<Swing Dev> OOM error parsing HTML with large <pre> Tag text

Mon Mar 16 17:08:30 UTC 2020

Hello,

After upgrading from Java 8 to 11, we started seeing OOM errors when parsing HTML files with a large <pre> tag text. The test program below works fine under Java 8, but terminates with an OutOfMemoryError under Java 9 or later. If the <pre> tag text is *not* '\n' separated, it works in all versions of Java.

We have tracked down the problem to a change originally committed to Java 9:
https://github.com/openjdk/jdk/commit/17679435a174f6a7f0e450309dc8775e77df968a

Reverting the above change or replacing `Arrays.copyOf(txt, txt.length)` with `Arrays.copyOfRange(txt, offs, offs + length)` fixes the OOM error.

Thank you,
Kenny Wong

--- 8< ---
import java.io.StringReader;

import javax.swing.text.html.HTMLEditorKit;

public class Test {
    public static void main(String[] args) throws Exception {
        StringBuilder html = new StringBuilder();
        html.append("<html><body><pre>");
        for (int i = 0; i < 10_000; i++) {
            html.append("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
                .append("\n");
        }
        html.append("</pre></body></html>");

        HTMLEditorKit kit = new HTMLEditorKit();
        kit.read(new StringReader(html.toString()), kit.createDefaultDocument(), 0);
    }
}
--

--- 8< ---
$ java --version
openjdk 11.0.3 2019-04-16 LTS
OpenJDK Runtime Environment Zulu11.31+11-CA (build 11.0.3+7-LTS)
OpenJDK 64-Bit Server VM Zulu11.31+11-CA (build 11.0.3+7-LTS, mixed mode)

-bash3.2$ java Test.java 
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
    at java.base/java.util.Arrays.copyOf(Arrays.java:3841)
    at java.desktop/javax.swing.text.DefaultStyledDocument$ElementSpec.<init>(DefaultStyledDocument.java:1267)
    at java.desktop/javax.swing.text.html.HTMLDocument$HTMLReader.addContent(HTMLDocument.java:3909)
    at java.desktop/javax.swing.text.html.HTMLDocument$HTMLReader.addContent(HTMLDocument.java:3883)
    at java.desktop/javax.swing.text.html.HTMLDocument$HTMLReader.preContent(HTMLDocument.java:3787)
    at java.desktop/javax.swing.text.html.HTMLDocument$HTMLReader.handleText(HTMLDocument.java:2766)
    at java.desktop/javax.swing.text.html.parser.DocumentParser.handleText(DocumentParser.java:271)
    at java.desktop/javax.swing.text.html.parser.Parser.handleText(Parser.java:409)
    at java.desktop/javax.swing.text.html.parser.Parser.endTag(Parser.java:524)
    at java.desktop/javax.swing.text.html.parser.Parser.parseTag(Parser.java:1934)
    at java.desktop/javax.swing.text.html.parser.Parser.parseContent(Parser.java:2195)
    at java.desktop/javax.swing.text.html.parser.Parser.parse(Parser.java:2372)
    at java.desktop/javax.swing.text.html.parser.DocumentParser.parse(DocumentParser.java:135)
    at java.desktop/javax.swing.text.html.parser.ParserDelegator.parse(ParserDelegator.java:113)
    at java.desktop/javax.swing.text.html.HTMLEditorKit.read(HTMLEditorKit.java:263)
    at Test.main(Test.java:16)
---