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JavaServlet的文件上传和下载

程序员文章站 2022-04-15 20:14:18
关于JSP中的文件上传和下载操作 先分析一下上传文件的流程 1-先通过前段页面中的选择文件选择要上传的图片index.jsp 2-点击提交按钮,通过ajax的文件上传访问服务器端 common.js 3-服务器端响应保存或者下载保存上传文件的FileUpload.java 下载文件的FileDown ......

关于JSP中的文件上传和下载操作

先分析一下上传文件的流程

 

1-先通过前段页面中的选择文件选择要上传的图片

index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"
    contentType="text/html; charset=UTF-8"%>


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
    <head>

        <title>My JSP 'index.jsp' starting page</title>
        <meta http-equiv="content-type" content="text/html;charset=utf-8">
        <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">
        
        <script type="text/javascript" src="js/jquery.min.js"></script>
        <script type="text/javascript" src="js/common.js"></script>
        <script type="text/javascript" src="js/ajaxfileupload.js"></script>

    </head>

    <body>
        <input type="file" value="上传" name="inputImage" id="inputImage">
        <input type="button" value="上传" id="upload">
        
        <a id="downLoad">下载</a>
    </body>
</html>

 

 

 

2-点击提交按钮,通过ajax的文件上传访问服务器端

common.js  

var path = (function() {
    //获取当前网址
    var curWwwPath = window.document.location.href;
    //获取主机地址之后的目录
    var pathName = window.document.location.pathname;
    var pos = curWwwPath.indexOf(pathName);
    //获取主机地址
    var localhostPath = curWwwPath.substring(0, pos);
    //获取带"/"的项目名
    var projectName = pathName.substring(0, pathName.substr(1).indexOf('/') + 1);
    return {
            curWwwPath: curWwwPath,
            pathName: pathName,
            localhostPath: localhostPath,
            projectName: projectName,
            //部署路径
            deployPath: localhostPath + projectName
        };
})();

 

// 文件下载
$("a[id=downLoad]").click(function(){
    window.location.href=path.deployPath+"/fileDown";
});

// 文件上传
$("input[id=upload]").click(function() {
    $.ajaxFileUpload( {
        url : path.deployPath + "/fileUp", // 处理页面的绝对路径
        fileElementId : "inputImage", //file空间的id属性
        dataType : "json",
        success : function(data) {
            alert("上传成功");
        }
    });
});

 

 

 

3-服务器端响应保存或者下载

保存上传文件的FileUpload.java

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
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 net.sf.json.JSONArray;

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;

import com.stu.util.HttpUtil;

/**
 * 文件名称: com.stu.fileupload.FileUpload.java<br/>
 * 初始作者: Administrator<br/>
 * 创建日期: 2018-1-31<br/>
 * 功能说明: 文件上传 <br/>
 * =================================================<br/>
 * 修改记录:<br/>
 * 修改作者 日期 修改内容<br/>
 * ================================================<br/>
 * Copyright (c) 2010-2011 .All rights reserved.<br/>
 */
public class FileUpload extends HttpServlet {

    private static final long    serialVersionUID    = 1L;

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse res)
    throws ServletException, IOException {

        // 获取到当前服务器所在的路径
        String serverPath = req.getSession().getServletContext().getRealPath("/");

        // 设置保存上传文件的路径
        String saveDirPath = serverPath + "img";

        File saveDirPathFileObj = new File(saveDirPath);
        // 如果当用来存放文件的目录不存在时,要创建该目录
        if (!saveDirPathFileObj.exists()) {
            saveDirPathFileObj.mkdirs();
        }

        // 创建一个解析器工厂
        DiskFileItemFactory factory = new DiskFileItemFactory();

        // 设置工厂的缓存区大小
        factory.setSizeThreshold(5 * 1024);

        // 文件上传的解析器(文件上传对象)
        ServletFileUpload upload = new ServletFileUpload(factory);

        // 设置上传文件的最大值
        upload.setSizeMax(3 * 1024 * 1024);

        // 设置编码格式
        upload.setHeaderEncoding("UTF-8");

        try {
            // 上传以后的文件名
            List<String> uploadFileNames = new ArrayList<String>();

