tomcat如何关闭response的outputStream

在写文件下载的时候,遇到了一个问题,就是这个ServletOutputStream到底要不要自己flush以及close。这里以tomcat容易为例,解读一下。

CoyoteAdapter

tomcat-embed-core-8.5.16-sources.jar!/org/apache/catalina/connector/CoyoteAdapter.java 主要看service这段代码:

@Override
    public void service(org.apache.coyote.Request req, org.apache.coyote.Response res)
            throws Exception {

        Request request = (Request) req.getNote(ADAPTER_NOTES);
        Response response = (Response) res.getNote(ADAPTER_NOTES);

        if (request == null) {
            // Create objects
            request = connector.createRequest();
            request.setCoyoteRequest(req);
            response = connector.createResponse();
            response.setCoyoteResponse(res);

            // Link objects
            request.setResponse(response);
            response.setRequest(request);

            // Set as notes
            req.setNote(ADAPTER_NOTES, request);
            res.setNote(ADAPTER_NOTES, response);

            // Set query string encoding
            req.getParameters().setQueryStringCharset(connector.getURICharset());
        }

        if (connector.getXpoweredBy()) {
            response.addHeader("X-Powered-By", POWERED_BY);
        }

        boolean async = false;
        boolean postParseSuccess = false;

        req.getRequestProcessor().setWorkerThreadName(THREAD_NAME.get());

        try {
            // Parse and set Catalina and configuration specific
            // request parameters
            postParseSuccess = postParseRequest(req, request, res, response);
            if (postParseSuccess) {
                //check valves if we support async
                request.setAsyncSupported(
                        connector.getService().getContainer().getPipeline().isAsyncSupported());
                // Calling the container
                // 这里调用具体的servlet方法,使用springmvc的话,就是调用mvc的方法
                connector.getService().getContainer().getPipeline().getFirst().invoke(
                        request, response);
            }
            if (request.isAsync()) {
                async = true;
                ReadListener readListener = req.getReadListener();
                if (readListener != null && request.isFinished()) {
                    // Possible the all data may have been read during service()
                    // method so this needs to be checked here
                    ClassLoader oldCL = null;
                    try {
                        oldCL = request.getContext().bind(false, null);
                        if (req.sendAllDataReadEvent()) {
                            req.getReadListener().onAllDataRead();
                        }
                    } finally {
                        request.getContext().unbind(false, oldCL);
                    }
                }

                Throwable throwable =
                        (Throwable) request.getAttribute(RequestDispatcher.ERROR_EXCEPTION);

                // If an async request was started, is not going to end once
                // this container thread finishes and an error occurred, trigger
                // the async error process
                if (!request.isAsyncCompleting() && throwable != null) {
                    request.getAsyncContextInternal().setErrorState(throwable, true);
                }
            } else {
                request.finishRequest();
                //这里去关闭response
                response.finishResponse();
            }

        } catch (IOException e) {
            // Ignore
        } finally {
            AtomicBoolean error = new AtomicBoolean(false);
            res.action(ActionCode.IS_ERROR, error);

            if (request.isAsyncCompleting() && error.get()) {
                // Connection will be forcibly closed which will prevent
                // completion happening at the usual point. Need to trigger
                // call to onComplete() here.
                res.action(ActionCode.ASYNC_POST_PROCESS,  null);
                async = false;
            }

            // Access log
            if (!async && postParseSuccess) {
                // Log only if processing was invoked.
                // If postParseRequest() failed, it has already logged it.
                Context context = request.getContext();
                // If the context is null, it is likely that the endpoint was
                // shutdown, this connection closed and the request recycled in
                // a different thread. That thread will have updated the access
                // log so it is OK not to update the access log here in that
                // case.
                if (context != null) {
                    context.logAccess(request, response,
                            System.currentTimeMillis() - req.getStartTime(), false);
                }
            }

            req.getRequestProcessor().setWorkerThreadName(null);

            // Recycle the wrapper request and response
            if (!async) {
                request.recycle();
                response.recycle();
            }
        }
    }

Response.finishResponse

tomcat-embed-core-8.5.16-sources.jar!/org/apache/catalina/connector/Response.java

public class Response implements HttpServletResponse {
    //......
    /**
     * The associated output buffer.
     */
    protected OutputBuffer outputBuffer;

    /**
     * The associated output stream.
     */
    protected CoyoteOutputStream outputStream;
   //......
   /**
     * Perform whatever actions are required to flush and close the output
     * stream or writer, in a single operation.
     *
     * @exception IOException if an input/output error occurs
     */
    public void finishResponse() throws IOException {
        // Writing leftover bytes
        outputBuffer.close();
    }

