dropwizard中上传和下载文件

传输格式基础知识

MIME 类型

MIME (Multipurpose Internet Mail Extensions) 是描述消息内容类型的因特网标准。

MIME 消息能包含文本、图像、音频、视频以及其他应用程序专用的数据。

MINE类型详细列表：https://www.w3school.com.cn/media/media_mimeref.asp

multipart/form-data

我们在通过 HTTP 向服务器发送 POST 请求提交数据，都是通过 form 表单形式提交的，如下：

<FORM method="POST" action="http://w.sohu.com/t2/upload.do" enctype="multipart/form-data">
    <INPUT type="text" name="city" value="Santa colo">
    <INPUT type="text" name="desc">
    <INPUT type="file" name="pic">
 FORM>

提交时会向服务器端发出这样的数据

POST /t2/upload.do HTTP/1.1
User-Agent: SOHUWapRebot
Accept-Language: zh-cn,zh;q=0.5
Accept-Charset: GBK,utf-8;q=0.7,*;q=0.7
Connection: keep-alive
Content-Length: 60408
Content-Type:multipart/form-data; boundary=ZnGpDtePMx0KrHh_G0X99Yef9r8JZsRJSXC
Host: w.sohu.com
 
--ZnGpDtePMx0KrHh_G0X99Yef9r8JZsRJSXC
Content-Disposition: form-data; name="city"
 
Santa colo
--ZnGpDtePMx0KrHh_G0X99Yef9r8JZsRJSXC
Content-Disposition: form-data;name="desc"
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
 
...
--ZnGpDtePMx0KrHh_G0X99Yef9r8JZsRJSXC
Content-Disposition: form-data;name="pic"; filename="photo.jpg"
Content-Type: application/octet-stream
Content-Transfer-Encoding: binary
 
... binary data of the jpg ...
--ZnGpDtePMx0KrHh_G0X99Yef9r8JZsRJSXC--

• application/x-www-urlencoded
• multipart/form-data
• text-plain

默认情况下是 application/x-www-urlencoded，当表单使用 POST 请求时，数据会被以 x-www-urlencoded 方式编码到 Body 中来传送， 而如果 GET 请求，则是附在 url 链接后面来发送。GET 请求只支持 ASCII 字符集，因此，如果我们要发送更大字符集的内容，我们应使用 POST 请求。

如果要发送大量的二进制数据（non-ASCII），"application/x-www-form-urlencoded" 显然是低效的。因此，这种情况下，应该使用 "multipart/form-data" 格式。

参考：https://www.jianshu.com/p/29e38bcc8a1d

代码实现

依赖

        <dependency>
            <groupId>org.glassfish.jersey.mediagroupId>
            <artifactId>jersey-media-multipartartifactId>
            <version>2.33version>
        dependency>
        <dependency>
            <groupId>commons-iogroupId>
            <artifactId>commons-ioartifactId>
            <version>2.11.0version>
        dependency>

接口实现

package com.jsq.hibernate.resource;
 
import com.google.common.collect.ImmutableMap;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.io.FileUtils;
import org.apache.commons.io.IOUtils;
import org.glassfish.jersey.media.multipart.FormDataContentDisposition;
import org.glassfish.jersey.media.multipart.FormDataParam;
 
import javax.servlet.http.HttpServletRequest;
import javax.ws.rs.*;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.StreamingOutput;
import java.io.*;
import java.util.Map;
 
@Path("file")
@Slf4j
@Produces(MediaType.APPLICATION_JSON)
public class FileResource {
 
