HttpClient是目前我们通讯组件中最常见的一个Api了吧。至少从我目前接触到与外部系统通讯的话是这样的。下面我将我自己常用的一些知识总结一下。

因为本猿也是边写边总结，有啥不对的还望多多指出。

1：利用httpClient发送https请求。

第一次遇到这种情况是开发与微信支付的接口。适用情形https请求，报文格式：字符串（包含json字符串和xml字符串）。

public String doPost(String url,String charset,String reqXmlData){
  HttpClient httpClient = null;
  HttpPost httpPost = null;
  String result = null;
  try{
   //这里是关键，SSLClient继承了DefaultHttpClient 忽略https校验过程。SSLClient具体如下。
   httpClient = new SSLClient();
   logger.info("call weixin pay url："+url);
   httpPost = new HttpPost(url);
   logger.info("call weixin pay requestXmlData："+reqXmlData);
   //设置最简单的字符串请求参数
   StringEntity strEntity = new StringEntity(reqXmlData, charset);
   httpPost.setEntity(strEntity);
   HttpResponse response = httpClient.execute(httpPost);
   int code = response.getStatusLine().getStatusCode();   
   if(code == 200){
    HttpEntity resEntity = response.getEntity();
    if(resEntity != null){
     result = EntityUtils.toString(resEntity,charset);
    }
   }else{
    //这里就不对其他code处理了
   }
   logger.info("call weixin pay responseXmlData："+result);
  }catch(Exception ex){
   ex.printStackTrace();
  }finally{
   if (httpClient != null){
    httpClient = null;
   }
  }
  return result;
 }

/**
 * 用于进行Https请求的HttpClient
 */
public class SSLClient extends DefaultHttpClient{
 public SSLClient() throws Exception{
        super();
        SSLContext ctx = SSLContext.getInstance("TLS");
        X509TrustManager tm = new X509TrustManager() {
                @Override
                public void checkClientTrusted(X509Certificate[] chain,
                        String authType) throws CertificateException {
                }
                @Override
                public void checkServerTrusted(X509Certificate[] chain,
                        String authType) throws CertificateException {
                }
                @Override
                public X509Certificate[] getAcceptedIssuers() {
                    return null;
                }
        };
        ctx.init(null, new TrustManager[]{tm}, null);
        SSLSocketFactory ssf = new SSLSocketFactory(ctx,SSLSocketFactory.ALLOW_ALL_HOSTNAME_VERIFIER);
        ClientConnectionManager ccm = this.getConnectionManager();
        SchemeRegistry sr = ccm.getSchemeRegistry();
        sr.register(new Scheme("https", 443, ssf));
    }
}

好了，今天就先更新到这里了。下班肥家。20151207

第二点：利用httpclient来模拟表单提交（兼容http请求和https请求）

相信有很多人遇到过和我一样的情形，与外部系统对接时。经常是测试环境使用的是http请求而生产正式环境则是https请求。这时候我是这样做的。

public static String httpPost(String reqUrl, BaseDto baseDto){
  DefaultHttpClient httpclient = new DefaultHttpClient();
  String result = "";
   try {
    if(reqUrl.startsWith("https")){
     logger.debug("请求地址为https请求");
     httpclient = new SSLClient();
    }

　//设置超时时间
    httpclient.getParams().setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, TIME_OUT * 1000);
    httpclient.getParams().setParameter(CoreConnectionPNames.SO_TIMEOUT, TIME_OUT * 1000);
    HttpPost httppost = new HttpPost(reqUrl);
    logger.debug("调用地址"+reqUrl);

//定义一个用来存储表单数据的集合
    List formParams = new ArrayList();
    formParams.add(new BasicNameValuePair("merchant_id", baseDto.getMerchant_id()));
    formParams.add(new BasicNameValuePair("key_enc", baseDto.getKey_enc()));
    formParams.add(new BasicNameValuePair("sign", baseDto.getSign()));
    formParams.add(new BasicNameValuePair("xml_enc", baseDto.getXml_enc()));

//UrlEncodedFormEntity与StringEntity相比较的话只能接受键值对的形式，试用与表单提交
    HttpEntity entity = new UrlEncodedFormEntity(formParams, "UTF-8");
    httppost.setEntity(entity);
    HttpResponse response=httpclient.execute(httppost);
    int httpCode = response.getStatusLine().getStatusCode();
    logger.debug("返回的code："+httpCode);
    switch (httpCode) {
    case 200:
     HttpEntity resEntity=response.getEntity();
     result = EntityUtils.toString(resEntity,"UTF-8");
     logger.debug("通讯原始结果："+result);
     return result;
    case 401:
     logger.debug("请求要求进行身份验证");
    case 403:
     logger.debug("请求被拒绝，请检查IP地址是否已经加入对方白名单");
    case 404:
     logger.debug("未找到，服务器找不到请求的地址");
    case 405:
     logger.debug("方法不允许，请确认是否为POST请求方式");
    case 500:
     logger.debug("查询请求失败，内部错误");
    default:
     logger.debug("未知的返回码：" + httpCode);
    }
   }  catch (Exception e) {
    e.printStackTrace();
    throw new ServiceException(e,"0006","获取渠道返回信息失败了，可能是超时了");
   }
 }

好了，今天就先更新到这里了，后面继续来整理利用httpclient来进行爬虫。httpclient的超时设置等等。20151208