簡約之美Jodd-http--深刻源碼理解http協議

Jodd 是一個開源的 Java 工具集， 包含一些實用的工具類和小型框架。簡單，卻很強大！

jodd-http是一個輕巧的HTTP客戶端。如今咱們以一個簡單的示例從源碼層看看是如何實現的？

HttpRequest httpRequest = HttpRequest.get("http://jodd.org"); //1. 構建一個get請求
 HttpResponse response = httpRequest.send(); //2.發送請求並接受響應信息
 System.out.println(response);//3.打印響應信息

構建一個get請求

先複習一下http請求報文的格式：

下圖展現通常請求所帶有的屬性

調用get方法構建http請求：

/**
 * Builds a GET request.
 */
 public static HttpRequest get(String destination) {
 return new HttpRequest()
 .method("GET")
 .set(destination);
 }

method方法以下：

/**
 * Specifies request method. It will be converted into uppercase.
 */
 public HttpRequest method(String method) {
 this.method = method.toUpperCase();
 return this;
 }

set方法以下：

/**
 * Sets the destination (method, host, port... ) at once.
 */
 public HttpRequest set(String destination) {
 destination = destination.trim();

 // http method

 int ndx = destination.indexOf(' ');

 if (ndx != -1) {
 method = destination.substring(0, ndx).toUpperCase();
 destination = destination.substring(ndx + 1);
 }

 // protocol

 ndx = destination.indexOf("://");

 if (ndx != -1) {
 protocol = destination.substring(0, ndx);
 destination = destination.substring(ndx + 3);
 }

 // host

 ndx = destination.indexOf('/');

 if (ndx == -1) {
 ndx = destination.length();
 }

 if (ndx != 0) {

 host = destination.substring(0, ndx);
 destination = destination.substring(ndx);

 // port

 ndx = host.indexOf(':');

 if (ndx == -1) {
 port = DEFAULT_PORT;
 } else {
 port = Integer.parseInt(host.substring(ndx + 1));
 host = host.substring(0, ndx);
 }
 }

 // path + query

 path(destination);

 return this;
 }

上述方法，根據destination解析出一下幾個部分：

1. 方法：HTTP1.1支持7種請求方法:GET、POST、HEAD、OPTIONS、PUT、DELETE和TARCE。

2. 協議：http或者https

3. 主機：請求的服務器地址

4. 端口：請求的服務器端口

5. 路徑+查詢參數，其中參數以「?」開頭，使用「&」鏈接

/**
 * Sets request path. Query string is allowed.
 * Adds a slash if path doesn't start with one.
 * Query will be stripped out from the path.
 * Previous query is discarded.
 * @see #query()
 */
 public HttpRequest path(String path) {
 // this must be the only place that sets the path

 if (path.startsWith(StringPool.SLASH) == false) {
 path = StringPool.SLASH + path;
 }

 int ndx = path.indexOf('?');

 if (ndx != -1) {
 String queryString = path.substring(ndx + 1);

 path = path.substring(0, ndx);

 query = HttpUtil.parseQuery(queryString, true);
 } else {
 query = HttpValuesMap.ofObjects();
 }

 this.path = path;

 return this;
 }

發送請求

先熟悉一下http響應報文的格式：

先熟悉一下http響應報文的格式：

響應首部通常包含以下內容：

/**
 * {@link #open() Opens connection} if not already open, sends request,
 * reads response and closes the request. If keep-alive mode is enabled
 * connection will not be closed.
 */
 public HttpResponse send() {
 if (httpConnection == null) {
 open();
 }

 // prepare http connection

 if (timeout != -1) {
 httpConnection.setTimeout(timeout);
 }

 // sends data
 HttpResponse httpResponse;
 try {
 OutputStream outputStream = httpConnection.getOutputStream();

 sendTo(outputStream);

 InputStream inputStream = httpConnection.getInputStream();

 httpResponse = HttpResponse.readFrom(inputStream);

 httpResponse.assignHttpRequest(this);
 } catch (IOException ioex) {
 throw new HttpException(ioex);
 }

 boolean keepAlive = httpResponse.isConnectionPersistent();

 if (keepAlive == false) {
 // closes connection if keep alive is false, or if counter reached 0
 httpConnection.close();
 httpConnection = null;
 }

 return httpResponse;
 }

1. 打開HttpConnection

/**
 * Opens a new {@link HttpConnection connection} using
 * {@link JoddHttp#httpConnectionProvider default connection provider}.
 */
 public HttpRequest open() {
 return open(JoddHttp.httpConnectionProvider);
 }

