远程接口调用

1.1          第二部分：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。

1.1.1         Httpclient简介

1.1.1.1     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/

1.1.1.2     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。

1.1.2         HttpClient测试

说明：在ego-base中测试

在ego-base工程中添加httpclient的pom依赖。

<dependency>        <groupId>org.apache.httpcomponents</groupId>        <artifactId>httpclient</artifactId> </dependency>

1.1.2.1     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();            }         }

1.1.2.2     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();            }         }     }

1.1.2.3     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();            }         }     }

1.1.2.4     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();         }     }

1.1.3         httpclient常见问题及解决方案

1.1.3.1     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");

1.1.3.2     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")