最近突然想做一个网络爬虫，爬取微博上的用户信息。这里说一下第一步登录的思路和奉上部分代码。

1.获得登录的参数信息
    /**
     * 初始登录信息
     * 返回false说明初始失败
     */
    public boolean preLogin(){
        boolean flag = false;
        try {
            this.su = new String(Base64.encodeBase64(URLEncoder.encode(username, "UTF-8").getBytes()));
            String url = "http://login.sina.com.cn/sso/prelogin.php?entry=weibo&rsakt=mod&checkpin=1&client=ssologin.js(v1.4.5)&_="+getTimestamp();
            url = url +"&su"+this.su;
            String content;
            HttpGet httpGet = new HttpGet(url);
            httpGet.addHeader("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8");
            httpGet.addHeader("Accept-Encoding", "gzip, deflate, sdch");
            httpGet.addHeader("Accept-Language", "zh-CN,zh;q=0.8");
            httpGet.addHeader("Cache-Control", "max-age=0");
            httpGet.addHeader("Host", "login.sina.com.cn");
            httpGet.addHeader("Proxy-Connection", "keep-alive");
            httpGet.addHeader("Upgrade-Insecure-Requests", "1");
            httpGet.addHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/44.0.2403.157 Safari/537.36");
            content = HttpTools.getRequest(this.httpClient,httpGet);
            JSONObject json = new JSONObject(content);
            servertime = json.getLong("servertime");
            nonce = json.getString("nonce");
            rsakv = json.getString("rsakv");
            pubkey = json.getString("pubkey");
            flag = encodePwd();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return flag;
    }

2.开始登录 POST请求

public boolean login() {
        boolean flag = false;
        String loginUrl = "http://login.sina.com.cn:80/sso/login.php?client=ssologin.js(v1.4.18)";
        if (preLogin()) {
            HttpPost httpPost = new HttpPost(loginUrl);
            // 设置请求头
            httpPost.addHeader("Host", "login.sina.com.cn");
            httpPost.addHeader("Proxy-Connection", "keep-alive");
            httpPost.addHeader("Accept",
                    "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8");
            httpPost.addHeader("Origin", "http://weibo.com");
            httpPost.addHeader("Upgrade-Insecure-Requests", "1");
            httpPost.addHeader(
                    "User-Agent",
                    "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/44.0.2403.157 Safari/537.36");
            // httpPost.addHeader("User-Agent",
            // "Mozilla/5.0 (Windows NT 6.3; WOW64; Trident/7.0; rv:11.0) like Gecko");
            httpPost.addHeader("Content-Type",
                    "application/x-www-form-urlencoded");
            httpPost.addHeader("Referer", "http://weibo.com/");
            httpPost.addHeader("Accept-Encoding", "gzip, deflate");
            httpPost.addHeader("Accept-Language", "zh-CN,zh;q=0.8");
            // 设置请求参数
            List<NameValuePair> parms = new ArrayList<NameValuePair>();
            parms.add(new BasicNameValuePair("entry", "weibo"));
            parms.add(new BasicNameValuePair("geteway", "1"));
            parms.add(new BasicNameValuePair("from", ""));
            parms.add(new BasicNameValuePair("savestate", "0"));
            parms.add(new BasicNameValuePair("useticket", "1"));
            parms.add(new BasicNameValuePair("pagerefer", ""));
            parms.add(new BasicNameValuePair("vsnf", "1"));
            parms.add(new BasicNameValuePair("su", this.su));
            parms.add(new BasicNameValuePair("service", "miniblog"));
            parms.add(new BasicNameValuePair("servertime", this.servertime + ""));
            parms.add(new BasicNameValuePair("nonce", this.nonce));
            parms.add(new BasicNameValuePair("pwencode", "rsa2"));
            parms.add(new BasicNameValuePair("rsakv", this.rsakv));
            parms.add(new BasicNameValuePair("sp", this.sp));
            parms.add(new BasicNameValuePair("sr", "1366*768"));
            parms.add(new BasicNameValuePair("encoding", "UTF-8"));
            parms.add(new BasicNameValuePair("prelt", "83"));
            parms.add(new BasicNameValuePair(
                    "url",
                    "http://weibo.com/ajaxlogin.php?framelogin=1&callback=parent.sinaSSOController.feedBackUrlCallBack"));
            parms.add(new BasicNameValuePair("returntype", "META"));
            // 执行
            try {
                String content = HttpTools.postRequest(this.httpClient,
                        httpPost, parms);
                content = content.replaceAll("'", "\"");
                // 解析返回的数据，判断是否登录成功
                String regex = "location\\.replace\\(\"(.+?)\"\\);";
                Pattern p = Pattern.compile(regex);
                Matcher m = p.matcher(content);
                if (m.find()) {
                    location = m.group(1);
                    if (location.contains("reason=")) {
                        errInfo = location.substring(location
                                .indexOf("reason=") + 7);
                        errInfo = URLDecoder.decode(errInfo, "UTF-8");
                    } else {
                        location = URLDecoder.decode(location, "UTF-8");
                        flag = ajaxLogin(location);
                    }
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return flag;
    }

public boolean ajaxLogin(String ajaxUrl){
        boolean flag = false;
        HttpGet ajaxGet = new HttpGet(ajaxUrl);
        String content ;
        try {
            content = HttpTools.getRequest(this.httpClient, ajaxGet);
            int beginIndex = content.indexOf("(");
            int endIndex = content.lastIndexOf(")");
            content = content.substring(beginIndex+1, endIndex);
            content = URLDecoder.decode(content, "UTF-8");
            JSONObject jsonObject = new JSONObject(content);
            this.uniqueid = jsonObject.getJSONObject("userinfo").getString("uniqueid");
            this.userdomain = jsonObject.getJSONObject("userinfo").getString("userdomain");
//          String lastUrl = "http://weibo.com/u/"+uniqueid+userdomain;
            //HttpTools.getRequest(httpClient, lastUrl);
            flag = true;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return flag;
    }

其中对用户名和密码加密部分百度一下你就知道。