转自：http://resolute.javaeye.com/blog/491701
commons-httpclient是apache下的一个开源项目，提供了一个纯java实现的http客户端。使用它能够非常方便发送HTTP请求，接受HTTP应答，自己主动管理Cookie等等。
对于contact-list类库来说，须要使用的功能有，自己主动管理Cookie，设置HTTP头。发送HTTP请求，接受HTTP应答，转发HTTP重定向，还有输出HTTP请求/应答日志，以下对这些功能的实现进行解释：
1. 自己主动管理Cookie
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1.public EmailImporter(String email, String password, String encoding) {
2. ......
3. client = new HttpClient();
4. client.getParams().setCookiePolicy(CookiePolicy.BROWSER_COMPATIBILITY);
5. client.getParams().setParameter("http.protocol.single-cookie-header", true);
6.}
当中将HttpClient的Cookie策略设置为CookiePolicy.BROWSER_COMPATIBILITY，即表示java client将依照浏览器的方式来自己主动处理Cookie。当然你也能够在执行过程中手动调整cookie。比方：
hotmail登录之前须要设置当前时间的Cookie：
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1.client.getState().addCookie(new Cookie("login.live.com", "CkTst", "G" + new Date().getTime()));
只是，httpclient似乎没有提供删除cookie的功能，于是我添加了两个cookie管理的接口。一个是保留指定的cookies，一个是删除指定的cookies：
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01.protected void retainCookies(String[] cookieNames) {
02. Cookie[] cookies = client.getState().getCookies();
03. ArrayList<Cookie> retainCookies = new ArrayList<Cookie>();
04. for (Cookie cookie : cookies) {
05. if (Arrays.binarySearch(cookieNames, cookie.getName()) >= 0) {
06. retainCookies.add(cookie);
07. }
08. }
09. client.getState().clearCookies();
10. client.getState().addCookies(retainCookies.toArray(new Cookie[0]));
11.}
12.
13.protected void removeCookies(String[] cookieNames) {
14. Cookie[] cookies = client.getState().getCookies();
15. ArrayList<Cookie> retainCookies = new ArrayList<Cookie>();
16. for (Cookie cookie : cookies) {
17. if (Arrays.binarySearch(cookieNames, cookie.getName()) < 0) {
18. retainCookies.add(cookie);
19. }
20. }
21. client.getState().clearCookies();
22. client.getState().addCookies(retainCookies.toArray(new Cookie[0]));
23.}
2. 设置HTTP头：
http头的设置，能够让邮件server觉得是在和浏览器打交道，而避免被refuse的可能：
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01.private void setHeaders(HttpMethod method) {
02. method.setRequestHeader("Accept", "text/html,application/xhtml+xml,application/xml;");
03. method.setRequestHeader("Accept-Language", "zh-cn");
04. method.setRequestHeader("User-Agent", "Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.0.3) Gecko/2008092417 Firefox/3.0.3");
05. method.setRequestHeader("Accept-Charset", encoding);
06. method.setRequestHeader("Keep-Alive", "300");
07. method.setRequestHeader("Connection", "Keep-Alive");
08. method.setRequestHeader("Cache-Control", "no-cache");
09.}
另外，在GET和POST的时候设置referer值。以及在POST的时候设置Content-Type：
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1.protected String doPost(String actionUrl, NameValuePair[] params, String referer) throws HttpException, IOException {
2. ......
3. method.setRequestHeader("Referer", referer);
4. method.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
5. ......
6.}
3. 发送HTTP请求，接收HTTP应答。
在contact-list中仅仅使用了GET和POST请求，我也做了简单的封装：
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01.protected String doGet(String url, String referer) throws HttpException, IOException {
02. GetMethod method = new GetMethod(url);
03. setHeaders(method);
04. method.setRequestHeader("Referer", referer);
05. // log request
06. client.executeMethod(method);
07. String responseStr = readInputStream(method.getResponseBodyAsStream());
08. // log response
09. method.releaseConnection();
10. lastUrl = method.getURI().toString();
11. return responseStr;
12.}
13.
14.protected String doPost(String actionUrl, NameValuePair[] params, String referer) throws HttpException, IOException {
15. PostMethod method = new PostMethod(actionUrl);
16. setHeaders(method);
17. method.setRequestHeader("Referer", referer);
18. method.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
19. method.setRequestBody(params);
20. // log request
21. client.executeMethod(method);
22. String responseStr = readInputStream(method.getResponseBodyAsStream());
23. // log response
24. method.releaseConnection();
25. if (method.getResponseHeader("Location") != null) {
26. // do redirect
27. } else {
28. lastUrl = method.getURI().toString();
29. return responseStr;
30. }
31.}
4. HTTP重定向，主要是两种，一种是依据HTTP头的Location
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1.if (method.getResponseHeader("Location").getValue().startsWith("http")) {
2. return doGet(method.getResponseHeader("Location").getValue());
3.} else {
4. return doGet("http://" + getResponseHost(method) + method.getResponseHeader("Location").getValue());
5.}
还有一种是依据javascript中的window.location.replace。
5. 输出请求/应答日志。这个对调试很重要：
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01.private void logGetRequest(GetMethod method) throws URIException {
02. logger.debug("do get request: " + method.getURI().toString());
03. logger.debug("header:/n" + getHeadersStr(method.getRequestHeaders()));
04. logger.debug("cookie:/n" + getCookieStr());
05.}
06.
07.private void logGetResponse(GetMethod method, String responseStr) throws URIException {
08. logger.debug("do get response: " + method.getURI().toString());
09. logger.debug("header: /n" + getHeadersStr(method.getResponseHeaders()));
10. logger.debug("body: /n" + responseStr);
11.}
12.
13.private void logPostRequest(PostMethod method) throws URIException {
14. logger.debug("do post request: " + method.getURI().toString());
15. logger.debug("header:/n" + getHeadersStr(method.getRequestHeaders()));
16. logger.debug("body:/n" + getPostBody(method.getParameters()));
17. logger.debug("cookie:/n" + getCookieStr());
18.}
19.
20.private void logPostResponse(PostMethod method, String responseStr) throws URIException {
21. logger.debug("do post response:" + method.getURI().toString());
22. logger.debug("header:/n" + getHeadersStr(method.getResponseHeaders()));
23. logger.debug("body:/n" + responseStr);
24.}
25.
26.private String getHeadersStr(Header[] headers) {
27. StringBuilder builder = new StringBuilder();
28. for (Header header : headers) {
29. builder.append(header.getName()).append(": ").append(header.getValue()).append("/n");
30. }
31. return builder.toString();
32.}
33.
34.private String getPostBody(NameValuePair[] postValues) {
35. StringBuilder builder = new StringBuilder();
36. for (NameValuePair pair : postValues) {
37. builder.append(pair.getName()).append(":").append(pair.getValue()).append("/n");
38. }
39. return builder.toString();
40.}
41.
42.private String getCookieStr() {
43. Cookie[] cookies = client.getState().getCookies();
44. StringBuilder builder = new StringBuilder();
45. for (Cookie cookie : cookies) {
46. builder.append(cookie.getDomain()).append(":")
47. .append(cookie.getName()).append("=").append(cookie.getValue()).append(";")
48. .append(cookie.getPath()).append(";")
49. .append(cookie.getExpiryDate()).append(";")
50. .append(cookie.getSecure()).append(";/n");
51. }
52. return builder.toString();
53.}