关于HTTP响应

URL编码和反编码

class URLParser{
    public static void main(String[] args) throws IOException {
        String s = "c++";
        String r = URLEncoder.encode(s,"UTF-8");
        System.out.println(r);

        //反编码
        s = URLDecoder.decode(r,"UTF-8");
        System.out.println(s);
    }
}

c%2B%2B
c++

class SimpleHttpClient{
    //GET http://www.baidu.com 1.0
    public static void main(String[] args) {
        StringBuilder request = new StringBuilder();
        request.append("GET / HTTP/1.0\r\n");
        request.append("Host:www.baidu.com\r\n");
        request.append("\r\n");//代表是空行
        System.out.println(request.toString());
    }
}

---

发送请求收到响应把他打印出来

class SimpleHttpClient{
    //GET http://www.baidu.com 1.0
    public static void main(String[] args) throws IOException {
        StringBuilder request = new StringBuilder();
        request.append("GET / HTTP/1.0\r\n");
        request.append("Host:www.baidu.com\r\n");
        request.append("\r\n");//代表是空行
        System.out.println(request.toString());
		//以上部分就是Request
		
        Socket socket = new Socket("www.baidu.com",80);
        socket.getOutputStream().write(request.toString().getBytes("UTF-8"));
        socket.getOutputStream().flush();
        socket.shutdownOutput();

        byte[] buffer = new byte[4096];
        int len = socket.getInputStream().read(buffer);
        socket.close();
        String response = new String(buffer,0,len,"UTF-8");
        System.out.println(response);
        //接

    }
}

---

class SimpleHttpClient{
    //GET http://www.baidu.com 1.0
    public static void main(String[] args) throws IOException {
        StringBuilder request = new StringBuilder();
        request.append("GET / HTTP/1.0\r\n");
        request.append("Host:www.baidu.com\r\n");
        request.append("\r\n");//代表是空行
        System.out.println(request.toString());

        Socket socket = new Socket("www.baidu.com",80);
        socket.getOutputStream().write(request.toString().getBytes("UTF-8"));
        socket.getOutputStream().flush();
        socket.shutdownOutput();

        //1解析响应
        //2把响应体 保存到一个文件,百度.html
        byte[] buffer = new byte[4096];
        int len = socket.getInputStream().read(buffer);
//        String response = new String(buffer,0,len,"UTF-8");
//        System.out.println(response);


        //假设已经把状态行+所有状态头+空行都读到了
        int index = -1;
        for (int i = 0; i < len ; i++) {
            if (buffer[i] == '\r' && buffer[i + 1] == '\n'
                    && buffer[i + 2] == '\r' && buffer[i + 3] == '\n'){
                index = i;
                break;
            }
        }
        System.out.println(index);
        int 已经读到的正文长度 = len - index - 4;
        ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(buffer,0,index + 4);
        Scanner scanner = new Scanner(byteArrayInputStream,"UTF-8");
        String statusLine = scanner.nextLine();
        System.out.println("状态行" + statusLine);
        String line;
        int contenetLength = -1;
        while ((line = scanner.nextLine()).length() != 0){
            //line 是空行
            String[] kv = line.split(":");
            String key = kv[0].trim();
            String value = kv[1].trim();
            System.out.println("响应头: " + key + " = " + value);
            if (key.equalsIgnoreCase("Content-Length")){
                contenetLength = Integer.parseInt(value);//代表正文长度,有了正文长度就可以把所有正文读出来
            }
        }
        int 还需要读的正文的长度  = contenetLength - 已经读到的正文长度;
        byte[] body = new byte[contenetLength];
        System.arraycopy(buffer,index+4,
                body,
                0,已经读到的正文长度);
        int 实际又读到的长度 = socket.getInputStream().read(body,已经读到的正文长度,还需要读的正文的长度);
        System.out.println(contenetLength);
        System.out.println(已经读到的正文长度);
        System.out.println(还需要读的正文的长度);
        System.out.println(实际又读到的长度);

        FileOutputStream os = new FileOutputStream("百度.html");
        os.write(body);
        os.close();

    }
}

http状态码

		StringBuilder request = new StringBuilder();
        request.append("GET /no_such_path HTTP/1.0\r\n");
        request.append("Host:www.baidu.com\r\n");
        request.append("\r\n");//代表是空行
        System.out.println(request.toString());

        Socket socket = new Socket("www.baidu.com",80);
        socket.getOutputStream().write(request.toString().getBytes("UTF-8"));
        socket.getOutputStream().flush();
        socket.shutdownOutput();

        //1解析响应
        //2把响应体 保存到一个文件,百度.html
        byte[] buffer = new byte[4096];
        int len = socket.getInputStream().read(buffer);
        String response = new String(buffer,0,len,"UTF-8");
        System.out.println(response);
        System.exit(0);

GET /no_such_path HTTP/1.0
Host:www.baidu.com


HTTP/1.0 302 Found
Cache-Control: max-age=86400
Content-Length: 222
Content-Type: text/html; charset=iso-8859-1
Date: Fri, 27 Dec 2019 08:52:28 GMT
Expires: Sat, 28 Dec 2019 08:52:28 GMT
Location: https://www.baidu.com/search/error.html
Server: Apache

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>302 Found</title>
</head><body>
<h1>Found</h1>
<p>The document has moved <a href="http://www.baidu.com/search/error.html">here</a>.</p>
</body></html>