SpringMvc 中的实用工具类介绍（包括 ResponseEntity、 RestTemplate、WebUtils 等）

此部分内容将包含 ResponseEntity、 RestTemplate、WebUtils 等

 

1. ResponseEntity

① Sprring Mvc 中作为方法的返回值使用法

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@RequestMapping("/demo") public ResponseEntity<?> getDemo(String username) {     User user = userService.getUserByUsername(username);     if (user != null)) {         return ResponseEntity.ok(user);     } else {         return ResponseEntity.badRequest().body(null);     } }

② 设置 header 与 多个 headers

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@RequestMapping("/demo") public ResponseEntity<?> getDemo(String username) {     User user = userService.getUserByUsername(username);     if (user != null)) {         return ResponseEntity.ok(user);     } else {         return ResponseEntity.notFound().header("MyResponseHeader", "MyValue").build("Could't found by the username");     } }

 ③ 文件下载

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@ResponseBody @RequestMapping(value = "/file_download", method = RequestMethod.GET) public ResponseEntity courseFileDownload(String name, String path) {     try {         String url = internalStorage + "/" + COURSE_MATERIAL_FILE_BUCKET + "/" + path;         InputStream inputStream = new URL(url).openStream();           InputStreamResource resource = new InputStreamResource(inputStream);         return ResponseEntity.ok().contentType(MediaType.APPLICATION_OCTET_STREAM).header(HttpHeaders.CONTENT_DISPOSITION,                 "attachment;filename=" + URLEncoder.encode(name, "UTF-8")).body(resource);     } catch (IOException e) {         return ResponseEntity.badRequest().body("文件不存在!");     } }

文件下载后自动删除

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@RequestMapping(value = "/download", method = RequestMethod.GET) public ResponseEntity<Object> download(@RequestParam String templetId) {     try {         File zipFile = templetFileService.download(templetId);         InputStream inputStream = new FileInputStream(zipFile) {             @Override             public void close() throws IOException {                 super.close();                 Files.delete(zipFile.toPath());             }         };         InputStreamResource resource = new InputStreamResource(inputStream);         return ResponseEntity.ok().contentType(MediaType.APPLICATION_OCTET_STREAM).header(HttpHeaders.CONTENT_DISPOSITION,                 "attachment;filename=" + URLEncoder.encode(zipFile.getName(), "UTF-8")).body(resource);     } catch (Exception e) {         return ResponseEntity.badRequest().body("文件不存在!");     } }

④ 在 RestTemplate 中作为 getForEntity() 与 exchange()返回值被使用

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ResponseEntity<String> entity = template.getForEntity("http://example.com", String.class); String body = entity.getBody(); MediaType contentType = entity.getHeaders().getContentType(); HttpStatus statusCode = entity.getStatusCode();

 ⑤ 可以很方便地返回不同类型的结果

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@RequestMapping(value = "/get_wx_acode", method = RequestMethod.GET) public ResponseEntity getWxACode(WxACodeRequest wxACodeRequest) {     List<HttpMessageConverter<?>> messageConverters = new ArrayList<>();     messageConverters.add(new MappingJackson2HttpMessageConverter());     messageConverters.add(new ByteArrayHttpMessageConverter());     RestTemplate restTemplate = new RestTemplate(messageConverters);     String accessToken = fetchToken();     String aCodeUrl = String.format(             "https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token=%s", accessToken);     HttpHeaders headers = new HttpHeaders();     headers.setAccept(Arrays.asList(MediaType.APPLICATION_OCTET_STREAM));     headers.setContentType(MediaType.APPLICATION_JSON);     HttpEntity<WxACodeRequest> entity = new HttpEntity<>(wxACodeRequest, headers);     try {         return restTemplate.postForEntity(aCodeUrl, entity, byte[].class);     } catch (RestClientException e) {         logger.error("get_wx_acode api error", e);         // or return ResponseEntity.badRequest().build(); // build for no body         return ResponseEntity.badRequest().body(ResponseResult.badRequest("400", "api error"));     } }

 

2.判断字符串是否为空

StringUtils .hasText(str) 与 StringUtils .hasLength(str)  前者包含后者，并且判断不为 null，有长度，并且不全为空白字符。

 

3.操作 cookie 与 session

获取 cookie

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1	@CookieValue(value="myCookie", defaultValue="someValue"，required=false)

设置 cookie （还可以直接在 response header 里添加）

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Cookie cookie = new Cookie(cookieName, cookieValue);   cookie.setSecure(useSecureCookie);  // determines whether the cookie should only be sent using a secure protocol, such as HTTPS or SSL   cookie.setMaxAge(expiryTime);   cookie.setPath(cookiePath);  // The cookie is visible to all the pages in the directory you specify, and all the pages in that directory's subdirectories   response.addCookie(cookie);

 显示声明存入 session 中的对象

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1	public String handle(@SessionAttribute User user) {

设置 RedirectAttributes 添加 FlashAttribute

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public String login(@RequestParam("username") String username,                     @RequestParam("password") String password,                     HttpSession session,                     final RedirectAttributes redirectAttributes) {     if (!verify(username, password)) {         redirectAttributes.addFlashAttribute("message", "username/password invalid");         return "redirect:/login";     }       session.setAttribute(SESSION_LOGGED_IN, true);     redirectAttributes.addFlashAttribute("message", "Login Success");     return "redirect:/"; }

　　

4.WebUtils 与 ServletRequestUtils

① 操作 参数

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String param       = ServletRequestUtils.getStringParameter(         request, "param", "DEFAULT");

② 操作  session 或 cookie

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WebUtils.setSessionAttribute(request, "parameter", param);        model.addAttribute("parameter", "You set: " + (String) WebUtils       .getSessionAttribute(request, "parameter"));

 

 

参考资料

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https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/http/ResponseEntity.html

https://www.baeldung.com/spring-webutils-servletrequestutils

https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/util/WebUtils.html

https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/util/StringUtils.html