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File IO with Servlet

Greenhorn

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posted 12 years ago

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Good Night or Good Day for others

My question today is

How is the right way to write an .txt , inside a Servlet.

Here is my jsp

I know the .do extension is a old and easy way but for me is working, for the moment.

Now the important, the servlet.....

import java.io.*;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class FileServlet extends HttpServlet{ 
	 
	 public void doPost(HttpServletRequest request, 
	  HttpServletResponse response) throws ServletException,IOException{
	  response.setContentType("text/html");
	  PrintWriter out = response.getWriter();

String ID="";
	  String name="";
	  String Fname="";
	  String Address="";
	  String Age="";
	  String City="";
	  
	  ID=request.getParameter("UID");
	  name=request.getParameter("Uname");
	  Fname=request.getParameter("UFname");
	  Address=request.getParameter("UAddress");
	  Age=request.getParameter("Uage");
	  City=request.getParameter("Ucity");
	
	  
	  DataOutputStream data = null;

if(request.getParameter("SAVE") != null)

try {

data = new DataOutputStream(new FileOutputStream("c:\\filedata.txt",true));

data.writeUTF(ID);

data.writeUTF(name);

data.writeUTF(Fname);
	  
	  data.writeUTF(Address);
	  
	  data.writeUTF(Age);
	  
	  data.writeUTF(City);

out.println(ID+": file saved");

}

catch(FileNotFoundException fnfe) {
		  
	  }

catch (IOException ioe) {};

data.close();

};
	 }

I create a filledata.txt in the C:\\, that txt is in white , no words no nothing. Now the idea, After the "SAVE" button inthe JSP , I want to save(write) my name (for example), my age, ......., in that txt. The question is ¿HOW? I know that my servlet is wrong. Can anyone help to fix it in the right way
thanks

Tim Quick

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posted 12 years ago

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I would suggest using a PrintWriter rather than a DataOutputStream if you want readable text in your file.

PrintWriter _FileWriter = new PrintWriter(new FileOutputStream("c:\\filedata.txt",true));
_FileWriter.println( ID + "," + name + "," + FName + "," + Address + "," + Age + "," + City);
_FileWriter.close();

Regards,
Tim

Bear Bibeault

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posted 12 years ago

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Tim Quick wrote:I would suggest using a PrintWriter rather than a DataOutputStream

Yes, a DataOutputStream is a poor choice.

However, be sure to use proper naming conventions for variable names: fileWriter rather than _FileWriter.

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Alen Mester

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posted 12 years ago

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Hello and thanks for the help

So after the suggestions you two give me it would be like this, right?

if you asking for the Fname,....., Fwords, is because F start with File so, for me easy to remember, in the jsp

And I have another problem , is not working, after the SAVE button, nothing, a white window shows.

I have only one answer my bad indentation in the servlet

import java.io.*;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

String ID="";
	  String name="";
	  String Fname="";
	  String Address="";
	  String Age="";
	  String City="";
	  
	  ID=request.getParameter("FID");
	  name=request.getParameter("Fname");
	  Fname=request.getParameter("FFname");
	  Address=request.getParameter("FAddress");
	  Age=request.getParameter("Fage");
	  City=request.getParameter("Fcity");
	
	
	  if(request.getParameter("SAVE") != null)

try {
		  PrintWriter fileWriter = new PrintWriter(new FileOutputStream("c:/example/filedata.txt",true));
		  fileWriter.println( ID + "," + name + "," + Fname + "," + Address + "," + Age + "," + City);
		  fileWriter.close(); 
	         }
      catch(FileNotFoundException fnfe) {  
          
      }
	  finally{
		  out.println(ID+": file saved");
	  }
   }
}

thanks

Bear Bibeault

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posted 12 years ago

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Not following standard conventions makes code unreasonably hard to read. Start all of your variable names with a lowercase character. Using uppercase is confusing and fewer people will be able to read your code easily.

