網(wǎng)絡(luò)協(xié)議的知識(shí)湖雹，數(shù)據(jù)在Internet上傳輸，一般通過(guò)三種協(xié)議來(lái)實(shí)現(xiàn)發(fā)送信息和實(shí)現(xiàn)：

HTTP協(xié)議程剥，也是在工作中最常用的劝枣，是建立在TCP/IP基礎(chǔ)上實(shí)現(xiàn)的。

FTP協(xié)議织鲸。

TCP/IP協(xié)議舔腾，它也是最低層的協(xié)議，其它的方式必須要通過(guò)它搂擦，但是想要實(shí)現(xiàn)這種協(xié)議必須要實(shí)現(xiàn)socket編程稳诚，這種方法是用來(lái)上傳一些比較大的文件，視頻瀑踢，進(jìn)行斷電續(xù)傳的操作扳还。

HTTP協(xié)議

　　下面詳細(xì)講解一下HTTP協(xié)議，因?yàn)镠TTP是無(wú)狀態(tài)的協(xié)議橱夭，所以服務(wù)端并不記錄客戶(hù)端之前發(fā)送信息氨距，一碼歸一碼，所以HTTP協(xié)議使用報(bào)文頭的形式記錄狀態(tài)棘劣，一般分為請(qǐng)求報(bào)文和響應(yīng)報(bào)文俏让。一般用戶(hù)使用瀏覽器訪問(wèn)網(wǎng)頁(yè)，是無(wú)需關(guān)心HTTP請(qǐng)求的報(bào)文頭的茬暇，因?yàn)殚_(kāi)發(fā)人員在瀏覽器中已經(jīng)幫忙處理了首昔，但是當(dāng)進(jìn)行開(kāi)發(fā)工作的時(shí)候，這些是必須要了解的糙俗。

　　對(duì)于報(bào)文勒奇，一般關(guān)心請(qǐng)求方式，是GET或者是POST巧骚；請(qǐng)求數(shù)據(jù)類(lèi)型赊颠，是文本還是音頻格二；數(shù)據(jù)的編碼格式，一般用utf-8巨税；發(fā)送的數(shù)據(jù)長(zhǎng)度蟋定；響應(yīng)返回碼，一般200為成功草添，其他響應(yīng)碼都是有問(wèn)題驶兜。具體了解還是看看上面推薦的博客。

　　HTTP/1.1協(xié)議中一共定義了八種方法（有時(shí)也叫“動(dòng)作”）來(lái)表明Request-URI指定的資源的不同操作方式远寸，但是一般常用的就是GET和POST方式抄淑。

　　這里簡(jiǎn)單說(shuō)一下GET方式和POST方式的差別：

GET是從服務(wù)器上獲取數(shù)據(jù)，POST是向服務(wù)器傳送數(shù)據(jù)驰后。

在客戶(hù)端肆资，GET方式在通過(guò)URL提交數(shù)據(jù)，數(shù)據(jù)在URL中可以看到灶芝；POST方式郑原，數(shù)據(jù)放在HTML HEADER內(nèi)提交。

對(duì)于GET方式夜涕，服務(wù)器端用Request.QueryString獲取變量的值犯犁，對(duì)于POST方式，服務(wù)器用Request.Form獲取提交的數(shù)據(jù)女器。

GET方式提交的數(shù)據(jù)不能大于2KB（主要是URL長(zhǎng)度限制）酸役，而POST則沒(méi)有此限制。

安全性問(wèn)題驾胆。正如2中提到涣澡，使用GET的時(shí)候，參數(shù)會(huì)顯示在地址欄上丧诺，而POST不會(huì)入桂。所以，如果這些數(shù)據(jù)是中文數(shù)據(jù)而且是非敏感數(shù)據(jù)驳阎，那么使用GET事格；如果用戶(hù)輸入的數(shù)據(jù)不是中文字符而且包含敏感數(shù)據(jù)，那么還是使用POST為好搞隐。

Java中使用HTTP

　　下面通過(guò)兩個(gè)例子來(lái)分別講解一下GET和POST在Java中的使用，如果在Java中需要使用HTTP協(xié)議進(jìn)行訪問(wèn)远搪，一般通過(guò)HttpURLConnection類(lèi)來(lái)實(shí)現(xiàn)劣纲。

