远程接口调用方式HttpClient
问题：现在我们已经开发好了接口了，那该如何调用这个接口呢？
答：使用Httpclient客户端。
Httpclient简介
什么是httpclient
HttpClient 是 Apache Jakarta Common 下的子项目，用来提供高效的、最新的、功能丰富的支持 HTTP 协议的客户端编程工具包，并且它支持 HTTP 协议最新的版本和建议。实现了所有 HTTP 的方法（GET,POST,PUT,HEAD 等）
下载地址：http://hc.apache.org/
httpclient作用
在java代码中，发送Http请求。通常用来实现远程接口调用。
HttpClient测试
在工程中添加httpclient的pom依赖。
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
</dependency>
执行GET请求
public static void doGet(){ // 创建Httpclient对象 CloseableHttpClient httpclient = HttpClients.createDefault(); // 创建http GET请求 HttpGet httpGet = new HttpGet("http://www.oschina.net/"); CloseableHttpResponse response = null; try { // 执行请求 response = httpclient.execute(httpGet); System.out.println(response.getStatusLine()); // 判断返回状态是否为200 if (response.getStatusLine().getStatusCode() == 200) { String content = EntityUtils.toString(response.getEntity(), "UTF-8"); System.out.println("内容长度：" + content.length()); } }catch(Exception e){ e.printStackTrace(); } finally { if (response != null) { try { response.close(); } catch (IOException e) { e.printStackTrace(); } } try { httpclient.close(); } catch (IOException e) { e.printStackTrace(); } }
执行GET带参数
public static void doGetParam(){ // 创建Httpclient对象 CloseableHttpClient httpclient = HttpClients.createDefault(); CloseableHttpResponse response = null; try { // 定义请求的参数 URI uri = new URIBuilder("http://www.baidu.com/s").setParameter("wd", "数据库").build(); System.out.println(uri); // 创建http GET请求 HttpGet httpGet = new HttpGet(uri); // 执行请求 response = httpclient.execute(httpGet); // 判断返回状态是否为200 if (response.getStatusLine().getStatusCode() == 200) { String content = EntityUtils.toString(response.getEntity(), "UTF-8"); System.out.println(content); } }catch(Exception e){ e.printStackTrace(); }finally { if (response != null) { try { response.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } try { httpclient.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }
执行post请求
public static void doPost(){ // 创建Httpclient对象 CloseableHttpClient httpclient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build(); // 创建http POST请求 HttpPost httpPost = new HttpPost("http://www.oschina.net/"); CloseableHttpResponse response = null; try { // 执行请求 response = httpclient.execute(httpPost); System.out.println(response.getStatusLine()); // 判断返回状态是否为200 if (response.getStatusLine().getStatusCode() == 200) { String content = EntityUtils.toString(response.getEntity(), "UTF-8"); System.out.println(content); } }catch(Exception e){ e.printStackTrace(); }finally { if (response != null) { try { response.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } try { httpclient.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }
执行post带参数
public static void doPostParam() throws Exception{ // 创建Httpclient对象 CloseableHttpClient httpclient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build(); // 创建http POST请求 HttpPost httpPost = new HttpPost("http://www.oschina.net/search"); // 设置2个post参数，一个是scope、一个是q List<NameValuePair> parameters = new ArrayList<NameValuePair>(); parameters.add(new BasicNameValuePair("scope", "project")); parameters.add(new BasicNameValuePair("q", "java")); // 构造一个form表单式的实体 UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(parameters); // 将请求实体设置到httpPost对象中 httpPost.setEntity(formEntity); CloseableHttpResponse response = null; try { // 执行请求 response = httpclient.execute(httpPost); System.out.println(response.getStatusLine()); // 判断返回状态是否为200 if (response.getStatusLine().getStatusCode() == 200) { String content = EntityUtils.toString(response.getEntity(), "UTF-8"); System.out.println(content); } } finally { if (response != null) { response.close(); } httpclient.close(); } }
httpclient常见问题及解决方案
请求参数乱码
设置请求的编码格式：
obj.addHeader("Content-Type","application/x-www-form-urlencoded; charset=UTF-8");
