HTTPClient系统学习
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HTTP协议时Internet上使用的很多也很重要的一个协议,越来越多的java应用程序需要通过HTTP协议来访问网络资源。
HTTPClient提供的主要功能:
1、实现了所有HTTP的方法(GET、POST、等PUT、HEAD);
2、支持自动转向;
3、支持HTTPS协议;
4、支持代理服务器等。
使用HttpClient需要以下6个步骤:
- 创建HttpClient的实例
- 创建某种连接方法的实例,GetMethod/PostMethod。在 GetMethod/PostMethod的构造函数中传入待连接的地址
- 调用第一步中创建好的实例的 execute 方法来执行第二步中创建好的 method 实例
- 读response
- 释放连接。无论执行方法是否成功,都必须释放连接
- 对得到后的内容进行处理
HTTP GET方法应用:
应用一:
String url = "";//构造HttpClient实例HttpClient httpClient = new HttpClient();//创建Get方法实例GetMethod getMethod = new GetMethod(url);//使用系统提供的默认的恢复策略getMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler( ));try{ int statusCode = httpClient.executeMethod(getMethod); if (statusCode == HttpStatus.SC_OK) { //方法一: byte[] respByte = getMethod.getResponseBody(); logger.info("返回信息:" + new String(respByte)); //方法二: String respStr = getMethod.getResponseBodyAsString(); logger.info("返回信息:" + respStr); } logger.error("Method failed: "+ getMethod.getStatusLine());}catch(HttpException e){ logger.error("发生致命的异常,可能是协议不对或者返回的内容有问题",e);}catch(IOException e){ logger.error("网络异常",e);}finally{ //释放连接 getMethod.releaseConnection();}
应用二:
public String getRequest(String url, String requestStr) { logger.debug("the getRest'params : url = " + "http://" + url + "?" + requestStr); String respStr = null; try { // 定义HttpClient DefaultHttpClient client = new DefaultHttpClient(); // 实例化HTTP方法 HttpGet request = new HttpGet(); url = url + "?" + requestStr; url = URLEncoder.encode(url, "UTF-8"); request.setURI(new URI("http://" + url)); HttpResponse response = client.execute(request); logger.debug("response status : " + response.getStatusLine().getStatusCode()); /**请求发送成功,并得到响应**/ if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { /**读取服务器返回过来的数据**/ respStr = EntityUtils.toString(response.getEntity()); } else { logger.error("get request fail:" + url); } }catch(Exception e){ logger.error("get request fail:" + url, e); } return respStr;}
HTTP POST方法应用:
POST方法用来向目的服务器发出请求,要求它接受被附在请求后的实体,并把它当作请求队列(Request-Line)中请求URI所指定资源的附加新子项。
应用一:
String url = "";String requestStr = "";//创建HttpClient实例HttpClient httpClient = new HttpClient();//创建Post方法实例PostMethod postMethod = new PostMethod(url);//******方法一:创建请求实体,发送请求start*************byte[] b = requestStr.getBytes();InputStream is = new ByteArrayInputStream(b, 0, b.length);RequestEntity re = new InputStreamRequestEntity(is, b.length, "text/xml; charset=UTF-8");//GBK//设置请求头postMethod.addRequestHeader("Content-Type", "application/x-www-form-urlencoded;charset=utf-8");//设置请求体postMethod.setRequestEntity(re);//******创建请求实体,发送请求end*************//******方法二:创建请求体,发送请求start*************// 构造名称值对节点类对象NameValuePair[] data = { new NameValuePair("id", "yourUserName"), new NameValuePair("passwd", "yourPwd") };// 设置请求体postMethod.setRequestBody(data);//******创建请求体,发送请求end*************try { int statusCode=httpClient.executeMethod(postMethod); if (statusCode == HttpStatus.SC_OK) { //方法一: String responseStr = postMethod.getResponseBodyAsString(); logger.info("返回信息:" + responseStr); //方法二: byte[] responseByte = postMethod.getResponseBody(); logger.info("返回信息:" + new String(responseByte)); } logger.error("Method failed: "+ postMethod.getStatusLine());} catch(HTTPException e){ logger.error("发生致命的异常,可能是协议不对或者返回的内容有问题",e);}catch (IOException e) { logger.error("网络异常",e);}finally{ //释放连接 postMethod.releaseConnection();}
