HTTP客户端警告：Going to buffer response body of large or unknown size

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原编码问题

HttpClient发现抛出Going to buffer response body of large or unknown size. Using getResponseBodyAsStream instead is recommended，查看原有代码中的逻辑如下：

HttpClient httpclient = new HttpClient();
GetMethod getMethod = new GetMethod(url);
int statusCode = httpclient.executeMethod(getMethod);
String respContent = getMethod.getResponseBodyAsString();

源码分析 getResponseBodyAsString()源码

	//getResponseBodyAsString()方法源码public String getResponseBodyAsString() throws IOException {byte[] rawdata = null;if (this.responseAvailable()) {//调用了getResponseBody()，容易消耗内存rawdata = this.getResponseBody();}return rawdata != null ? EncodingUtil.getString(rawdata, this.getResponseCharSet()) : null;}//responseAvailable()方法源码private boolean responseAvailable() {return this.responseBody != null || this.responseStream != null;}//getResponseBody()方法源码public byte[] getResponseBody() throws IOException {if (this.responseBody == null) {InputStream instream = this.getResponseBodyAsStream();if (instream != null) {long contentLength = this.getResponseContentLength();if (contentLength > 2147483647L) {throw new IOException("Content too large to be buffered: " + contentLength + " bytes");}int limit = this.getParams().getIntParameter("http.method.response.buffer.warnlimit", 1048576);if (contentLength == -1L || contentLength > (long)limit) {//这里是warn的原文LOG.warn("Going to buffer response body of large or unknown size. Using getResponseBodyAsStream instead is recommended.");}LOG.debug("Buffering response body");ByteArrayOutputStream outstream = new ByteArrayOutputStream(contentLength > 0L ? (int)contentLength : 4096);byte[] buffer = new byte[4096];int len;while((len = instream.read(buffer)) > 0) {outstream.write(buffer, 0, len);}outstream.close();this.setResponseStream((InputStream)null);this.responseBody = outstream.toByteArray();}}return this.responseBody;}

从源码中可以看出，warn的条件是(contentLength == -1L || contentLength > (long)limit)，如果http头没有指定contentLength或大于上限值（默认1M），就会抛异常。其实，如果返回的结果比较确定，对程序没有太大影响。而对于返回结果不确定时，源码也建议我们使用下面的getResponseBodyAsStream()方法。

getResponseBodyAsStream()源码

public InputStream getResponseBodyAsStream() throws IOException {if (this.responseStream != null) {return this.responseStream;} else if (this.responseBody != null) {InputStream byteResponseStream = new ByteArrayInputStream(this.responseBody);LOG.debug("re-creating response stream from byte array");return byteResponseStream;} else {return null;}}

从源码中可以看出，getResponseBodyAsStream()内部没有使用getResponseBody()方法，避免了内存耗尽问题，而是使用了InputStream流方式处理。

优化原编码

HttpClient httpclient = new HttpClient();
GetMethod getMethod = new GetMethod(url);
int statusCode = httpclient.executeMethod(getMethod);
//String respContent = getMethod.getResponseBodyAsString();
//使用getResponseBodyAsStream()
InputStream inputStream = getMethod.getResponseBodyAsStream();
BufferedReader br = new BufferedReader(new InputStreamReader(inputStream));
StringBuffer stringBuffer = new StringBuffer();
String str = "";
while ((str = br.readLine()) != null) {stringBuffer.append(str);
}
LOGGER.info("respContent: {}", stringBuffer.toString());