Struts2入门(七)——Struts2的文件上传和下载

时间：2023-12-04 18:07:44

一、前言

在之前的随笔之中，我们已经了解Java通过上传组件来实现上传和下载，这次我们来了解Struts2的上传和下载。

注意：文件上传时，我们需要将表单提交方式设置为"POST"方式，并且将enctype属性设置为"multipart/form-data"，该属性的默认值为"application/x-www-form-urlencoded",就是说，表单要写成以下这种形式：

<form action="" method="post" enctype="multipart/form-data"></form>

而且Struts2中并没有提供自己的文件上传解析器，默认使用的是Jakarta的Common-FileUpload的文件上传组件，所以我们还需要在添加两个包：

commons-io

commons-fileupload

至于版本根据自己需要选择(笔者在第一篇已经搭建好环境了。地址)

注意点如下：

1.1、文件上传的前提是表单属性method="post" enctype="multipart/form-data";

1.2、web应用中必须包含common-fileupload.jar和common-io.jar，因为struts2默认上传解析器使用的是jakarta；

1.3、可以在struts.xml中配置最大允许上传的文件大小：<constant name="struts.multipart.maxSize" value="....."/>,默认为2M；

二、文件上传案例

2.1、在Action中定义属性：

private File upload;       　　　　  　　 //包含文件内容

private String uploadFileName;   　　  //上传文件的名称；

private String uploadContentType;    //上传文件的MIME类型；

这些属性都会随着文件的上传自动赋值；

2.2、上传图片的例子

新建视图界面：Upload.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>Struts2 FileUpload</title>

</head>

<body>

    <form action="fileupload" method="post" enctype="multipart/form-data">

        文件标题：<input type="text" name="title"/><br/>

        选择文件:<input type="file" name="upload"/><br/>

        <input type="submit" value="上传"/>

    </form>

</body>

</html>

新建UploadAction继承ActionSupport

package com.Struts2.load;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionSupport;

//上传单个文件

public class UploadAction extends ActionSupport {

    //文件标题请求参数的属性

    private String title;

    //上传文件域的属性

    private File upload;

    //上传文件类型

    private String uploadContentType;

    //上传文件名

    private String uploadFileName;

    //接受依赖注入的属性

    private String savePath;

    public String getTitle() {

        return title;

    }

    public void setTitle(String title) {

        this.title = title;

    }

    public File getUpload() {

        return upload;

    }

    public void setUpload(File upload) {

        this.upload = upload;

    }

    public String getUploadContentType() {

        return uploadContentType;

    }

    public void setUploadContentType(String uploadContentType) {

        this.uploadContentType = uploadContentType;

    }

    public String getUploadFileName() {

        return uploadFileName;

    }

    public void setUploadFileName(String uploadFileName) {

        this.uploadFileName = uploadFileName;

    }

    //返回上传文件的保存位置

    public String getSavePath() {

        return ServletActionContext.getRequest().getRealPath(savePath);

    }

    //接受依赖注入的方法

    public void setSavePath(String savePath) {

        this.savePath = savePath;

    }

    public String execute() throws Exception{

        System.out.println(getSavePath());

        System.out.println(getUploadFileName());

        //以服务器的文件保存地址和原文件名建立上传文件输出流

        FileOutputStream fos = new FileOutputStream(getSavePath()+"\\"+getUploadFileName());

        //以上传文件建立一个文件上传流

        FileInputStream fis = new FileInputStream(getUpload());

        //将上传文件的内容写入服务器

        byte[] buffer = new byte[1024];

        int leng = 0;

        while((leng=fis.read(buffer))>0){

            fos.write(buffer,0,leng);

            buffer = new byte[1024];

        }

        return SUCCESS;

    }

}

struts.xml配置文件中部署

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.5//EN"
"http://struts.apache.org/dtds/struts-2.5.dtd">
<struts>