}

OutputBuffer.close

tomcat-embed-core-8.5.16-sources.jar!/org/apache/catalina/connector/OutputBuffer.java

/**
     * Close the output buffer. This tries to calculate the response size if
     * the response has not been committed yet.
     *
     * @throws IOException An underlying IOException occurred
     */
    @Override
    public void close() throws IOException {

        if (closed) {
            return;
        }
        if (suspended) {
            return;
        }

        // If there are chars, flush all of them to the byte buffer now as bytes are used to
        // calculate the content-length (if everything fits into the byte buffer, of course).
        if (cb.remaining() > 0) {
            flushCharBuffer();
        }

        if ((!coyoteResponse.isCommitted()) && (coyoteResponse.getContentLengthLong() == -1)
                && !coyoteResponse.getRequest().method().equals("HEAD")) {
            // If this didn't cause a commit of the response, the final content
            // length can be calculated. Only do this if this is not a HEAD
            // request since in that case no body should have been written and
            // setting a value of zero here will result in an explicit content
            // length of zero being set on the response.
            if (!coyoteResponse.isCommitted()) {
                coyoteResponse.setContentLength(bb.remaining());
            }
        }

        if (coyoteResponse.getStatus() == HttpServletResponse.SC_SWITCHING_PROTOCOLS) {
            doFlush(true);
        } else {
            doFlush(false);
        }
        closed = true;

        // The request should have been completely read by the time the response
        // is closed. Further reads of the input a) are pointless and b) really
        // confuse AJP (bug 50189) so close the input buffer to prevent them.
        Request req = (Request) coyoteResponse.getRequest().getNote(CoyoteAdapter.ADAPTER_NOTES);
        req.inputBuffer.close();

        coyoteResponse.action(ActionCode.CLOSE, null);
    }

这里flush了一下

    private void flushCharBuffer() throws IOException {
        realWriteChars(cb.slice());
        clear(cb);
    }

    /**
     * Flush bytes or chars contained in the buffer.
     *
     * @param realFlush <code>true</code> if this should also cause a real network flush
     * @throws IOException An underlying IOException occurred
     */
    protected void doFlush(boolean realFlush) throws IOException {

        if (suspended) {
            return;
        }

        try {
            doFlush = true;
            if (initial) {
                coyoteResponse.sendHeaders();
                initial = false;
            }
            if (cb.remaining() > 0) {
                flushCharBuffer();
            }
            if (bb.remaining() > 0) {
                flushByteBuffer();
            }
        } finally {
            doFlush = false;
        }

        if (realFlush) {
            coyoteResponse.action(ActionCode.CLIENT_FLUSH, null);
            // If some exception occurred earlier, or if some IOE occurred
            // here, notify the servlet with an IOE
            if (coyoteResponse.isExceptionPresent()) {
                throw new ClientAbortException(coyoteResponse.getErrorException());
            }
        }

    }

这个正好印证了servlet3.1规范里头说的(5.6 Closure of Response Object)

When a response is closed, the container must immediately flush all remaining content in the response buffer to the client.

Response.getOutputStream

/**
     * @return the servlet output stream associated with this Response.
     *
     * @exception IllegalStateException if <code>getWriter</code> has
     *  already been called for this response
     * @exception IOException if an input/output error occurs
     */
    @Override
    public ServletOutputStream getOutputStream()
        throws IOException {

        if (usingWriter) {
            throw new IllegalStateException
                (sm.getString("coyoteResponse.getOutputStream.ise"));
        }

        usingOutputStream = true;
        if (outputStream == null) {
            outputStream = new CoyoteOutputStream(outputBuffer);
        }
        return outputStream;

    }

CoyoteOutputStream的flush和close方法

tomcat-embed-core-8.5.16-sources.jar!/org/apache/catalina/connector/CoyoteOutputStream.java

    /**
     * Will send the buffer to the client.
     */
    @Override
    public void flush() throws IOException {
        boolean nonBlocking = checkNonBlockingWrite();
        ob.flush();
        if (nonBlocking) {
            checkRegisterForWrite();
        }
    }
  
@Override
    public void close() throws IOException {
        ob.close();
    }

也都是调用OutputBuffer的flush和close方法。因此手工调用貌似没有必要。

doc

  • servlet-3_1-fr-eval-spec
  • Response.getWriter() should it be closed / flushed
  • Do I need to flush the servlet outputstream?

原文发布于微信公众号 - 码匠的流水账(geek_luandun)

原文发表时间:2017-08-12

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