java文件上传到服务器上不显示，Java文件上传到服务器技术详解，实现高效、安全的文件传输

Java文件上传至服务器不显示，本文深入解析Java文件上传技术，涵盖高效、安全传输策略，助您掌握文件上传至服务器的关键步骤。

随着互联网技术的不断发展，文件上传到服务器已经成为企业级应用中不可或缺的一部分，Java作为主流的编程语言之一，在文件上传领域具有广泛的应用，本文将详细讲解Java文件上传到服务器的方法，包括HTTP协议、FTP协议、Java API等，旨在帮助开发者实现高效、安全的文件传输。

HTTP协议上传文件

1、使用Java原生的HTTP客户端

Java原生的HttpURLConnection类可以方便地实现HTTP协议上传文件，以下是一个使用HttpURLConnection上传文件的示例代码：

import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
public class HttpFileUpload {
    public static void uploadFile(String fileUrl, String targetUrl, String fileName) {
        HttpURLConnection connection = null;
        DataOutputStream outputStream = null;
        FileInputStream fileInputStream = null;
        try {
            URL url = new URL(fileUrl);
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("POST");
            connection.setRequestProperty("Content-Type", "multipart/form-data;boundary=BORDER");
            connection.setDoOutput(true);
            connection.setDoInput(true);
            outputStream = new DataOutputStream(connection.getOutputStream());
            outputStream.writeBytes("--BORDER

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

");
            outputStream.writeBytes("Content-Type: " + Files.probeContentType(Paths.get(fileName)) + "



");
            fileInputStream = new FileInputStream(new File(fileName));
            byte[] buffer = new byte[1024];
            int bytesRead;
            while ((bytesRead = fileInputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bytesRead);
            }
            outputStream.writeBytes("

");
            outputStream.writeBytes("--BORDER--

");
            int responseCode = connection.getResponseCode();
            if (responseCode == HttpURLConnection.HTTP_OK) {
                System.out.println("File uploaded successfully!");
            } else {
                System.out.println("Failed to upload file.");
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (outputStream != null) {
                try {
                    outputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (fileInputStream != null) {
                try {
                    fileInputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (connection != null) {
                connection.disconnect();
            }
        }
    }
}

2、使用第三方库上传文件

在实际开发中，为了简化HTTP文件上传的代码，我们可以使用第三方库，如Apache HttpClient、OkHttp等，以下是一个使用Apache HttpClient上传文件的示例代码：

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
public class ApacheHttpClientFileUpload {
    public static void uploadFile(String fileUrl, String targetUrl, String fileName) {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpPost httpPost = new HttpPost(targetUrl);
        MultipartEntityBuilder builder = MultipartEntityBuilder.create();
        builder.addBinaryBody("file", new File(fileName), ContentType.create(Files.probeContentType(Paths.get(fileName))), fileName);
        HttpEntity multipart = builder.build();
        httpPost.setEntity(multipart);
        try (CloseableHttpResponse response = httpClient.execute(httpPost)) {
            HttpEntity responseEntity = response.getEntity();
            if (responseEntity != null) {
                String result = EntityUtils.toString(responseEntity);
                System.out.println("File uploaded successfully: " + result);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

FTP协议上传文件

1、使用Java原生的FTPClient类

Java原生的FTPClient类可以方便地实现FTP协议上传文件，以下是一个使用FTPClient上传文件的示例代码：

import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;
public class FtpFileUpload {
    public static void uploadFile(String host, int port, String username, String password, String remotePath, String fileName) {
        FTPClient ftpClient = new FTPClient();
        try {
            ftpClient.connect(host, port);
            ftpClient.login(username, password);
            ftpClient.enterLocalPassiveMode();
            ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
            ftpClient.storeFile(remotePath + fileName, new FileInputStream(new File(fileName)));
            System.out.println("File uploaded successfully to: " + remotePath + fileName);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (ftpClient.isConnected()) {
                    ftpClient.logout();
                    ftpClient.disconnect();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

2、使用第三方库上传文件

在实际开发中，为了简化FTP文件上传的代码，我们可以使用第三方库，如Apache Commons Net、jclouds等，以下是一个使用Apache Commons Net上传文件的示例代码：

import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPReply;
public class ApacheCommonsNetFtpFileUpload {
    public static void uploadFile(String host, int port, String username, String password, String remotePath, String fileName) {
        FTPClient ftpClient = new FTPClient();
        try {
            ftpClient.connect(host, port);
            int replyCode = ftpClient.getReplyCode();
            if (!FTPReply.isPositiveCompletion(replyCode)) {
                ftpClient.disconnect();
                return;
            }
            ftpClient.login(username, password);
            ftpClient.enterLocalPassiveMode();
            ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
            ftpClient.storeFile(remotePath + fileName, new FileInputStream(new File(fileName)));
            System.out.println("File uploaded successfully to: " + remotePath + fileName);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (ftpClient.isConnected()) {
                    ftpClient.logout();
                    ftpClient.disconnect();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

本文详细讲解了Java文件上传到服务器的方法，包括HTTP协议和FTP协议，在实际开发中，我们可以根据需求选择合适的上传方式，并使用Java原生的API或第三方库来实现高效、安全的文件传输，希望本文对您的开发工作有所帮助。