聊聊HttpClient的NoHttpResponseException

本文主要是介绍聊聊HttpClient的NoHttpResponseException，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

序

本文主要研究一下HttpClient的NoHttpResponseException

NoHttpResponseException

org/apache/http/NoHttpResponseException.java

/*** Signals that the target server failed to respond with a valid HTTP response.** @since 4.0*/
public class NoHttpResponseException extends IOException {private static final long serialVersionUID = -7658940387386078766L;/*** Creates a new NoHttpResponseException with the specified detail message.** @param message exception message*/public NoHttpResponseException(final String message) {super(HttpException.clean(message));}}

NoHttpResponseException继承了IOException，用于表示目标服务器没有返回一个正常的http response

DefaultHttpResponseParser

org/apache/http/impl/conn/DefaultHttpResponseParser.java

public class DefaultHttpResponseParser extends AbstractMessageParser<HttpResponse> {private final Log log = LogFactory.getLog(getClass());private final HttpResponseFactory responseFactory;private final CharArrayBuffer lineBuf;//......@Overrideprotected HttpResponse parseHead(final SessionInputBuffer sessionBuffer) throws IOException, HttpException {//read out the HTTP status stringint count = 0;ParserCursor cursor = null;do {// clear the bufferthis.lineBuf.clear();final int i = sessionBuffer.readLine(this.lineBuf);if (i == -1 && count == 0) {// The server just dropped connection on usthrow new NoHttpResponseException("The target server failed to respond");}cursor = new ParserCursor(0, this.lineBuf.length());if (lineParser.hasProtocolVersion(this.lineBuf, cursor)) {// Got onebreak;} else if (i == -1 || reject(this.lineBuf, count)) {// Giving upthrow new ProtocolException("The server failed to respond with a " +"valid HTTP response");}if (this.log.isDebugEnabled()) {this.log.debug("Garbage in response: " + this.lineBuf.toString());}count++;} while(true);//create the status line from the status stringfinal StatusLine statusline = lineParser.parseStatusLine(this.lineBuf, cursor);return this.responseFactory.newHttpResponse(statusline, null);}protected boolean reject(final CharArrayBuffer line, final int count) {return false;}
}

DefaultHttpResponseParser继承了AbstractMessageParser，其parseHead方法读取sessionBuffer，若该数据为空则抛出NoHttpResponseException(“The target server failed to respond”)

小结

NoHttpResponseException继承了IOException，用于表示目标服务器没有返回一个正常的http response，一般是目标服务器负载太高处理不过来因而断开了连接，也有可能是目标服务器把这个空闲连接关闭了，而HttpClient则继续用这个连接发送请求则会读取不到正常的reponse，因而抛出NoHttpResponseException。大多数情况下，可以通过重试解决。另外针对因为keep-alive超时断开的，可以配置HttpClient的connTimeToLive值小于服务端的keepAlive值(通常是60s)。