Question

我使用简单的代码进行文件上传，但我不知道为什么会收到此错误。我是java的新手，所以我没有太多想法

二手代码： -

package net.codejava.upload;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Iterator;
import java.util.List;
import javax.servlet.ServletException;
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;

public class UploadServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private static final String UPLOAD_DIRECTORY = "upload";
private static final int THRESHOLD_SIZE     = 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

/**
 * handles file upload via HTTP POST method
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // checks if the request actually contains upload file
    if (!ServletFileUpload.isMultipartContent(request)) {
        PrintWriter writer = response.getWriter();
        writer.println("Request does not contain upload data");
        writer.flush();
        return;
    }

    // configures upload settings
    DiskFileItemFactory factory = new DiskFileItemFactory();
    factory.setSizeThreshold(THRESHOLD_SIZE);
    factory.setRepository(new File(System.getProperty("java.io.tmpdir")));

    ServletFileUpload upload = new ServletFileUpload(factory);
    upload.setFileSizeMax(MAX_FILE_SIZE);
    upload.setSizeMax(MAX_REQUEST_SIZE);

    // constructs the directory path to store upload file
    String uploadPath = getServletContext().getRealPath("")
        + File.separator + UPLOAD_DIRECTORY;
    // creates the directory if it does not exist
    File uploadDir = new File(uploadPath);
    if (!uploadDir.exists()) {
        uploadDir.mkdir();
    }

    try {
        // parses the request's content to extract file data
        List formItems = upload.parseRequest(request);
        Iterator iter = formItems.iterator();

        // iterates over form's fields
        while (iter.hasNext()) {
            FileItem item = (FileItem) iter.next();
            // processes only fields that are not form fields
            if (!item.isFormField()) {
                String fileName = new File(item.getName()).getName();
                String filePath = uploadPath + File.separator + fileName;
                File storeFile = new File(filePath);

                // saves the file on disk
                item.write(storeFile);
            }
        }
        request.setAttribute("message", "Upload has been done successfully!");
    } catch (Exception ex) {
        request.setAttribute("message", "There was an error: " + ex.getMessage());
    }
    getServletContext().getRequestDispatcher("/message.jsp").forward(request, response);
}
}

得到错误： -

HTTP Status 500 - type Exception report
message description The server encountered an internal error () that
prevented it from fulfilling this request.

例外

javax.servlet.ServletException：Servlet执行引发异常

根本原因

java.lang.NoClassDefFoundError: javax/servlet/http/HttpServletRequest
org.apache.commons.fileupload.servlet.ServletFileUpload.isMultipartContent(ServletFileUpload.java:68)

net.codejava.upload.UploadServlet.doPost(UploadServlet.java:35)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
javax.servlet.http.HttpServlet.service(HttpServlet.java:820)

根本原因

java.lang.ClassNotFoundException: javax.servlet.http.HttpServletRequest
java.net.URLClassLoader$1.run(Unknown Source)
java.net.URLClassLoader$1.run(Unknown Source)
java.security.AccessController.doPrivileged(Native Method)
java.net.URLClassLoader.findClass(Unknown Source)
java.lang.ClassLoader.loadClass(Unknown Source)
java.lang.ClassLoader.loadClass(Unknown Source)
org.apache.commons.fileupload.servlet.ServletFileUpload.isMultipartContent(ServletFileUpload.java:68)
net.codejava.upload.UploadServlet.doPost(UploadServlet.java:35)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
javax.servlet.http.HttpServlet.service(HttpServlet.java:820)

注意Apache enter code here Tomcat / 6.0.20日志中提供了根本原因的完整堆栈跟踪。

请帮助我，我正在等待解决方案

在java中上传文件的异常错误

0 个答案: