如何解决这个java.lang.NoClassDefFoundError:org/apache/commons/io/output/DeferredFileOutputStream？

Question

我使用下面的代码将文件上传到tomcat5.5,它给了我以下异常

java.lang.NoClassDefFoundError: org/apache/commons/io/output/DeferredFileOutputStream

你能帮我找一下吗？

import java.io.File;
import java.io.IOException;
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.FileItemFactory;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

/**
 * Servlet implementation class FileUploadServlet
 */
public class FileUploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public FileUploadServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    @SuppressWarnings("rawtypes")
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        boolean isMultipart = ServletFileUpload.isMultipartContent(request);
        System.out.println("Status : "+isMultipart);
        if (isMultipart) {
            FileItemFactory factory = new DiskFileItemFactory();
            ServletFileUpload upload = new ServletFileUpload(factory);

            try {
                List items = upload.parseRequest(request);
                Iterator iterator = items.iterator();
                while (iterator.hasNext()) {
                    FileItem item = (FileItem) iterator.next();

                    if (!item.isFormField()) {
                        String fileName = item.getName();

                        String root = getServletContext().getRealPath("/");
                        File path = new File(root + "/uploads");
                        if (!path.exists()) {
                            boolean status = path.mkdirs();
                        }

                        File uploadedFile = new File(path + "/" + fileName);
                        System.out.println(uploadedFile.getAbsolutePath());
                        item.write(uploadedFile);
                    }
                }
            } catch (FileUploadException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        response.sendRedirect("upload.jsp");
    }

}

这是我用的罐子 commons-fileupload-1.2.2.jar

Answer 1

特定的异常消息告诉您类路径中缺少所提到的类.当org.apache.commons.io包名称提示时,提到的类是http://commons.apache.org/io项目的一部分.

事实上,Commons FileUpload将Commons IO作为依赖项.您还需要下载并commons-io.jar放入/WEB-INF/lib.

也可以看看:

• 如何使用JSP/Servlet将文件上传到服务器？
• 如何在不面对java.lang.ClassNotFoundException的情况下将JAR库添加到WAR项目中？Classpath vs Build Path vs/WEB-INF/lib
• 如何在Eclipse项目中导入javax.servlet API？

Answer 2

使用maven依赖

<dependency> 
  <groupId>org.apache.commons</groupId>
  <artifactId>commons-io</artifactId> 
  <version>1.3.2</version> 
</dependency> 

或者将commons-io.1.3.2.jar下载到您的lib文件夹中

Answer 3

解

默认情况下,Struts使用Apache"commons-io.jar"进行文件上传过程.要修复它,您必须将此库包含到项目依赖项库文件夹中.

1. 直接获取

从官方网站获取"commons-io.jar" - http://commons.apache.org/io/

2. 从Maven获取

首选方法是从Maven存储库获取"commons-io.jar"

文件:pom.xml

  <dependency>
    <groupId>commons-io</groupId>
      <artifactId>commons-io</artifactId>
    <version>1.4</version>
  </dependency>