            List<FileItem> fileItems = upload.parseRequest(req);
            System.out.println(fileItems);
            for (FileItem file : fileItems) {
                // 新的文件名
                String saveFileName = UUID.randomUUID().toString().replace("-", "");
                // 文件的后缀
                String oldFileName = new String(file.getName().getBytes(),
                "UTF-8");
                System.out.println("oldFileName" + oldFileName);
                String fileType = oldFileName.substring(oldFileName.lastIndexOf("."));
                // 新的文件路径
                String saveFilePath = saveDirPath + File.separator
                + saveFileName + fileType;
                uploadFileNames.add(saveFileName + fileType);
                // 保存上传的文件
                file.write(new File(saveFilePath));
            }
            System.out.println(uploadFileNames);
            HttpUtil.setAttribute(req, "urls", uploadFileNames);
            res.setContentType("application/json;charset=utf-8");
            PrintWriter pw = res.getWriter();
            pw.print(JSONArray.fromObject(uploadFileNames));
        } catch (FileUploadException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

 


下载文件的FileDownload.java

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
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 net.sf.json.JSONArray;

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;

import com.stu.util.HttpUtil;

/**
 * 文件名称: com.stu.fileupload.FileUpload.java<br/>
 * 初始作者: Administrator<br/>
 * 创建日期: 2018-1-31<br/>
 * 功能说明: 文件上传 <br/>
 * =================================================<br/>
 * 修改记录:<br/>
 * 修改作者 日期 修改内容<br/>
 * ================================================<br/>
 * Copyright (c) 2010-2011 .All rights reserved.<br/>
 */
public class FileUpload extends HttpServlet {

    private static final long    serialVersionUID    = 1L;

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse res)
    throws ServletException, IOException {

        // 获取到当前服务器所在的路径
        String serverPath = req.getSession().getServletContext().getRealPath("/");

        // 设置保存上传文件的路径
        String saveDirPath = serverPath + "img";

        File saveDirPathFileObj = new File(saveDirPath);
        // 如果当用来存放文件的目录不存在时,要创建该目录
        if (!saveDirPathFileObj.exists()) {
            saveDirPathFileObj.mkdirs();
        }

        // 创建一个解析器工厂
        DiskFileItemFactory factory = new DiskFileItemFactory();

        // 设置工厂的缓存区大小
        factory.setSizeThreshold(5 * 1024);

        // 文件上传的解析器(文件上传对象)
        ServletFileUpload upload = new ServletFileUpload(factory);

        // 设置上传文件的最大值
        upload.setSizeMax(3 * 1024 * 1024);

        // 设置编码格式
        upload.setHeaderEncoding("UTF-8");

        try {
            // 上传以后的文件名
            List<String> uploadFileNames = new ArrayList<String>();

            List<FileItem> fileItems = upload.parseRequest(req);
            System.out.println(fileItems);
            for (FileItem file : fileItems) {
                // 新的文件名
                String saveFileName = UUID.randomUUID().toString().replace("-", "");
                // 文件的后缀
                String oldFileName = new String(file.getName().getBytes(),
                "UTF-8");
                System.out.println("oldFileName" + oldFileName);
                String fileType = oldFileName.substring(oldFileName.lastIndexOf("."));
                // 新的文件路径
                String saveFilePath = saveDirPath + File.separator
                + saveFileName + fileType;
                uploadFileNames.add(saveFileName + fileType);
                // 保存上传的文件
                file.write(new File(saveFilePath));
            }
            System.out.println(uploadFileNames);
            HttpUtil.setAttribute(req, "urls", uploadFileNames);
            res.setContentType("application/json;charset=utf-8");
            PrintWriter pw = res.getWriter();
            pw.print(JSONArray.fromObject(uploadFileNames));
        } catch (FileUploadException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

 

 

这里面用到了一个HttpUtil类,代码如下:

import javax.servlet.FilterConfig;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

