HttpUtil.getContentLength can throw parse error even when default value is supplied

Fairly straight-forward to fix, but not sure if we should actually change the behavior or just change the javadoc. I can contribute a PR.

Expected behavior

Calling HttpUtil.getContentLength(HttpMessage, int) should return the default value when the header is not a number, in accordance with the javadoc:

Returns: the content length or defaultValue if this message does not have the “Content-Length” header or its value is not a number. Not to exceed the boundaries of integer.

Actual behavior

For invalid inputs, the method throws an exception:

Exception in thread "main" java.lang.NumberFormatException: For input string: "foo"
	at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:67)
	at java.base/java.lang.Long.parseLong(Long.java:711)
	at java.base/java.lang.Long.parseLong(Long.java:836)
	at io.netty.handler.codec.http.HttpUtil.getContentLength(HttpUtil.java:181)
	at io.netty.handler.codec.http.HttpUtil.getContentLength(HttpUtil.java:203)
	at io.micronaut.http.server.netty.fuzzing.X.main(X.java:12)

Steps to reproduce

Run the reproducer code.

Minimal yet complete reproducer code (or URL to code)

package io.micronaut.http.server.netty.fuzzing;

import io.netty.handler.codec.http.DefaultFullHttpRequest;
import io.netty.handler.codec.http.HttpMethod;
import io.netty.handler.codec.http.HttpUtil;
import io.netty.handler.codec.http.HttpVersion;

public class X {
    public static void main(String[] args) {
        DefaultFullHttpRequest request = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.GET, "/");
        request.headers().add("Content-Length", "foo");
        System.out.println(HttpUtil.getContentLength(request, 0));
    }
}

Netty version

4.1.73.Final

JVM version (e.g. java -version)

openjdk version “17.0.1” 2021-10-19 OpenJDK Runtime Environment Temurin-17.0.1+12 (build 17.0.1+12) OpenJDK 64-Bit Server VM Temurin-17.0.1+12 (build 17.0.1+12, mixed mode, sharing)

OS version (e.g. uname -a)

Linux yawkat-oracle 5.13.0-28-generic #31-Ubuntu SMP Thu Jan 13 17:41:06 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

[normanmaurer]

I think we should fix the code… Let me do it.

[normanmaurer]

yeah I think we should keep it simple