您可以自己扩展和处理所有与低级相关的内容。ProxiedHttpsConnection
需要执行以下步骤才能通过 HTTP 代理与 https 网站建立连接：
注意：与代理和 http 服务器的通信应采用 ASCII7 格式。
- 发送到代理
CONNECT stackoverflow.com:443 HTTP/1.0\r\n
- 发送您的身份验证：。
Proxy-Authorization: Basic c2F5WW91SGF2ZVNlZW5UaGlzSW5UaGVDb21tZW50cw==\r\n
- 结束第一个请求：
\r\n
- 从代理读取响应，直到看到组合“\r\n\r\n”。
- 解析从代理获取的响应的第一行，并检查它是否以 开头。
HTTP/1.0 200
- 通过现有连接就地启动 SSL 会话。
- 发送 http 请求的开始：
GET /questions/3304006/persistent-httpurlconnection-in-java HTTP/1.0\r\n
- 设置正确的主机标头：
Host: stackoverflow.com\r\n
- 结束对 http 服务器的请求：
\r\n
- 读取 till 并将第一行解析为状态消息
\r\n
- 读取到请求正文的流结束
当我们想要实现 HttpUrlConnection 类时，我们还需要考虑以下几点：
- 在构造类时，类应存储数据以供将来连接使用，但不要直接进行
- 可以按任何顺序调用任何方法
- 关闭意味着数据传输已完成，而不是连接必须完成
OutputStream
- 每个 API 都以不同的顺序使用这些方法
- HTTP 标头不区分大小写，Java 映射区分大小写。
快速说，有很多陷阱
在我设计的类中，它使用布尔标志来记住方法和方法是否被调用，如果在关闭之前调用，它也具有支持。connectafterPostClosuregetInputStream()OutputStream
此类还对套接字返回的流使用尽可能少的包装，以防止非常复杂。
public class ProxiedHttpsConnection extends HttpURLConnection {
private final String proxyHost;
private final int proxyPort;
private static final byte[] NEWLINE = "\r\n".getBytes();//should be "ASCII7"
private Socket socket;
private final Map<String, List<String>> headers = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
private final Map<String, List<String>> sendheaders = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
private final Map<String, List<String>> proxyheaders = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
private final Map<String, List<String>> proxyreturnheaders = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
private int statusCode;
private String statusLine;
private boolean isDoneWriting;
public ProxiedHttpsConnection(URL url,
String proxyHost, int proxyPort, String username, String password)
throws IOException {
super(url);
socket = new Socket();
this.proxyHost = proxyHost;
this.proxyPort = proxyPort;
String encoded = Base64.encode((username + ":" + password).getBytes())
.replace("\r\n", "");
proxyheaders.put("Proxy-Authorization", new ArrayList<>(Arrays.asList("Basic " + encoded)));
}
@Override
public OutputStream getOutputStream() throws IOException {
connect();
afterWrite();
return new FilterOutputStream(socket.getOutputStream()) {
@Override
public void write(byte[] b, int off, int len) throws IOException {
out.write(String.valueOf(len).getBytes());
out.write(NEWLINE);
out.write(b, off, len);
out.write(NEWLINE);
}
@Override
public void write(byte[] b) throws IOException {
out.write(String.valueOf(b.length).getBytes());
out.write(NEWLINE);
out.write(b);
out.write(NEWLINE);
}
@Override
public void write(int b) throws IOException {
out.write(String.valueOf(1).getBytes());
out.write(NEWLINE);
out.write(b);
out.write(NEWLINE);
}
@Override
public void close() throws IOException {
afterWrite();
}
};
}
private boolean afterwritten = false;
@Override
public InputStream getInputStream() throws IOException {
connect();
return socket.getInputStream();
}
@Override
public void setRequestMethod(String method) throws ProtocolException {
this.method = method;
}
@Override
public void setRequestProperty(String key, String value) {
sendheaders.put(key, new ArrayList<>(Arrays.asList(value)));
}
@Override
public void addRequestProperty(String key, String value) {
sendheaders.computeIfAbsent(key, l -> new ArrayList<>()).add(value);
}
@Override
public Map<String, List<String>> getHeaderFields() {
return headers;
}
@Override
public void connect() throws IOException {
if (connected) {
return;
}
connected = true;
socket.setSoTimeout(getReadTimeout());
socket.connect(new InetSocketAddress(proxyHost, proxyPort), getConnectTimeout());
StringBuilder msg = new StringBuilder();
msg.append("CONNECT ");
msg.append(url.getHost());
msg.append(':');
msg.append(url.getPort() == -1 ? 443 : url.getPort());
msg.append(" HTTP/1.0\r\n");
for (Map.Entry<String, List<String>> header : proxyheaders.entrySet()) {
for (String l : header.getValue()) {
msg.append(header.getKey()).append(": ").append(l);
msg.append("\r\n");
}
}
msg.append("Connection: close\r\n");
msg.append("\r\n");
byte[] bytes;
try {
bytes = msg.toString().getBytes("ASCII7");
} catch (UnsupportedEncodingException ignored) {
bytes = msg.toString().getBytes();
}
socket.getOutputStream().write(bytes);
socket.getOutputStream().flush();
byte reply[] = new byte[200];
byte header[] = new byte[200];
int replyLen = 0;
int headerLen = 0;
int newlinesSeen = 0;
boolean headerDone = false;
/* Done on first newline */
InputStream in = socket.getInputStream();
while (newlinesSeen < 2) {
int i = in.read();
if (i < 0) {
