CAS在客户端进行登录验证

1.原理：

用户在发起登录请求，把自己的用户名和密码传到后台，后台使用httpclient进行模拟登录

登录成功后，CAS服务器会给httpclient发一个cookie（TGT，ticket granting ticket），

服务器会把这个cookie返回给用户，完成一次模拟登录的过程。

2.核心代码：

package ecen.mip.sys.action;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.cookie.Cookie;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HTTP;
import org.apache.log4j.Logger;
import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.Namespace;
import org.apache.struts2.convention.annotation.Result;
import org.apache.struts2.convention.annotation.Results;
import org.springframework.stereotype.Component;

@Namespace("/")
@Action("sysSingleSignOnAction")
@Component("sysSingleSignOnAction")
@Results({ @Result(name = "SUCCESS", location = "/sys/sys_new_index.jsp") })
public class SysSingleSignOnAction extends BaseAction {

	private static final long serialVersionUID = -2096730223578871319L;
	private static final Logger log = Logger.getLogger(SysSingleSignOnAction.class);
	final String server = "http://192.168.0.142:8080/cas/login";
	private String username;
	private String password;

	@Override
	public String execute() throws Exception {
		Cookie cookie = getTicketGrantingTicket(server, username, password);
		if(cookie!=null){
			getResponse().addCookie(convertToServletCookie(cookie));
			log.info("The user authenticated successfully whose nickname code is "+username+" ! ");
			return "SUCCESS";
		}
		return super.execute();
	}


	private Cookie getTicketGrantingTicket(final String server,final String username, final String password) throws IOException {
		DefaultHttpClient client = new DefaultHttpClient();
		HttpPost post = new HttpPost(server);

		List <NameValuePair> nvps = new ArrayList <NameValuePair>();  
		nvps.add(new BasicNameValuePair("username", username));
		nvps.add(new BasicNameValuePair("password", password));
		nvps.add(new BasicNameValuePair("lt", doCasLoginRequest(client, server)));
		nvps.add(new BasicNameValuePair("_eventId", "submit"));
		post.setEntity(new UrlEncodedFormEntity(nvps, HTTP.UTF_8));  
		try {
			HttpResponse response = client.execute(post);
			HttpEntity entity = response.getEntity();  
			if(entity!=null){
				Cookie cookie = getCookieValue(client, "CASTGC");
				entity.consumeContent();
				return cookie;
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		return null;
	}

	
	private Cookie getCookieValue(DefaultHttpClient httpclient, String name) {
		List<Cookie> cookies = httpclient.getCookieStore().getCookies();
		if (cookies.isEmpty()) {
			return null;
		} else {
			for (int i = 0; i < cookies.size(); i++) {
				Cookie cookie = cookies.get(i);
				if (cookie.getName().equalsIgnoreCase(name)) {
					return cookie;
				}
			}
		}
		return null;
	}
	
	
	private String doCasLoginRequest(DefaultHttpClient httpclient, String url) throws IOException {  
		     String result = "";  
		     HttpGet httpget = new HttpGet(url);  
		        HttpResponse response = httpclient.execute(httpget);  
		        HttpEntity entity = response.getEntity();  
		        BufferedReader rd = new BufferedReader(new InputStreamReader(entity.getContent(), "UTF-8"));  
		        String tempLine = rd.readLine();  
		        String s = "<input type=\"hidden\" name=\"lt\" value=\"";  
		        while (tempLine != null){  
		          int index = tempLine.indexOf(s);  
		             if(index != -1) {  
		              String s1 = tempLine.substring(index + s.length());  
		             int index1 = s1.indexOf("\"");  
		             if(index1 != -1)  
		              result = s1.substring(0, index1);  
		             }  
		            tempLine = rd.readLine();  
		        }  
		        if (entity != null) {  
		            entity.consumeContent();  
		        }  
		        return result;  
		    }

	
	private javax.servlet.http.Cookie convertToServletCookie(Cookie cookie){
		javax.servlet.http.Cookie retCookie = new javax.servlet.http.Cookie(cookie.getName(), cookie.getValue());
		retCookie.setComment(cookie.getComment());
		retCookie.setDomain(cookie.getDomain());
		retCookie.setHttpOnly(false);
		retCookie.setSecure(false);
		retCookie.setPath(cookie.getPath());
		retCookie.setVersion(cookie.getVersion());
		retCookie.setMaxAge((int) ((cookie.getExpiryDate().getTime()-System.currentTimeMillis())/1000));
		return retCookie;
	}
	
	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}  
	
}

写完就贴上来了，所以没写注释，不过，应该都能看懂吧

3.注意事项：

通过这种途径登录后，request.getRemoteUser()不能使用，具体原因还不知道。