客戶端解析伺服器響應的multipart/form-data資料
阿新 • • 發佈:2020-08-26
multipart/form-data
,多部件請求體。這個請求體比較特殊,它可以拆分為多個部件,每個部件都有自己的header
和body
,最常用的地方就是:客戶端檔案上傳,因為有多個部件,在上傳檔案的時候,還可以在body
中新增其他的資料。json
,form
。。。
一般來說,都是客戶端發起multipart/form-data
請求 ,伺服器進行解析。而且這種東西的編碼解碼工作一般都是由底層的容器/框架完成。開發根本不必關心。但是我最近遇到了一個需求:
伺服器響應
multipart/form-data
(包含了一個二進位制檔案和其他的文字資料),客戶端來解析
意味著,需要自己完成2個東西
- 在服務端完成
multipart/form-data
- 在客戶端獲取到響應後,進行資料的解碼
multipart/form-data
的請求體,看起來像這樣(省略了部分 header)
POST /foo HTTP/1.1 Content-Length: 68137 Content-Type: multipart/form-data; boundary=---------------------------974767299852498929531610575 ---------------------------974767299852498929531610575 Content-Disposition: form-data; name="description" some text ---------------------------974767299852498929531610575 Content-Disposition: form-data; name="myFile"; filename="foo.txt" Content-Type: text/plain (content of the uploaded file foo.txt) ---------------------------974767299852498929531610575
服務端的編碼
使用 org.apache.httpcomponents
庫進行編碼
<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpmime --> <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpmime</artifactId> <version>4.5.12</version> </dependency>
Controller
通過 MultipartEntityBuilder
, 新增多個部件,每個部件有自己的名字,型別。構建出一個 HttpEntity
物件。可以從這個物件中獲取到編碼後的IO流以及ContentType
,直接響應給 客戶端就完事兒,比較簡單。
import java.io.File;
import java.nio.charset.StandardCharsets;
import javax.servlet.http.HttpServletResponse;
import org.apache.http.HttpEntity;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.entity.mime.content.StringBody;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.util.UriUtils;
@RestController
@RequestMapping("/test")
public class TestController {
@GetMapping
public void test (HttpServletResponse response) throws Exception {
HttpEntity httpEntity = MultipartEntityBuilder.create()
// 表單 => (部件名稱,資料,型別),要注意uri編碼
.addPart("name", new StringBody(UriUtils.encode("SpringBoot中文社群", StandardCharsets.UTF_8), ContentType.APPLICATION_FORM_URLENCODED))
// JSON => (部件名稱,JSON,型別)
.addPart("info", new StringBody("{\"site\": \"https://springboot.io\", \"year\": 2019}", ContentType.APPLICATION_JSON))
// 檔案 => ( 部件名稱,檔案,型別,檔名稱)
.addBinaryBody("logo", new File("D:\\logo.png"), ContentType.IMAGE_PNG, "logo.png")
.build();
// 設定ContentType
response.setContentType(httpEntity.getContentType().getValue());
// 響應客戶端
httpEntity.writeTo(response.getOutputStream());
}
}
客戶端的解碼
使用commons-fileupload
庫進行解碼
<!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.4</version>
</dependency>
MultipartTest
看這個程式碼,會覺得似曾相識。不錯,在Servlet3.0
以前,HttpServletRequest
還沒有getPart
方法的時候 ,大家都是通過 commons-fileupload
來從multipart/form-data
請求中解析出資料的。
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.Iterator;
import java.util.List;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
import org.apache.commons.fileupload.FileItemHeaders;
import org.apache.commons.fileupload.FileUploadBase;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.RequestContext;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.portlet.PortletFileUpload;
import org.springframework.core.io.Resource;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.client.RestTemplate;
/**
* 自己定義一個RequestContext的實現
*/
class SimpleRequestContext implements RequestContext {
private final Charset charset; // 編碼
private final MediaType contentType; // contentType
private final InputStream content; // 資料
public SimpleRequestContext(Charset charset, MediaType contentType, InputStream content) {
this.charset = charset;