    <!--文件上传  -->

    <package name="default" extends="struts-default">

        <action name="fileupload" class="com.Struts2.load.UploadAction">

            <!--使用拦截器过滤：1、配置默认拦截器，2、配置input的逻辑视图-->

            <interceptor-ref name="fileUpload">

                <param name="allowedTypes">image/jpeg,image/jpg,/image/gif,image/png</param>

            </interceptor-ref>

            <!-- 必须显示配置defaultStack拦截器的引用 -->

            <interceptor-ref name="defaultStack"/>

            <param name="savePath">/upload</param>

            <result name="success">succ.jsp</result>

            <!--必须配置input的逻辑视图  -->

            <result name="input">Error.jsp</result>

        </action>

<struts>

注意:web.xml中需要配置struts2的拦截器

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">

  <display-name>LearStruts2</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>

  <!--为Struts2定义一个过滤器  -->

   <filter>

      <filter-name>struts2</filter-name>

      <filter-class>

          org.apache.struts2.dispatcher.filter.StrutsPrepareAndExecuteFilter

      </filter-class>

  </filter>

  <filter-mapping>

      <filter-name>struts2</filter-name>

      <url-pattern>/*</url-pattern>

  </filter-mapping>

</web-app>

web.xml

succ.jsp视图代码

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<%@ taglib uri="/struts-tags" prefix="s"%>

<!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>上传成功</title>

</head>

<body>

    上传成功<br/>

    文件标题:<s:property value="title"/><br/>

    <s:property value="uploadFileName"/>

    文件为:<img src="<s:property value="'/LearStruts2/upload/'+uploadFileName"/>"/><br/>

</body>

</html>

Error.jsp视图代码

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<%@ taglib prefix="s" uri="/struts-tags" %>

<!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>Error 界面</title>

</head>

<body>

    <s:fielderror/>

</body>

</html>

Error.jsp

代码效果如下：

Struts2入门(七)——Struts2的文件上传和下载

注意：在struts.xml配置文件中，已经限制只能上传图片格式，如果上传别的文件的话，则会报错。

2.3、多个文件上传

新建Upliads.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>上传多个文件</title>

</head>

<body>

    <form action="filesupload" method="post" enctype="multipart/form-data">

        文件标题:<input type="text" name="title"><br/>

        选择第一个文件:<input type="file" name="uploads"><br/>

        选择第二个文件:<input type="file" name="uploads"><br/>

        选择第三个文件:<input type="file" name="uploads"><br/>

        <input type="submit" value="上传"/>

    </form>

</body>

</html>

Upliads.jsp

新建UploadsAction类继承ActionSupport

package com.Struts2.load;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionSupport;

//上传多个文件

public class UploadsAction extends ActionSupport {

    private String title;    //对应jsp的title

    private File[] uploads;    //对应jsp的uploads

    private String[] uploadsContentType;

    private String[] uploadsFileName;

    //savePath:通过配置文件进行赋值"'\'upload"，

    //其中的'\'表示项目的根目录D:\\tomcat-8.0\\wtpwebapps\\LearStruts2\\upload

    private String savePath;

    public String getTitle() {

        return title;

    }

    public void setTitle(String title) {

        this.title = title;

    }

    public File[] getUploads() {

        return uploads;

    }

    public void setUploads(File[] upload) {

        this.uploads = upload;

    }

    public String[] getUploadsContentType() {

        return uploadsContentType;

    }

    public void setUploadsContentType(String[] uploadsContentType) {

        this.uploadsContentType = uploadsContentType;

    }

    public String[] getUploadsFileName() {

        return uploadsFileName;

    }

    public void setUploadsFileName(String[] uploadsFileName) {

        this.uploadsFileName = uploadsFileName;

    }

    public String getSavePath() {

        return ServletActionContext.getRequest().getRealPath(savePath);

    }

    public void setSavePath(String savePath) {

        this.savePath = savePath;

    }

    public String execute() throws Exception{

        File[] files = getUploads();

        for(int i = 0;i<files.length;i++){

            System.out.println(getSavePath());

