java httppost 获取pdf文件流生成pdf文件

获取 PDF 文件流后，我们可以使用 Java 的 IO 流操作将其写入本地文件系统中，从而生成 PDF 文件。以下是示例代码：

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
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.mime.MultipartEntityBuilder;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;

public class HttpPostExample {
    public static void main(String[] args) throws Exception {
        String url = "http://example.com/pdf";
        String filePath = "/path/to/file.pdf";
        
        // Create POST request
        HttpClient client = HttpClientBuilder.create().build();
        HttpPost post = new HttpPost(url);
        
        // Add file to request body
        HttpEntity entity = MultipartEntityBuilder.create()
                .addBinaryBody("file", new File(filePath))
                .build();
        post.setEntity(entity);
        
        // Send request and receive response
        HttpResponse response = client.execute(post);
        HttpEntity responseEntity = response.getEntity();
        
        // Get PDF file stream from response entity and write to local file system
        InputStream inputStream = responseEntity.getContent();
        FileOutputStream outputStream = new FileOutputStream(new File("output.pdf"));
        byte[] buffer = new byte[1024];
        int len;
        while ((len = inputStream.read(buffer)) != -1) {
            outputStream.write(buffer, 0, len);
        }
        outputStream.close();
        
        // Release resources
        EntityUtils.consume(responseEntity);
    }
}

在上面的代码中，我们首先创建了一个 HttpClient 对象，然后创建一个 HttpPost 对象并设置 URL。接下来，我们使用 MultipartEntityBuilder 类创建一个包含 PDF 文件的请求体，并将其设置为 HttpPost 对象的实体。最后，我们发送请求并从响应中获取 PDF 文件流，并将其写入本地文件系统中来生成 PDF 文件。注意，我们需要手动释放响应实体的资源，以避免内存泄漏。