Servlet文件上传下载

今天我们来学习Servlet文件上传下载

Servlet文件上传主要是使用了ServletInputStream读取流的方法，其读取方法与普通的文件流相同。

一.文件上传相关原理

第一步，构建一个upload.jsp文件

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
     
    <title>My JSP 'index.jsp' starting page</title>
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
  </head>
  <body>
    <form enctype="application/x-www-form-urlencoded" action="${pageContext.request.contextPath }/servlet/UploadServlet1" method="post">
    <input type="text" name="name" value="name" /><br/>
    <div id="div1">
    <div>
    <input type="file" name="photo" />
    </div>
    </div>
    <input type="submit" name="上传" /><br/>
    </form>
  </body>
</html>

第二步，构建一个servlet UploadServlet1.java

package com.zk.upload;
 
import java.io.IOException;
import java.io.PrintWriter;
 
import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
public class UploadServlet1 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
            String name=request.getParameter("name");
            String photo=request.getParameter("photo");
             
            ServletInputStream inputstream=request.getInputStream();
            int len=0;
            byte[] b=new byte[1024];
            while((len=inputstream.read(b))!=-1){
                System.out.println(new String(b,0,len));
            }
            inputstream.close();
    }<br>
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        ServletInputStream inputstream=request.getInputStream();
        int len=0;
        byte[] b=new byte[1024];
        while((len=inputstream.read(b))!=-1){
            System.out.println(new String(b,0,len));
        }
        inputstream.close();
    }
 
    /**
     * Initialization of the servlet. <br>
     *
     * @throws ServletException if an error occurs
     */
    public void init() throws ServletException {
        // Put your code here
    }
 
}

最后执行UploadServlet1.java之后，输出上传文件的信息。

这里涉及到文件上传的相关原理，在我本地浏览器中调试显示信息如下：

这是一些有关文件上传的相关信息。

二.文件上传

接下来，我们开始进行文件上传的工作。

第一部，创建jsp

这里的form表单需要更改一下enctype属性，这个属性是规定在发送到服务器之前应该如何对表单数据进行编码。

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
     
    <title>My JSP 'index.jsp' starting page</title>
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
  </head>
  <body>
     <form enctype="multipart/form-data" action="${pageContext.request.contextPath }/servlet/UploadServlet2" method="post">
    <input type="text" name="name" value="name" /><br/>
    <div id="div1">
    <div>
    <input type="file" name="photo" />
    </div>
    </div>
    <input type="submit" name="上传" /><br/>
    </form>
  </body>
</html>

　　UploadServlet2.java

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package com.zk.upload;
 
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;
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.FileUploadBase;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.FilenameUtils;
 
public class UploadServlet2 extends HttpServlet {
 
    /**
     * Constructor of the object.
     */
    public UploadServlet2() {
        super();
    }
 
    /**
     * Destruction of the servlet. <br>
     */
    public void destroy() {
        super.destroy(); // Just puts "destroy" string in log
        // Put your code here
    }
 
    /**
     * 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 {
        //优先级不高
        request.setCharacterEncoding("UTF-8");
         
        //要执行文件上传的操作
        //判断表单是否支持文件上传
        boolean isMultipartContent=ServletFileUpload.isMultipartContent(request);
        if(!isMultipartContent){
            throw new RuntimeException("your form is not multipart/form-data");
        }
        //创建一个DiskFileItemFactory工厂类
        DiskFileItemFactory factory=new DiskFileItemFactory();
        //创建一个ServletFileUpload核心对象
        ServletFileUpload sfu=new ServletFileUpload(factory);
        //解决上传表单乱码的问题
        sfu.setHeaderEncoding("UTF-8");
        try {
            //限制上传文件的大小
            //sfu.setFileSizeMax(1024);
            //sfu.setSizeMax(6*1024*1024);
            //解析requst对象，得到一个表单项的集合
            List<FileItem> fileitems=sfu.parseRequest(request);
            //遍历表单项数据
            for(FileItem fileItem:fileitems){
                if(fileItem.isFormField()){
                    //普通表单项
                    processFormField(fileItem);
                }
                else{
                    //上传表单项
                    processUploadField(fileItem);
                }
            }
        } catch(FileUploadBase.FileSizeLimitExceededException e){
            throw new RuntimeException("文件过大");
        }catch (FileUploadException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    private void processUploadField(FileItem fileItem) {
        // TODO Auto-generated method stub
        //得到上传的名字
        String filename=fileItem.getName();
        //得到文件流
        try {
            InputStream is=fileItem.getInputStream();
            String dictory=this.getServletContext().getRealPath("/upload");
            System.out.println(dictory);
            //创建一个存盘的路径
            File storeDirecctory=new File(dictory);//既代表文件又代表目录
            if(!storeDirecctory.exists()){
                storeDirecctory.mkdirs();//创建一个指定目录
            }
            //处理文件名
            filename=filename.substring(filename.lastIndexOf(File.separator)+1);
            if(filename!=null){
                filename=FilenameUtils.getName(filename);
            }
            //解决文件同名的问题
            filename=UUID.randomUUID()+"_"+filename;
             
            //目录打散
            //String childDirectory=makeChildDirectory(storeDictory);//2015-10-
            String childDirectory=makeChildDirectory2(storeDirecctory,filename);
            //System.out.println(childDirectory);
            //上传文件,自动删除临时文件
            fileItem.write(new File(storeDirecctory,childDirectory+File.separator+filename));
 
             
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
         
         
    }
 
    //上传表单项
    private void processUploadField1(FileItem fileItem) {
        // TODO Auto-generated method stub
         
        //得到上传的名字
        String filename=fileItem.getName();
        //得到文件流
        try {
            //得到文件流
            InputStream is=fileItem.getInputStream();
             
