Java 下载 Response 的几种方式

在 Java 中，从服务器下载响应内容可以通过多种方式实现,以下是几种常见的方法：

使用 HttpURLConnection 下载文件

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
public class HttpDownload {
    public static void downloadFile(String fileUrl, String savePath) throws IOException {
        URL url = new URL(fileUrl);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        try (InputStream in = connection.getInputStream();
             FileOutputStream out = new FileOutputStream(savePath)) {
            byte[] buffer = new byte[4096];
            int bytesRead;
            while ((bytesRead = in.read(buffer)) != -1) {
                out.write(buffer, 0, bytesRead);
            }
        } finally {
            connection.disconnect();
        }
    }
}

使用 Apache HttpClient 下载文件

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import java.io.FileOutputStream;
import java.io.InputStream;
public class HttpClientDownload {
    public static void downloadFile(String fileUrl, String savePath) throws Exception {
        try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
            HttpGet httpGet = new HttpGet(fileUrl);
            try (CloseableHttpResponse response = httpClient.execute(httpGet)) {
                HttpEntity entity = response.getEntity();
                if (entity != null) {
                    try (InputStream in = entity.getContent();
                         FileOutputStream out = new FileOutputStream(savePath)) {
                        byte[] buffer = new byte[4096];
                        int bytesRead;
                        while ((bytesRead = in.read(buffer)) != -1) {
                            out.write(buffer, 0, bytesRead);
                        }
                    }
                }
            }
        }
    }
}

使用 Java 11+ 的 HttpClient 下载文件

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
public class Java11HttpClientDownload {
    public static void downloadFile(String fileUrl, String savePath) throws IOException, InterruptedException {
        HttpClient client = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create(fileUrl))
                .build();
        HttpResponse<InputStream> response = client.send(request, HttpResponse.BodyHandlers.ofInputStream());
        Path path = Paths.get(savePath);
        try (InputStream in = response.body();
             OutputStream out = Files.newOutputStream(path)) {
            byte[] buffer = new byte[4096];
            int bytesRead;
            while ((bytesRead = in.read(buffer)) != -1) {
                out.write(buffer, 0, bytesRead);
            }
        }
    }
}

下载并显示进度

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
public class ProgressDownload {
    public static void downloadWithProgress(String fileUrl, String savePath) throws IOException {
        URL url = new URL(fileUrl);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        int fileSize = connection.getContentLength();
        try (InputStream in = connection.getInputStream();
             FileOutputStream out = new FileOutputStream(savePath)) {
            byte[] buffer = new byte[4096];
            int bytesRead;
            long totalBytesRead = 0;
            while ((bytesRead = in.read(buffer)) != -1) {
                out.write(buffer, 0, bytesRead);
                totalBytesRead += bytesRead;
                int progress = (int) ((totalBytesRead * 100) / fileSize);
                System.out.printf("Download progress: %d%%\n", progress);
            }
        } finally {
            connection.disconnect();
        }
    }
}

注意事项

1. 异常处理：实际应用中需要更完善的异常处理
2. 资源管理：确保所有流和连接都正确关闭
3. 大文件处理：对于大文件，考虑使用缓冲区优化
4. 网络超时：设置合理的连接和读取超时
5. 认证：如果需要认证，添加相应的认证头信息
6. 并发下载：对于大文件，可以考虑分块并发下载

方法可以根据你的具体需求和环境选择使用，Java 11+ 的 HttpClient 是目前最现代和推荐的方式。