将文件从REST Web服务发送到客户端的正确方法是什么？

4 回答

• 5

  我不建议在base64中编码二进制数据并将其包装在JSON中 . 它只会不必要地增加响应的大小并减慢速度 .

  只需使用GET和 application/octect-stream 使用javax.ws.rs.core.Response（JAX-RS API的一部分，因此您没有锁定到Jersey）的工厂方法之一来提供文件数据：

  @GET
  @Produces(MediaType.APPLICATION_OCTET_STREAM)
  public Response getFile() {
    File file = ... // Initialize this to the File path you want to serve.
    return Response.ok(file, MediaType.APPLICATION_OCTET_STREAM)
        .header("Content-Disposition", "attachment; filename=\"" + file.getName() + "\"" ) //optional
        .build();
  }
  

  如果你没有实际的 File 对象，但 InputStream ，Response.ok(entity, mediaType)也应该能够处理它 .

  回复于 2024-04-27T19:18:10+08:00
• -3

  如果你想返回一个要下载的文件，特别是如果你想要与文件上传/下载的一些javascript库集成，那么下面的代码应该做的工作：

  @GET
  @Path("/{key}")
  public Response download(@PathParam("key") String key,
                           @Context HttpServletResponse response) throws IOException {
      try {
          //Get your File or Object from wherever you want...
              //you can use the key parameter to indentify your file
              //otherwise it can be removed
          //let's say your file is called "object"
          response.setContentLength((int) object.getContentLength());
          response.setHeader("Content-Disposition", "attachment; filename="
                  + object.getName());
          ServletOutputStream outStream = response.getOutputStream();
          byte[] bbuf = new byte[(int) object.getContentLength() + 1024];
          DataInputStream in = new DataInputStream(
                  object.getDataInputStream());
          int length = 0;
          while ((in != null) && ((length = in.read(bbuf)) != -1)) {
              outStream.write(bbuf, 0, length);
          }
          in.close();
          outStream.flush();
      } catch (S3ServiceException e) {
          e.printStackTrace();
      } catch (ServiceException e) {
          e.printStackTrace();
      }
      return Response.ok().build();
  }
  

  回复于 2024-04-27T19:18:10+08:00
• 107

  将机器地址从localhost更改为您希望客户端连接的IP地址，以便调用下面提到的服务 .

  客户端调用REST Web服务：

  package in.india.client.downloadfiledemo;
  
  import java.io.BufferedInputStream;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.FileOutputStream;
  import java.io.IOException;
  
  import javax.ws.rs.core.MediaType;
  import javax.ws.rs.core.Response.Status;
  
  import com.sun.jersey.api.client.Client;
  import com.sun.jersey.api.client.ClientHandlerException;
  import com.sun.jersey.api.client.ClientResponse;
  import com.sun.jersey.api.client.UniformInterfaceException;
  import com.sun.jersey.api.client.WebResource;
  import com.sun.jersey.multipart.BodyPart;
  import com.sun.jersey.multipart.MultiPart;
  
  public class DownloadFileClient {
  
      private static final String BASE_URI = "http://localhost:8080/DownloadFileDemo/services/downloadfile";
  
      public DownloadFileClient() {
  
          try {
              Client client = Client.create();
              WebResource objWebResource = client.resource(BASE_URI);
              ClientResponse response = objWebResource.path("/")
                      .type(MediaType.TEXT_HTML).get(ClientResponse.class);
  
              System.out.println("response : " + response);
              if (response.getStatus() == Status.OK.getStatusCode()
                      && response.hasEntity()) {
                  MultiPart objMultiPart = response.getEntity(MultiPart.class);
                  java.util.List<BodyPart> listBodyPart = objMultiPart
                          .getBodyParts();
                  BodyPart filenameBodyPart = listBodyPart.get(0);
                  BodyPart fileLengthBodyPart = listBodyPart.get(1);
                  BodyPart fileBodyPart = listBodyPart.get(2);
  