注意:(自动转向问题的代码实现)
// HttpClient对于要求接受后继服务的请求,象POST和PUT等不能自动处理转发// 301(永久移走)或者302(暂时转向)if (statusCode == HttpStatus.SC_MOVED_PERMANENTLY || statusCode == HttpStatus.SC_MOVED_TEMPORARILY) {// 从头中取出转向的地址Header locationHeader = (Header) postMethod.getResponseHeader("location");if (locationHeader != null) { String location = locationHeader.getValue(); logger.info("The page was redirected to:" + location);} else { logger.info("Location field value is null.");}
应用二:
public static JSONObject httpPost(String url,JSONObject jsonParam, boolean noNeedResponse){ //post请求返回结果 DefaultHttpClient httpClient = new DefaultHttpClient(); JSONObject jsonResult = null; HttpPost method = new HttpPost(url); try { if (null != jsonParam) { //解决中文乱码问题 StringEntity entity = new StringEntity(jsonParam.toString(), "utf-8"); entity.setContentEncoding("UTF-8"); entity.setContentType("application/json"); method.setEntity(entity); } HttpResponse result = httpClient.execute(method); url = URLDecoder.decode(url, "UTF-8"); /**请求发送成功,并得到响应**/ if (result.getStatusLine().getStatusCode() == 200) { String str = ""; try { /**读取服务器返回过来的json字符串数据**/ str = EntityUtils.toString(result.getEntity()); if (noNeedResponse) { return null; } /**把json字符串转换成json对象**/ jsonResult = JSONObject.fromObject(str); } catch (Exception e) { logger.error("post请求提交失败:" + url, e); } } } catch (IOException e) { logger.error("post请求提交失败:" + url, e); } return jsonResult;}
使用HttpClient调用webservice服务:
import java.nio.charset.Charset;import org.apache.http.HttpEntity;import org.apache.http.client.config.RequestConfig;import org.apache.http.client.methods.CloseableHttpResponse;import org.apache.http.client.methods.HttpPost;import org.apache.http.entity.StringEntity;import org.apache.http.impl.client.CloseableHttpClient;import org.apache.http.impl.client.HttpClientBuilder;import org.apache.http.util.EntityUtils;import org.apache.log4j.Logger;/** * 使用HttpClient调用webservice服务 * @author lmb * @date 2017-4-18 */public class HttpClientCallSoapUtil { private static final Logger logger = Logger.getLogger(HttpClientCallSoapUtil.class); static int socketTimeout = 60000; static int connectTimeout = 60000; public static void main(String[] args) { String soapXml = "<?xml version = \"1.0\" ?>" + "<soapenv:Envelope xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:soapenv=\"http://schemas.xmlsoap.org/soap/envelope/\" xmlns:web=\"http://webservices.b.com\">" + " <soapenv:Header/>" + " <soapenv:Body>" + " <web:query soapenv:encodingStyle=\"http://schemas.xmlsoap.org/soap/encoding/\">" + " <in0 xsi:type=\"web:QueryRequest\">" + " <endTime xsi:type=\"xsd:dateTime\">?</endTime>" + " <mobile xsi:type=\"soapenc:string\" xmlns:soapenc=\"http://schemas.xmlsoap.org/soap/encoding/\">?</mobile>" + " <startTime xsi:type=\"xsd:dateTime\">?