服务器使用Gzip压缩JSON数据报“socket write error: Connection reset by peer.”错误

        现有服务器部署及问题出现点：

原因分析：

        JsonDispatherHandler对response.getWriter()进行write和flush方法后，response.getWriter()就被Web服务器关闭了，这样在过滤器中去获取输出流并writer时，就会抛出Connection reset by peer的错误。

 

解决方法：

        新建JsonDispatcherHandlerWithGzip.java，继承JsonDispatherHandler对相应方法进行重写，并修改配置文件，将配置文件相关配置都改成JsonDispatcherHandlerWithGzip.java。

public class JsonDispatcherHandlerWithGzip extends JsonDispatcherHandler {
	
    public final static String RESULT = "JsonView4WebDispatcherHandler_result";
    private static final String NULL_JSON_STRING = "{}";
    private String defaultContentType = "text/html";

    @Override
    protected void renderMergedOutputModel(Map<String, Object> model, HttpServletRequest request,
            HttpServletResponse response) throws Exception {
        long startTime = System.currentTimeMillis();
        addResponseHeader(response);
        byte[] bytes = (byte[]) model.get(RESULT);
        if (isGZipEncoding(request)) {
            byte[] outData = null;
            if (bytes.length > 512) {
                byte[] gzipData = toGzipBytes(bytes);
                response.setHeader("Content-Encoding", "gzip");
                response.setHeader("Transfer-Encoding", "");
                response.setContentLength(gzipData.length);
                outData = gzipData;
                PASLogUtils.debugTrace("gzip end ,cost:" + (System.currentTimeMillis() - startTime));
            } else {
                outData = bytes.length == 0 ? NULL_JSON_STRING.getBytes(response.getCharacterEncoding()):bytes;
            }
            ServletOutputStream output = response.getOutputStream();
            output.write(outData);
            output.flush();
        }else{
            String resp = bytes.length == 0 ? NULL_JSON_STRING : new String(bytes, response.getCharacterEncoding());
            PASLogUtils.debugTrace("Rest result =" + resp);
            Writer out = response.getWriter();        
            out.write(resp);
            out.flush();
        }
    }

    /*
     * 增加响应头信息 
     */
    private void addResponseHeader(HttpServletResponse response) {
        if (!StringUtils.hasText(response.getContentType())) {
            StringBuffer contentTypeBuffer = new StringBuffer();
            contentTypeBuffer.append(defaultContentType);
            contentTypeBuffer.append(";charset=" + response.getCharacterEncoding());
            response.setContentType(contentTypeBuffer.toString());
        }
    }
    /*
     * 判断浏览器是否支持GZIP
     */
    private boolean isGZipEncoding(HttpServletRequest request) {
        boolean flag = false;
        String encoding = request.getHeader("Accept-Encoding");
        if (encoding.indexOf("gzip") != -1) {
            flag = true;
        }
        return flag;
    }
    
    public static byte[] toGzipBytes(byte[] srcData) {
        if (srcData == null || srcData.length == 0) {
            return null;
        }
        
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        
        GZIPOutputStream gzip = null;
        try {
            gzip = new GZIPOutputStream(out);
            gzip.write(srcData);
        } catch (IOException e) {
            PASLogUtils.debugErorr(e.getMessage());
        } finally {
            if (gzip != null) {
                try {
                    gzip.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return out.toByteArray();
    }
}

        这样问题就解决了。特别注意response.setHeader("Transfer-Encoding", "");这条语句，Transfer-Encoding: chunked表示输出的内容长度不能确定，普通的静态页面、图片之类的基本上都用不到这个。详细可以参见http://bijian1013.iteye.com/blog/2280945。

        在这我特意做了如下测试：

        1.将response.setHeader("Transfer-Encoding", "");这条语句去掉，请求后台都没有报错，但浏览器未能正常展示，分析发现是因为实际返回到浏览器的长度和Content-Length长度不一致导致浏览器未能正确解析。

        2.将response.setHeader("Transfer-Encoding", "");改成将response.setHeader("Transfer-Encoding", "chunked");报“Could not complete request java.net.SocketException: Connection reset by peer: socket write error”错。

        3.而如果将response.setHeader("Transfer-Encoding", "");和response.setContentLength(gzipData.length);这两条语句都去掉，就能正常。此时用http Watch看到信息如下：