文件上传&文件下载

一.单个文件上传

文件上传需要两个jar包：

首先制作一个简单的页面，用于实现文件上传

<h1>单个文件上传</h1>
        <s:form action="upload.action" enctype="multipart/form-data"
            method="post" namespace="/">
            <s:textfield name="title" lable="标题"></s:textfield>
            <s:file name="upload" lable="选择文件"></s:file>
            <s:submit value="上传文件"></s:submit>
        </s:form>

开发实现文件上传的Action

package cn.action;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionSupport;

public class UploadAction  extends ActionSupport{
    //封装上传文件属性
        private File upload;

        //封装上传文件的类型
        private String uploadContentType;

        //封装上传文件名称
        private String uploadFileName;

        //封装文件上传的路径
        private String savePath;

        public String execute(){
            byte[] buffer=new byte[1024];
            try {
                FileInputStream fis=new FileInputStream(getUpload());
                FileOutputStream fos=new FileOutputStream(getSavePath()+"\\"+this.getUploadFileName());
                int length=fis.read(buffer);
                while(length>0){
                    fos.write(buffer, 0, length);
                    length=fis.read(buffer);
                }
                fos.flush();
                fos.close();
                fis.close();
            } catch (FileNotFoundException e) {

                e.printStackTrace();
            } catch (IOException e) {

                e.printStackTrace();
            }
            System.out.println("========================");
            return SUCCESS;
        }

        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;
        }

        public String getSavePath() {
            return ServletActionContext.getServletContext().getRealPath(savePath);
        }

        public void setSavePath(String savePath) {
            this.savePath = savePath;
        }

}

在Action中使用了三个属性封装文件信息

File类型的XXX属性，与表单的File控件的name属性一样，用于封装File控件对应的文件内容

String类型的xxxFileName属性，该属性名称由前面的File类型属性和FileName组合，是固定的语法，是封装File控件对应文件的文件名

String类型的XXXContentType属性，同样由xxx属性和ContentType组合而成，是固定语法，封装File控件对应文件的文件类型

配置Action

<!-- 单个文件上传 -->
        <action name="upload" class="cn.action.UploadAction">
            <!-- 通过param参数设置保存目录的路径 -->
            <param name="savePath">/upload</param>
            <result name="success">success.jsp</result>
        </action>

效果图：

二.多个文件上传

只需在上传Action中将原本处理单个文件的操作改成对集合操作即可。

其他的都跟单个上传的一样

页面

<!-- 多个文件上传 -->
        <action name="someupload" class="cn.action.SomeUploadAction">
            <!-- 通过param参数设置保存目录的路径 -->
            <param name="savePath">/upload</param>
            <result name="success">success.jsp</result>
        </action>

开发实现文件上传的Action

package cn.action;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionSupport;

public class SomeUploadAction extends ActionSupport {
    //封装上传文件属性
        private File[] upload;

        //封装上传文件的类型
        private String[] uploadContentType;

        //封装上传文件名称
        private String[] uploadFileName;

        //封装文件上传的路径
        private String savePath;

        public String execute() throws Exception{
            byte[] buffer=new byte[1024];
            for (int i = 0; i < upload.length; i++) {
                FileInputStream fis=new FileInputStream(getUpload()[i]);
                FileOutputStream fos=new FileOutputStream(getSavePath()+"\\"+this.getUploadFileName()[i]);
                int length=fis.read(buffer);
                while(length>0){
                    fos.write(buffer, 0, length);
                    length=fis.read(buffer);
                }
                fos.flush();
                fos.close();
                fis.close();
            }
            return SUCCESS;
        }

        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;
        }

        public String getSavePath() {
            return ServletActionContext.getServletContext().getRealPath(savePath);
        }

        public void setSavePath(String savePath) {
            this.savePath = savePath;
        }

}

配置Action

<!-- 多个文件上传 -->
        <action name="someupload" class="cn.action.SomeUploadAction">
            <!-- 通过param参数设置保存目录的路径 -->
            <param name="savePath">/upload</param>
            <result name="success">success.jsp</result>
        </action>

效果：

三.文件下载

文件下载需要InputStream，首先在文件下载Action中提供一个获得InputStream的方法，通过输入流可以获取希望下载的文件内容

package cn.action;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionSupport;

public class FileDownAction extends ActionSupport {
    //读取下载文件的目录
        private String inputPath;

        //下载文件的文件名
        private String fileName;

        //读取下载文件的输入流
        private InputStream inputStream;

        //下载文件的类型
        private String conetntType;

        public String execute(){
            return SUCCESS;

        }

        public String getInputPath() {
            return inputPath;
        }

        public void setInputPath(String inputPath) {
            this.inputPath = inputPath;
        }

        public String getFileName() {
            return fileName;
        }

        public void setFileName(String fileName) {
            this.fileName = fileName;
        }
        //创建InputStream输入流
        public InputStream getInputStream() throws Exception {
            String path=ServletActionContext.getServletContext().getRealPath(inputPath);
            BufferedInputStream stream = new BufferedInputStream(new FileInputStream(path+"\\"+fileName));
            return stream;
        }

        public void setInputStream(InputStream inputStream) {
            this.inputStream = inputStream;
        }

        public String getConetntType() {
            return conetntType;
        }

        public void setConetntType(String conetntType) {
            this.conetntType = conetntType;
        }

}

通过Context得到下载文件的实际路径，构建一个InputStream输入流实现文件的下载读取。

在配置文件中，同样对Action进行配置，并对stream结果类型的参数进行设置。

<!-- download指定的Action -->
        <action name="download" class="cn.action.FileDownAction">
            <param name="inputPath">/upload</param>
            <result name="success" type="stream">
                <param name="contentType">application/octet-stream</param>
                <param name="inputName">inputStream</param>
                <param name="contentDisposition">
                    attachment;filename="${fileName}"
                </param>
                <param name="bufferSize">4096</param>
            </result>
        </action>

ContentType参数决定了下载文件的类型，不同的文件类型对应的参数值也是不同的。通常情况下，ContentType参数直接设置为application/octet-stream即可。

contentDisposition参数由两部分组成，前面的部分表示处理文件的形式，如attachement表示在下载时弹出对话框，提出用户保存或直接打开该文件；而后一部分表示下载文件的文件名称。两部分之间用“；”进行分隔。

然后开发一个简单的下载页面，在页面中设置一个超链接，通过超链接请求下载Action

<h1>文件下载</h1>
        <s:a href="download.action?fileName=2.jpg">点击此处下载文件</s:a>

效果：