Mega Code Archive
A simple FilterReader that strips HTML tags out of a stream of characters
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/*
* Copyright (c) 2004 David Flanagan. All rights reserved.
* This code is from the book Java Examples in a Nutshell, 3nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose,
* including teaching and use in open-source projects.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book,
* please visit http://www.davidflanagan.com/javaexamples3.
*/
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FilterReader;
import java.io.IOException;
import java.io.Reader;
/**
* A simple FilterReader that strips HTML tags (or anything between pairs of
* angle brackets) out of a stream of characters.
*/
public class RemoveHTMLReader extends FilterReader {
/** A trivial constructor. Just initialize our superclass */
public RemoveHTMLReader(Reader in) {
super(in);
}
boolean intag = false; // Used to remember whether we are "inside" a tag
/**
* This is the implementation of the no-op read() method of FilterReader. It
* calls in.read() to get a buffer full of characters, then strips out the
* HTML tags. (in is a protected field of the superclass).
*/
public int read(char[] buf, int from, int len) throws IOException {
int numchars = 0; // how many characters have been read
// Loop, because we might read a bunch of characters, then strip them
// all out, leaving us with zero characters to return.
while (numchars == 0) {
numchars = in.read(buf, from, len); // Read characters
if (numchars == -1)
return -1; // Check for EOF and handle it.
// Loop through the characters we read, stripping out HTML tags.
// Characters not in tags are copied over previous tags
int last = from; // Index of last non-HTML char
for (int i = from; i < from + numchars; i++) {
if (!intag) { // If not in an HTML tag
if (buf[i] == '<')
intag = true; // check for tag start
else
buf[last++] = buf[i]; // and copy the character
} else if (buf[i] == '>')
intag = false; // check for end of tag
}
numchars = last - from; // Figure out how many characters remain
} // And if it is more than zero characters
return numchars; // Then return that number.
}
/**
* This is another no-op read() method we have to implement. We implement it
* in terms of the method above. Our superclass implements the remaining
* read() methods in terms of these two.
*/
public int read() throws IOException {
char[] buf = new char[1];
int result = read(buf, 0, 1);
if (result == -1)
return -1;
else
return (int) buf[0];
}
/** The test program: read a text file, strip HTML, print to console */
public static void main(String[] args) {
try {
if (args.length != 1)
throw new IllegalArgumentException("Wrong number of args");
// Create a stream to read from the file and strip tags from it
BufferedReader in = new BufferedReader(new RemoveHTMLReader(new FileReader(args[0])));
// Read line by line, printing lines to the console
String line;
while ((line = in.readLine()) != null)
System.out.println(line);
in.close(); // Close the stream.
} catch (Exception e) {
System.err.println(e);
System.err.println("Usage: java RemoveHTMLReader$Test" + " <filename>");
}
}
}
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