httpclient 如何上传附件

Httpclient 可以通过 MultipartEntityBuilder 来上传附件，示例代码如下：

CloseableHttpClient httpClient = HttpClients.createDefault();
HttpPost httpPost = new HttpPost(url);

MultipartEntityBuilder builder = MultipartEntityBuilder.create();
builder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);

File file = new File(filePath);
builder.addBinaryBody("file", file, ContentType.DEFAULT_BINARY, file.getName());

HttpEntity entity = builder.build();
httpPost.setEntity(entity);

HttpResponse response = httpClient.execute(httpPost);

其中，url 是上传接口的地址，filePath 是要上传的文件路径。通过 addBinaryBody 方法将文件添加到请求体中，然后将请求体设置到 HttpPost 中，最后执行请求即可。

相关问题

httpclient 下载附件

您可以使用 Apache HttpClient 库来下载附件。以下是一个示例代码：

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class AttachmentDownloader {
    public static void main(String[] args) {
        String attachmentUrl = "http://example.com/attachment.pdf";
        String savePath = "path/to/save/attachment.pdf";

        try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
            HttpGet httpGet = new HttpGet(attachmentUrl);
            HttpResponse response = httpClient.execute(httpGet);

            HttpEntity entity = response.getEntity();
            if (entity != null) {
                try (InputStream inputStream = entity.getContent();
                     OutputStream outputStream = new FileOutputStream(savePath)) {

                    byte[] buffer = new byte[1024];
                    int bytesRead;
                    while ((bytesRead = inputStream.read(buffer)) != -1) {
                        outputStream.write(buffer, 0, bytesRead);
                    }
                }
            }

            EntityUtils.consume(entity);
            System.out.println("Attachment downloaded successfully!");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

请确保您已经导入 Apache HttpClient 的相关依赖。在上述示例中，您需要替换 `attachmentUrl` 为要下载的附件的 URL，`savePath` 为要保存附件的本地路径。执行代码后，附件将被下载并保存在指定的路径下。

注意：在实际应用中，您可能需要添加适当的错误处理和异常处理代码，以及合适的资源释放操作来确保代码的稳健性和可靠性。

httpclient 上传文件

你可以使用 HttpClient 来上传文件。下面是一个使用 HttpClient 上传文件的示例代码：

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.mime.HttpMultipartMode;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.impl.client.HttpClientBuilder;

import java.io.File;
import java.io.IOException;

public class FileUploader {
    public static void main(String[] args) {
        HttpClient httpClient = HttpClientBuilder.create().build();
        HttpPost httpPost = new HttpPost("http://example.com/upload");

        MultipartEntityBuilder builder = MultipartEntityBuilder.create();
        builder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);

        // 添加文件参数
        File file = new File("path/to/file.txt");
        builder.addBinaryBody("file", file, ContentType.DEFAULT_BINARY, file.getName());

        HttpEntity entity = builder.build();
        httpPost.setEntity(entity);

        try {
            HttpResponse response = httpClient.execute(httpPost);
            // 处理上传结果
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

你需要将 `http://example.com/upload` 替换为你要上传文件的目标 URL，将 `"path/to/file.txt"` 替换为你要上传的文件路径。在这个示例中，我们使用了 HttpClient 4.x 版本的库进行文件上传。