如何回收或者关闭OSSClient实例的连接

以下是我上传文件到OSS的部分代码:

try {
            // 创建OSS客户端
            client = new OSSClient(endpoint, keyId, key, conf);
            
            // 设置过期时间
            Date expires = new Date (new Date().getTime() + 1000 * second);
            
            // 创建请求
            GeneratePresignedUrlRequest generatePresignedUrlRequest =
                    new GeneratePresignedUrlRequest(bucketName, DestPathName);
            generatePresignedUrlRequest.setBucketName(bucketName);
            // HttpMethod为PUT
            generatePresignedUrlRequest.setMethod(HttpMethod.PUT);
            generatePresignedUrlRequest.setExpiration(expires);
            // ContentType必须设置, 否则签名失败
            generatePresignedUrlRequest.setContentType(contentType);
            // 生成签名的URL
            URL url = client.generatePresignedUrl(generatePresignedUrlRequest);
            
            
            HashMap<String, String> requestHeaders = new HashMap<String, String>();
            requestHeaders.put("Content-Length", inputLength+"");
            requestHeaders.put("Content-Type", contentType);
            // 使用URL签名方式上传指定输入流
            PutObjectResult result = client.putObject(url, inputStream, inputLength, requestHeaders);
//                System.out.println(result.getETag());
            return 0;
        } catch(Exception e) {
            logger.error("上传异常: " + e.getMessage());
        } finally {
//            if(null != client) {
//                client.shutdown();
//            }
        }


如果完成操作之后使用shutdown方法, 会抛出线程异常, 如果对OSSClient不做任何处理, 每隔60秒就有关闭空闲连接的日志输出(new了2个OSSClient实例, 完成操作之后断点停住):

2015-09-09 15:56:50,517 DEBUG [org.apache.http.impl.conn.PoolingClientConnectionManager] - <Closing connections idle longer than 60 SECONDS>
2015-09-09 15:56:50,517 DEBUG [org.apache.http.impl.conn.PoolingClientConnectionManager] - <Closing connections idle longer than 60 SECONDS>
2015-09-09 15:57:50,517 DEBUG [org.apache.http.impl.conn.PoolingClientConnectionManager] - <Closing connections idle longer than 60 SECONDS>
2015-09-09 15:57:50,517 DEBUG [org.apache.http.impl.conn.PoolingClientConnectionManager] - <Closing connections idle longer than 60 SECONDS>
2015-09-09 15:58:50,519 DEBUG [org.apache.http.impl.conn.PoolingClientConnectionManager] - <Closing connections idle longer than 60 SECONDS>
2015-09-09 15:58:50,519 DEBUG [org.apache.http.impl.conn.PoolingClientConnectionManager] - <Closing connections idle longer than 60 SECONDS>
2015-09-09 15:59:50,520 DEBUG [org.apache.http.impl.conn.PoolingClientConnectionManager] - <Closing connections idle longer than 60 SECONDS>
2015-09-09 15:59:50,520 DEBUG [org.apache.http.impl.conn.PoolingClientConnectionManager] - <Closing connections idle longer than 60 SECONDS>
2015-09-09 16:00:50,521 DEBUG [org.apache.http.impl.conn.PoolingClientConnectionManager] - <Closing connections idle longer than 60 SECONDS>
2015-09-09 16:00:50,521 DEBUG [org.apache.http.impl.conn.PoolingClientConnectionManager] - <Closing connections idle longer than 60 SECONDS>
2015-09-09 16:01:50,521 DEBUG [org.apache.http.impl.conn.PoolingClientConnectionManager] - <Closing connections idle longer than 60 SECONDS>
2015-09-09 16:01:50,522 DEBUG [org.apache.http.impl.conn.PoolingClientConnectionManager] - <Closing connections idle longer than 60 SECONDS>
2015-09-09 16:02:50,522 DEBUG [org.apache.http.impl.conn.PoolingClientConnectionManager] - <Closing connections idle longer than 60 SECONDS>
2015-09-09 16:02:50,522 DEBUG [org.apache.http.impl.conn.PoolingClientConnectionManager] - <Closing connections idle longer than 60 SECONDS>


这样上传文件是否合适? 该如何回收连接?