图片上传功能

痛定思痛。 2022-08-18 00:43 392阅读 0赞

以前也实现过上传，只不过每次都是，写完之后没有总结，下次遇到时，还要重新写，重新调式，很是浪费时间，所以，今天实现一个上传图片的功能，包括简单的页面和servlet，下次再要写这个功能时，直接拿过来就可以了，没有理论，直接上代码+少量的注释。在最下面我会把项目上传，大家需要jar包，可以从项目中拿。

该项目用到的jar包如图，在下面的项目demo中有jar包：

![Center][]

一、upload.jsp页面代码：

<%@ page language="java" contentType="text/html; charset=UTF-8"  
        pageEncoding="UTF-8"%>  
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">  
    <html>  
    <head>  
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">  
    <meta http-equiv="pragma" content="no-cache" />  
    <base target="_self">  
    <title>文件上传</title>  
    </head>  
    <body>  
        <h5>文件上传</h5><hr/>  
        <form id="file_upload_id" name="file_upload_name" action="upload" method="post" enctype="multipart/form-data">  
            文件名称：<input type="text" name="fileName" value="aaa.jpg"/>  
            作       者： <input type="text" name="author" value="jack"/>  
            <div><input type="file" name="file_upload"/></div>  
            <div><input type="submit" value="上传"	/></div>  
        </form>  
    </body>  
    </html>

二、web.xml配置文件代码：

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
      <display-name>UploadDemo</display-name>
      <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
      </welcome-file-list>
      
      
      <servlet>
    		<servlet-name>uploadPhoto</servlet-name>
    		<servlet-class>com.upload.demo.UploadServlet</servlet-class>
    	</servlet>
    	<servlet-mapping>
    		<servlet-name>uploadPhoto</servlet-name>
    		<url-pattern>/upload</url-pattern>
    	</servlet-mapping>
      
    </web-app>

三、UploadServlet代码：

package com.upload.demo;
    
    import java.io.BufferedReader;
    import java.io.File;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    import java.util.ArrayList;
    import java.util.Date;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    import java.util.Properties;
    import java.util.UUID;
    
    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;
    
    import com.lidroid.xutils.http.RequestParams;
    
    
    public class UploadServlet extends HttpServlet{
    
    	@Override
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
    			throws ServletException, IOException {
    		doPost(req, resp);
    	};
    
    	@Override
    	protected void doPost(HttpServletRequest request,
    			HttpServletResponse response) throws ServletException, IOException {
    		//服务器端接收,请求被后台拦截到这里
    		exeUploadedInfos(request, response);
    		
    	};
    
    	/**
    	 *  定义接口
    	 */
    	public interface UploadStatusListener {
    		public void status(boolean status, Map<String, String> params,
    				List<String> files, HttpServletRequest request);
    	}
    	UploadStatusListener mUploadStatusListener = null;
    	// 注册监听器，如果这里没有使用Vector而是使用ArrayList那么要注意同步问题
    	public void addStatusListener(UploadStatusListener listener) {
    		mUploadStatusListener = listener;
    	}
    
    	/**
    	 * @function：回调方法，执行图片上传，根据成功或失败的状态完成其他的操作
    	 * @param request
    	 * @param response
    	 */
    	private void exeUploadedInfos(HttpServletRequest request,
    			HttpServletResponse response) {
    		UploadServlet up = new UploadServlet();
    		up.addStatusListener(new UploadStatusListener() {
    			public void status(boolean status, Map<String, String> params,
    					List<String> files, HttpServletRequest request) {
    				if (status) {//成功
    					//Map中取值
    					String memberId = params.get("memberId");
    					//List中取值
    					String fileUrl = files.get(0);
    					System.out.println("===================================成功");
    				} else {
    					//失败
    					System.out.println("========================================失败");
    				}
    			}
    		});
    		up.upload(request, response);
    