</startTime>" + " </in0>" + " </web:query>" + " </soapenv:Body>" + "</soapenv:Envelope>"; String postUrl = "http://localhost:8381/services/WebService"; doPostSoap(postUrl, soapXml, ""); } /** * HttpClient发送soap请求 * @param postUrl 请求webservice地址 * @param soapXml 请求报文 * @param soapAction * @return */ public static String doPostSoap(String postUrl, String soapXml, String soapAction) { String retStr = ""; // 创建HttpClientBuilder HttpClientBuilder httpClientBuilder = HttpClientBuilder.create(); // HttpClient CloseableHttpClient closeableHttpClient = httpClientBuilder.build(); HttpPost httpPost = new HttpPost(postUrl); // 设置请求和传输超时时间 RequestConfig requestConfig = RequestConfig.custom() .setSocketTimeout(socketTimeout) .setConnectTimeout(connectTimeout).build(); httpPost.setConfig(requestConfig); try { httpPost.setHeader("Content-Type", "text/xml;charset=UTF-8"); httpPost.setHeader("SOAPAction", soapAction); StringEntity data = new StringEntity(soapXml, Charset.forName("UTF-8")); httpPost.setEntity(data); CloseableHttpResponse response = closeableHttpClient .execute(httpPost); HttpEntity httpEntity = response.getEntity(); if (httpEntity != null) { // 打印响应内容 retStr = EntityUtils.toString(httpEntity, "UTF-8"); logger.info("response:" + retStr); } // 释放资源 closeableHttpClient.close(); } catch (Exception e) { logger.error("exception in doPostSoap1_1", e); } return retStr; } }
HttpClient常用方法总结:
import java.io.File;import java.io.FileInputStream;import java.security.KeyStore;import java.util.ArrayList;import java.util.List;import org.apache.http.Header;import org.apache.http.HttpEntity;import org.apache.http.HttpResponse;import org.apache.http.NameValuePair;import org.apache.http.client.CookieStore;import org.apache.http.client.HttpClient;import org.apache.http.client.methods.HttpGet;import org.apache.http.client.methods.HttpPost;import org.apache.http.conn.scheme.Scheme;import org.apache.http.conn.ssl.SSLSocketFactory;import org.apache.http.cookie.Cookie;import org.apache.http.entity.InputStreamEntity;import org.apache.http.impl.client.BasicCookieStore;import org.apache.http.impl.client.DefaultHttpClient;import org.apache.http.protocol.BasicHttpContext;import org.apache.http.protocol.HttpContext;/** * HttpClient常用方法总结 * @param args * @author lmb * @date 2017-4-18 */public class HttpClientUtil { //总结一:**********当httpClient的示例不在需要时,可以使用连接管理器关闭********** httpClient.getConnectionManager().shutdown(); //总结二:**********针对HTTPs的协议的HttpClient请求必须用户和密码 ********** httpclient.getCredentialsProvider() .setCredentials(new AuthScope("localhost", 443), new UsernamePasswordCredentials("username", "password")); //总结三:**********如果不想获取HTTPClient返回的信息********** httpclient.abort(); //总结四:**********httpclient传送文件的方式********** HttpClient httpclient = new DefaultHttpClient(); HttpPost httppost = new HttpPost("http://www.apache.org"); File file = new File(""); InputStreamEntity reqEntity = new InputStreamEntity( new FileInputStream(file), -1); reqEntity.setContentType("binary/octet-stream"); reqEntity.setChunked(true); // It may be more appropriate to use FileEntity class in this particular // instance but we are using a more generic InputStreamEntity to demonstrate // the capability to stream out data from any arbitrary source // // FileEntity entity = new FileEntity(file, "binary/octet-stream"); httppost.setEntity(reqEntity); System.out.println("executing request " + httppost.getRequestLine()); HttpResponse response = httpclient.execute(httppost); //总结五:**********获取Cookie的信息********** HttpClient