实现文件上传功能

现在随着网站的人性化提升，提高用户的个性化体验，所以很多项目中都少不了文件和图片上传功能。上传图片功能，我们可以用来实现用户上传头像的功能，提高用户的个性化体验，本文将实现图片和文件上传的功能。

对于文件上传，浏览器在上传的过程中是将文件以流的形式提交到服务器端的，如果直接使用Servlet获取上传文件的输入流然后再解析里面的请求参数是比较麻烦，所以一般选择采用apache的开源工具common-fileupload这个文件上传组件。这个common-fileupload上传组件的jar包可以去apache官网上面下载，也可以在struts的lib文件夹下面找到，struts上传的功能就是基于这个实现的。common-fileupload是依赖于common-io这个包的，所以还需要下载这个包。

首先看html页面——————UploadFile.jsp

<%@ 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">
<title>Insert title here</title>
</head>
<body>
    <form action="UploadFile.do" method="post" enctype="multipart/form-data">
        <input type="text" name="username"> <br> 
        <input    type="file" name="userimg">
        <input type="submit" value="提交">
    </form>
</body>
</html>

接下来看后台处理 ————UploadFile.java

import java.io.File;
import java.io.IOException;
import java.util.List;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
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;

@WebServlet("/UploadFile.do")
public class UploadFile extends HttpServlet {
    private static final long serialVersionUID = 1L;
   
    public UploadFile() {
        super();
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //借助工具解析 Commons——fileupload smartupload
    //判断传递的是否是文件内型
    boolean isMultipart =ServletFileUpload.isMultipartContent(request);
    if(isMultipart){
    DiskFileItemFactory factory=new DiskFileItemFactory();
    ServletContext servletContext =this.getServletConfig().getServletContext();
    //获取临时文件夹
    File repository =(File) servletContext.getAttribute("javax.servlet.context..tempdir");
    factory.setRepository(repository);
    ServletFileUpload upload =new ServletFileUpload(factory);
    //解决中文乱码
    upload.setHeaderEncoding("utf-8");
    //解析request获取到上传的参数
    try {
        List<FileItem> items=upload.parseRequest(request);
        //进行参数处理
        for(FileItem  item:items){
            if(item.isFormField()){
                System.out.println(item.getFieldName());
                System.out.println(item.getString("utf-8"));
            }else{
                System.out.println(item.getFieldName());
                System.out.println(item.getName());
                System.out.println(item.getContentType());
                System.out.println(item.getSize());
                //写入文件  "//"表示绝对路径
                String rootPath = servletContext.getRealPath("//");
                System.out.println(rootPath);
                String savaPath =rootPath+File.separator+"upload";
                File fileSavaFolder =new File(savaPath);
                if(!fileSavaFolder.exists()){
                    fileSavaFolder.mkdirs();
                }
                //完整的存储文件名
            String savaFileName=savaPath+File.separator+item.getName();
            System.out.println("name:"+savaFileName);
            File uploadedFile =new File(savaFileName);
            try {
                item.write(uploadedFile);
            } catch (Exception e) {
            
                e.printStackTrace();
            }
            }
        }
    } catch (FileUploadException e) {
        
        e.printStackTrace();
    }
    
    
      }
    }

}

通过以上代码我们就实现了文件上传功能