Servlet 文件上传

阳光穿透心脏的1/2处 2021-09-30 08:14 327阅读 0赞

# 前端代码 #

关键点

*  form上必须设置这两个属性 method=“post” enctype=“multipart/form-data”
 *  input 的type 是 type=“file”

<!DOCTYPE html>
    <html>
    <head>
      <title>Bootstrap 实例</title>
      <meta charset="utf-8">
      <meta name="viewport" content="width=device-width, initial-scale=1">
      <link rel="stylesheet" href="https://cdn.staticfile.org/twitter-bootstrap/4.1.0/css/bootstrap.min.css">
      <script src="https://cdn.staticfile.org/jquery/3.2.1/jquery.min.js"></script>
      <script src="https://cdn.staticfile.org/popper.js/1.12.5/umd/popper.min.js"></script>
      <script src="https://cdn.staticfile.org/twitter-bootstrap/4.1.0/js/bootstrap.min.js"></script>
    </head>
    <body>
    
    <form action="FileUploadDemo1Servlet" method="post" enctype="multipart/form-data">
      <p>默认上传文件样式:</p>
       <input type="file" id="myFile" name="filename2">
      <button type="submit" class="btn btn-primary">提交</button>
    </form>
    
    </body>
    </html>

# Servlet 后台 #

*  pom 文件添加包

<dependency>
        <groupId>commons-fileupload</groupId>
        <artifactId>commons-fileupload</artifactId>
        <version>1.3</version>
    </dependency>

*  创建servelet

package com.base.servlet;
    
    import java.io.File;
    import java.io.IOException;
    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.FileUploadException;
    import org.apache.commons.fileupload.disk.DiskFileItemFactory;
    import org.apache.commons.fileupload.servlet.ServletFileUpload;
    
    /**
     * Servlet implementation class FileUploadDemo1Servlet
     */
    public class FileUploadDemo1Servlet extends HttpServlet {
    	private static final long serialVersionUID = 1L;
           
        /**
         * @see HttpServlet#HttpServlet()
         */
        public FileUploadDemo1Servlet() {
            super();
            // TODO Auto-generated constructor stub
        }
    
    	/**
    	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
    	 */
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		response.getWriter().append("Served at: ").append(request.getContextPath());
    	}
    
    	/**
    	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
    	 */
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		 	DiskFileItemFactory factory = new DiskFileItemFactory(); 
    		    //当内存中文件数据达到THRESHOLD_SIZE后，就写入临时文件中，避免上传大文件时，消化太多内存 
    		    ServletFileUpload upload = new ServletFileUpload(factory); 
    		    upload.setHeaderEncoding("UTF-8"); 
    		    upload.setSizeMax(2*1024*1024); 
    		    //上传以后，文件保存的地址
    		    String savePath="C:/tmp/demo1/";
    		    try {
    		    	// 获取 from表单里面，所有的元素
    				List items = upload.parseRequest(request);
    				
    				//form 循环 遍历表单里面的元素集合
    				for(int i=0;i<items.size();i++){
    					//每个表单元素，都封装到一个FileItem类型的对象中
    					FileItem fitem=(FileItem) items.get(i);
    					System.out.println("元素name属性的值是="+fitem.getFieldName());
    					
    					//  fitem.isFormField() 表示，如果当前这个元素的类型type不等于file,那么就返回true
    					if(fitem.isFormField() ){
    						System.out.println("这是一个普通的非文件字段");
    						System.out.println("输入框，前端输入的值是---"+fitem.getString());
    						
    					}else{
    						
    						System.out.println("这是一个文件字段");
    						System.out.println("fitem.getName() 原始的文件名字--"+fitem.getName());
    						//File.separator 这是一个静态的变量。 
    						// 在windows的操作系统返回值是 \\  如果是linux系统，返回是一个  /
    						
    						
    						//设置文件的名字
    						String filename=System.currentTimeMillis()+"-"+fitem.getName();
    						//存储上传的文件
    						File file=new File(savePath+File.separator+filename);
    						try {
    							fitem.write(file);
    						} catch (Exception e) {
    							// TODO Auto-generated catch block
    							e.printStackTrace();
    						}
    						
    					}
    				}
    			} catch (FileUploadException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    		    
    		    
    		
    		
    	}
    
    }

# 效果展示 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2gzNTYzNjM_size_16_color_FFFFFF_t_70]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2gzNTYzNjM_size_16_color_FFFFFF_t_70 1]

![在这里插入图片描述][20190728214027687.png]

*  **上传成功以后**  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2gzNTYzNjM_size_16_color_FFFFFF_t_70 2]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2gzNTYzNjM_size_16_color_FFFFFF_t_70]: /images/20210726/20e6cbbbc8924e1a903fdeeaf9a9b4ae.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2gzNTYzNjM_size_16_color_FFFFFF_t_70 1]: /images/20210726/cc59cfd314dd41ae86ab9a79ffa96248.png
[20190728214027687.png]: /images/20210726/870e2e85544644878af582ca2ca02bba.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2gzNTYzNjM_size_16_color_FFFFFF_t_70 2]: /images/20210726/06c2b56847b94c878751b0ae34ee8f71.png