httpclient = new DefaultHttpClient(); // 创建一个本地Cookie存储的实例 CookieStore cookieStore = new BasicCookieStore(); //创建一个本地上下文信息 HttpContext localContext = new BasicHttpContext(); //在本地上下问中绑定一个本地存储 localContext.setAttribute(ClientContext.COOKIE_STORE, cookieStore); //设置请求的路径 HttpGet httpget = new HttpGet("http://www.google.com/"); //传递本地的http上下文给服务器 HttpResponse response = httpclient.execute(httpget, localContext); //获取本地信息 HttpEntity entity = response.getEntity(); System.out.println(response.getStatusLine()); if (entity != null) { System.out.println("Response content length: " + entity.getContentLength()); } //获取cookie中的各种信息 List<Cookie> cookies = cookieStore.getCookies(); for (int i = 0; i < cookies.size(); i++) { System.out.println("Local cookie: " + cookies.get(i)); } //获取消息头的信息 Header[] headers = response.getAllHeaders(); for (int i = 0; i<headers.length; i++) { System.out.println(headers[i]); } //总结六:**********针对典型的SSL请求的处理********** DefaultHttpClient httpclient = new DefaultHttpClient(); //获取默认的存储密钥类 KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType()); //加载本地的密钥信息 FileInputStream instream = new FileInputStream(new File("my.keystore")); try { trustStore.load(instream, "nopassword".toCharArray()); } finally { instream.close(); } //创建SSLSocketFactory,创建相关的Socket SSLSocketFactory socketFactory = new SSLSocketFactory(trustStore); //设置协议的类型和密钥信息,以及断开信息 Scheme sch = new Scheme("https", socketFactory, 443); //在连接管理器中注册中信息 httpclient.getConnectionManager().getSchemeRegistry().register(sch); //总结七:**********设置请求的参数的几种方式********** //A.在请求的路径中以查询字符串格式传递参数 //B.在请求的实体中添加参数 List <NameValuePair> nvps = new ArrayList <NameValuePair>(); nvps.add(new BasicNameValuePair("IDToken1", "username")); nvps.add(new BasicNameValuePair("IDToken2", "password")); httpost.setEntity(new UrlEncodedFormEntity(nvps, HTTP.UTF_8));}
以下内容来自百度百科:
下面介绍在使用HttpClient过程中常见的一些问题。
1、字符编码
某目标页的编码可能出现在两个地方,第一个地方是服务器返回的http头中,另外一个地方是得到的html/xml页面中。
在http头的Content-Type字段可能会包含字符编码信息。例如可能返回的头会包含这样子的信息:Content-Type: text/html; charset=UTF-8。这个头信息表明该页的编码是UTF-8,但是服务器返回的头信息未必与内容能匹配上。比如对于一些双字节语言国家,可能服务器返回的编码类型是UTF-8,但真正的内容却不是UTF-8编码的,因此需要在另外的地方去得到页面的编码信息;但是如果服务器返回的编码不是UTF-8,而是具体的一些编码,比如gb2312等,那服务器返回的可能是正确的编码信息。通过method对象的getResponseCharSet()方法就可以得到http头中的编码信息。
对于象xml或者html这样的文件,允许作者在页面中直接指定编码类型。比如在html中会有<meta http-equiv="Content-Type" content="text/html; charset=gb2312"/>
这样的标签;或者在xml中会有<?xml version="1.0" encoding="gb2312"?>
这样的标签,在这些情况下,可能与http头中返回的编码信息冲突,需要用户自己判断到底那种编码类型应该是真正的编码。
2、自动转向
根据RFC2616中对自动转向的定义,主要有两种:301和302。301表示永久的移走(Moved Permanently),当返回的是301,则表示请求的资源已经被移到一个固定的新地方,任何向该地址发起请求都会被转到新的地址上。302表示暂时的转向,比如在服务器端的servlet程序调用了sendRedirect方法,则在客户端就会得到一个302的代码,这时服务器返回的头信息中location的值就是sendRedirect转向的目标地址。
HttpClient支持自动转向处理,但是象POST和PUT方式这种要求接受后继服务的请求方式,暂时不支持自动转向,因此如果碰到POST方式提交后返回的是301或者302的话需要自己处理。就像刚才在POSTMethod中举的例子:如果想进入登录BBS后的页面,必须重新发起登录的请求,请求的地址可以在头字段location中得到。不过需要注意的是,有时候location返回的可能是相对路径,因此需要对location返回的值做一些处理才可以发起向新地址的请求。
另外除了在头中包含的信息可能使页面发生重定向外,在页面中也有可能会发生页面的重定向。引起页面自动转发的标签是:<meta http-equiv="refresh" content="5; url=....">
。如果你想在程序中也处理这种情况的话得自己分析页面来实现转向。需要注意的是,在上面那个标签中url的值也可以是一个相对地址,如果是这样的话,需要对它做一些处理后才可以转发。
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