SpringBoot中文件下载与JSON响应冲突的深度解析与解决方案

@RestController
public class FileController {
    
    @GetMapping("/download/pdf")
    public R downCustStmt(CustStmtReq req, HttpServletResponse response) {
        // 设置PDF响应头
        response.setContentType("application/pdf");
        response.setHeader("Content-Disposition", "attachment; filename=simple.pdf");
        
        try {
            Document document = new Document();
            PdfWriter.getInstance(document, response.getOutputStream());
            document.open();
            document.add(new Paragraph("Hello PDF"));
            document.close();
            
            // 问题所在：PDF已经写入，却还要返回R对象
            return R.ok("接口正在开发中，敬请期待~");
            
        } catch (Exception e) {
            e.printStackTrace();
            return R.error("PDF生成失败");
        }
    }
}

@GetMapping("/download/pdf")
public void downloadPdf(CustStmtReq req, HttpServletResponse response) {
    try {
        // 1. 设置响应头
        response.setContentType("application/pdf");
        response.setHeader("Content-Disposition", 
            "attachment; filename=" + URLEncoder.encode("对账单.pdf", "UTF-8"));
        
        // 2. 生成PDF
        Document document = new Document(PageSize.A4);
        PdfWriter.getInstance(document, response.getOutputStream());
        document.open();
        
        // 添加PDF内容
        document.add(new Paragraph("客户对账单"));
        document.add(new Paragraph("生成时间：" + LocalDateTime.now()));
        document.add(new Paragraph("请求参数：" + req.toString()));
        
        document.close();
        
    } catch (Exception e) {
        log.error("PDF生成失败", e);
        throw new RuntimeException("PDF生成失败", e);
    }
}