本文目录导读：
下面给你一个HttpUtils的完整案例，包含常见的GET、POST、上传文件、下载文件以及带Header/Token的请求示例。
这个案例基于 Apache HttpClient 和 Jackson（处理JSON），这是目前最主流的写法，如果你用的是其他框架（如OkHttp、Spring RestTemplate）,也可以根据注释做对应调整。
引入依赖（Maven）
<!-- Apache HttpClient -->
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.14</version>
</dependency>
<!-- 处理JSON：Jackson -->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.15.2</version>
</dependency>
<!-- 文件上传需要 -->
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpmime</artifactId>
<version>4.5.14</version>
</dependency>
HttpUtils 工具类核心代码
import com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.http.HttpEntity;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.*;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.entity.mime.content.FileBody;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import java.io.*;
import java.nio.charset.StandardCharsets;
import java.util.Map;
public class HttpUtils {
private static final ObjectMapper MAPPER = new ObjectMapper();
private static final int TIMEOUT = 10000; // 10秒超时
private static final RequestConfig CONFIG = RequestConfig.custom()
.setConnectTimeout(TIMEOUT) // 连接超时
.setSocketTimeout(TIMEOUT) // 响应超时
.setConnectionRequestTimeout(TIMEOUT)
.build();
// 全局单例（线程安全）
private static final CloseableHttpClient HTTP_CLIENT = HttpClients.custom()
.setDefaultRequestConfig(CONFIG)
.build();
// ======================== GET 请求 ========================
/**
* GET请求，返回String
*/
public static String doGet(String url, Map<String, String> headers) throws IOException {
HttpGet httpGet = new HttpGet(url);
if (headers != null) {
headers.forEach(httpGet::setHeader);
}
return executeAndReturnString(httpGet);
}
/**
* GET请求，最简版（无Header）
*/
public static String doGet(String url) throws IOException {
return doGet(url, null);
}
// ======================== POST 请求 ========================
/**
* POST JSON，返回String
* @param url 地址
* @param jsonBody JSON字符串
* @param headers 请求头（可传Token等）
*/
public static String doPostJson(String url, String jsonBody, Map<String, String> headers) throws IOException {
HttpPost httpPost = new HttpPost(url);
// 默认设置JSON
httpPost.setHeader("Content-Type", "application/json;charset=UTF-8");
if (headers != null) {
headers.forEach(httpPost::setHeader);
}
StringEntity entity = new StringEntity(jsonBody, StandardCharsets.UTF_8);
entity.setContentType("application/json");
httpPost.setEntity(entity);
return executeAndReturnString(httpPost);
}
/**
* POST 表单（application/x-www-form-urlencoded）
*/
public static String doPostForm(String url, Map<String, String> formData) throws IOException {
HttpPost httpPost = new HttpPost(url);
httpPost.setHeader("Content-Type", "application/x-www-form-urlencoded");
if (formData != null) {
StringBuilder sb = new StringBuilder();
for (Map.Entry<String, String> entry : formData.entrySet()) {
if (sb.length() > 0) sb.append("&");
sb.append(entry.getKey()).append("=").append(entry.getValue());
}
StringEntity entity = new StringEntity(sb.toString(), StandardCharsets.UTF_8);
httpPost.setEntity(entity);
}
return executeAndReturnString(httpPost);
}
// ======================== 文件上传 ========================
/**
* 上传文件（multipart/form-data）
* @param url 上传地址
* @param file 本地文件
* @param formData 其他表单字段（可选）
*/
public static String doUploadFile(String url, File file, Map<String, String> formData) throws IOException {
HttpPost httpPost = new HttpPost(url);
MultipartEntityBuilder builder = MultipartEntityBuilder.create();
builder.setCharset(StandardCharsets.UTF_8);
// 添加文件字段，字段名为 file（可根据后端要求调整）
FileBody fileBody = new FileBody(file, ContentType.APPLICATION_OCTET_STREAM, file.getName());
builder.addPart("file", fileBody);
// 添加普通表单字段
if (formData != null) {
for (Map.Entry<String, String> entry : formData.entrySet()) {
builder.addTextBody(entry.getKey(), entry.getValue(), ContentType.TEXT_PLAIN);
}
}
httpPost.setEntity(builder.build());
return executeAndReturnString(httpPost);
}
// ======================== 下载文件 ========================
/**
* 下载文件到本地
* @param url 文件URL
