add<文件上传与下载>

readme.md

@@ -1,6 +1,8 @@
-# jsp+servlet
+# 改进版
+
+- 登录验证码
+- 图片上传下载
 
-## 全局过滤器的应用（鉴权，异常统一处理）
 
 
 

src/main/java/example/controller/FileDownloadServlet.java

@@ -0,0 +1,57 @@
+package example.controller;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import javax.servlet.ServletException;
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+@WebServlet("/download")
+public class FileDownloadServlet extends HttpServlet {
+    private static final long serialVersionUID = 1L;
+
+    // 设置文件上传路径（webapp/uploads）
+    private static final String UPLOAD_DIRECTORY = "uploads";
+
+    protected void doGet(HttpServletRequest request, HttpServletResponse response)
+            throws ServletException, IOException {
+
+        // 动态解析 webapp/uploads 的路径
+        String uploadPath = getServletContext().getRealPath("/") + UPLOAD_DIRECTORY;
+
+        // 获取请求的文件名
+        String fileName = request.getParameter("file");
+        if (fileName == null || fileName.isEmpty()) {
+            response.getWriter().println("File parameter is missing");
+            return;
+        }
+
+        // 构造文件的完整路径
+        File file = new File(uploadPath + File.separator + fileName);
+
+        // 检查文件是否存在
+        if (!file.exists()) {
+            response.getWriter().println("File not found: " + fileName);
+            return;
+        }
+
+        // 设置响应的内容类型
+        response.setContentType(getServletContext().getMimeType(file.getName()));
+        response.setContentLength((int) file.length());
+        response.setHeader("Content-Disposition", "inline; filename=\"" + fileName + "\"");
+
+        // 读取文件并写入到响应输出流
+        try (FileInputStream fis = new FileInputStream(file);
+             OutputStream os = response.getOutputStream()) {
+            byte[] buffer = new byte[4096];
+            int bytesRead;
+            while ((bytesRead = fis.read(buffer)) != -1) {
+                os.write(buffer, 0, bytesRead);
+            }
+        }
+    }
+}

src/main/java/example/controller/UploadServlet.java

@@ -0,0 +1,83 @@
+package example.controller;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.List;
+import javax.servlet.ServletException;
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+import org.apache.commons.fileupload.FileItem;
+import org.apache.commons.fileupload.disk.DiskFileItemFactory;
+import org.apache.commons.fileupload.servlet.ServletFileUpload;
+
+@WebServlet("/UploadServlet")
+public class UploadServlet extends HttpServlet {
+    private static final long serialVersionUID = 1L;
+
+    // 设置上传目录
+    private static final String UPLOAD_DIRECTORY = "uploads";
+
+    // 上传配置
+    private static final int MEMORY_THRESHOLD = 1024 * 1024 * 3; // 3MB
+    private static final int MAX_FILE_SIZE = 1024 * 1024 * 40;   // 40MB
+    private static final int MAX_REQUEST_SIZE = 1024 * 1024 * 50; // 50MB
+
+    protected void doPost(HttpServletRequest request, HttpServletResponse response)
+            throws ServletException, IOException {
+
+        // 检查请求是否为多部分内容
+        if (!ServletFileUpload.isMultipartContent(request)) {
+            response.getWriter().println("Error: Form must have enctype=multipart/form-data.");
+            return;
+        }
+
+        // 配置上传参数
+        DiskFileItemFactory factory = new DiskFileItemFactory();
+        factory.setSizeThreshold(MEMORY_THRESHOLD);
+        factory.setRepository(new File(System.getProperty("java.io.tmpdir")));
+
+        ServletFileUpload upload = new ServletFileUpload(factory);
+        upload.setFileSizeMax(MAX_FILE_SIZE);
+        upload.setSizeMax(MAX_REQUEST_SIZE);
+
+        // 构造上传路径
+        String uploadPath = getServletContext().getRealPath("") + File.separator + UPLOAD_DIRECTORY;
+
+        // 如果目录不存在，则创建
+        File uploadDir = new File(uploadPath);
+        if (!uploadDir.exists()) {
+            uploadDir.mkdir();
+        }
+
+        try {
+            // 解析请求的内容
+            @SuppressWarnings("unchecked")
+            List<FileItem> formItems = upload.parseRequest(request);
+
+            if (formItems != null && formItems.size() > 0) {
+                for (FileItem item : formItems) {
+                    // 处理非表单字段
+                    if (!item.isFormField()) {
+                        String fileName = new File(item.getName()).getName();
+                        String filePath = uploadPath + File.separator + fileName;
+                        File storeFile = new File(filePath);
+
+                        // 保存文件到磁盘
+                        item.write(storeFile);
+
+                        request.setAttribute("message", "文件上传成功: " + fileName);
+                        request.setAttribute("fileName",fileName);
+                    }
+                }
+            }
+        } catch (Exception ex) {
+            request.setAttribute("message", "错误信息: " + ex.getMessage());
+        }
+
+        // 转发到 JSP 显示消息
+        getServletContext().getRequestDispatcher("/msg.jsp").forward(request, response);
+    }
+}

src/main/webapp/index.jsp

@@ -28,6 +28,13 @@
         </c:if>
     </div>
 
+    <form action="UploadServlet" method="post" enctype="multipart/form-data">
+        <label for="file">选择图片:</label>
+        <input type="file" name="file" id="file" required>
+        <button type="submit">上传</button>
+    </form>
+
+
 
 </body>
 </html>

src/main/webapp/msg.jsp

@@ -9,6 +9,11 @@
     <body>
         <h2>提示:</h2>
         <h3>${sessionScope.msg}</h3>
+        <h3>${message}</h3>
+            <!-- 动态生成图片标签 -->
+            <c:if test="${not empty fileName}">
+                <img src="/download?file=/${fileName}" alt="Uploaded Image" style="max-width: 100%; height: auto;">
+            </c:if>
         <button onclick="window.history.back();">返回</button>
 
     </body>