    	}
    	
    	/**
    	 * @function：具体上传图片的功能在这里完成，
    	 * 然后调用接口回调方法mUploadStatusListener.status(flag, params, filenames , request);跳转到回调函数中
    	 * @param request
    	 * @param response
    	 */
    	public void upload(HttpServletRequest request, HttpServletResponse response) {
    		boolean flag = false;
    		Map<String, String> params = new HashMap<String, String>();
    		List<String> filenames = new ArrayList<String>();
    		try {
    			System.out.println("开始文件上传****************");
    			request.setCharacterEncoding("utf-8"); // 设置编码
    			// 设置上传文件最大为 3M
                final long MAX_SIZE = 3 * 1024 * 1024;
    			// 1.创建一个解析器工厂
    			DiskFileItemFactory factory = new DiskFileItemFactory();
    			// 获取临时文件路径
    			String savePath = "F:/upload/" ;//具体的路径
    			if(!new File(savePath).exists()){
    				new File(savePath).mkdirs();
    			}
    			factory.setRepository(new File(savePath));
    			factory.setSizeThreshold(4096);
    			// 2.得到一个解析器
    			ServletFileUpload upload = new ServletFileUpload(factory);
    			upload.setSizeMax(MAX_SIZE);
    			// upload.setHeaderEncoding("UTF-8");
    			// 3.将请求传入解析器，对请求进行解析
    			List<FileItem> list = upload.parseRequest(request);
    			// 4.迭代list集合，得到每个输入项的数据
    			int count = 0 ;
    			for (FileItem item : list) {
    				count ++ ;
    				// 5.判断item的类型
    				if (item.isFormField()) {
    					// 普通文本输入项
    					String inputName = item.getFieldName();
    					String inputValue = item.getString();
    					params.put(inputName, inputValue);
    					System.out.println("==================传进来的参数：  "+count+"、"+inputName + "=" + inputValue);
    					
    				} else {
    					// 上传文件输入项（如图片）
    					String fileName = item.getName();// 获取文件名
    					if (!"".equals(fileName)) {
    						fileName = fileName.substring(fileName.lastIndexOf("\\") + 1);
    						System.out.println("*************存放传过来的图片****************");
    						InputStream in = item.getInputStream();
    						FileOutputStream out = new FileOutputStream(savePath+fileName);
    						byte[] buf = new byte[1024];
    						int len = 0;
    						while ((len = in.read(buf)) > 0) {
    							out.write(buf, 0, len);
    						}
    						in.close();
    						out.close();
    						item.delete();// 删除临时文件
    						filenames.add("上传成功了") ;
    						flag = true;
    						if (mUploadStatusListener != null) {
    							System.out.println("======文件上传：  ===flag=" + flag +";==="+ params.toString()
    									+ "==文件名fileName：=" + fileName);
    							mUploadStatusListener.status(flag, params, filenames , request);
    						}
    						System.out.println("文件上传结束****************");
    					}
    				}
    			}
    			
    		} catch (Exception e) {
    			e.printStackTrace();
    			request.setAttribute("message", "上传失败");
    			System.out.println("***********上传失败******************");
    			if (mUploadStatusListener != null) {
    				System.out.println("****************上传失败*******************************");
    				mUploadStatusListener.status(flag, params, filenames , request);
    			}
    		}
    	}
    
    	
    }

四、代码解释：

1、访问路径：http://localhost:8080/UploadDemo/upload.jsp

如图：

![Center 1][]

2、点击上传后，进入UploadServlet类

List<FileItem> list = upload.parseRequest(request);  
产生临时上传文件

如图：

![Center 2][]

3、FileOutputStream out = new FileOutputStream(savePath+fileName);  
创建要生成的图片

如图：

![Center 3][]

4、out.close();  
执行完这行代码，上传图片的字节流写入完毕，完整图片如图

![Center 4][]

5、item.delete();// 删除临时文件，删除后如图：

![Center 5][]

五、项目下载：

[ 上传图片demo下载，点这里][_demo]

[Center]: /images/20220731/87b410a0985843cbac8d41ca49ccc435.png
[Center 1]: /images/20220731/517e6dba5990410a9851b89a8fe83574.png
[Center 2]: /images/20220731/cb8a9c59c07a40e3ac21671f69166313.png
[Center 3]: /images/20220731/6559b939c6c04f0a9a972f2e9a8fd27c.png
[Center 4]: /images/20220731/d0d3f4eea82a4eeeb7bb470284063dd2.png
[Center 5]: /images/20220731/2042a7afbed2482891ef3e4431770053.png
[_demo]: http://download.csdn.net/detail/u011159417/9314927