The FileSystemObject Object. Active Server Pages

Transcription

1 The FileSystemObject Object Active Server Pages Objectives In this chapter, you will: Describe a drive, a folder, and a file Describe and use the different objects in the FileSystemObject object Describe the properties and methods of the FileSystemObject object 1

2 Objectives In this chapter, you will: Use the FileSystemObject object to save data on the server Understand the code that the use of the FileSystemObject object dictates Use the SiteGalaxy Upload component to upload files from a client to a server Review of Drives, Folders, and Files On the average PC, you can store folders and files on either a floppy disk drive or on a hard disk drive A hard drive may be divided into multiple storage areas (known as partitions) You can also use drive letters to represent CD- ROM drives or remote network drives A remote network drive, also called a share, is a pointer to a folder stored on another computer The storage area on a hard or floppy drive is divided into directories, or folders, that you can use to organize your files 2

3 Review of Drives, Folders, and Files A file or folder can have one or more of the following attributes Normal Read only Hidden System Directory Archive Alias Compressed Review of Drives, Folders, and Files There are three types of files: binary ASCII Unicode A binary file contains data that is stored in the form of 1 s and 0 s An ASCII file stores data as a series of characters (as text) A Unicode file is a file that stores data as a series of characters 3

4 FileSystemObject Object Overview ASP applications often must have the ability to manipulate drives, folders, and files on a Web server You can give your application this ability by using the CreateObject function to create an instance of the FileSystemObject object The FileSystemObject object itself provides functionality to the programmer Important Properties and Methods of the FileSystemObject Object

5 Drive Object A Drive object provides properties and methods to interact with a particular drive Folder Object A Folder object provides the properties and methods to interact with a folder on a computer 5

6 Properties and Methods of the Folder Object File Object Each Folder object contains a property called Files This property contains the collection of File objects 6

7 Displaying File and Folder Information To display the files and folders, you would use the FileSystemObject, Drive, Folder, and File objects In our example, we will use the objects in VBScript To begin our sample scenario, we will prepare PWS to handle our target application, which will have its files and folders investigated by a second application Displaying File and Folder Information To make a virtual directory, use the steps on page 93 of the textbook 7

8 Displaying File and Folder Information To preview the Student Contacts Application refer to the procedures on pages 9-96 of the textbook Displaying File and Folder Information 8

9 Displaying File and Folder Information Displaying File and Folder Information Now is your chance to get a very overt look at the power of ASP by following the instructions and code on pages of the textbook 9

10 Opening New and Existing Files The syntax for creating a new file in VBScript and JavaScript is as follows: objfilesystemobject.createtextfile (filename,[,overwrite [,unicode]]) The following example creates a new file named newfile.txt in VBScript: Create the text file objfilesystemobject.createtextfile( C:\temp\newfile.txt ) The syntax for opening an existing file in VBScript and JavaScript is as follows: objfilesystemobject.opentextfile (filename,[,iomode[,create[,format]]) The TextStream Object Steps In The TextStream object allows you to manipulate the contents of folders and files With TextStream objects, your application can open, read, write, and close a file on a server As always, our objects come with a plethora of useful methods and properties, and the TextStream object is no exception 10

11 Important Properties and Methods of the TextStream Object Reviewing the Student Contacts Application With the FileSystemObject object, we saw how we could write code that produced the dynamic drive, folder, and file information that we wanted to see With just our browser, we obtained realtime information about a root directory and its contents 11

12 The QueryString Property of the Request Object Start by going back to a subject that we briefly mentioned during the hands-on steps: the query string During those steps, we directed your attention to the Address text box, which appeared as you see in Figure -6 The QueryString Property of the Request Object A query string is a collection of variable and value pairs that allow an application to pass data between Web pages You can create your own query string using one of two methods: First, you can place (by hand) a question mark right after the URL, followed by one or more control items Alternately, you can create a form that contains the GET method, which then stores data in the QueryString collection 12

13 The QueryString Property of the Request Object Typically, you use a GET method for a very simple form such as a search form, which requests keywords to search for You should not use a GET method on a form for large amounts of data Use the GET method of an HTML form for data you do not need to store in a database or file, and that is only needed for short periods of time Examples of Query Strings 13

14 Default.htm This page contains the search form that the user can use to find contact information for an existing student It also includes the link that the user can click in order to enter information for a new student The HTML for the default.htm page is shown on pages 102 and 103 of the textbook ClsForm.cls The ClsForm.cls class provides the main functionality of the student contact form The script code in this file creates a form class that contains the reusable properties and methods for processing the input It contains three properties: strmode colformelements strserverfilepath 1

15 ClsForm.cls The ClsForm.cls class contains two methods: Search method Save method To use the Save method, you will need to know the physical path The physical path specifies the precise location, of a file, including the drive letter and all the relevant folders and subfolders ClsForm.cls When you access a Web page via PWS, you are using a logical path The logical path is the URL that the user types in the browser; it does not point to the physical location of a file; instead it provides a path from the virtual directory to the file The code for the clsform.class is as shown on pages of the textbook 15

16 Form.asp The form.asp script uses the clsform class to search for information for existing students, or to save information for a new student This script also uses the query string to pass search information between the search form to the form.asp page The code for the form.asp is shown on pages of the textbook for your review register_me.asp The register_me.asp script file takes the data from the form.asp script, and saves the information to a file named students.txt if all the mandatory fields are filled in If some of the mandatory fields are empty, then the script displays an error page The Register_me.asp page is similar to other pages you have seen thus far 16

17 Uploading Files to the Server How It s Really Done To complete the last section of this chapter, you will need to have installed the SiteGalaxy ASP Upload component, as outlined in the Front Matter of this book In the real word of ASP programming, you are going to want to take an entire file from a client computer and save it to a directory on a server Regardless of the end use you have in mind, you ll find the SiteGalaxy Upload freeware component to be a handy device SiteGalaxy Upload Component The SiteGalaxy Upload component uses a special MIME type, multipart/form, to allow the SiteGalaxy component to upload files from a client to the server The SiteGalaxy Upload component includes two objects: Form: A collection of form elements returned by the client FileField: An object that supplies information about a file passed to the server by the client 17

18 Important Properties and Methods of the Form Object Properties and Methods of the FileField Object 18

19 Using the SiteGalaxy Upload Component To create the code to upload a file follow the directions laid out on page of the textbook Summary On the average PC, you can store folders and files on either a floppy disk drive or a hard disk drive The FileSystemObject object itself provides functionality to the programmer This object is also at the top of a hierarchy of functionality that is provided by a series of child objects A Drive object provides properties and methods to interact with a particular drive (such as A or C) 19

20 Summary You can use the FileSystemObject object to create new files and existing files You use the TextStream object to manipulate the information contained in the files A query string is a collection of variable and pairs that allow an application to pass data between Web pages Depending on the application you are creating, you will use one or many variable/value pairs in your query strings Summary Hidden HTML form elements are useful when you do not want the user to see an HTML element on the form, but you want to send data to the server The SiteGalaxy Upload freeware component uses a special MIME type, multipart/formdata, to allow the SiteGalaxy component to upload files from the client to the server 20