HttpClient基础使用

引入Maven依赖：

    <properties>
		<httpclient-version>4.4.1</httpclient-version>
	</properties>
	<dependencies>
		<!-- httpclient -->
		<dependency>
			<groupId>org.apache.httpcomponents</groupId>
			<artifactId>httpclient</artifactId>
			<version>${httpclient-version}</version>
		</dependency>
	</dependencies>

Get方式请求不带参数：

        //创建一个httpclient对象
		CloseableHttpClient httpClient = HttpClients.createDefault();
		//创建一个GET对象
		HttpGet get = new HttpGet("http://www.baidu.com");
		//执行请求
		CloseableHttpResponse response = httpClient.execute(get);
		//获取响应状态码
	   	int statusCode = response.getStatusLine().getStatusCode();
		System.out.println(statusCode);
        //获取响应结果
		HttpEntity entity = response.getEntity();
		String string = EntityUtils.toString(entity, "utf-8");
		System.out.println(string);
		//关闭httpclient
		response.close();
		httpClient.close();

Get方式请求携带参数：

1.    使用List进行参数传递时注意参数类型为NameValuePair，需要使用new BasicNameValuePair("key","value")进行参数绑定;

       URIBuilder uriBuilder = new URIBuilder("http://localhost/second");
   
   	ArrayList<NameValuePair> nvps = new ArrayList<NameValuePair>();
   	nvps.add(new BasicNameValuePair("username", "Steven"));
   	nvps.add(new BasicNameValuePair("password", "Russell"));
   	uriBuilder.addParameters(nvps);
       HttpGet get = new HttpGet(uriBuilder.build());

    

2.    直接进行参数绑定。

           // 创建一个uri对象
   		URIBuilder uriBuilder = new URIBuilder("http://localhost/second");
           uriBuilder.addParameter("username", "Steven");
           uriBuilder.addParameter("password","Russell");
   		HttpGet get = new HttpGet(uriBuilder.build());

    

        //创建一个httpclient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //创建一个uri对象
        URIBuilder uriBuilder = new URIBuilder("http://www.baidu.com/web");
        //设置传递的参数
        uriBuilder.addParameter("username", "Steven");
        uriBuilder.addParameter("password","Russell");
         //这里参数传递可以使用List也可以直接设置参数进行传递
        //List<NameValuePair> nvps = new ArrayList<NameValuePair>();
		//nvps.add(new BasicNameValuePair("username", "Steven"));
		//nvps.add(new BasicNameValuePair("password", "Russell"));
		//uriBuilder.addParameters(nvps);

		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();

Post方式请求不带参数：

        CloseableHttpClient httpClient = HttpClients.createDefault();

		// 创建一个post对象
		HttpPost post = new HttpPost("http://localhost/first");
		// 执行post请求
		CloseableHttpResponse response = httpClient.execute(post);
		// 获取相应结果
		int statusCode = response.getStatusLine().getStatusCode();
		System.out.println("响应状态码为："+statusCode);
		String string = EntityUtils.toString(response.getEntity());
		System.out.println(string);
		response.close();
		httpClient.close();

Post方式请求携带参数：

1. 使用List进行参数传递模拟表单

		CloseableHttpClient httpClient = HttpClients.createDefault();

		// 创建一个post对象
		HttpPost post = new HttpPost("http://localhost/second");
		// 使用List进行参数传递(模拟表单)
		List<NameValuePair> kvList = new ArrayList<>();
		kvList.add(new BasicNameValuePair("username", "Steven"));
		kvList.add(new BasicNameValuePair("password", "Russell"));
		
		// 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();

2、使用reset方式进行参数传递

        CloseableHttpClient httpClient = HttpClients.createDefault();

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