最近忙于一个项目,了解下httpclient,在这里总结出来,和大家一起学习分享,希望各位朋友提出宝贵的意见。
首先介绍一下项目的背景:
目标:把国内一家保险公司的“WEB一账通”改成“WAP一账通”。
资源:客户不提供任何的webservice接口。
本项目中用到的第三方组件是apache的httpclient,一个非常强大的网页抓取工具(抓这个字用得可能不太好), 这里和大家
一起讨论下httpclient的一些常用用法和要注意的地方。
本文引用的资源列表:
httpclient入门: http://www.ibm.com/developerworks/cn/opensource/os-httpclient/
httpclient证书导入:http://www.blogjava.net/happytian/archive/2006/12/22/89447.html
httpclient高级认识:http://laohuang.iteye.com/blog/55613
httpclient官方文档:http://hc.apache.org/httpcomponents-client/index.html
httpclient资源关闭:http://www.iteye.com/topic/234759
上面的文章写得很好,看完之后也就知道怎么用httpclient这个很好的工具了,但是在这里还是补充一些比较重要的东西,也是项目中经
常碰到的问题。
首先要注意的有以下几点:
1、httpclient连接后资源释放问题很重要,就跟我们用database connection要释放资源一样。
2、https网站采用ssl加密传输,证书导入要注意。
3、做这样的项目最好先了解下http协义,比如302,301,200,404返回代码的含义(这是最基本的),cookie,session的机制。
4、httpclient的redirect状态默认是自动的,这在很大程度上给开发者很大的方便(如一些授权获得cookie),但是有时要手动管理下,比如
有时会遇到CircularRedirectException异常,出现这样的情况是因为返回的头文件中location值指向之前重复(端口号可以不同)地址,导致可能会出现死
循环递归重定向,这时可以手动关闭:method.setFollowRedirects(false)
5、有的网站会先判别用户的请求是否是来自浏览器,如不是,则返回不正确的文本,所以用httpclient抓取信息时在头部加入如下信息:
header.put("User-Agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 1.7; .NET CLR 1.1.4322; CIBA; .NET CLR 2.0.50727)");
6、当post请求提交数据时要改变默认编码,不然的话提交上去的数据会出现乱码。重写postMethod的setContentCharSet()方法就可以了:
下面写一个通用类来处理request请求返回的文本:
Java代码
- /*
- * HttpRequestProxy.java
- *
- * Created on November 3, 2008, 9:53 AM
- */
-
- package cn.com.mozat.net;
-
- import java.io.BufferedReader;
- import java.io.IOException;
- import java.io.InputStream;
- import java.io.InputStreamReader;
- import java.util.HashMap;
- import java.util.Iterator;
- import java.util.Map;
- import java.util.Set;
-
- import org.apache.commons.httpclient.Header;
- import org.apache.commons.httpclient.HttpClient;
- import org.apache.commons.httpclient.HttpException;
- import org.apache.commons.httpclient.HttpMethod;
- import org.apache.commons.httpclient.NameValuePair;
- import org.apache.commons.httpclient.SimpleHttpConnectionManager;
- import org.apache.commons.httpclient.methods.GetMethod;
- import org.apache.commons.httpclient.methods.PostMethod;
-
- import cn.com.mozat.exception.CustomException;
-
- /**
- *
- * @author bird email:lihongfu-84@163.com
- *
- * 2008-11-4 09:49:48
- */
- public class HttpRequestProxy{
- //超时间隔
- private static int connectTimeOut = 60000;
- //让connectionmanager管理httpclientconnection时是否关闭连接
- private static boolean alwaysClose = false;
- //返回数据编码格式
- private String encoding = "UTF-8";
-
- private final HttpClient client = new HttpClient(new SimpleHttpConnectionManager(alwaysClose));
-
- public HttpClient getHttpClient(){
- return client;
- }
-
- /**
- * 用法:
- * HttpRequestProxy hrp = new HttpRequestProxy();
- * hrp.doRequest("http://www.163.com",null,null,"gbk");
- *
- * @param url 请求的资源URL
- * @param postData POST请求时form表单封装的数据 没有时传null
- * @param header request请求时附带的头信息(header) 没有时传null
- * @param encoding response返回的信息编码格式 没有时传null
- * @return response返回的文本数据
- * @throws CustomException
- */
- public String doRequest(String url,Map postData,Map header,String encoding) throws CustomException{
- String responseString = null;
- //头部请求信息
- Header[] headers = null;
- if(header != null){
- Set entrySet = header.entrySet();
- int dataLength = entrySet.size();
- headers= new Header[dataLength];
- int i = 0;
- for(Iterator itor = entrySet.iterator();itor.hasNext();){
- Map.Entry entry = (Map.Entry)itor.next();
- headers[i++] = new Header(entry.getKey().toString(),entry.getValue().toString());
- }
- }
- //post方式
- if(postData!=null){
- PostMethod postRequest = new PostMethod(url.trim());
- if(headers != null){
- for(int i = 0;i < headers.length;i++){
- postRequest.setRequestHeader(headers[i]);
- }
- }
- Set entrySet = postData.entrySet();
- int dataLength = entrySet.size();
- NameValuePair[] params = new NameValuePair[dataLength];
- int i = 0;
- for(Iterator itor = entrySet.iterator();itor.hasNext();){
- Map.Entry entry = (Map.Entry)itor.next();
- params[i++] = new NameValuePair(entry.getKey().toString(),entry.getValue().toString());
- }
- postRequest.setRequestBody(params);
- try {
- responseString = this.executeMethod(postRequest,encoding);
- } catch (CustomException e) {
- throw e;
- } finally{
- postRequest.releaseConnection();
- }
- }
- //get方式
- if(postData == null){
