Question

replace tokens in inputstream

Asked by: ICPooreman

So I have a text file that can potentially get very large.  In that file is a bunch of tokens that I want to be replaced but I don't want to alter that file in any way.

Basically below is what I'm doing now.  I want to get the same effect without loading the whole file as a string at any point for memory reasons.  I want to end up with an inputstream or reader or writer or something of the sort (basically never use strings) anybody know how to do this?

InputStream is = theClass.class.getResourceAsStream("/"
                + fileName);
        
        String theString;
        try {
            theString = IOUtils.toString(is);
        } finally {
            IOUtils.closeQuietly(is);
        }
   
 
        theString = theString.replaceAll("TokenToBeReplaced", "OtherString");

                                  
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Asked On
2009-01-08 at 08:30:19ID24035469
Topics

Java Programming Language

,

New to Java Programming

Participating Experts
4
Points
500
Comments
8

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Answers

 

by: humanonomicsPosted on 2009-01-08 at 09:03:22ID: 23327034

how about reading the file line by line and replacing it ? Like in following example.

BufferedReader br = null;
InputStream is= null;
try {
is = theClass.class.getResourceAsStream("/"
                + fileName);
 
br = new BuffereReader(new InputStreamReader(is));
 
String str = br.readLine();
 
while(str != null)
{
   str = str.replaceAll("TokenToBeReplaced", "OtherString");
 
//Store value of str 
 str = br.readLine();
}
}
catch(IOException e)
{
    e.printStackTrace();
}
finally
{
if(is!=null) is.close();
if(br!=null) br.close();
}

                                              
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by: ICPooremanPosted on 2009-01-08 at 09:07:32ID: 23327077

Thats got the jist of what I'm looking for but I want my end result to be the entire file as like an inputstream or something of the sort how do I load the string back into that line by line.

Like I start with an inputstream of the file I'd like to finish with an inputstream of the file changed but only without actually changing the file and without having the entire file loaded in at once as a string.

 

by: humanonomicsPosted on 2009-01-08 at 09:13:42ID: 23327161

you don't want to modify the contents of the file right ?

And when you read Line by line, it does not store entire file in the memory just stores it line by line.

 

by: ICPooremanPosted on 2009-01-08 at 09:20:52ID: 23327260

yes that's what I'm attempting to do but your solution doesn't change the value of br does it?  

str = str.replaceAll("TokenToBeReplaced", "OtherString");
 changes the value of the string then it appears that you just ignore the new string I want to store it somewhere so that eventually I can have the changed file just not loaded as a giant string in memory.

 

by: humanonomicsPosted on 2009-01-08 at 09:23:36ID: 23327298

Thats your call, thats why I had a comment on line 15, that you need to store it somewhere.

Where do you want to store ? in some collection ? or write it to some other file ?

 

by: CEHJPosted on 2009-01-08 at 09:59:51ID: 23327764

You'd probably be better off storing the replacement as a temporary file then opening a stream on it later

 

by: bluebelldiscoveryPosted on 2009-01-08 at 18:09:36ID: 23332281

Try this

replaceText(String srFile, String dtFile, String oldText, String newText)

srcFile - source file
dtFile - destination file
oldText - text to be replace
newText - text to change to

public static void replaceText(String srFile, String dtFile, String oldText, String newText) throws Exception
{
	File f1 = new File(srFile);
	File f2 = new File(dtFile);
 
	BufferedReader br = new BufferedReader( new InputStreamReader( new FileInputStream(f1) ) );
	BufferedWriter bw = new BufferedWriter( new OutputStreamWriter( new FileOutputStream(f2) ) );
 
	String str = br.readLine();
	while(str != null)
	{
		str = str.replaceAll(oldText, newText);
		bw.write(str+"\r\n");
		str = br.readLine();
	}
	bw.close();
	br.close();
}
 
static public void main(String[] arg) throws Exception
{
	replaceText("c:\\test.txt","c:\\test1.txt", "Hello", "Goodbye");
}

                                              
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by: objectsPosted on 2009-01-20 at 02:22:21ID: 23418628

you could either create a FilterInputStream subclass
or use a templating tool such as velocity to handle it for you.

20120131-EE-VQP-002

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