HttpClient从基础请求到工具类封装使用详解
HttpClient是进行HTTP请求的常用工具，熟练掌握它的使用方法，能够让我们更高效地与网络资源进行交互。本文将详细介绍HttpClient的各种使用方式，并给出工具类封装示例。
一、引入httpclient依赖
在使用HttpClient之前，首先要确保项目中引入了相应的依赖。若项目中尚未引入，需在pom.xml文件中添加以下代码：
<dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient</artifactId> <version>4.5.13</version> </dependency> 添加这个依赖后，项目就具备了使用HttpClient的基础环境，后续便能调用相关的类和方法来发起HTTP请求。
二、发送GET请求
2.1 无参数GET请求
当我们需要发送不携带参数的GET请求时，可以参考以下代码：
import org.apache.http.HttpStatus; 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; import java.io.IOException; import java.nio.charset.StandardCharsets; public class HttpClientUtils { public static String doGet() throws IOException { // 创建默认的CloseableHttpClient实例，用于发送请求 try (CloseableHttpClient httpClient = HttpClients.createDefault()) { // 创建HttpGet请求对象，指定请求的URL HttpGet httpGet = new HttpGet("https://www.example.com/getDataList"); // 执行请求并获取响应 try (CloseableHttpResponse httpResponse = httpClient.execute(httpGet)) { // 判断响应状态码是否为200（OK） if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { // 将响应实体转换为字符串并返回 return EntityUtils.toString(httpResponse.getEntity(), StandardCharsets.UTF_8); } return null; } } } } 这段代码中，先创建了CloseableHttpClient实例，接着构建HttpGet请求对象，发送请求后根据响应状态码判断请求是否成功，若成功则返回响应内容。
2.2 带参数GET请求
带参数的GET请求有两种常见实现方式：
- 直接在URL上拼接参数：直接在请求的URL后面拼接参数，示例如下：
HttpGet httpGet = new HttpGet("https://www.example.com/getDataList?pageIndex=1&pageSize=20"); 这种方式简单直接，但当参数较多时，URL可能会变得冗长且不易维护。
- 使用URIBuilder添加参数：通过
URIBuilder来添加参数，代码如下：
import org.apache.http.HttpStatus; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpGet; import org.apache.http.client.utils.URIBuilder; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.util.EntityUtils; import java.io.IOException; import java.net.URISyntaxException; import java.nio.charset.StandardCharsets; public class HttpClientUtils { public static String doGet() throws IOException, URISyntaxException { try (CloseableHttpClient httpClient = HttpClients.createDefault()) { // 创建URIBuilder对象，指定请求的URL URIBuilder uriBuilder = new URIBuilder("https://www.example.com/getDataList"); // 添加参数 uriBuilder.addParameter("pageIndex", "1"); uriBuilder.addParameter("pageSize", "20"); // 根据构建好的URI创建HttpGet请求对象 HttpGet httpGet = new HttpGet(uriBuilder.build()); try (CloseableHttpResponse httpResponse = httpClient.execute(httpGet)) { if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { return EntityUtils.toString(httpResponse.getEntity(), StandardCharsets.UTF_8); } return null; } } } } 使用URIBuilder添加参数的方式更加灵活，参数管理也更方便，推荐在实际开发中使用。
三、发送POST请求
3.1 无参数POST请求
发送不携带参数的POST请求，代码如下：
import org.apache.http.HttpStatus; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpPost; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.util.EntityUtils; import java.io.IOException; import java.nio.charset.StandardCharsets; public class HttpClientUtils { public static String doPost() throws IOException { try (CloseableHttpClient httpClient = HttpClients.createDefault()) { // 创建HttpPost请求对象，指定请求的URL HttpPost httpPost = new HttpPost("https://www.example.com/updateData"); try (CloseableHttpResponse httpResponse = httpClient.execute(httpPost)) { if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { return EntityUtils.toString(httpResponse.getEntity(), StandardCharsets.UTF_8); } return null; } } } } 该代码与无参数GET请求的代码结构类似，只是将HttpGet换成了HttpPost，用于发送POST请求。
3.2 带参数（form表单方式）POST请求
以form表单方式发送带参数的POST请求，示例代码如下：