- GetMethod getRequest = new GetMethod(url.trim());
- if(headers != null){
- for(int i = 0;i < headers.length;i++){
- getRequest.setRequestHeader(headers[i]);
- }
- }
- try {
- responseString = this.executeMethod(getRequest,encoding);
- } catch (CustomException e) {
- e.printStackTrace();
- throw e;
- }finally{
- getRequest.releaseConnection();
- }
- }
-
- return responseString;
- }
-
- private String executeMethod(HttpMethod request, String encoding) throws CustomException{
- String responseContent = null;
- InputStream responseStream = null;
- BufferedReader rd = null;
- try {
- this.getHttpClient().executeMethod(request);
- if(encoding != null){
- responseStream = request.getResponseBodyAsStream();
- rd = new BufferedReader(new InputStreamReader(responseStream,
- encoding));
- String tempLine = rd.readLine();
- StringBuffer tempStr = new StringBuffer();
- String crlf=System.getProperty("line.separator");
- while (tempLine != null)
- {
- tempStr.append(tempLine);
- tempStr.append(crlf);
- tempLine = rd.readLine();
- }
- responseContent = tempStr.toString();
- }else
- responseContent = request.getResponseBodyAsString();
-
- Header locationHeader = request.getResponseHeader("location");
- //返回代码为302,301时,表示页面己经重定向,则重新请求location的url,这在
- //一些登录授权取cookie时很重要
- if (locationHeader != null) {
- String redirectUrl = locationHeader.getValue();
- this.doRequest(redirectUrl, null, null,null);
- }
- } catch (HttpException e) {
- throw new CustomException(e.getMessage());
- } catch (IOException e) {
- throw new CustomException(e.getMessage());
-
- } finally{
- if(rd != null)
- try {
- rd.close();
- } catch (IOException e) {
- throw new CustomException(e.getMessage());
- }
- if(responseStream != null)
- try {
- responseStream.close();
- } catch (IOException e) {
- throw new CustomException(e.getMessage());
-
- }
- }
- return responseContent;
- }
-
-
- /**
- * 特殊请求数据,这样的请求往往会出现redirect本身而出现递归死循环重定向
- * 所以单独写成一个请求方法
- * 比如现在请求的url为:http://localhost:8080/demo/index.jsp
- * 返回代码为302 头部信息中location值为:http://localhost:8083/demo/index.jsp
- * 这时httpclient认为进入递归死循环重定向,抛出CircularRedirectException异常
- * @param url
- * @return
- * @throws CustomException
- */
- public String doSpecialRequest(String url,int count,String encoding) throws CustomException{
- String str = null;
- InputStream responseStream = null;
- BufferedReader rd = null;
- GetMethod getRequest = new GetMethod(url);
- //关闭httpclient自动重定向动能
- getRequest.setFollowRedirects(false);
- try {
-
- this.client.executeMethod(getRequest);
- Header header = getRequest.getResponseHeader("location");
- if(header!= null){
- //请求重定向后的URL,count同时加1
- this.doSpecialRequest(header.getValue(),count+1, encoding);
- }
- //这里用count作为标志位,当count为0时才返回请求的URL文本,
- //这样就可以忽略所有的递归重定向时返回文本流操作,提高性能
- if(count == 0){
- getRequest = new GetMethod(url);
- getRequest.setFollowRedirects(false);
- this.client.executeMethod(getRequest);
- responseStream = getRequest.getResponseBodyAsStream();
- rd = new BufferedReader(new InputStreamReader(responseStream,
- encoding));
- String tempLine = rd.readLine();
- StringBuffer tempStr = new StringBuffer();
- String crlf=System.getProperty("line.separator");
- while (tempLine != null)
- {
- tempStr.append(tempLine);
- tempStr.append(crlf);
- tempLine = rd.readLine();
- }
- str = tempStr.toString();
- }
-
- } catch (HttpException e) {
- throw new CustomException(e.getMessage());
- } catch (IOException e) {
- throw new CustomException(e.getMessage());
- } finally{
- getRequest.releaseConnection();
- if(rd !=null)
- try {
- rd.close();
- } catch (IOException e) {
- throw new CustomException(e.getMessage());
- }
- if(responseStream !=null)
- try {
- responseStream.close();
- } catch (IOException e) {
- throw new CustomException(e.getMessage());
- }
- }
- return str;
- }
-
-
-
-
- public static void main(String[] args) throws Exception{
- HttpRequestProxy hrp = new HttpRequestProxy();
- Map header = new HashMap();
- header.put("User-Agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 1.7; .NET CLR 1.1.4322; CIBA; .NET CLR 2.0.50727)");
- String str = hrp.doRequest(
- "http://www.cma-cgm.com/en/eBusiness/Tracking/Default.aspx?BolNumber=GZ2108827",
- null, header,null);
- System.out.println(str.contains("row_CRXU1587647"));
- // System.out.println(str);
- }
-
- }