Java使用代理服务器

HTTP协议是基于TCP协议的,TCP协议在Java中的体现就是套接字.在了解HTTP协议的基础上,完全可以通过TCP来实现一套HTTP库,这个库可以发起网络请求和接受网络请求.只要能用URLConnection能实现的事情,用Socket同样能够实现.

代理是"代理服务器",我不直接向百度发起请求,而是向代理服务器发起请求,然后代理服务器代替我向百度发起请求.这样一来,我的IP地址就不会暴露.在编写爬虫时,同一个IP爬多了就会被要求输入验证码,这时就可以通过代理来不停地换IP从而规避验证码.

本文提供四种方法,第一种方法通过设置环境变量,第二种方法通过URLConnection,第三种方法通过nio中的SocketChannel,第四种方法通过Socket.

public class TestProxy {
static String host = "112.126.65.26";
static int port = 12345;
static String url = "http://1212.ip138.com/ic.asp";
public static void main(String[] args) throws Exception {
four();
}
static void one() throws MalformedURLException, IOException {
// 没有这句话是不行的
System.setProperty("http.proxySet", "true");
System.setProperty("http.proxyHost", host);
System.setProperty("http.proxyPort", port + "");
URLConnection connection = new URL(url).openConnection();
show(connection.getInputStream());
}
static void two() throws MalformedURLException, IOException {
SocketAddress addr = new InetSocketAddress(host, port);
Proxy proxy = new Proxy(Proxy.Type.HTTP, addr);
// 下面这个网址会告诉你你的ip地址
URLConnection connection = new URL(url).openConnection(proxy);
show(connection.getInputStream());
}
// 使用socket也是一样
static void three() throws IOException {
SocketChannel sc = SocketChannel
.open(new InetSocketAddress(host, port));
sc.write(Charset.forName("utf8")
.encode("GET " + url + " HTTP/1.1\r\n\r\n"));
ByteBuffer buffer = ByteBuffer.allocate(1024);
while (sc.read(buffer) != -1) {
buffer.flip();
System.out.println(Charset.forName("utf8").decode(buffer));
buffer.clear();
}
sc.close();
}
static void four() throws IOException {
// 以下地址是代理服务器的地址
Socket socket = new Socket(host, port);
// 写与的内容就是遵循HTTP请求协议格式的内容，请求百度
socket.getOutputStream().write(
new String("GET " + url + " HTTP/1.1\r\n\r\n").getBytes());
show(socket.getInputStream());
socket.close();
}
static void show(InputStream in) throws IOException {
Scanner cin = new Scanner(in);
StringBuilder builder = new StringBuilder();
while (cin.hasNext()) {
builder.append(cin.nextLine());
}
cin.close();
Pattern pattern = Pattern
.compile("\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}");
Matcher matcher = pattern.matcher(builder.toString());
matcher.find();
System.out.println(matcher.group());
}
}