import org.apache.http.HttpStatus; import org.apache.http.NameValuePair; import org.apache.http.client.entity.UrlEncodedFormEntity; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpPost; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.message.BasicNameValuePair; import org.apache.http.util.EntityUtils; import java.io.IOException; import java.nio.charset.StandardCharsets; import java.util.ArrayList; import java.util.List; public class HttpClientUtils { public static String doPost() throws IOException { try (CloseableHttpClient httpClient = HttpClients.createDefault()) { HttpPost httpPost = new HttpPost("https://www.example.com/updateData"); // 创建参数列表 List<NameValuePair> params = new ArrayList<>(); // 添加参数 params.add(new BasicNameValuePair("id", "1")); params.add(new BasicNameValuePair("name", "新名字")); // 创建UrlEncodedFormEntity对象，设置参数和字符编码 UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(params, StandardCharsets.UTF_8); // 将参数实体设置到HttpPost请求中 httpPost.setEntity(formEntity); try (CloseableHttpResponse httpResponse = httpClient.execute(httpPost)) { if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { return EntityUtils.toString(httpResponse.getEntity(), StandardCharsets.UTF_8); } return null; } } } } 这段代码构建了参数列表，并将其转换为UrlEncodedFormEntity后设置到HttpPost请求中，实现了以form表单方式发送带参数的POST请求。
3.3 带参数（json方式）POST请求
以JSON方式发送带参数的POST请求，代码如下：
import org.apache.http.HttpStatus; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpPost; import org.apache.http.entity.StringEntity; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.util.EntityUtils; import java.io.IOException; import java.nio.charset.StandardCharsets; public class HttpClientUtils { public static String doPost() throws IOException { try (CloseableHttpClient httpClient = HttpClients.createDefault()) { HttpPost httpPost = new HttpPost("https://www.example.com/updateData"); // 设置JSON格式的请求体 String jsonBody = "{"id":"1","name":"新名字"}"; StringEntity stringEntity = new StringEntity(jsonBody); // 设置请求体的内容类型和字符编码 stringEntity.setContentType("application/json;charset=utf-8"); // 将请求体设置到HttpPost请求中 httpPost.setEntity(stringEntity); try (CloseableHttpResponse httpResponse = httpClient.execute(httpPost)) { if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { return EntityUtils.toString(httpResponse.getEntity(), StandardCharsets.UTF_8); } return null; } } } } 此代码将JSON格式的字符串作为请求体，通过StringEntity设置到HttpPost请求中，并指定了请求体的内容类型，实现了以JSON方式发送带参数的POST请求。
四、发送PUT请求
4.1 无参数PUT请求
发送无参数的PUT请求，代码如下：
import org.apache.http.HttpStatus; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpPut; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.util.EntityUtils; import java.io.IOException; import java.nio.charset.StandardCharsets; public class HttpClientUtils { public static String doPut() throws IOException { try (CloseableHttpClient httpClient = HttpClients.createDefault()) { // 创建HttpPut请求对象，指定请求的URL HttpPut httpPut = new HttpPut("https://www.example.com/updateData"); try (CloseableHttpResponse httpResponse = httpClient.execute(httpPut)) { if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { return EntityUtils.toString(httpResponse.getEntity(), StandardCharsets.UTF_8); } return null; } } } } 该代码与无参数的GET、POST请求代码类似，只是使用了HttpPut来发送PUT请求。
4.2 带参数（form表单方式）PUT请求
以form表单方式发送带参数的PUT请求，代码如下：
