HttpClient之EntityUtils工具类

今天看到tttpclient-tutorial上面有这样一句话-----非常的不推荐使用EntityUtils，除非知道Entity是来自可信任的Http Server 而且还需要知道它的最大长度。文档上面给了如下示例：

CloseableHttpClient httpclient = HttpClients.createDefault();
HttpGet httpget = new HttpGet("http://localhost/");
CloseableHttpResponse response = httpclient.execute(httpget);
try {
    HttpEntity entity = response.getEntity();
    if (entity != null) {
        long len = entity.getContentLength();
        if (len != -1 && len < 2048) {
            System.out.println(EntityUtils.toString(entity));
        } else {
            // Stream content out
        }
    }
} finally {
    response.close();
}

看这意思，contentLength < 2048，你就直接干吧， 否则你还是自已拿着stream玩吧！

无论看了下EntityUtils.toString(entity)方法的源码，现记录一下，以便于复习

private static String toString(
            final HttpEntity entity,
            final ContentType contentType) throws IOException {
        final InputStream inStream = entity.getContent();
        if (inStream == null) {
            return null;
        }
        try {
            Args.check(entity.getContentLength() <= Integer.MAX_VALUE,
                    "HTTP entity too large to be buffered in memory");
            int capacity = (int)entity.getContentLength();
            if (capacity < 0) {
                capacity = DEFAULT_BUFFER_SIZE;
            }
            Charset charset = null;
            if (contentType != null) {
                charset = contentType.getCharset();
                if (charset == null) {
                    final ContentType defaultContentType = ContentType.getByMimeType(contentType.getMimeType());
                    charset = defaultContentType != null ? defaultContentType.getCharset() : null;
                }
            }
            if (charset == null) {
                charset = HTTP.DEF_CONTENT_CHARSET;
            }
            final Reader reader = new InputStreamReader(inStream, charset);
            final CharArrayBuffer buffer = new CharArrayBuffer(capacity);
            final char[] tmp = new char[1024];
            int l;
            while((l = reader.read(tmp)) != -1) {
                buffer.append(tmp, 0, l);
            }
            return buffer.toString();
        } finally {
            inStream.close();
        }
    }

需要注意以下两点：

　　（1）Args.check(entity.getContentLength() <= Integer.MAX_VALUE, "HTTP entity too large to be buffered in memory"); 其实就是对Entity的大小做了一次检测，

如果太大推荐就放到内存中，只是这里的阈值是Integer.MAX_VALUE。

　　（2）将InputStream还原成String是时，使用了CharArrayBuffer 类，以前都没用过了呢， 以后也可以尝试着用用！

　　（3）关流！