HttpClient使用详解

转载自:https://www.cnblogs.com/guxiong/p/6661272.html

一、使用方法

使用HttpClient发送请求、接收响应很简单，一般需要如下几步即可。

1. 创建HttpClient对象。

2. 创建请求方法的实例，并指定请求URL。如果需要发送GET请求，创建HttpGet对象；如果需要发送POST请求，创建HttpPost对象。

3. 如果需要发送请求参数，可调用HttpGet、HttpPost共同的setParams(HetpParams params)方法来添加请求参数；对于HttpPost对象而言，也可调用setEntity(HttpEntity entity)方法来设置请求参数。

4. 调用HttpClient对象的execute(HttpUriRequest request)发送请求，该方法返回一个HttpResponse。

5. 调用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可获取服务器的响应头；调用HttpResponse的getEntity()方法可获取HttpEntity对象，该对象包装了服务器的响应内容。程序可通过该对象获取服务器的响应内容。

6. 释放连接。无论执行方法是否成功，都必须释放连接

二、实例

  1 import java.io.IOException;
  2 import java.net.URI;
  3 import java.util.ArrayList;
  4 import java.util.List;
  5 import java.util.Map;
  6 
  7 import org.apache.http.NameValuePair;
  8 import org.apache.http.client.entity.UrlEncodedFormEntity;
  9 import org.apache.http.client.methods.CloseableHttpResponse;
 10 import org.apache.http.client.methods.HttpGet;
 11 import org.apache.http.client.methods.HttpPost;
 12 import org.apache.http.client.utils.URIBuilder;
 13 import org.apache.http.entity.ContentType;
 14 import org.apache.http.entity.StringEntity;
 15 import org.apache.http.impl.client.CloseableHttpClient;
 16 import org.apache.http.impl.client.HttpClients;
 17 import org.apache.http.message.BasicNameValuePair;
 18 import org.apache.http.util.EntityUtils;
 19 
 20 
 21 　　public static String doGet(String url, Map param) {
 22 
 23         // 创建Httpclient对象
 24         CloseableHttpClient httpclient = HttpClients.createDefault();
 25 
 26         String resultString = "";
 27         CloseableHttpResponse response = null;
 28         try {
 29             // 创建uri
 30             URIBuilder builder = new URIBuilder(url);
 31             if (param != null) {
 32                 for (String key : param.keySet()) {
 33                     builder.addParameter(key, param.get(key));
 34                 }
 35             }
 36             URI uri = builder.build();
 37 
 38             // 创建http GET请求
 39             HttpGet httpGet = new HttpGet(uri);
 40 
 41             // 执行请求
 42             response = httpclient.execute(httpGet);
 43             // 判断返回状态是否为200
 44             if (response.getStatusLine().getStatusCode() == 200) {
 45                 resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
 46             }
 47         } catch (Exception e) {
 48             e.printStackTrace();
 49         } finally {
 50             try {
 51                 if (response != null) {
 52                     response.close();
 53                 }
 54                 httpclient.close();
 55             } catch (IOException e) {
 56                 e.printStackTrace();
 57             }
 58         }
 59         return resultString;
 60     }
 61 
 62     public static String doGet(String url) {
 63         return doGet(url, null);
 64     }
 65 
 66     public static String doPost(String url, Map param) {
 67         // 创建Httpclient对象
 68         CloseableHttpClient httpClient = HttpClients.createDefault();
 69         CloseableHttpResponse response = null;
 70         String resultString = "";
 71         try {
 72             // 创建Http Post请求
 73             HttpPost httpPost = new HttpPost(url);
 74             // 创建参数列表
 75             if (param != null) {
 76                 List paramList = new ArrayList<>();
 77                 for (String key : param.keySet()) {
 78                     paramList.add(new BasicNameValuePair(key, param.get(key)));
 79                 }
 80                 // 模拟表单
 81                 UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList);
 82                 httpPost.setEntity(entity);
 83             }
 84             // 执行http请求
 85             response = httpClient.execute(httpPost);
 86             resultString = EntityUtils.toString(response.getEntity(), "utf-8");
 87         } catch (Exception e) {
 88             e.printStackTrace();
 89         } finally {
 90             try {
 91                 response.close();
 92             } catch (IOException e) {
 93                 // TODO Auto-generated catch block
 94                 e.printStackTrace();
 95             }
 96         }
 97 
 98         return resultString;
 99     }
100 
101     public static String doPost(String url) {
102         return doPost(url, null);
103     }
104     
105     public static String doPostJson(String url, String json) {
106         // 创建Httpclient对象
107         CloseableHttpClient httpClient = HttpClients.createDefault();
108         CloseableHttpResponse response = null;
109         String resultString = "";
110         try {
111             // 创建Http Post请求
112             HttpPost httpPost = new HttpPost(url);
113             // 创建请求内容
114             StringEntity entity = new StringEntity(json, ContentType.APPLICATION_JSON);
115             httpPost.setEntity(entity);
116             // 执行http请求
117             response = httpClient.execute(httpPost);
118             resultString = EntityUtils.toString(response.getEntity(), "utf-8");
119         } catch (Exception e) {
120             e.printStackTrace();
121         } finally {
122             try {
123                 response.close();
124             } catch (IOException e) {
125                 // TODO Auto-generated catch block
126                 e.printStackTrace();
127             }
128         }
129 
130         return resultString;
131     }

 3、用到的一些jar包

 https://pan.baidu.com/s/1kNZWQoZNyYEudL7DbotT0A　　　　k4yt