/**
 * 文件名称_com.niit.model2.util.Httputil.java</br>
 * 初始作逯ܿAdministrator</br>
 * 创建日期_2018-1-23</br>
 * 功能说明_这里用一句话描述这个类的作用--此句话需删除 <br/>
 * =================================================<br/>
 * 修改记录_br/>
 * 修改作迠日期 修改内容<br/>
 * ================================================<br/>
 * Copyright (c) 2010-2011 .All rights reserved.<br/>
 */
public class HttpUtil {

    private HttpUtil() {

    }

    /**
     * 方法描述: [用于向不同的作用域存放属性]</br>
     * 初始作迺 Administrator<br/>
     * 创建日期: 2018-1-23-上午11:24:45<br/>
     * 弿Nj版本: 2.0.0<br/>
     * =================================================<br/>
     * 修改记录_br/>
     * 修改作迠日期 修改内容<br/>
     * ================================================<br/>
     * void
     */
    public static void setAttribute(Object scopeObj, String name, Object value) {

        if (scopeObj instanceof HttpServletRequest) {
            ((HttpServletRequest) scopeObj).setAttribute(name, value);
        }
        if (scopeObj instanceof HttpSession) {
            ((HttpSession) scopeObj).setAttribute(name, value);
        }
        if (scopeObj instanceof ServletContext) {
            ((ServletContext) scopeObj).setAttribute(name, value);
        }
    }

    /**
     * 方法描述: [获取作用域中指定名称的属性思</br>
     * 初始作迺 Administrator<br/>
     * 创建日期: 2018-1-23-上午11:29:17<br/>
     * 弿Nj版本: 2.0.0<br/>
     * =================================================<br/>
     * 修改记录_br/>
     * 修改作迠日期 修改内容<br/>
     * ================================================<br/>
     * 
     * @param scopeObj
     * @param name
     * @return
     *         Object
     */
    public static Object getAttribute(Object scopeObj, String name) {

        if (scopeObj instanceof HttpServletRequest) {
            return ((HttpServletRequest) scopeObj).getAttribute(name);
        }
        if (scopeObj instanceof HttpSession) {
            return ((HttpSession) scopeObj).getAttribute(name);
        }
        if (scopeObj instanceof ServletContext) {
            return ((ServletContext) scopeObj).getAttribute(name);
        }
        return null;
    }

    /**
     * 方法描述: [获取上下文对象的方法]</br>
     * 初始作迺 Administrator<br/>
     * 创建日期: 2018-1-23-上午11:31:26<br/>
     * 弿Nj版本: 2.0.0<br/>
     * =================================================<br/>
     * 修改记录_br/>
     * 修改作迠日期 修改内容<br/>
     * ================================================<br/>
     * 
     * @return
     *         ServletContext
     */
    public static ServletContext getServletContext(Object sourceObj) {

        if (sourceObj instanceof HttpServletRequest) {
            return ((HttpServletRequest) sourceObj).getSession().getServletContext();
        }
        if (sourceObj instanceof ServletConfig) {
            return ((ServletConfig) sourceObj).getServletContext();
        }
        if (sourceObj instanceof FilterConfig) {
            return ((FilterConfig) sourceObj).getServletContext();
        }
        return null;
    }

    /**
     * 方法描述: [获取项目的实际路径]</br>
     * 初始作迺 Administrator<br/>
     * 创建日期: 2018-1-23-上午11:45:47<br/>
     * 弿Nj版本: 2.0.0<br/>
     * =================================================<br/>
     * 修改记录_br/>
     * 修改作迠日期 修改内容<br/>
     * ================================================<br/>
     * 
     * @param req
     * @return
     *         String
     */
    public static String getContextPath(HttpServletRequest req) {

        return req.getContextPath();
    }
}

 

 

  

当然,代码编辑好了也不要忘了在 WebRoot/WEB-INF/web.xml 中添加新建的Servlet,就是刚刚的两个Java文件啦

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>

    <!-- 文件上传 -->
    <servlet>
        <servlet-name>fileUpload</servlet-name>
        <servlet-class>com.stu.fileupload.FileUpload</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>fileUpload</servlet-name>
        <url-pattern>/fileUp</url-pattern>
    </servlet-mapping>

    <!-- 文件下载 -->
    <servlet>
        <servlet-name>fileDownload</servlet-name>
        <servlet-class>com.stu.fileupload.FileDownload</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>fileDownload</servlet-name>
        <url-pattern>/fileDown</url-pattern>
    </servlet-mapping>
</web-app>

 

  这样的话就可以运行啦。

 

TIP: 不要忘记相关的jar包和 js 包哦

    在 WebRoot / WEB-INF / lib 下,有 commons-fileupload.jar 和 commons-io.jar  ,另外 json-lib-x.x.x-jdkxx.jar 包是用来把上传的返回数据修改为JSON格式的

    在 WebRoot / js 下,导入 jquery.js , common.js , ajaxfileupload.js