 /**
 * Opens a new {@link jodd.http.HttpConnection connection}
 * using given {@link jodd.http.HttpConnectionProvider}.
 */
 public HttpRequest open(HttpConnectionProvider httpConnectionProvider) {
 if (this.httpConnection != null) {
 throw new HttpException("Connection already opened");
 }
 try {
 this.httpConnectionProvider = httpConnectionProvider;
 this.httpConnection = httpConnectionProvider.createHttpConnection(this);
 } catch (IOException ioex) {
 throw new HttpException(ioex);
 }

 return this;
 }

判斷是否有鏈接，若沒有鏈接則建立一個新的鏈接。

2. 建立鏈接實現

/**
 * Creates new connection from current {@link jodd.http.HttpRequest request}.
 *
 * @see #createSocket(String, int)
 */
 public HttpConnection createHttpConnection(HttpRequest httpRequest) throws IOException {
 Socket socket;

 if (httpRequest.protocol().equalsIgnoreCase("https")) {
 SSLSocket sslSocket = createSSLSocket(httpRequest.host(), httpRequest.port());

 sslSocket.startHandshake();

 socket = sslSocket;
 } else {
 socket = createSocket(httpRequest.host(), httpRequest.port());
 }

 return new SocketHttpConnection(socket);
 }

3. 建立socket

　　根據協議的不一樣，http使用SocketFactory建立socket，https使用SSLSocketFactory建立SSLSocket。最終使用SocketHttpConnection進行包裝。

SocketHttpConnection繼承自HttpConnection，實現了socket的輸入輸出流鏈接。注意：https建立完SSLSocket時須要進行握手。

public class SocketHttpConnection implements HttpConnection {

 protected final Socket socket;

 public SocketHttpConnection(Socket socket) {
 this.socket = socket;
 }

 public OutputStream getOutputStream() throws IOException {
 return socket.getOutputStream();
 }

 public InputStream getInputStream() throws IOException {
 return socket.getInputStream();
 }

 public void close() {
 try {
 socket.close();
 } catch (IOException ignore) {
 }
 }

 public void setTimeout(int milliseconds) {
 try {
 socket.setSoTimeout(milliseconds);
 } catch (SocketException sex) {
 throw new HttpException(sex);
 }
 }

 /**
 * Returns <code>Socket</code> used by this connection.
 */
 public Socket getSocket() {
 return socket;
 }
}

打開Connection的輸出流發送信息，打開connection的輸入流接受返回信息。

OutputStream outputStream = httpConnection.getOutputStream();

 sendTo(outputStream);

 InputStream inputStream = httpConnection.getInputStream();

發送過程：

protected HttpProgressListener httpProgressListener;

 /**
 * Sends request or response to output stream.
 */
 public void sendTo(OutputStream out) throws IOException {
 Buffer buffer = buffer(true);

 if (httpProgressListener == null) {
 buffer.writeTo(out);
 }
 else {
 buffer.writeTo(out, httpProgressListener);
 }

 out.flush();
 }

將緩衝區的數據寫入輸出流，併發送。

接受數據並讀取報文內容：

/**
 * Reads response input stream and returns {@link HttpResponse response}.
 * Supports both streamed and chunked response.
 */
 public static HttpResponse readFrom(InputStream in) {
 InputStreamReader inputStreamReader;
 try {
 inputStreamReader = new InputStreamReader(in, StringPool.ISO_8859_1);
 } catch (UnsupportedEncodingException ignore) {
 return null;
 }
 BufferedReader reader = new BufferedReader(inputStreamReader);

 HttpResponse httpResponse = new HttpResponse();

 // the first line
 String line;
 try {
 line = reader.readLine();
 } catch (IOException ioex) {
 throw new HttpException(ioex);
 }

 if (line != null) {

 line = line.trim();

 int ndx = line.indexOf(' ');
 httpResponse.httpVersion(line.substring(0, ndx));

 int ndx2 = line.indexOf(' ', ndx + 1);
 if (ndx2 == -1) {
 ndx2 = line.length();
 }
 httpResponse.statusCode(Integer.parseInt(line.substring(ndx, ndx2).trim()));

 httpResponse.statusPhrase(line.substring(ndx2).trim());
 }

 httpResponse.readHeaders(reader);
 httpResponse.readBody(reader);

 return httpResponse;
 }

小結

從上面的代碼，咱們能夠看出http使用socket來創建和destination的鏈接，而後經過鏈接的輸出流和輸入流來進行通訊。

參考文獻：

【1】http://www.it165.net/admin/html/201403/2541.html

【2】http://jodd.org/doc/http.html