java用springboot写一个controller接口通过restful调用获取excel文件，下载到本地

在Spring Boot项目中，你可以使用`Spring MVC`和`Apache POI`库来创建一个Controller接口，该接口用于通过RESTful API返回Excel文件并供客户端下载。以下是简单的步骤：

1. 添加依赖：
在`pom.xml`中添加Spring Web、Spring MVC和Apache POI的依赖：

   <dependencies>
       <!-- ... -->
       <dependency>
           <groupId>org.springframework.boot</groupId>
           <artifactId>spring-boot-starter-web</artifactId>
       </dependency>
       <dependency>
           <groupId>org.springframework.boot</groupId>
           <artifactId>spring-boot-starter-data-jpa</artifactId> <!-- 如果需要数据库支持，可以加上这行 -->
       </dependency>
       <dependency>
           <groupId>net.sf.opencsv</groupId>
           <artifactId>opencsv</artifactId>
       </dependency>
       <dependency>
           <groupId>org.apache.poi</groupId>
           <artifactId>poi</artifactId>
       </dependency>
       <dependency>
           <groupId>org.apache.poi</groupId>
           <artifactId>poi-ooxml</artifactId>
       </dependency>
   </dependencies>

2. 创建Excel生成服务：

   @Service
   public class ExcelGeneratorService {
       // 使用CSV或XLSX生成数据的方法，这里仅展示CSV示例
       public byte[] generateExcelData(List<String[]> data) throws IOException {
           try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {
               CSVWriter writer = new CSVWriter(new OutputStreamWriter(outputStream));
               for (String[] row : data) {
                   writer.writeNext(row);
               }
               writer.flush();
               return outputStream.toByteArray();
           }
       }
   }

3. 创建Controller接口：

   @RestController
   public class ExcelController {

       private final ExcelGeneratorService excelGeneratorService;

       public ExcelController(ExcelGeneratorService excelGeneratorService) {
           this.excelGeneratorService = excelGeneratorService;
       }

       @GetMapping("/download-excel")
       public ResponseEntity<byte[]> downloadExcelFile(@RequestParam("data") List<String[]> dataList) throws IOException {
           byte[] fileContent = excelGeneratorService.generateExcelData(dataList);

           // 设置响应头，告诉浏览器这是一个下载请求
           HttpHeaders headers = new HttpHeaders();
           headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
           headers.add(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=example.csv");

           return ResponseEntity.ok().headers(headers).body(fileContent);
       }
   }

4. 测试API：
通过发送GET请求到`/download-excel?data={your_data_array}`来触发下载。