　　HttpURLConnection繼承了URLConnection，所以在URLConnection的基礎(chǔ)上進(jìn)一步改進(jìn)谁鳍，增加了一些用于操作HTTP資源的便捷方法癞季。Java中HttpURLConnection對(duì)象通過(guò)URL.openConnection()方法來(lái)獲得劫瞳，需要進(jìn)行強(qiáng)制轉(zhuǎn)換。先來(lái)介紹幾個(gè)HttpURLConnection的常用方法：

void?setConnectTimeout(int timeout)：設(shè)置連接超時(shí)時(shí)長(zhǎng)绷柒，如果超過(guò)timeout時(shí)長(zhǎng)志于，則放棄連接，單位以毫秒計(jì)算废睦。

void?setDoInput(boolean newValue) ：標(biāo)志是否允許輸入伺绽。

void?setDoOutput(boolean newValue)：標(biāo)志是否允許輸出。

String getRequestMethod():獲取發(fā)送請(qǐng)求的方法嗜湃。

int getResponseCode():獲取服務(wù)器的響應(yīng)碼奈应。

void setRequestMethod(String method)：設(shè)置發(fā)送請(qǐng)求的方法。

void setRequestProperty(String field,String newValue)：設(shè)置請(qǐng)求報(bào)文頭购披，并且只對(duì)當(dāng)前HttpURLConnection有效杖挣。

FutureTask可用于異步獲取執(zhí)行結(jié)果或取消執(zhí)行任務(wù)的場(chǎng)景。通過(guò)傳入Runnable或者Callable的任務(wù)給FutureTask刚陡，直接調(diào)用其run方法或者放入線程池執(zhí)行惩妇，之后可以在外部通過(guò)FutureTask的get方法異步獲取執(zhí)行結(jié)果，因此筐乳，F(xiàn)utureTask非常適合用于耗時(shí)的計(jì)算歌殃，主線程可以在完成自己的任務(wù)后，再去獲取結(jié)果哥童。另外挺份，F(xiàn)utureTask還可以確保即使調(diào)用了多次run方法，它都只會(huì)執(zhí)行一次Runnable或者Callable任務(wù)贮懈，或者通過(guò)cancel取消FutureTask的執(zhí)行等匀泊。

因?yàn)榭紤]到連接時(shí)間比較長(zhǎng)，采用FutureTask

GET方式

public static String get(final String url) throws Exception {
??????? String r = null;
??????? FutureTask<String> task = new FutureTask<>(new Callable<String>() {
??????????? @Override
??????????? public String call() throws Exception {
??????????????? BufferedReader bufferedReader = null;
??????????????? String result = null;
??????????????? try {
??????????????????? URL realUrl = new URL(url);
??????????????????? HttpURLConnection connection = (HttpURLConnection) realUrl.openConnection();
??????????????????? if (connection instanceof HttpsURLConnection) {
??????????????????????? SSLContext sslContext = SSLContextUtil.getSSLContext(mContext, "證書(shū)");
??????????????????????? if (sslContext != null) {
??????????????????????????? SSLSocketFactory sslSocketFactory = sslContext.getSocketFactory();
??????????????????????????? ((HttpsURLConnection) connection).setSSLSocketFactory(sslSocketFactory);
??????????????????????? }
??????????????????? }

connection.connect();

//向本地寫(xiě)入數(shù)據(jù)

??????????????????? bufferedReader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
??????????????????? String line;
??????????????????? StringBuffer sb = new StringBuffer();
??????????????????? while ((line = bufferedReader.readLine()) != null) {
??????????????????????? sb.append(line);
??????????????????? }
??????????????????? result = sb.toString();
??????????????? } catch (IOException e) {
???????????????????
??????????????? } catch (Exception e) {
??????????????????

