为什么httpclient老是卡住

最近在修改快门下载功能时，发现同一文件只能下载成功2次，此后再点下载就没反应了。

我的httpclient是如下方式创建的，使用了连接池。

private static CloseableHttpClient httpclient = HttpClientBuilder.create().build();

我的调用方式如下：

public static byte[] executeQuery(String url, String chartSet) throws ClientProtocolException, IOException {
        if (StringUtil.isBlank(chartSet)) {
            chartSet = "UTF-8";
        }
        byte[] bytes = null;
        HttpGet httpget = new HttpGet(url);
        HttpResponse respOnse= httpclient.execute(httpget);
        HttpEntity entity = response.getEntity();
        if (entity != null) {
		InputStream instream = entity.getContent();
		bytes = FileUtil.readAsByteArray(instream); 
        }
        return bytes;
}

尝试几次后发现，下载成功的次数和maxConnPerRoute相同，该参数默认值就是2，并且可以采用以下方式修改：

private static CloseableHttpClient httpclient = HttpClientBuilder.create().setMaxConPerRoute(5).build();

于是，我怀疑是连接没有释放。但我又不可能调用httpclient.close()，否则连接池就失效了。

最终发现，错误原因是我既没有释放instream，也没有释放httpget（http://www.oschina.net/question/925814_131284）。

那么，可以通过释放instream或httpget的方法来解决。

方案一：释放instream

public static byte[] executeQuery(String url, String chartSet) throws ClientProtocolException, IOException {
        if (StringUtil.isBlank(chartSet)) {
            chartSet = "UTF-8";
        }
        byte[] bytes = null;
        HttpGet httpget = new HttpGet(url);
        HttpResponse respOnse= httpclient.execute(httpget);
        HttpEntity entity = response.getEntity();
        if (entity != null) {
		InputStream instream = entity.getContent();
		bytes = FileUtil.readAsByteArray(instream); 
                // Closing the input stream will trigger connection release
                instream.close();
        }
	return bytes;
}

public static byte[] executeQuery(String url, String chartSet) throws ClientProtocolException, IOException {
        if (StringUtil.isBlank(chartSet)) {
            chartSet = "UTF-8";
        }
        byte[] bytes = null;
        HttpGet httpget = new HttpGet(url);
        HttpResponse respOnse= httpclient.execute(httpget);
        HttpEntity entity = response.getEntity();
        if (entity != null) {
		InputStream instream = entity.getContent();
		bytes = FileUtil.readAsByteArray(instream); 
        }
	// release links
	httpget.releaseConnection();
	return bytes;
}