public with sharing class FilePreviewDownVFController {
    public String staticResource {get; set;}
    public String fileKey {get; set;}
    public String fileName {get; set;}
    public String type {get; set;}
    public String url {get; set;}
    public string body{get;set;}
    public FilePreviewDownVFController(ApexPages.StandardController controller) {
        // staticResource = JSON.serialize(PIHelper.getPIIntegrationInfo('Document'));
        Pagereference pf = ApexPages.currentPage();
        if(pf != null){
            fileKey = pf.getParameters().get('key');
            fileName = pf.getParameters().get('name');
            type = pf.getParameters().get('type');
            url = pf.getParameters().get('url');
        }
        List<ContentVersion> contentList = [select Id, VersionData from ContentVersion where Id = '068C50000000nrxIAA'];
        body = EncodingUtil.base64Encode(contentList[0].VersionData);
        System.debug(body);
    }
}