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java: read file and insert content

Posted on 2008-11-03
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Last Modified: 2013-11-23
I have a html file that I am reading in using filereader/bufferedreader.  I want to add content to the file when the first <body> tag is read.  What would the logic be for this condition and inserting data?
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Question by:newbieal
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11 Comments
 
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Expert Comment

by:Kevin Cross
ID: 22867528
Using filereader/bufferedreader you would have to create separate code using the writer versions of these classes (i.e. FileWriter) that will write the data to another file.  Since the buffered reader is giving each line one at a time, you would just insert your data through writer when you have read/written the opening body tag.
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Expert Comment

by:Kevin Cross
ID: 22867542
These may be helpful for you:

Java Tutorials -- Basic I/O:
http://java.sun.com/docs/books/tutorial/essential/io/

Java Practices -- Reading and Writing Files:
http://www.javapractices.com/topic/TopicAction.do?Id=42
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by:newbieal
ID: 22867859
Thank you, but none of the examples demonstrate insertion of text at a particular point.
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LVL 4

Author Comment

by:newbieal
ID: 22867893
This is what I have so far. The text is appended at the end of the file and not after the <body> tag.
BufferedReader bIn = new BufferedReader(new FileReader(
			    "testing.html"));
		String line = bIn.readLine();
		while (line != null) {
			
		if(line.contains("<body>"))
		{
			createOrAppendFile("testing.html", "some text");
		}
		line = bIn.readLine();
		}
	}
	   private static void createOrAppendFile (String f, String text) throws IOException {  
		   BufferedWriter bw = new BufferedWriter (new FileWriter (f, true));  
		   bw.write (text);  
		   bw.newLine();  
		   bw.flush();  
		   bw.close();  
		   }  

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Kevin Cross earned 500 total points
ID: 22868703
+Think you want to write to a different file.  You could always delete old and rename new one to old name at the end, but safer this way IMHO.
+Not sure you can insert data that way.  IIRC, the method you are using will write data at the end since you have the append option set to true.  Again, this may not be wrong if you are using a different file, since the text contained would only be up to point you have read and written from your other file so append would be right to insert data.

When you write to different file, you will see that you will need to write the original line data in first then do check for if you are at the <body> line and then insert additional data then when you code continues in loop it will write the remainder of the HTML thus leaving your new data inserted immediately after the <body> tag.
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Author Comment

by:newbieal
ID: 22869512
Ok, I found this code that seems to do what I am looking for, however I need to insert content after the <body> tag.  How do I determine the line at which the content needs inserted? In this example the line number is provided via input.

http://www.java-tips.org/java-se-tips/java.io/insert-a-line-in-a-file.html
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Assisted Solution

by:Kevin Cross
Kevin Cross earned 500 total points
ID: 22869796
That is basically the concept -- as you can see they are reading in the file and writing one line at a time to the new file then at the end they delete and rename.

In their case, a simple line number works.  For you though, you need logic like you have above to check if line contains "<body>" in its text.  To mimic what they are doing you have to change the logic around i++ to set the a temp string that has the contents of the line you have just written then the next time through it will check if temp string equals/contains string you are looking then write extra line(s) of data.

Then will continue to write lines of data until file is fully recreated.
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Author Comment

by:newbieal
ID: 22871360
The <body> tag may contain some additional info, eg. <body lang=EN-US style='tab-interval:.5in'>

When I check for the tag what expression to I need to check it against so that my new values aren't inserted within the body tag.
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Expert Comment

by:Kevin Cross
ID: 22872854
You will probably need to look into writing a regular expression to check for "<body" + any amount of characters + ">".
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Author Comment

by:newbieal
ID: 22872886
Yeah, that's what I thought.  Do you have an example of a regex for my specific case?
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Expert Comment

by:Kevin Cross
ID: 22872940
You can try "<body[a-zA-Z0-9]*>" but I would give it a try it and then create a question in the regular expressions zone...

Hopefully that helps!
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