httpclient 实例教程

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。

      HttpClient特性：基于标准、纯净的Java语言。实现了Http1.0和Http1.1。支持HTTPS协议。通过Http代理建立透明的连接。

      下载地址：http://hc.apache.org/

2、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。

3、实例

添加依赖

<!-- httpclient -->
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>${httpclient.version}</version>
</dependency>

3.1、get 请求抓取网页信息

/*get 请求抓取网页信息*/
@Test
public void doGet() throws Exception {
//创建一个httpclient对象
CloseableHttpClient httpClient = HttpClients.createDefault();
//创建一个GET对象
HttpGet get = new HttpGet("http://www.sogou.com");
//执行请求
CloseableHttpResponse response = httpClient.execute(get);
//取响应的结果
int statusCode = response.getStatusLine().getStatusCode();
System.out.println(statusCode);
HttpEntity entity = response.getEntity();
String string = EntityUtils.toString(entity, "utf-8");
System.out.println(string);
//关闭httpclient
response.close();
httpClient.close();
}

 


3.2、带参数的get请求

/*带参数的get 请求*/
@Test
public void doGetWithParam() throws Exception{
//创建一个httpclient对象
CloseableHttpClient httpClient = HttpClients.createDefault();
//创建一个uri对象
URIBuilder uriBuilder = new URIBuilder("http://www.sogou.com/web");
uriBuilder.addParameter("query", "花千骨");
HttpGet get = new HttpGet(uriBuilder.build());
//执行请求
CloseableHttpResponse response = httpClient.execute(get);
//取响应的结果
int statusCode = response.getStatusLine().getStatusCode();
System.out.println(statusCode);
HttpEntity entity = response.getEntity();
String string = EntityUtils.toString(entity, "utf-8");
System.out.println(string);
//关闭httpclient
response.close();
httpClient.close();
}

3.3、post请求

/*post 请求*/
@Test
public void doPost() throws Exception {
CloseableHttpClient httpClient = HttpClients.createDefault();

//创建一个post对象
HttpPost post = new HttpPost("http://localhost:8082/httpclient/post.html");
//执行post请求
CloseableHttpResponse response = httpClient.execute(post);
String string = EntityUtils.toString(response.getEntity());
System.out.println(string);
response.close();
httpClient.close();
}

[b]SpringMVC的Controller本地模拟：http://localhost:8082/httpclient/post.html [/b]

//测试：乱码produces= MediaType.TEXT_PLAIN_VALUE+";charset=utf-8"
@RequestMapping(value="/httpclient/post", method= RequestMethod.POST, produces= MediaType.TEXT_PLAIN_VALUE+";charset=utf-8")
@ResponseBody
public String testPost(String username, String password) {
String result = "username:" + username + "\tpassword:" + password;
System.out.println(result);
return "username:" + username + ",password:" + password;
}

3.4、带参数的post请求

/*post 带参数请求*/
@Test
public void doPostWithParam() throws Exception{
CloseableHttpClient httpClient = HttpClients.createDefault();

//创建一个post对象
HttpPost post = new HttpPost("http://localhost:8082/httpclient/param.html");
//创建一个Entity。模拟一个表单
List<NameValuePair> kvList = new ArrayList<>();
kvList.add(new BasicNameValuePair("username", "zhangsan"));
kvList.add(new BasicNameValuePair("password", "123"));

//包装成一个Entity对象
StringEntity entity = new UrlEncodedFormEntity(kvList, "utf-8");
//设置请求的内容
post.setEntity(entity);

//执行post请求
CloseableHttpResponse response = httpClient.execute(post);
String string = EntityUtils.toString(response.getEntity());
System.out.println(string);
response.close();
httpClient.close();
}

[b]SpringMVC的Controller本地模拟：http://localhost:8082/httpclient/param 的Controller[/b]

//测试
@RequestMapping(value = "/httpclient/param",method = RequestMethod.POST)
@ResponseBody
public String testPostParam(String username,String password){
return "username:"+ username + "\tpassword:" +password;
}