【Java】HTTP请求工具类_java 请求工具类-优快云博客

本文介绍如何使用Java代码调用外部API，并提供了一个携带参数的POST请求示例。此外，还分享了一个实用的HTTP请求工具类，支持GET、POST等请求方式。

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前言

在工作中可能存在要去调用其他项目的接口，这篇文章我们实现在Java代码中实现调用其他项目的接口。

本章内容：
创建一个携带参数的POST请求，去请求其他项目的接口并返回数据。
附加HTTP请求工具类，包含（GET、POST、无参GET、无参POST）

准备

导入pom依赖

	<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpcore -->
   <dependency>
       <groupId>org.apache.httpcomponents</groupId>
       <artifactId>httpcore</artifactId>
   </dependency>
   <!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->
   <dependency>
       <groupId>org.apache.httpcomponents</groupId>
       <artifactId>httpclient</artifactId>
   </dependency>
   <!--json工具-->
	<dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.76</version>
    </dependency>

案例

创建一个携带参数的POST请求

public static String doPost(String url, String str, String encoding) {
    String body = "";
     try {
         // 创建httpclient对象
         CloseableHttpClient client = HttpClients.createDefault();
         // 创建post方式请求对象
         HttpPost httpPost = new HttpPost(url);
         // 设置参数到请求对象中
         httpPost.setEntity(new StringEntity(str, encoding));
         // 设置header信息
         // 指定报文头【Content-type】、【User-Agent】
         httpPost.setHeader("Content-type", "application/json;charset=UTF-8");
         // 执行请求操作，并拿到结果（同步阻塞）
         CloseableHttpResponse response = client.execute(httpPost);
         // 获取结果实体
         HttpEntity entity = response.getEntity();
         if (entity != null) {
             // 按指定编码转换结果实体为String类型
             body = EntityUtils.toString(entity, encoding);
         }
         EntityUtils.consume(entity);
         // 释放链接
         response.close();
         return body;
     } catch (Exception e1) {
         e1.printStackTrace();
         return "";

     }
 }

参数列表：

url：请求的接口地址（例：http://IP地址:8080/user/login）
str：发送请求时候携带的参数（必须为JSON格式的字符串）
encoding：编码字符集（一般都为UTF-8）

通过调用doPost()可以接受一个返回值，返回值的类型是String类型的JSON字符串，通过fastjson工具进行转换在进行其他业务操作。

测试

JSONObject json= new JSONObject();
json.put("id", "10010");
json.put("name", "蔡徐坤");

String url = "http://IP地址:8080/user/login";
String encoding = "UTF-8";

String result = doPost(url, json.toString(), encoding);
logger.info("请求地址返回的数据为 = {}", result);

返回结果：

{code : 500, msg: "登录失败"}

完整的HTTP请求工具类

public class HttpClientUtil {
	
	/**
	 * 带参数的get请求
	 * @param url
	 * @param param
	 * @return String
	 */
	public static String doGet(String url, Map<String, String> param) {
		// 创建Httpclient对象
		if(url==null||"".equals(url))
			return null;
		CloseableHttpClient httpclient = HttpClients.createDefault();
 
		String resultString = "";
		CloseableHttpResponse response = null;
		try {
			// 创建uri
			URIBuilder builder = new URIBuilder(url);
			if (param != null) {
				for (String key : param.keySet()) {
					builder.addParameter(key, param.get(key));
				}
			}
			URI uri = builder.build();
			// 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) {
				resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				if (response != null) {
					response.close();
				}
				httpclient.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		return resultString;
	}
	
	/**
	 * 不带参数的get请求
	 * @param url
	 * @return String
	 */
	public static String doGet(String url) {
		return doGet(url, null);
	}
	
	public static String doGetByHeader(String url, String orgKey) {
		// 创建Httpclient对象
		if(url==null||"".equals(url))
			return null;
		CloseableHttpClient httpclient = HttpClients.createDefault();
 
		String resultString = "";
		CloseableHttpResponse response = null;
		try {
			// 创建uri
			URIBuilder builder = new URIBuilder(url);
			URI uri = builder.build();
			// 创建http GET请求
			HttpGet httpGet = new HttpGet(uri);
			httpGet.addHeader("Org-Key", orgKey);
			// 执行请求
			response = httpclient.execute(httpGet);
			// 判断返回状态是否为200
			if (response.getStatusLine().getStatusCode() == 200) {
				resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				if (response != null) {
					response.close();
				}
				httpclient.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		return resultString;
	}
 
	/**
	 * 带参数的post请求
	 * @param url
	 * @param param
	 * @return String
	 */
	public static String doPost(String url, Map<String, String> param) {
		// 创建Httpclient对象
		CloseableHttpClient httpClient = HttpClients.createDefault();
		CloseableHttpResponse response = null;
		String resultString = "";
		try {
			// 创建Http Post请求
			HttpPost httpPost = new HttpPost(url);
			httpPost.addHeader("Content-Type","application/json; charset=utf-8");
			httpPost.addHeader("X-Api-Sign-Version","2.0.0");
			// 创建参数列表
			if (param != null) {
				List<NameValuePair> paramList = new ArrayList<>();
				for (String key : param.keySet()) {
					paramList.add(new BasicNameValuePair(key, param.get(key)));
				}
				// 模拟表单
				UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList);
				httpPost.setEntity(entity);
//				httpPost.setEntity(new UrlEncodedFormEntity(nvps, encoding));
//				httpPost.setEntity(new StringEntity(str, encoding));
			}
			// 执行http请求
			response = httpClient.execute(httpPost);
			resultString = EntityUtils.toString(response.getEntity(), "utf-8");
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				response.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		return resultString;
	}
 
	/**
	 * 不带参数的post请求
	 * @param url
	 * @return String
	 */
	public static String doPost(String url) {
		return doPost(url, null);
	}
	
	/**
	 * 传送json类型的post请求
	 * @param url
	 * @param json
	 * @return String
	 */
	public static String doPostJson(String url, String json, String token) {
		// 创建Httpclient对象
		CloseableHttpClient httpClient = HttpClients.createDefault();
		CloseableHttpResponse response = null;
		String resultString = "";
		try {
			if(url.contains("?")){
				url = url + "&access_token=" + token;
			} else {
				url = url + "?access_token=" + token;
			}
			// 创建Http Post请求
			HttpPost httpPost = new HttpPost(url);
			//httpPost.addHeader("Org-Key", orgKey);
			// 创建请求内容
			StringEntity entity = new StringEntity(json, ContentType.APPLICATION_JSON);
			httpPost.setEntity(entity);
			// 执行http请求
			response = httpClient.execute(httpPost);
			resultString = EntityUtils.toString(response.getEntity(), "utf-8");
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				response.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		return resultString;
	}

}