Java Curl 上传文件实现教程

1. 流程图

st=>start: 开始
op1=>operation: 创建URL对象
op2=>operation: 打开连接
op3=>operation: 设置请求方法
op4=>operation: 设置请求头
op5=>operation: 设置请求体
op6=>operation: 发送请求
op7=>operation: 解析响应结果
op8=>operation: 关闭连接
e=>end: 结束

st->op1->op2->op3->op4->op5->op6->op7->op8->e

2. 实现步骤

步骤 描述
1 创建URL对象
2 打开连接
3 设置请求方法
4 设置请求头
5 设置请求体
6 发送请求
7 解析响应结果
8 关闭连接

3. 代码实现

3.1 创建URL对象

URL url = new URL(" // 替换为实际的上传接口URL

3.2 打开连接

HttpURLConnection conn = (HttpURLConnection) url.openConnection();

3.3 设置请求方法

conn.setRequestMethod("POST");

3.4 设置请求头

conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW");

3.5 设置请求体

String boundary = "----WebKitFormBoundary7MA4YWxkTrZu0gW";
String CRLF = "\r\n";

StringBuilder requestBody = new StringBuilder();
requestBody.append("--").append(boundary).append(CRLF);
requestBody.append("Content-Disposition: form-data; name=\"file\"; filename=\"example.txt\"").append(CRLF);
requestBody.append("Content-Type: text/plain").append(CRLF).append(CRLF);
requestBody.append("This is the content of the file.").append(CRLF);
requestBody.append("--").append(boundary).append("--").append(CRLF);

byte[] requestBodyBytes = requestBody.toString().getBytes(StandardCharsets.UTF_8);

3.6 发送请求

conn.setDoOutput(true);
try (OutputStream outputStream = conn.getOutputStream()) {
    outputStream.write(requestBodyBytes);
}

3.7 解析响应结果

int responseCode = conn.getResponseCode();
if (responseCode == HttpURLConnection.HTTP_OK) {
    try (BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()))) {
        String line;
        while ((line = reader.readLine()) != null) {
            System.out.println(line);
        }
    }
}

3.8 关闭连接

conn.disconnect();

4. 完整示例代码

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;

public class FileUploader {
    public static void main(String[] args) throws IOException {
        URL url = new URL(" // 替换为实际的上传接口URL
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();

        conn.setRequestMethod("POST");
        conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW");

        String boundary = "----WebKitFormBoundary7MA4YWxkTrZu0gW";
        String CRLF = "\r\n";

        StringBuilder requestBody = new StringBuilder();
        requestBody.append("--").append(boundary).append(CRLF);
        requestBody.append("Content-Disposition: form-data; name=\"file\"; filename=\"example.txt\"").append(CRLF);
        requestBody.append("Content-Type: text/plain").append(CRLF).append(CRLF);
        requestBody.append("This is the content of the file.").append(CRLF);
        requestBody.append("--").append(boundary).append("--").append(CRLF);

        byte[] requestBodyBytes = requestBody.toString().getBytes(StandardCharsets.UTF_8);

        conn.setDoOutput(true);
        try (OutputStream outputStream = conn.getOutputStream()) {
            outputStream.write(requestBodyBytes);
        }

        int responseCode = conn.getResponseCode();
        if (responseCode == HttpURLConnection.HTTP_OK) {
            try (BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()))) {
                String line;
                while ((line = reader.readLine()) != null) {
                    System.out.println(line);
                }
            }
        }

        conn.disconnect();
    }
}

5. 结论

通过以上步骤的实现，我们可以在Java中使用Curl上传文件。关键步骤包括创建URL对象、打开连接、设置请求方法、设置请求头、设置请求体、发送请求、解析响应结果和