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Bear Bibeault

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posted 12 years ago

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Alen Mester wrote:And I have another problem , is not working, after the SAVE button, nothing, a white window shows.

You are not writing anything to the response. So what else would you expect?

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Tim Quick

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posted 12 years ago

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Try changing the finally { } clause to something like this:

finally{
out.println("<html><body>");
out.println(ID+": file saved");
out.println("</body></html>");

}

That's the bare bones version of html necessary for your browser to render.

Good luck!
Tim

Bear Bibeault

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The misuse of finally in this code is disturbing.

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Alen Mester

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posted 12 years ago

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Thanks guys

Let me check it, beause I still have problems with the response

Angad Yadav

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posted 12 years ago

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Use PrintWriter rather than a DataOutputStream if you want readable text in your file.

PrintWriter _FileWriter = new PrintWriter(new FileOutputStream("c:\\sampleFile.txt",true));
_FileWriter.println( ID + "," + Fname + "," + LName + "," + Address + "," + Age + "," + City);
_FileWriter.close();

Regards,
Angad Yadav
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Alen Mester

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posted 12 years ago

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I still dont get it how is the "response"

For the moment , I resolve a basic error, in the servlet in where "if" is, a key "{" was need it

now after the "save" button the console show this

_________________________________________________________________________________________________

http://localhost:8080/PIntranet/file.do?FID=01&Fname=Alex&FFname=Mester&FAddress=terra&Fage=23&Fcity=Dallas
___________________________________________________________________________________________________

Here is the servlet.

import java.io.*;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class FileServlet extends HttpServlet{

String id="";
	  String name="";
	  String fname="";
	  String address="";
	  String age="";
	  String city="";

public void doGet(HttpServletRequest request, 
	  HttpServletResponse response) throws ServletException,IOException
	  {
		PrintWriter out = response.getWriter();
		response.setContentType("text/html");

id=request.getParameter("fid");
		name=request.getParameter("fname");
		fname=request.getParameter("ffname");
		address=request.getParameter("faddress");
		age=request.getParameter("fage");
		city=request.getParameter("fcity");
		
	  if(request.getParameter("save") != null){
		  
	    		   
	  try {	                                                                                 //("c:\\filedata.txt",true));										
		  PrintWriter fileWriter = new PrintWriter(new FileOutputStream("c:/example/filedata.txt",true));
		  fileWriter.println( id + "," + name + "," + fname + "," + address + "," + age + "," + city);
		  
		  fileWriter.close();  
	   }
      catch(FileNotFoundException fnfe) {  
    	  	fnfe.printStackTrace();
      }
	  finally{
		 System.out.println("The data is now in the datafile");

}
	 }
   }
}

Bear Bibeault

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posted 12 years ago

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Alen Mester wrote:I still dont get it how is the "response"

I do not understand this question.

The misuse if finally is still very disturbing.

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Alen Mester

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posted 12 years ago

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I will do something about the misuse if finally

The principal matter is that the localhost have the data

http://localhost:8080/PIntranet/file.do?fid=01&fname=Alen&ffname=Mester&faddress=terra&fage=23&fcity=Dallas

I want this data in a text file.

Bear Bibeault say:

You are not writing anything to the response. So what else would you expect?

So how, I do this "response" because i dont know

Paul Clapham

Marshal

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posted 12 years ago

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Alen Mester wrote:The principal matter is that the localhost have the data

http://localhost:8080/PIntranet/file.do?fid=01&fname=Alen&ffname=Mester&faddress=terra&fage=23&fcity=Dallas

I want this data in a text file.

Why do you keep posting this link? Surely you don't expect us to click on it and see something?

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Randall Twede

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posted 12 years ago

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without reading all the posts in this thread, i will just post how i did text files in servlets. i created a FileIO helper class.

i wrote this 10 years ago when still new to java so forgive my braces and indenting etc, i do it different now

oops... almost forgot to mention that there were only 2 text files involved and i created them manually. anyway, if this helps great if not oh well

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