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                        /Java中的文件上传下载

点击下载提示java.io.FileInputStream cannot be cast to java.lang.String

    //Action
    private List<File> upload;
     
    private List<String> uploadContentType;
     
    private List<String> uploadFileName;
     
    private String result;
 
    private String inputPath;
     
    private String filename;
     
    set/get方法省略
     
    @Override
    public String execute() throws Exception {
        if(upload==null){
            result = "请选择文件";
            return INPUT;
        }
        String path  =  ServletActionContext.getServletContext().getRealPath("/images");
        System.out.println(path);
        File file = new File(path);
        if(!file.exists()){
            file.mkdirs();
        }
        int i=0;
        //循环将批量上传的文件保存到本地
        for (i = 0; i < upload.size(); i++) {
            FileUtils.copyFile(upload.get(i), new File(file,uploadFileName.get(i)));
        }
        System.out.println("共上传了："+i+"个文件");
        result="上传成功";
        return SUCCESS;
    }
     
    /*
     * 下载action
     */
    public InputStream getDownload() throws IOException{
        String path = ServletActionContext.getServletContext().getRealPath("/images/");
        String filepath = path+filename;
        System.out.println("路径为："+filepath);
        File file = new File(filepath);
        //像页面输出流
        return FileUtils.openInputStream(file);
    }

//配置文件
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN" "http://struts.apache.org/dtds/struts-2.1.dtd">
<struts>
<!-- 配置临时文件位置 -->
<constant name="struts.multipart.saveDir" value="/tmp"/>
<!-- 配置国际化信息 对应app是指配置文件的基础名称 里面key为异常信息，value为提示信息 -->
<constant name="struts.custom.i18n.resources" value="app"></constant>
    <package name="uploadAndDownload" extends="struts-default">
        <action name="uploadAndDownload3" class="com.imooc.action.BatchUploadAndDownloadAction">
            <result>/03.jsp</result>
            <result name="input">/03.jsp</result>
            <!-- 配置拦截器 -->
        <interceptor-ref name="fileUpload">
                <param name="allowedTypes">image/jpeg,image/png</param>
                <param name="maximumSize">2M</param>
        </interceptor-ref>
        <!-- 配置默认拦截器  如果不配置则获取不到file-->
          <interceptor-ref name="defaultStack"></interceptor-ref> 
        </action>
        <action name="download3" class="com.imooc.action.BatchUploadAndDownloadAction" method="getDownload">
            <param name="inputPath">/images/img2-lg.jpg</param>
            <result type="stream">
                <param name="contentType">application/octet-stream</param>
                <!-- 由getDownloadFile（）获得inputStream -->
                <param name="inputName">download</param>
                <param name="contentDisposition">attachment;filename="${filename}"</param>
                <param name="bufferSize">8192</param>
            </result>
        </action>
    </package>
</struts>