            System.out.println(getUploadsFileName()[i]);

            //getSavePath : 获得根目录

            //getUploadsFileName() ： 获得文件名

            FileOutputStream fos = new FileOutputStream(getSavePath()+"\\"+getUploadsFileName()[i]);

            FileInputStream fis = new FileInputStream(files[i]);

            byte[] buffer = new byte[1024];

            int len = 0;

            while((len=fis.read(buffer))>0){

                fos.write(buffer,0,len);

                buffer = new byte[1024];

            }

        }

        return SUCCESS;

    }

}

struts.xml中配置信息

        <!--多个文件上传  -->

        <action name="filesupload" class="com.Struts2.load.UploadsAction">

            <!--该属性是依赖注入：通过配置文件给savePath赋值 ，是必须的 -->

            <param name="savePath">/upload</param>

            <result name="success">succ1.jsp</result>

        </action>

succ1.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>多个文件上传</title>

</head>

<body>

    上传成功

</body>

</html>

succ1.jsp

代码效果如下:

Struts2入门(七)——Struts2的文件上传和下载

2.3、Struts2的文件下载

视图下载界面

<%@ 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>Struts 2实现的文件下载</title>

</head>

<body>

    <a href="down.action">图片下载</a>

</body>

</html>

fuledown.jsp

Action类

package com.Struts2.load;

import java.io.InputStream;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionSupport;

public class DownAction extends ActionSupport {

    private String inputPath;

    private String contentType;

    private String filename;

    public String getContentType() {

        return contentType;

    }

    public void setContentType(String contentType) {

        this.contentType = contentType;

    }

    public String getFilename() {

        return filename;

    }

    public void setFilename(String filename) {

        this.filename = filename;

    }

    public String getInputPath() {

        return inputPath;

    }

    public void setInputPath(String inputPath) {

        this.inputPath = inputPath;

    }

     //下载用的Action应该返回一个InputStream实例

     //该方法对应在result里的inputName属性值为targetFile

    //第二步

    public InputStream getTargetFile() throws Exception{

            System.out.println("1");

            InputStream in=ServletActionContext.getServletContext().getResourceAsStream(inputPath);

           return in;

    }

    //第一步

    public String execute(){

         System.out.println("???");

         inputPath="/upload/1.jpg";//要下载的文件名称

         filename="1.jpg"; //保存文件时的名称

         contentType="image/jpg";//保存文件的类型

        return SUCCESS;

    }

}

Struts.xml配置文件

     <!-- 下载文件的Action -->

        <action name="down" class="com.Struts2.load.DownAction">

          <!-- 指定被下载资源的位置 -->

          <param name="inputPath">${inputPath}</param>

          <!-- 配置结果类型为stream的结果 -->

          <result name="success" type="stream">

             <!--

                 contentType：指定下载文件的类型 ，和互联网MIME标准中的规定类型一致，

                 例如text/plain代表纯文本，text/xml表示XML，image/gif代表GIF图片，image/jpeg代表JPG图片

             -->

             <param name="contentType">${contentType}</param>

             <!-- 指定下载文件的位置 -->

             <!--

             inputName：下载文件的来源流，对应着action类中某个类型为Inputstream的属性名，

                                       例如取值为inputStream的属性需要编写getInputStream()方法

             -->

             <param name="inputName">targetFile</param>

             <!--

             contentDisposition

　　               文件下载的处理方式，包括内联(inline)和附件(attachment)两种方式，

               而附件方式会弹出文件保存对话框，否则浏览器会尝试直接显示文件。

              默认情况是代表inline，浏览器会尝试自动打开它

               -->

             <param name="contentDisposition">attachement;filename="${filename}"</param>

             <!-- 指定下载文件的缓冲大小 -->

             <param name="bufferSize">50000000</param>

          </result>

       </action>

代码都有笔者测试过，至于解析，笔者会在后期理解好之后再重新写。

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