HttpClient

HttpClient类：第三方添加jar包 apache 提供
灵活：避免底层流的操作

步骤：
1 创建Client对象
   HttpClient 接口   = new DefaultHttpClient();
2 创建请求方式对象
   HttpGet(url) //url?a=1&b=2
   HttpPost(url) //url

3 针对于post请求，多一步操作
   NameValuePair par = new BasicNameValuePair(参数名，参数);
   List<NameValuePair> list;
   HttpEntity entity = new UrlEncodingFormEntity(list);
   httpPost.setEntity(entity);

4 客户端对象执行请求方式，得到相应对象
   HttpResponse = httpClient.execute(httpGet|httpPost);

5 获取状态码 200
   httpResponse.getStatusLine().getStatusCode();

6 获取数据
   HttpEntity httpEntity = httpResponse.getEntity(); 获得服务器响应的数据
   1）通过流
       InputStream is = httpEntity.getContent()
   2)通过工具类
       byte[] d = EntityUtils.toByteArray(httpEntity);
       String str = EntityUtils.toString(httpEntity,"utf-8");

    例：

 1 import java.io.FileOutputStream;
 2 import java.io.IOException;
 3 import java.io.InputStream;
 4 
 5 import org.apache.http.HttpEntity;
 6 import org.apache.http.HttpResponse;
 7 import org.apache.http.client.ClientProtocolException;
 8 import org.apache.http.client.HttpClient;
 9 import org.apache.http.client.methods.HttpGet;
10 import org.apache.http.impl.client.DefaultHttpClient;
11 import org.apache.http.util.EntityUtils;
12 
13 //通过HttpClient，使用get请求获取网络图片
14 public class Client1 {
15 
16     public static void main(String[] args) throws ClientProtocolException, IOException {
17         //1 创建客户端
18         HttpClient client = new DefaultHttpClient();
19         //2 创建请求方式对象
20         String baseUrl = "http://10.0.171.234:8080/day28Server/a.jpg";
21         HttpGet httpGet = new HttpGet(baseUrl);
22         //3 客户端执行请求方式，获取响应对象
23         HttpResponse httpResponse = client.execute(httpGet);
24         //4 判断状态码 200 成功
25         int code = httpResponse.getStatusLine().getStatusCode();
26         if(code == 200){
27             //5 获取服务器数据:服务器返回的数据就存在于该entity中
28             HttpEntity httpEntity = httpResponse.getEntity();
29             //6
30             // 从数据载体中获得数据：方式一：使用IO流
31 //            InputStream is = httpEntity.getContent();
32 //            FileOutputStream fos = new FileOutputStream("src/a.jpg");
33 //            int len =0;
34 //            byte[] b = new byte[1024];
35 //            while((len=is.read(b))!=-1){
36 //                fos.write(b,0,len);
37 //                fos.flush();
38 //            }
39 //            fos.close();
40             
41             //从数据载体中获得数据：方式二 使用工具类 EntityUtils 从数据载体直接转换成字节数组
42             byte[] data = EntityUtils.toByteArray(httpEntity);
43             FileOutputStream fos = new FileOutputStream("src/b.jpg");
44             fos.write(data);
45             fos.close();
46             
47             System.out.println("下载完毕");
48         }
49         
50     }
51 
52 }