this.response = response;
        this.response.setStatus(status.getCode());
    }

    public OutputStream getOutputStream() {
        return response.getOutputStream();
    }

    // ...
}

您最终在
操作中使用了以下内容：

public ActionImpl implements Action {
    public Response get(Request request) {
        Response response = request.newResponse(OK);
        response.getOutputStream().write("body");
        return response;
    }
}


或者，您也可以创建一个
上下文
，该上下文接受
HttpServletRequest
和
HttpServletResponse
，并将其传入，而不是
Request
。这也是一般MVC框架所做的事情。例如

protected void service(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
    Context context = new ContextImpl(req, res);
    Action action = ActionFactory.getAction(req); // Do whatever way you do to locate the `Action`.
    action.execute(context);
    context.render(); // Do here whatever you'd initially to do with the obtained Response.
}

与


这就是说，我建议您也看看现有的API，而不是重新设计。根据您想要做什么，JSF、JAX-RS或JAX-WS可能是您真正想要的。除非这纯粹是出于爱好；）