httpclient模拟浏览器下载文件-常用方法集锦

需求 ：下载资源文件到本地

public void getDownloadResource(String url, String filePath) throws IOException {        File file = new File(filePath);        if (!file.exists()) {            file.createNewFile();        }        try {            OutputStream out = new FileOutputStream(file);            // Method1            downLoadByJdk(url, out);            // method2            // downLoadByHttpCommons(url, out);            // method3            downloadByCommonsHttpclient(url, out);        } catch (Exception e) {        }    }

Java自带的API实现

public static void downLoadByJdk(String url, OutputStream out) {        try {            URL realUrl = new URL(url);            // 打开和URL之间的连接            URLConnection conn = realUrl.openConnection();            // 设置通用的请求属性            conn.setRequestProperty("accept", "*/*");            conn.setRequestProperty("connection", "Keep-Alive");            conn.setRequestProperty("user-agent",                    "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");            // 发送POST请求必须设置如下两行            conn.setDoOutput(true);            conn.setDoInput(true);            // 获取URLConnection对象对应的输出流            IOUtils.copy(conn.getInputStream(), out);            out.close();        } catch (Exception e) {            System.out.println("发送 POST 请求出现异常！"+e);            e.printStackTrace();        }    }

httpClient

• pom

<dependency><groupId>org.apache.httpcomponents</groupId><artifactId>httpclient</artifactId><version>4.5.2</version></dependency>

• demo

 public static void downLoadByHttpClient(String url, OutputStream out) throws IOException {        //创建httpclient实例，采用默认的参数配置        CloseableHttpClient httpClient = HttpClients.createDefault();        HttpGet get = new HttpGet(url);   //使用Get方法提交        //请求的参数配置，分别设置连接池获取连接的超时时间，连接上服务器的时间，服务器返回数据的时间        RequestConfig config = RequestConfig.custom()                .setConnectionRequestTimeout(3000)                .setConnectTimeout(3000)                .setSocketTimeout(3000)                .build();        //配置信息添加到Get请求中        get.setConfig(config);        //通过httpclient的execute提交 请求 ，并用CloseableHttpResponse接受返回信息        CloseableHttpResponse response = httpClient.execute(get);        //服务器返回的状态        int statusCode = response.getStatusLine().getStatusCode();        //判断返回的状态码是否是200 ，200 代表服务器响应成功，并成功返回信息        if (statusCode == HttpStatus.SC_OK) {            //EntityUtils 获取返回的信息。官方不建议使用使用此类来处理信息//            System.out.println("Demo.example -------->" + EntityUtils.toString(response.getEntity() , Consts.UTF_8));            IOUtils.copy(response.getEntity().getContent(), out);            out.flush();            out.close();        } else {            System.out.println("Demo.example -------->" + "获取信息失败");        }    }

• 参考文档

commons-httpclient

• pom

    <dependency>         <groupId>apache-httpclient</groupId>        <artifactId>commons-httpclient</artifactId>          <version>3.1</version>     </dependency>

• demo

downloadByCommonsHttpclient

/**     * 下载资源     *     * @param url     * @param filePath     * @throws IOException     */    public boolean getDownloadResource(String url, OutputStream out) throws IOException {        long begin = System.currentTimeMillis();        try {            HttpClientParams httpClientParams = new HttpClientParams();            httpClientParams.setSoTimeout(2000);            httpClientParams.setConnectionManagerTimeout(2000);            // http请求            getHttpResponse(url, out, httpClientParams);            out.flush();            out.close();            System.out.println("下载资源耗时:" + (System.currentTimeMillis() - begin));            return true;        } catch (Exception e) {            return false;        }    }

getHttpResponse

/**     * 根据url 获得http response返回结果OutputStream。     *      * @param url     * @param out     * @param httpClientParams 不能为null，为null会抛出异常;至少new一个空对象放入     * @return     * @throws IOException     */    public static OutputStream getHttpResponse(String url, OutputStream out, HttpClientParams httpClientParams)            throws IOException {        if (url.indexOf("//") == -1) {            url = "http://" + url;        }        HttpClient httpClient = getHttpClient(httpClientParams);        GetMethod getMethod = new GetMethod(url);        InputStream inputStream = null;        try {            getMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler());            // 执行            int statusCode = httpClient.executeMethod(getMethod);            if (statusCode != HttpStatus.SC_OK) {                throw new IOException("connect url error:" + getMethod.getStatusLine() + " url: " + url);            } else {                inputStream = getMethod.getResponseBodyAsStream();                IOUtils.copy(inputStream, out);            }        } catch (IOException e) {            throw e;        } finally {            try {                getMethod.releaseConnection();            } catch (Exception e) {                LOG.error(e.getMessage(), e);            }            try {                if (inputStream != null) {                    inputStream.close();                }            } catch (Exception e) {                LOG.error(e.getMessage(), e);            }        }        return out;    }

getHttpClient

private static HttpClient getHttpClient(HttpClientParams httpClientParams) {        HttpClient httpClient = new HttpClient(httpClientParams);        if (httpClientParams.getConnectionManagerTimeout() > Integer.MAX_VALUE) {            httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(Integer.MAX_VALUE);        } else {            httpClient.getHttpConnectionManager().getParams()                    .setConnectionTimeout((int) httpClientParams.getConnectionManagerTimeout());        }        return httpClient;    }