http://www.cnblogs.com/chenying99/p/3735282.html

依赖

1. httpclient-4.4.1.jar
2. httpcore-4.4.1.jar

不要引错了包

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

Get请求示例

CloseableHttpClient httpClient = HttpClients.createDefault(); 
    HttpGet httpget = new HttpGet(url.toString());
    CloseableHttpResponse  httpresponse = httpClient.execute(httpget);
    try {
        HttpEntity entity = httpresponse.getEntity();
        String responseBody = EntityUtils.toString(entity);
        // responseBody 就是返回的内容
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if(httpClient != null){
            httpClient.close();
        }
        if(httpresponse != null){
            httpresponse.close();
        }
    }

HTTP请求

HttpClient支持HTTP/1.1这个版本定义的所有Http方法：GET,HEAD,POST,PUT,DELETE,TRACE和OPTIONS。对于每一种http方法，HttpClient都定义了一个相应的类：HttpGet, HttpHead, HttpPost, HttpPut, HttpDelete, HttpTrace和HttpOpquertions。
HttpClient提供URIBuilder工具类来简化URIs的创建和修改过程。

URI uri = new URIBuilder()  
    .setScheme("http")  
    .setHost("www.google.com")  
    .setPath("/search")  
    .setParameter("q", "httpclient")  
    .setParameter("btnG", "Google Search")  
    .setParameter("aq", "f")  
    .setParameter("oq", "")  
    .build();  
    HttpGet httpget = new HttpGet(uri);  
    System.out.println(httpget.getURI());
    //http://www.google.com/search?q=httpclient&btnG=Google+Search&aq=f&oq=  

HTTP响应

HttpResponse response = 
  new BasicHttpResponse(HttpVersion.HTTP_1_1,   HttpStatus.SC_OK, "OK");  
HttpResponse response = 
new BasicHttpResponse(HttpVersion.HTTP_1_1,   
HttpStatus.SC_OK, "OK");  
System.out.println(response.getProtocolVersion());  
System.out.println(response.getStatusLine().getStatusCode());  
System.out.println(response.getStatusLine().getReasonPhrase());  
System.out.println(response.getStatusLine().toString());  

结果

HTTP/1.1  
200  
OK  
HTTP/1.1 200 OK 

消息头

HttpResponse response = new BasicHttpResponse(HttpVersion.HTTP_1_1,   
HttpStatus.SC_OK, "OK");  
response.addHeader("Set-Cookie",  "c1=a; path=/; domain=localhost");  
response.addHeader("Set-Cookie", "c2=b; path=\"/\", c3=c; domain=\"localhost\"");  
Header h1 = response.getFirstHeader("Set-Cookie");  
System.out.println(h1);  
Header h2 = response.getLastHeader("Set-Cookie");  
System.out.println(h2);  
Header[] hs = response.getHeaders("Set-Cookie");  
System.out.println(hs.length);  

结果

  Set-Cookie: c1=a; path=/; domain=localhost  
  Set-Cookie: c2=b; path="/", c3=c; domain="localhost"  
  2 

HeaderIterator也提供非常便捷的方式，将Http消息解析成单独的消息头元素。

HttpResponse response = new BasicHttpResponse(HttpVersion.HTTP_1_1,   
HttpStatus.SC_OK, "OK");  
response.addHeader("Set-Cookie",   
"c1=a; path=/; domain=localhost");  
response.addHeader("Set-Cookie",   
"c2=b; path=\"/\", c3=c; domain=\"localhost\"");  

HeaderElementIterator it = new BasicHeaderElementIterator(  
response.headerIterator("Set-Cookie"));  

while (it.hasNext()) {  
    HeaderElement elem = it.nextElement();   
    System.out.println(elem.getName() + " = " + elem.getValue());  
    NameValuePair[] params = elem.getParameters();  
    for (int i = 0; i < params.length; i++) {  
        System.out.println(" " + params[i]);  
    }  
}  

结果

c1 = a  
path=/  
domain=localhost  
c2 = b  
path=/  
c3 = c  
domain=localhost 

HTTP实体