* @param savePath 保存路径（含文件名）
*/
public static void doDownload(String url, String savePath) throws IOException {
HttpGet httpGet = new HttpGet(url);
try (CloseableHttpResponse response = HTTP_CLIENT.execute(httpGet)) {
if (response.getStatusLine().getStatusCode() == 200) {
HttpEntity entity = response.getEntity();
byte[] bytes = EntityUtils.toByteArray(entity);
saveFile(bytes, savePath);
System.out.println("文件下载成功：" + savePath);
} else {
throw new IOException("下载失败，状态码：" + response.getStatusLine().getStatusCode());
}
}
}
// ======================== 公共私有方法 ========================
private static String executeAndReturnString(HttpUriRequest request) throws IOException {
try (CloseableHttpResponse response = HTTP_CLIENT.execute(request)) {
int statusCode = response.getStatusLine().getStatusCode();
String result = EntityUtils.toString(response.getEntity(), StandardCharsets.UTF_8);
if (statusCode >= 200 && statusCode < 300) {
return result;
} else {
throw new IOException("HTTP错误码: " + statusCode + "，响应内容: " + result);
}
}
}
private static void saveFile(byte[] data, String filePath) throws IOException {
File dir = new File(filePath).getParentFile();
if (dir != null && !dir.exists()) {
dir.mkdirs(); // 创建父目录
}
try (FileOutputStream fos = new FileOutputStream(filePath)) {
fos.write(data);
}
}
}
具体使用案例（Demo）
GET请求 + 带Token
public class TestGet {
public static void main(String[] args) throws IOException {
String url = "https://api.example.com/user/info";
Map<String, String> headers = new HashMap<>();
headers.put("Authorization", "Bearer xxxx-token");
headers.put("Accept", "application/json");
String response = HttpUtils.doGet(url, headers);
System.out.println("GET响应: " + response);
}
}
POST 提交 JSON
public class TestPostJson {
public static void main(String[] args) throws IOException {
String url = "https://api.example.com/user/create";
String jsonBody = "{\"name\":\"张三\", \"age\":25}";
Map<String, String> headers = new HashMap<>();
headers.put("token", "abc123");
String response = HttpUtils.doPostJson(url, jsonBody, headers);
System.out.println("POST响应: " + response);
}
}
上传文件
public class TestUpload {
public static void main(String[] args) throws IOException {
String url = "https://api.example.com/upload/avatar";
File file = new File("D:/photo.jpg");
Map<String, String> extraForm = new HashMap<>();
extraForm.put("userId", "1001");
extraForm.put("source", "admin");
String response = HttpUtils.doUploadFile(url, file, extraForm);
System.out.println("上传响应: " + response);
}
}
下载文件
public class TestDownload {
public static void main(String[] args) throws IOException {
String fileUrl = "https://example.com/templates/report.xlsx";
String savePath = "D:/downloads/report.xlsx";
HttpUtils.doDownload(fileUrl, savePath);
}
}
使用 Spring Boot（RestTemplate）的简化版（备选）
如果你的项目是 Spring 生态，直接用 Spring 的 RestTemplate 更简洁：
import org.springframework.http.*;
import org.springframework.web.client.RestTemplate;
public class SpringHttpUtils {
private static final RestTemplate restTemplate = new RestTemplate();
public static String doPostJson(String url, String json) {
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
HttpEntity<String> entity = new HttpEntity<>(json, headers);
ResponseEntity<String> response = restTemplate.exchange(url, HttpMethod.POST, entity, String.class);
return response.getBody();
}
public static String doGet(String url, String token) {
HttpHeaders headers = new HttpHeaders();
headers.set("Authorization", "Bearer " + token);
HttpEntity<String> entity = new HttpEntity<>(headers);
ResponseEntity<String> response = restTemplate.exchange(url, HttpMethod.GET, entity, String.class);
return response.getBody();
}
}
| 功能点 | 方法名 |
|---|---|
| GET请求 | doGet(url, headers) |
| POST JSON | doPostJson(url, json, headers) |
| POST 表单 | doPostForm(url, formData) |
| 上传文件 | doUploadFile(url, file, formData) |
| 下载文件 | doDownload(url, savePath) |
这个 HttpUtils 已经覆盖了日常开发 90% 以上的 HTTP 请求场景，可以直接复制到项目中使用，如果后端接口有特殊要求（如自定义域名、证书忽略），可以在 HttpClients.custom() 里额外配置。