    @POST
    @Path("upload")
    @Consumes(MediaType.MULTIPART_FORM_DATA)
    public Response uploadFile(@Context HttpServletRequest request,
                               @FormDataParam("file") InputStream inputStream,
                               @FormDataParam("file") FormDataContentDisposition formDataContentDisposition) {
        log.info("start tp upload");
        Map parameters = formDataContentDisposition.getParameters();
        log.info("parameters is {}", parameters);
        String fileName = formDataContentDisposition.getFileName();
        String path = "D:";
        File file = new File(path + File.separator + fileName);
        try (FileOutputStream outputStream = FileUtils.openOutputStream(file);
             BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream)) {
            IOUtils.copy(inputStream, bufferedOutputStream, 8192);
            return Response.ok().entity(ImmutableMap.of("code", 0, "message", "success")).build();
        } catch (IOException e) {
            return Response.ok().type(MediaType.APPLICATION_JSON).entity(ImmutableMap.of("code", 0, "message", e.getMessage())).build();
        }
    }
 
    @GET
    @Path("download")
    public Response downloadFile(@QueryParam("filename") String filename, @Context HttpServletRequest request) {
        Map parameterMap = request.getParameterMap();
        log.info("parameters of request is {}", parameterMap);
        String path = "D:";
        File file = new File(path + File.separator + filename);
        if (!file.exists()) {
            return Response.ok().entity(ImmutableMap.of("code", 1, "message", "file does not exist")).build();
        }
        return Response.ok().entity(file).header("Content-disposition", "attachment;filename=" + filename)
                .header("Cache-Control", "no-cache").build();
    }
 
    @GET
    @Path("download/stream")
    public Response downloadStream(@QueryParam("filename") String filename, @Context HttpServletRequest request) throws IOException {
        Map parameterMap = request.getParameterMap();
        log.info("parameters of request is {}", parameterMap);
        String path = "D:";
        File file = new File(path + File.separator + filename);
        if (!file.exists()) {
            return Response.ok().entity(ImmutableMap.of("code", 1, "message", "file does not exist")).build();
        }
        return Response.ok().entity(new StreamingOutput() {
                    @Override
                    public void write(OutputStream output) throws IOException, WebApplicationException {
                        output.write(FileUtils.readFileToByteArray(file));
                    }
                }).header("Content-disposition", "attachment;filename=" + filename)
                .header("Cache-Control", "no-cache").build();
    }
}

上传文件

1. @Consumes(MediaType.MULTIPART_FORM_DATA),消费的是表单样式

2. @Produces(MediaType.APPLICATION_JSON),返回的响应是json样式

3. 输入参数：@FormDataParam("file") InputStream inputStream,文件流

4. 输入参数：@FormDataParam("file") FormDataContentDisposition formDataContentDisposition，文件相关信息

5. 将输入的流转化为文件存于本地

6. postman操作

   

   

下载文件

1. 两种下载文件的方式：文件形式和流的形式
2. 响应头中放入"Content-disposition", "attachment;filename=" + filename，**Content-Disposition**响应标头是指示内容是否预期在浏览器中内联显示的标题，即，作为网页或作为网页的一部分或作为附件下载并且本地保存
3. header中相关知识点见：https://cloud.tencent.com/developer/section/1189916

启动类

package com.jsq.hibernate;
 
import com.jsq.hibernate.config.HelloWorldConfiguration;
import com.jsq.hibernate.resource.FileResource;
import io.dropwizard.Application;
import io.dropwizard.setup.Bootstrap;
import io.dropwizard.setup.Environment;
import org.glassfish.jersey.media.multipart.MultiPartFeature;
 
import java.net.URL;
 
public class HelloWorldApplication extends Application {
 
    public static void main(String[] args) throws Exception {
        URL yml = HelloWorldApplication.class.getClassLoader().getResource("server.yml");
        String configFile = yml.getFile();
        System.out.println(configFile);
        args = new String[]{"server", configFile};
        new HelloWorldApplication().run(args);
    }
 
    @Override
    public void run(HelloWorldConfiguration helloWorldConfiguration, Environment environment) {
        environment.jersey().register(new MultiPartFeature());
        environment.jersey().register(new FileResource());
    }
 
    @Override
    public String getName() {
        return "hello-world";
    }
 
    @Override
    public void initialize(Bootstrap bootstrap) {      
    }
}

注：

1. MultiPartFeature必须注册
2. 注册Resource类