How to parse a large HTML file with Java HTMLParser library

Question

I have some html files created by Filemaker export. Each file is basically a huge HTML table. I want to iterate through the table rows and populate them into a database. I have tried to do it with HTMLParser as follows:

String inputHTML = readFile("filemakerExport.htm","UTF-8");
Parser parser = new Parser();
parser.setInputHTML(inputHTML);
parser.setEncoding("UTF-8");    
NodeList nl = parser.parse(null); 
NodeList trs = nl.extractAllNodesThatMatch(new TagNameFilter("tr"),true);
for(int i=0;i<trs.size();i++) {
    NodeList nodes = trs.elementAt(i).getChildren();
    NodeList tds  = nodes.extractAllNodesThatMatch(new TagNameFilter("td"),true);
    // Do stuff with tds
}

The above code works with files under 1 Mb. Unfortunately I have a 4.8 Mbs html file and I get an out of memory error.

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
    at org.htmlparser.lexer.Lexer.parseTag(Lexer.java:1002)
    at org.htmlparser.lexer.Lexer.nextNode(Lexer.java:369)
    at org.htmlparser.scanners.CompositeTagScanner.scan(CompositeTagScanner.java:111)
    at org.htmlparser.util.IteratorImpl.nextNode(IteratorImpl.java:92)
    at org.htmlparser.Parser.parse(Parser.java:701)
    at Tools.main(Tools.java:33)

Is there a more efficient way to solve this problem with HTMLParser (I am totally new to the library), or should I use a different library or approach?

Answer 1

Have you tried increased the max heap size of the JVM

The following command line argument will up it to 512 megabytes: -Xmx512M

E.g.

java -Xmx512M myrunclass

Answer 2

Don't build a DOM when you only want to extract some information and you are not interested to perform some XPath queries or other type of queries which perform best on a DOM structure(parent-child relations, etc).

Use Parser.visitAllNodesWith() instead of Prser.parse().