import org.apache.http.HttpStatus; import org.apache.http.NameValuePair; import org.apache.http.client.entity.UrlEncodedFormEntity; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpPut; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.message.BasicNameValuePair; import org.apache.http.util.EntityUtils; import java.io.IOException; import java.nio.charset.StandardCharsets; import java.util.ArrayList; import java.util.List; public class HttpClientUtils { public static String doPut() throws IOException { try (CloseableHttpClient httpClient = HttpClients.createDefault()) { HttpPut httpPut = new HttpPut("https://www.example.com/updateData"); // 创建参数列表 List<NameValuePair> params = new ArrayList<>(); // 添加参数 params.add(new BasicNameValuePair("id", "1")); params.add(new BasicNameValuePair("name", "新名字")); // 创建UrlEncodedFormEntity对象，设置参数和字符编码 UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(params, StandardCharsets.UTF_8); // 将参数实体设置到HttpPut请求中 httpPut.setEntity(formEntity); try (CloseableHttpResponse httpResponse = httpClient.execute(httpPut)) { if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { return EntityUtils.toString(httpResponse.getEntity(), StandardCharsets.UTF_8); } return null; } } } } 这段代码与带参数（form表单方式）的POST请求类似，只是将HttpPost替换为HttpPut，用于发送PUT请求。
4.3 带参数（json方式）PUT请求
以JSON方式发送带参数的PUT请求，代码如下：
import org.apache.http.HttpStatus; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpPut; import org.apache.http.entity.StringEntity; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.util.EntityUtils; import java.io.IOException; import java.nio.charset.StandardCharsets; public class HttpClientUtils { public static String doPut() throws IOException { try (CloseableHttpClient httpClient = HttpClients.createDefault()) { HttpPut httpPut = new HttpPut("https://www.example.com/updateData"); // 设置JSON格式的请求体 String jsonBody = "{"id":"1","name":"新名字"}"; StringEntity stringEntity = new StringEntity(jsonBody); // 设置请求体的内容类型和字符编码 stringEntity.setContentType("application/json;charset=utf-8"); // 将请求体设置到HttpPut请求中 httpPut.setEntity(stringEntity); try (CloseableHttpResponse httpResponse = httpClient.execute(httpPut)) { if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { return EntityUtils.toString(httpResponse.getEntity(), StandardCharsets.UTF_8); } return null; } } } } 该代码与以JSON方式发送带参数的POST请求类似，只是使用HttpPut来发送PUT请求。
五、发送DELETE请求
5.1 无参数DELETE请求
发送无参数的DELETE请求，代码如下：
import org.apache.http.HttpStatus; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpDelete; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.util.EntityUtils; import java.io.IOException; import java.nio.charset.StandardCharsets; public class HttpClientUtils { public static String doDelete() throws IOException { try (CloseableHttpClient httpClient = HttpClients.createDefault()) { // 创建HttpDelete请求对象，指定请求的URL HttpDelete httpDelete = new HttpDelete("https://www.example.com/updateData"); try (CloseableHttpResponse httpResponse = httpClient.execute(httpDelete)) { if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { return EntityUtils.toString(httpResponse.getEntity(), StandardCharsets.UTF_8); } return null; } } } } 此代码使用HttpDelete发送无参数的DELETE请求，并根据响应状态码处理响应结果。
六、添加请求头
在实际开发中，请求第三方接口时通常需要添加签名、时间戳等请求头。以POST请求为例，添加请求头的代码如下：
httpPost.setHeader("Content-Type", "application/json;charset=utf-8"); httpPost.setHeader("signature", "3045022100875efcef9eb54626bb0168a6baa7c61265d0001d49243f"); httpPost.setHeader("timestamp", String.valueOf(System.currentTimeMillis())); GET、PUT、DELETE请求添加请求头的方式与POST请求相同，通过setHeader方法设置相应的请求头信息即可。
七、超时时间设置
如果需要自定义HTTP请求的连接超时时间和数据传输超时时间，可以参考以下代码（以POST请求为例）：
import org.apache.http.client.config.RequestConfig; import org.apache.http.client.methods.HttpPost; RequestConfig requestConfig = RequestConfig.custom() .setConnectTimeout(5000) .setSocketTimeout(10000) .build(); httpPost.setConfig(requestConfig); 在这段代码中，使用RequestConfig.custom()创建配置对象，设置连接超时时间为5000毫秒，数据传输超时时间为10000毫秒，然后通过httpPost.setConfig(requestConfig)将配置应用到HttpPost请求中。GET、PUT、DELETE请求设置超时时间的方法与之相同。
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