                  String filename = filenameBodyPart.getEntityAs(String.class);
                  String fileLength = fileLengthBodyPart
                          .getEntityAs(String.class);
                  File streamedFile = fileBodyPart.getEntityAs(File.class);
  
                  BufferedInputStream objBufferedInputStream = new BufferedInputStream(
                          new FileInputStream(streamedFile));
  
                  byte[] bytes = new byte[objBufferedInputStream.available()];
  
                  objBufferedInputStream.read(bytes);
  
                  String outFileName = "D:/"
                          + filename;
                  System.out.println("File name is : " + filename
                          + " and length is : " + fileLength);
                  FileOutputStream objFileOutputStream = new FileOutputStream(
                          outFileName);
                  objFileOutputStream.write(bytes);
                  objFileOutputStream.close();
                  objBufferedInputStream.close();
                  File receivedFile = new File(outFileName);
                  System.out.print("Is the file size is same? :\t");
                  System.out.println(Long.parseLong(fileLength) == receivedFile
                          .length());
              }
          } catch (UniformInterfaceException e) {
              e.printStackTrace();
          } catch (ClientHandlerException e) {
              e.printStackTrace();
          } catch (FileNotFoundException e) {
              e.printStackTrace();
          } catch (IOException e) {
              e.printStackTrace();
          }
  
      }
  
      public static void main(String... args) {
          new DownloadFileClient();
      }
  }
  

  服务响应客户：

  package in.india.service.downloadfiledemo;
  
  import javax.ws.rs.GET;
  import javax.ws.rs.Path;
  import javax.ws.rs.Produces;
  import javax.ws.rs.core.MediaType;
  import javax.ws.rs.core.Response;
  
  import com.sun.jersey.multipart.MultiPart;
  
  @Path("downloadfile")
  @Produces("multipart/mixed")
  public class DownloadFileResource {
  
      @GET
      public Response getFile() {
  
          java.io.File objFile = new java.io.File(
                  "D:/DanGilbert_2004-480p-en.mp4");
          MultiPart objMultiPart = new MultiPart();
          objMultiPart.type(new MediaType("multipart", "mixed"));
          objMultiPart
                  .bodyPart(objFile.getName(), new MediaType("text", "plain"));
          objMultiPart.bodyPart("" + objFile.length(), new MediaType("text",
                  "plain"));
          objMultiPart.bodyPart(objFile, new MediaType("multipart", "mixed"));
  
          return Response.ok(objMultiPart).build();
  
      }
  }
  

  JAR需要：

  jersey-bundle-1.14.jar
  jersey-multipart-1.14.jar
  mimepull.jar
  

  WEB.XML：

  <?xml version="1.0" encoding="UTF-8"?>
  <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
      xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
      id="WebApp_ID" version="2.5">
      <display-name>DownloadFileDemo</display-name>
      <servlet>
          <display-name>JAX-RS REST Servlet</display-name>
          <servlet-name>JAX-RS REST Servlet</servlet-name>
          <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
          <init-param>
               <param-name>com.sun.jersey.config.property.packages</param-name> 
               <param-value>in.india.service.downloadfiledemo</param-value>
          </init-param>
          <load-on-startup>1</load-on-startup>
      </servlet>
      <servlet-mapping>
          <servlet-name>JAX-RS REST Servlet</servlet-name>
          <url-pattern>/services/*</url-pattern>
      </servlet-mapping>
      <welcome-file-list>
          <welcome-file>index.jsp</welcome-file>
      </welcome-file-list>
  </web-app>
  

  回复于 2024-04-27T19:18:10+08:00
• 5

  由于您使用的是JSON，我会在通过网络发送之前对Base64进行编码 .

  如果文件很大，请尝试查看BSON，或其他一些二进制传输更好的格式 .

  如果文件压缩得很好，你也可以压缩文件，然后再对base64进行编码 .

  回复于 2024-04-27T19:18:10+08:00