J2EE学习笔记——文件的上传

最新推荐文章于 2022-10-17 16:25:49 发布

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最新推荐文章于 2022-10-17 16:25:49 发布

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分类专栏： J2EE

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本文介绍了一个使用Java实现的文件上传示例，包括所需的commons.io和commons-fileupload库，通过一个简单的JSP页面和Servlet来处理文件上传逻辑，并对上传文件的类型和大小进行了限制。

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文件上传需要两个JAR包：

commons.io-1.4.0.jar

org.apache.commons-fileupload-1.2.1.jar

index.jsp:

<body>
    上传文件 <br>
    
    <form action="UpLoadServer" method="post" enctype="multipart/form-data" >
    
     用户名： <input type="text" name="username" ><br>
     
     文件： <input type="file" name="file" >
       <input type="submit" value="上传">
        
    
    
    </form>
  </body>
</html>

==============================================================================
servlet代码：

package xuyan.com;

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.*;

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.FileUploadException;
import org.apache.commons.fileupload.FileUploadBase.FileSizeLimitExceededException;
import org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

public class UpLoadServer extends HttpServlet {

	private  String[] fileExts={"doc","zip","rar","jpg","txt"};
	
	/**
	 * The doGet method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to get.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

	
		
		//检查请求是否是一个上传表单(必须是post请求，和enctype=“multipart/form-date”)
		
		Boolean isMultipart=ServletFileUpload.isMultipartContent(request);
		
		if(isMultipart)
		{
			//创建一个临时文件存放要上传的文件，第一个参数是上传文件大小，第二个参数是存放的临时目录
			DiskFileItemFactory factory=new DiskFileItemFactory(1024*1024*5,new File("D:\\temp"));
		  	
			//创建一个文件上传的句柄
			ServletFileUpload upload=new ServletFileUpload(factory);
			
			//设置文件上传的整个大小和上传的单个文件大小
			upload.setSizeMax(1024*1024*50);
			upload.setFileSizeMax(1024*1024*5);
			
			try {
				
				//把页面表单中每一个表单元解析成一个Fileitem
				List<FileItem> items=upload.parseRequest(request);
				for(FileItem fileItem:items)
				{
					//如果是一个普通的表单元素（type不是files的表单元素）
					if(fileItem.isFormField())
					{
						//System.out.println(fileItem.getFieldName()); //得到对应表单元素的名字
						System.out.println(fileItem.getString());//得到表单元素的值
						
					}
					else 
					{
						//获取文件的后缀名
						String filename=fileItem.getName();//得到文件名
						String fileExt=filename.substring(filename.lastIndexOf(".")+1, filename.length());
						
						if(Arrays.binarySearch(fileExts, fileExt)!=-1)
						{
							try {
								
								//将文件上传到upload目录并命名  ,getreadplth可以得到该目录下包含/upload的绝对路径
								
								fileItem.write(new File(getServletContext().getRealPath("/upload")+"/"+UUID.randomUUID().toString()+"."+fileExt));
								System.out.println("该文件上传成功！！");
								
								
							} catch (Exception e) {
								// TODO: handle exception
								e.printStackTrace();
							}
						}
						
						else
						{
							System.out.println("该文件类型不能上传");
						}
					}
				}
				
			} catch (SizeLimitExceededException e) {
				// TODO: handle exception
				 System.out.println("整个请求的大小超过了规定的大小..."); 
			}
			
			catch (FileSizeLimitExceededException e)
			{
				System.out.println("请求中一个上传文件的大小超过了规定的大小...");
			}
			
			catch(FileUploadException e)
			{
				e.printStackTrace();
			}
			
		
		}
		
	}

	/**
	 * The doPost method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to post.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		this.doGet(request, response);
	}

}