写出一个Springmvc的文件下载的案例

下面是一个Spring MVC的文件下载案例：

创建一个控制器类 FileDownloadController.java：

@Controller
public class FileDownloadController {

    @RequestMapping("/download")
    public void downloadFile(HttpServletRequest request, HttpServletResponse response) throws IOException {
        String filePath = "D:/files/file.txt"; // 文件路径

        File file = new File(filePath);
        if (file.exists()) {
            // 设置响应头
            response.setContentType("application/octet-stream");
            response.setHeader("Content-Disposition", "attachment; filename=" + file.getName());

            // 创建输入流，读取文件内容
            InputStream inputStream = new FileInputStream(file);

            // 创建输出流，写入响应
            OutputStream outputStream = response.getOutputStream();
            byte[] buffer = new byte[1024];
            int length;
            while ((length = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, length);
            }

            // 关闭流
            outputStream.flush();
            outputStream.close();
            inputStream.close();
        }
    }
}

在Spring MVC的配置文件中配置视图解析器和请求映射：

<!-- 配置视图解析器 -->
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix" value="/WEB-INF/views/" />
    <property name="suffix" value=".jsp" />
</bean>

<!-- 配置请求映射 -->
<mvc:annotation-driven />
<context:component-scan base-package="com.example.controller" />

创建一个 JSP 文件 download.jsp 用于触发文件下载：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>File Download Example</title>
</head>
<body>
    <h1>File Download Example</h1>
    <form action="${pageContext.request.contextPath}/download" method="GET">
        <input type="submit" value="Download File">
    </form>
</body>
</html>

创建一个启动类 MainApp.java：

public class MainApp {
    public static void main(String[] args) {
        SpringApplication.run(MainApp.class, args);
    }
}

启动应用并访问 http://localhost:8080/download，点击 "Download File" 按钮即可下载文件