<form th:action="@{/testRequestBody}" method="post">
    用戶名：<input type="text" name="username"><br>
    密碼：<input type="password" name="password"><br>
    <input type="submit">
</form>

@RequestMapping("/testRequestBody")
public String testRequestBody(@RequestBody String requestBody){
    System.out.println("requestBody:"+requestBody);
    return "success";
}

@RequestMapping("/testRequestEntity")
public String testRequestEntity(RequestEntity<String> requestEntity){
    System.out.println("requestHeader:"+requestEntity.getHeaders());
    System.out.println("requestBody:"+requestEntity.getBody());
    return "success";
}

@RequestMapping("/testResponseBody")
@ResponseBody
public String testResponseBody(){
    return "success";
}

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.12.1</version>
</dependency>

<mvc:annotation-driven />

@RequestMapping("/testResponseUser")
@ResponseBody
public User testResponseUser(){
    return new User(1001,"admin","123456",23,"男");
}

@RequestMapping("/testDown")
public ResponseEntity<byte[]> testResponseEntity(HttpSession session) throws IOException {
    //獲取ServletContext對(duì)象
    ServletContext servletContext = session.getServletContext();
    //獲取服務(wù)器中文件的真實(shí)路徑
    String realPath = servletContext.getRealPath("/static/img/1.jpg");
    //創(chuàng)建輸入流
    InputStream is = new FileInputStream(realPath);
    //創(chuàng)建字節(jié)數(shù)組
    byte[] bytes = new byte[is.available()];
    //將流讀到字節(jié)數(shù)組中
    is.read(bytes);
    //創(chuàng)建HttpHeaders對(duì)象設(shè)置響應(yīng)頭信息
    MultiValueMap<String, String> headers = new HttpHeaders();
    //設(shè)置要下載方式以及下載文件的名字
    headers.add("Content-Disposition", "attachment;filename=1.jpg");
    //設(shè)置響應(yīng)狀態(tài)碼
    HttpStatus statusCode = HttpStatus.OK;
    //創(chuàng)建ResponseEntity對(duì)象
    ResponseEntity<byte[]> responseEntity = new ResponseEntity<>(bytes, headers, statusCode);
    //關(guān)閉輸入流
    is.close();
    return responseEntity;
}

<!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->
<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.3.1</version>
</dependency>

<!--必須通過文件解析器的解析才能將文件轉(zhuǎn)換為MultipartFile對(duì)象-->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"></bean>

@RequestMapping("/testUp")
public String testUp(MultipartFile photo, HttpSession session) throws IOException {
    //獲取上傳的文件的文件名
    String fileName = photo.getOriginalFilename();
    //處理文件重名問題
    String hzName = fileName.substring(fileName.lastIndexOf("."));
    fileName = UUID.randomUUID().toString() + hzName;
    //獲取服務(wù)器中photo目錄的路徑
    ServletContext servletContext = session.getServletContext();
    //得到photo文件夾
    String photoPath = servletContext.getRealPath("photo");
    File file = new File(photoPath);
    if(!file.exists()){
        file.mkdir();
    }
    String finalPath = photoPath + File.separator + fileName;
    //實(shí)現(xiàn)上傳功能
    photo.transferTo(new File(finalPath));
    return "success";
}

<form enctype="multipart/form-data" action="./testUp" method="post">
    <input type="file" name="photo">
    <button>提交</button>
</form>