this.contentType = contentType;
this.content = content;
}
@Override
public String getCharacterEncoding() {
return this.charset.displayName();
}
@Override
public String getContentType() {
return this.contentType.toString();
}
@Override
public int getContentLength() {
try {
return this.content.available();
} catch (IOException e) {
}
return 0;
}
@Override
public InputStream getInputStream() throws IOException {
return this.content;
}
}
public class MultipartTest {
public static void main(String[] args) throws IOException, FileUploadException {
// 獲取伺服器響應的IO流
RestTemplate restTemplate = new RestTemplate();
ResponseEntity<Resource> responseEntity = restTemplate.getForEntity("http://localhost:8081/test", Resource.class);
// 建立RequestContext物件
RequestContext requestContext = new SimpleRequestContext(StandardCharsets.UTF_8, responseEntity.getHeaders().getContentType(),
responseEntity.getBody().getInputStream());
// 解析器建立
FileUploadBase fileUploadBase = new PortletFileUpload();
FileItemFactory fileItemFactory = new DiskFileItemFactory();
fileUploadBase.setFileItemFactory(fileItemFactory);
fileUploadBase.setHeaderEncoding(StandardCharsets.UTF_8.displayName());
// 解析出所有的部件
List<FileItem> fileItems = fileUploadBase.parseRequest(requestContext);
for (FileItem fileItem : fileItems) {
// 請求頭
System.out.println("headers:==========================");
FileItemHeaders fileItemHeaders = fileItem.getHeaders();
Iterator<String> headerNamesIterator = fileItemHeaders.getHeaderNames();
while (headerNamesIterator.hasNext()) { // 迭代name
String headerName = headerNamesIterator.next();
Iterator<String> headerValueIterator = fileItemHeaders.getHeaders(headerName);
while (headerValueIterator.hasNext()) { // 迭代value
String headerValue = headerValueIterator.next();
System.out.println(headerName + ":" + headerValue);
}
}
// 請求體
System.out.println("body:==========================");
if(fileItem.isFormField()) { // 是普通表單項
byte[] data = fileItem.get();
System.out.println(new String(data, StandardCharsets.UTF_8));
} else { // 是檔案表單項
String fileName = fileItem.getName(); // 檔案的原始名稱
InputStream inputStream = fileItem.getInputStream(); // 檔案的IO流
System.out.println("fileName=" + fileName + ", size=" + inputStream.available());
}
System.out.println();
}
}
}
完整的日誌輸出
17:18:55.384 [main] DEBUG org.springframework.web.client.RestTemplate - HTTP GET http://localhost:8081/test
17:18:55.449 [main] DEBUG org.springframework.web.client.RestTemplate - Accept=[application/json, application/*+json, */*]
17:18:56.426 [main] DEBUG org.springframework.web.client.RestTemplate - Response 200 OK
17:18:56.461 [main] DEBUG org.springframework.web.client.RestTemplate - Reading to [org.springframework.core.io.Resource] as "multipart/form-data;boundary=0W40KHiHJTyo5H_n1EIL68aM4tNRhPa-7Vp"
headers:==========================
content-disposition:form-data; name="name"
content-type:application/x-www-form-urlencoded; charset=ISO-8859-1
content-transfer-encoding:8bit
body:==========================
SpringBoot%E4%B8%AD%E6%96%87%E7%A4%BE%E5%8C%BA
headers:==========================
content-disposition:form-data; name="info"
content-type:application/json; charset=UTF-8
content-transfer-encoding:8bit
body:==========================
{"site": "https://springboot.io", "year": 2019}
headers:==========================
content-disposition:form-data; name="logo"; filename="logo.png"
content-type:image/png
content-transfer-encoding:binary
body:==========================
fileName=logo.png, size=2423
客戶端準確的解析出了伺服器響應的 multipart/form-data
資料。