//最終要關(guān)閉流

????????????? } finally {
??????????????????? if (bufferedReader != null) {
??????????????????????? try {
??????????????????????????? bufferedReader.close();
??????????????????????? } catch (IOException e) {
???????????????????????????
??????????????????????? }
??????????????????? }
??????????????? }
??????????????? return result;
??????????? }
??????? });
??????? new Thread(task).start();

???? try {
??????????? r = task.get();
??????? } catch (InterruptedException e) {
???????????
??????? } catch (ExecutionException e) {
??????????
??????? }
??????? return r;
??? }

POST方式

public static String post(final String url, final Map<String, Object> params) throws Exception {
??????? String r = null;
??????? final String TAG = "PostTag";
??????? FutureTask<String> task = new FutureTask<>(new Callable<String>() {
??????????? @Override
??????????? public String call() throws Exception {
??????????????? String result = null;
??????????????? BufferedReader bufferedReader = null

??????????????? PrintWriter out = null;
??????????????? LogUtil.d(TAG, "call: start ");
??????????????? try {
???????????????
??????????????????? String line = null;
??????????????????? StringBuffer sb = new StringBuffer();
??????????????????? URL realUrl = new URL(url);
??????????????????? int outTime = 5 * 1000; //超時(shí)設(shè)置
??????????????????? URLConnection connection = realUrl.openConnection();

//添加證書(shū)

??????????????????? if (connection instanceof HttpsURLConnection) {
??????????????????????? SSLContext sslContext = SSLContextUtil.getSSLContext(mContext, "證書(shū)");
??????????????????????? if (sslContext != null) {
??????????????????????????? SSLSocketFactory sslSocketFactory = sslContext.getSocketFactory();
??????????????????????????? ((HttpsURLConnection) connection).setSSLSocketFactory(sslSocketFactory);
??????????????????????? }
??????????????????? }

//添加證書(shū)

////設(shè)置請(qǐng)求報(bào)文頭朵你，設(shè)定請(qǐng)求數(shù)據(jù)類(lèi)型

??????????????????? connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
??????????????????? connection.setConnectTimeout(outTime);

//設(shè)置允許輸入輸出

??????????????????? connection.setDoOutput(true);
??????????????????? connection.setDoInput(true);
??????????????????? connection.setUseCaches(false);
??????????????????? out = new PrintWriter(connection.getOutputStream());
??????????????????? out.print(getParams(params));
???????????????????
??????????????????? out.flush();

//把服務(wù)端返回的輸入流轉(zhuǎn)換成字符串格式

??????????????????? bufferedReader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
??????????????????? while ((line = bufferedReader.readLine()) != null) {
??????????????????????? sb.append(line);
??????????????????????? Log.d(TAG, "call: while ");
??????????????????? }

?????????????????? result = sb.toString(); //結(jié)果返回
??????????????????? Log.d(TAG, "result: " + result);
??????????????? } catch (IOException e) {
??????????????????
??????????????????? throw e;
??????????????? } finally {
??????????????????? if (bufferedReader != null) {
??????????????????????? try {
??????????????????????????? bufferedReader.close();
??????????????????????? } catch (IOException e) {
??????????????????????????? Log.e(TAG, e.getCause(), "");
??????????????????????? }
??????????????????? }
??????????????? }

??????????????? return result;
??????????? }
??????? });

????? new Thread(task).start();
??????? try {
??????????? r = task.get();
??????? } catch (InterruptedException e) {
??????????? Log.e(TAG, e.getCause(), "");
??????????? Log.d(TAG, "post: " + "InterruptedException");
??????? } catch (ExecutionException e) {
??????????? Log.e(TAG, e.getCause(), "");
??????????? Log.d(TAG, "post: " + "ExecutionException");
??????? } catch (Exception e) {
??????????? Log.e(TAG, e.getCause(), "");
??????????? Log.d(TAG, "post: " + "");
??????? }
??????? return r;
??? }

//將請(qǐng)求參數(shù)轉(zhuǎn)換格式各聘，//請(qǐng)求的參數(shù)之間使用&分割。

?? private static String getParams(Map<String, Object> params) {
??????? StringBuffer sb = new StringBuffer();
??????? if (params != null) {
??????????? for (String key : params.keySet()) {
??????????????? sb.append(key).append("=").append(params.get(key).toString()).append("&");
??????????? }
??????????? if (sb.indexOf("&") == sb.length() - 1) {
??????????????? sb.deleteCharAt(sb.length() - 1);
??????????? }
??????? }
??????? return sb.toString();
??? }