throw new IOException("Unexpected EOF from remote server");
}
if (i == '\n') {
if (newlinesSeen != 0) {
String h = new String(header, 0, headerLen);
String[] split = h.split(": ");
if (split.length != 1) {
proxyreturnheaders.computeIfAbsent(split[0], l -> new ArrayList<>()).add(split[1]);
}
}
headerDone = true;
++newlinesSeen;
headerLen = 0;
} else if (i != '\r') {
newlinesSeen = 0;
if (!headerDone && replyLen < reply.length) {
reply[replyLen++] = (byte) i;
} else if (headerLen < reply.length) {
header[headerLen++] = (byte) i;
}
}
}
String replyStr;
try {
replyStr = new String(reply, 0, replyLen, "ASCII7");
} catch (UnsupportedEncodingException ignored) {
replyStr = new String(reply, 0, replyLen);
}
// Some proxies return http/1.1, some http/1.0 even we asked for 1.0
if (!replyStr.startsWith("HTTP/1.0 200") && !replyStr.startsWith("HTTP/1.1 200")) {
throw new IOException("Unable to tunnel. Proxy returns \"" + replyStr + "\"");
}
SSLSocket s = (SSLSocket) ((SSLSocketFactory) SSLSocketFactory.getDefault())
.createSocket(socket, url.getHost(), url.getPort(), true);
s.startHandshake();
socket = s;
msg.setLength(0);
msg.append(method);
msg.append(" ");
msg.append(url.toExternalForm().split(String.valueOf(url.getPort()), -2)[1]);
msg.append(" HTTP/1.0\r\n");
for (Map.Entry<String, List<String>> h : sendheaders.entrySet()) {
for (String l : h.getValue()) {
msg.append(h.getKey()).append(": ").append(l);
msg.append("\r\n");
}
}
if (method.equals("POST") || method.equals("PUT")) {
msg.append("Transfer-Encoding: Chunked\r\n");
}
msg.append("Host: ").append(url.getHost()).append("\r\n");
msg.append("Connection: close\r\n");
msg.append("\r\n");
try {
bytes = msg.toString().getBytes("ASCII7");
} catch (UnsupportedEncodingException ignored) {
bytes = msg.toString().getBytes();
}
socket.getOutputStream().write(bytes);
socket.getOutputStream().flush();
}
private void afterWrite() throws IOException {
if (afterwritten) {
return;
}
afterwritten = true;
socket.getOutputStream().write(String.valueOf(0).getBytes());
socket.getOutputStream().write(NEWLINE);
socket.getOutputStream().write(NEWLINE);
byte reply[] = new byte[200];
byte header[] = new byte[200];
int replyLen = 0;
int headerLen = 0;
int newlinesSeen = 0;
boolean headerDone = false;
/* Done on first newline */
InputStream in = socket.getInputStream();
while (newlinesSeen < 2) {
int i = in.read();
if (i < 0) {
throw new IOException("Unexpected EOF from remote server");
}
if (i == '\n') {
if (headerDone) {
String h = new String(header, 0, headerLen);
String[] split = h.split(": ");
if (split.length != 1) {
headers.computeIfAbsent(split[0], l -> new ArrayList<>()).add(split[1]);
}
}
headerDone = true;
++newlinesSeen;
headerLen = 0;
} else if (i != '\r') {
newlinesSeen = 0;
if (!headerDone && replyLen < reply.length) {
reply[replyLen++] = (byte) i;
} else if (headerLen < header.length) {
header[headerLen++] = (byte) i;
}
}
}
String replyStr;
try {
replyStr = new String(reply, 0, replyLen, "ASCII7");
} catch (UnsupportedEncodingException ignored) {
replyStr = new String(reply, 0, replyLen);
}
/* We asked for HTTP/1.0, so we should get that back */
if ((!replyStr.startsWith("HTTP/1.0 200")) && !replyStr.startsWith("HTTP/1.1 200")) {
throw new IOException("Server returns \"" + replyStr + "\"");
}
}
@Override
public void disconnect() {
try {
socket.close();
} catch (IOException ex) {
Logger.getLogger(ProxiedHttpsConnection.class.getName()).log(Level.SEVERE, null, ex);
}
}
@Override
public boolean usingProxy() {
return true;
}
}
上述代码的当前错误：
- 在发布过程中，流不会因错误而关闭
- 在与代理的初始联系错误期间，流不会关闭
- 它不支持 http 重定向
- 它不支持http 1.1的东西，如分块和gzip编码，但这没有问题，因为我们宣布自己是http1.0客户端。
上面的代码可以像这样使用：
ProxiedHttpsConnection n = new ProxiedHttpsConnection(
new URL("https://stackoverflow.com:443/questions/3304006/persistent-httpurlconnection-in-java"),
"proxy.example.com", 8080, "root", "flg83yvem#");
n.setRequestMethod("GET");
n.addRequestProperty("User-Agent", "Java test https://stackoverflow.com/users/1542723/ferrybig");
//try (OutputStream out = n.getOutputStream()) {
// out.write("Hello?".getBytes());
//}
try (InputStream in = n.getInputStream()) {
byte[] buff = new byte[1024];
int length;
while ((length = in.read(buff)) >= 0) {
System.out.write(buff, 0, length);
}
}
如果您要将其与某种代理选择器一起使用，则应检查url的协议以查看其http或https，如果其http，则不使用此类，而是手动附加标头，如下所示：
httpURLConnection.setRequestProperty("Proxy-Authorization", "Basic " + encoded);
虽然java有这种方法，但尝试使用它将向您展示为什么它不起作用，java只是不断调用createSocket（Socket s，String host，int port，boolean autoClose）已经打开的连接，使得无法手动执行代理操作。
