J2EE:Servlet上传文件到服务器，并相应显示

2018-07-06 01:25:13来源：博客园阅读 ()

Servlet 可以与HTML一起使用来允许用户上传文件到服务器

编辑上传文件的页面upload.html

注意事项：上传方式使用POST不能使用GET（GET不能上传文件）

表单 enctype 属性应该设置为 multipart/form-data.（表示提交的数据是二进制文件）

upload.html

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>文件上传</title>
</head>
<body>
    <form action="UploadPhotoServlet" method="POST" enctype="multipart/form-data">
        人物名称:<input type="text" name="heroName"/><br>
        上传头像:<input type="file" name="filepath"/><br>
        <input type="submit" value="上传">
        
    </form>
</body>
</html>

UPloadPtotoServlet文件上传类--上传功能的开发

将commons-io-1.4.jar和commons-fileupload-1.2.2.jar 两个jar包放到WEB-INF/lib 目录下。

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Iterator;
import java.util.List;

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;

/**
 * Servlet implementation class UploadPhotoServlet
 */
@WebServlet("/UploadPhotoServlet")
public class UploadPhotoServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public UploadPhotoServlet() {
        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());
        String filename=null;
        
        DiskFileItemFactory factory=new DiskFileItemFactory();    //磁盘文件条目工厂
        ServletFileUpload upload=new ServletFileUpload(factory); //负责处理上传的文件数据，并将表单中每个输入项封装成一个fileitem对象中
        //设置上传文件的大小为10M
        factory.setSizeThreshold(2*1024*1024);
        List items=null;
        
        try {
            //parse  解析
            items=upload.parseRequest(request);   //得到一个保存了所有上传内容的List对象
        } catch (FileUploadException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        Iterator iter=items.iterator();   //迭代上传的文件数据
        while(iter.hasNext()){
            FileItem item=(FileItem) iter.next();
            if(!item.isFormField()){  //如果不是上传的
                //根据时间戳创建头像文件
                filename=System.currentTimeMillis()+".jpg";
                //通过getrealpath获取上传文件夹，如果项目存在将存在当前项目下  不存在的话创建项目文件夹
                //图片文件夹
                String photoFolder=request.getServletContext().getRealPath("uploaded");
                File f=new File(photoFolder,filename);
                f.getParentFile().mkdirs();  //如果父文件夹不存在则自动创建
                //通过item.getInputStream() 获取浏览器上传的文件
                InputStream is = item.getInputStream();   //将文件读进来
                //复制文件
                FileOutputStream fos=new FileOutputStream(f);  //往界面上显示
                byte[] b=new byte[2*1024*1024];
                int len=0;
                while((len=is.read(b))!=-1){
                    fos.write(b, 0, len);
                }
                fos.close();
                
            }else{
                System.out.println(item.getFieldName());//heroName
                String value=item.getString();   
                value=new String(value.getBytes("ISO-8859-1"), "UTF-8");
                System.out.println(value);   //桑葚
            }
        }
        String html="<img width='200' height='150' src='uploaded/%s'/>";
        response.setContentType("text/html");
        PrintWriter pw=response.getWriter();
        pw.format(html, filename);
        
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}