            String dictory=this.getServletContext().getRealPath("/upload");
            System.out.println(dictory);
            //创建一个存盘的路径
            File storeDictory=new File(dictory);//既代表文件又代表目录
            if(!storeDictory.exists()){
                storeDictory.mkdirs();//创建一个指定目录
            }
            //处理文件名
            filename=filename.substring(filename.lastIndexOf(File.separator)+1);
            if(filename!=null){
                filename=FilenameUtils.getName(filename);
            }
            //解决文件同名的问题
            filename=UUID.randomUUID()+"_"+filename;
             
            //目录打散
            //String childDirectory=makeChildDirectory(storeDictory);//2015-10-
            String childDirectory2=makeChildDirectory2(storeDictory,filename);
            //System.out.println(childDirectory);
            //在storeDictory目录下创建完整的文件
            //File file=new File(storeDictory,filename);
            //File file=new File(storeDictory,childDirectory+File.separator+filename);
            File file2=new File(storeDictory,childDirectory2+File.separator+filename);
 
            //通过文件输出流将上传的文件保存到磁盘
            //FileOutputStream fos=new FileOutputStream(file);
            FileOutputStream fos2=new FileOutputStream(file2);
 
            int len=0;
            byte[] b=new byte[1024];
            while((len=is.read(b))!=-1){
            //  fos.write(b,0,len);
                fos2.write(b,0,len);
            }
            //fos.close();
            fos2.close();
            is.close();
            System.out.println("success");
            //删除临时文件
            fileItem.delete();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
         
    }
    //目录打散
    private String makeChildDirectory(File storeDictory) {
        // TODO Auto-generated method stub
        SimpleDateFormat sm=new SimpleDateFormat("yyyy-MM-dd");
        String date=sm.format(new Date());
        //创建目录
        File file=new File(storeDictory,date);
        if(!file.exists()){
            file.mkdirs();
        }
        return date;
    }
    //目录打散
    private String makeChildDirectory2(File storeDictory,String filename){
        int hashcode=filename.hashCode();
        System.out.println(hashcode);
        String code=Integer.toHexString(hashcode);
        String childDirectory=code.charAt(0)+File.separator+code.charAt(1);
        //创建指定目录
        File file=new File(storeDictory,childDirectory);
        if(!file.exists()){
            file.mkdirs();
        }
        return childDirectory;
    }
    //普通表单项
    private void processFormField(FileItem fileItem) {
        // TODO Auto-generated method stub
        String fieldname=fileItem.getFieldName();
         
        try {
            String valuename=fileItem.getString("UTF-8");
        //  fieldname=new String(valuename.getBytes("iso-8859-1"),"utf-8");
            System.out.println(fieldname+":"+valuename);
        } catch (UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            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 {
        request.setCharacterEncoding("UTF-8");
        //要执行文件上传的操作
                //判断表单是否支持文件上传
                boolean isMultipartContent=ServletFileUpload.isMultipartContent(request);
                if(!isMultipartContent){
                    throw new RuntimeException("your form is not multipart/form-data");
                }
                //创建一个DiskFileItemFactory工厂类
                DiskFileItemFactory factory=new DiskFileItemFactory();
                //产生临时文件
                factory.setRepository(new File("f:\\temp"));
                //创建一个ServletFileUpload核心对象
                ServletFileUpload sfu=new ServletFileUpload(factory);
                sfu.setHeaderEncoding("UTF-8");
                try {
                    //限制上传文件的大小
                    //sfu.setFileSizeMax(1024*1024*1024);
                    //sfu.setSizeMax(6*1024*1024);
                    //解析requst对象，得到一个表单项的集合
                    List<FileItem> fileitems=sfu.parseRequest(request);
                    //遍历表单项数据
                    for(FileItem fileItem:fileitems){
                        if(fileItem.isFormField()){
                            //普通表单项
                            processFormField(fileItem);
                        }
                        else{
                            //上传表单项
                            processUploadField(fileItem);
                        }
                    }
                } catch(FileUploadBase.FileSizeLimitExceededException e){
                    //throw new RuntimeException("文件过大");
                    System.out.println("文件过大");
                }catch (FileUploadException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
    }
 
    /**
     * Initialization of the servlet. <br>
     *
     * @throws ServletException if an error occurs
     */
    public void init() throws ServletException {
        // Put your code here
    }
 
}

　这里面加了文件大小限制、文件重命名、目录打散等方法。

最后，我们运行一下这个demo

我们在web-apps的目录下可以看到我们刚刚上传的文件

三.文件下载

现在我们进行文件下载

package com.zk.upload;
 
import java.io.FileInputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLEncoder;
 
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
public class DownloadServlet1 extends HttpServlet {
 
    /**
     * Constructor of the object.
     */
    public DownloadServlet1() {
        super();
    }
 
    /**
     * Destruction of the servlet. <br>
     */
    public void destroy() {
        super.destroy(); // Just puts "destroy" string in log
        // Put your code here
    }
 
    /**
     * 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 {
        //设置一个要下载的文件
        String filename="a.csv";
        filename=new String(filename.getBytes("UTF-8"),"iso-8859-1");
        //告知浏览器要下载文件
        response.setHeader("content-disposition", "attachment;filename="+filename);
        response.setContentType(this.getServletContext().getMimeType(filename));//根据文件明自动获取文件类型
        response.setCharacterEncoding("UTF-8");//告知文件用什么服务器编码
         
        PrintWriter pw=response.getWriter();
        pw.write("Hello,world");
         
         
    }
 
    /**
     * 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 {
        doGet(request,response);
    }
 
    /**
     * Initialization of the servlet. <br>
     *
     * @throws ServletException if an error occurs
     */
    public void init() throws ServletException {
        // Put your code here
    }
 
}