java如何上传本地文件

在Java中，上传本地文件到服务器通常使用`HttpURLConnection`类或者第三方库如Apache HttpClient、OkHttp等。以下是一个使用`HttpURLConnection`类上传文件的简单示例：

```java

import java.io.DataOutputStream;

import java.io.FileInputStream;

import java.io.IOException;

import java.net.HttpURLConnection;

import java.net.URL;

public class FileUploadExample {

public static void uploadFile(String filePath, String serverURL) {

HttpURLConnection connection = null;

try {

// 创建URL对象

URL url = new URL(serverURL);

// 打开连接

connection = (HttpURLConnection) url.openConnection();

// 设置请求方法为POST

connection.setRequestMethod("POST");

// 设置允许输出

connection.setDoOutput(true);

// 设置请求头

connection.setRequestProperty("Content-Type", "multipart/form-data");

// 设置连接超时和读取超时

connection.setConnectTimeout(10000);

connection.setReadTimeout(10000);

// 创建文件输入流

FileInputStream fileInputStream = new FileInputStream(filePath);

// 创建数据输出流

DataOutputStream outputStream = new DataOutputStream(connection.getOutputStream());

// 写入文件信息

String boundary = "----WebKitFormBoundary7MA4YWxkTrZu0gW";

outputStream.writeBytes("--" + boundary + "rn");

outputStream.writeBytes("Content-Disposition: form-data; name="file"; filename="" + filePath + ""rn");

outputStream.writeBytes("Content-Type: " + URLConnection.guessContentTypeFromName(filePath) + "rn");

outputStream.writeBytes("Content-Transfer-Encoding: binaryrn");

outputStream.writeBytes("rn");

// 写入文件内容

byte[] buffer = new byte[4096];

int bytesRead;

while ((bytesRead = fileInputStream.read(buffer)) != -1) {

outputStream.write(buffer, 0, bytesRead);