响应HTTP/1.1 403 Forbidden
原因：网站设置了反爬虫机制，禁止非法访问。
解决方案：伪装浏览器。
obj.addHeader("User-Agent"," Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537. 36 (KHTML, like Gecko) Chrome/31.0.1650.63")
封装通用工具类HttpClientUtils
package org.chu.ego.base.utils; import java.io.IOException; import java.util.ArrayList; import java.util.List; import java.util.Map; import org.apache.http.HttpEntity; import org.apache.http.NameValuePair; import org.apache.http.client.entity.UrlEncodedFormEntity; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpGet; import org.apache.http.client.methods.HttpPost; import org.apache.http.client.utils.URIBuilder; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClientBuilder; import org.apache.http.impl.client.HttpClients; import org.apache.http.impl.client.LaxRedirectStrategy; import org.apache.http.message.BasicNameValuePair; import org.apache.http.util.EntityUtils; /** * --发送get请求的api * CloseableHttpClient类 ，client实现类 * HttpClients类 ，client工具类，用于创建客户端对象。 * CloseableHttpResponse接口，请求的响应对象 * URIBuilder类 ：url构建类，用于设置get请求的路径变量 * HttpGet类 ：get请求的发送对象 * EntityUtils类 实体处理类 * * --发送post 请求使用的api * CloseableHttpClient类 * HttpClientBuilder client构建对象，用于创建客户端对象。 * LaxRedirectStrategy类，post请求重定向的策略 * CloseableHttpResponse 请求的响应对象 * HttpPost post请求的发送对象 * NameValuePair 类，用于设置参数值 * UrlEncodedFormEntity：用于设置表单参数给发送对象HttpPost * * @author ranger * */ public class HttpClientUtils { public static String doGet(String url,Map<String, String> params){ //获取httpclient客户端 CloseableHttpClient httpclient = HttpClients.createDefault(); String resultString = ""; CloseableHttpResponse response = null; try { URIBuilder builder = new URIBuilder(url); if(null!=params){ for (String key:params.keySet()) { builder.setParameter(key, params.get(key)); } } HttpGet get = new HttpGet(builder.build()); response = httpclient.execute(get); System.out.println(response.getStatusLine()); if(200==response.getStatusLine().getStatusCode()){ HttpEntity entity = response.getEntity(); resultString = EntityUtils.toString(entity, "utf-8"); } } catch (Exception e) { e.printStackTrace(); } finally { if(null!=response){ try { response.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } if(null!=httpclient){ try { httpclient.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } return resultString; } public static String doGet(String url){ return doGet(url, null); } public static String doPost(String url,Map<String,String> params){ /** * 在4.0及以上httpclient版本中，post需要指定重定向的策略，如果不指定则按默认的重定向策略。 * * 获取httpclient客户端 */ CloseableHttpClient httpclient = HttpClientBuilder.create().setRedirectStrategy( new LaxRedirectStrategy()).build(); String resultString = ""; CloseableHttpResponse response = null; try { HttpPost post = new HttpPost(url); List<NameValuePair> paramaters = new ArrayList<>(); if(null!=params){ for (String key : params.keySet()) { paramaters.add(new BasicNameValuePair(key,params.get(key))); } UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity (paramaters); post.setEntity(formEntity); } /** * HTTP/1.1 403 Forbidden * 原因： * 有些网站，设置了反爬虫机制 * 解决的办法： * 设置请求头，伪装浏览器 */ post.addHeader("user-agent", "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"); response = httpclient.execute(post); System.out.println(response.getStatusLine()); if(200==response.getStatusLine().getStatusCode()){ HttpEntity entity = response.getEntity(); resultString = EntityUtils.toString(entity, "utf-8"); } } catch (Exception e) { e.printStackTrace(); } finally { if(null!=response){ try { response.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } if(null!=httpclient){ try { httpclient.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } return resultString; } public static String doPost(String url){ return doPost(url, null); } }
