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Calling Java methods with a Time argument loses microseconds #3081

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frsyuki opened this issue Jun 24, 2015 · 2 comments
Closed

Calling Java methods with a Time argument loses microseconds #3081

frsyuki opened this issue Jun 24, 2015 · 2 comments
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Invalid or Duplicate

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@frsyuki
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frsyuki commented Jun 24, 2015

When I have this method in Java,

public void set(Object v) {
  System.out.println("java: "+v.getClass());
}

calling this method using following JRuby code shows java: class java.util.Date:

set(Time.now)

On the other hand, following java method won't be called:

public set(RubyTime v) {
  System.out.println("this method is not called because JRuby's Time won't be coerced to org.jruby.RubyTime");
}

Ruby's Time object represents seconds and nanoseconds. However, java.util.Date represents only milliseconds. So, with the first natural ruby code, microsecond and nanosecond information is lost.

I want to avoid this behavior when I implement a library in Java which deals with timestamp objects. An options is to require users of my library to use java_method(:set, [org.jruby.RubyTime]) but I also want to avoid it because user's code becomes verbose.

Is it possible to change this behavior so that set(Time.now) calls set(RubyTime v) if this Java class has this overload?
@kares
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kares commented Jun 24, 2015

sounds like you're designing a native JRuby extention part maybe? ... in that case you're probably be able to handle this on you own (@JRubyMethod public set(IRubyObject v)).

the coercion needs to happen if there's a set(Object v) version, I'm not sure if the RubyTime version would work if you remove the Object version so that its the only one ...

@frsyuki
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frsyuki commented Jun 25, 2015

Thank you for your comment. I'm creating a Java library which works both for Java and JRuby.

I could solve this! Apparently, @JRubyMethod annotation is ignored if the class does not extend RubyObject? So alternatively, I used this approach:

First, I added setRubyObject(IRubyObject) method to the java class:

public class DynamicColumnSetter
{
    public void setNull() { ... }

    public void set(boolean value) { ... }

    public void set(long value) { ... }

    public void set(double value) { ... }

    public void set(String value) { ... }

    public void set(Instant value) { ... }

    public IRubyObject setRubyObject(IRubyObject rubyObject)
    {
        if (rubyObject instanceof RubyNil) {
            setNull();
        } else if (rubyObject instanceof RubyBoolean) {
            RubyBoolean b = (RubyBoolean) rubyObject;
            set(b.isTrue());
        } else if (rubyObject instanceof RubyInteger) {
            RubyInteger i = (RubyInteger) rubyObject;
            set(i.getLongValue());
        } else if (rubyObject instanceof RubyFloat) {
            RubyFloat f = (RubyFloat) rubyObject;
            set(f.getDoubleValue());
        } else if (rubyObject instanceof RubyString) {
            RubyString s = (RubyString) rubyObject;
            set(s.asJavaString());
        } else if (rubyObject instanceof RubyTime) {
            RubyTime time = (RubyTime) rubyObject;
            long msec = time.getDateTime().getMillis();
            long nsec = time.getNSec();
            long sec = msec / 1000 + nsec / 1000000000;
            int nano = (int) ((msec % 1000) * 1000000 + nsec % 1000000000);
            set(Instant.ofEpochSecond(sec, nano));
        } else {
            throw rubyObject.getRuntime().newTypeError("cannot convert instance of " + rubyObject.getMetaClass() + " to nil, true, false, Integer, Float, String, or Time");
        }
        return rubyObject.getRuntime().getNil();
    }
}

And added following lines to Ruby code:

org.embulk.spi.util.dynamic.DynamicColumnSetter.module_eval do
  alias_method(:set, :setRubyObject)
end

With this way, both Java and Ruby code can call set method simply. But internally, set method in Ruby is translated to setRubyObject method.

@frsyuki frsyuki closed this as completed Jun 25, 2015
@kares kares added this to the Invalid or Duplicate milestone Jun 25, 2015
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@frsyuki @kares