Optimize object creation in RequestMappingHandlerMapping#handleNoMatch

[koo-taejin]

related issue: #29611

RequestMappingInfoHandlerMapping handleNoMatch() method has the following format.
https://github.com/spring-projects/spring-framework/blob/main/spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/RequestMappingInfoHandlerMapping.java#L246
https://github.com/spring-projects/spring-framework/blob/main/spring-webflux/src/main/java/org/springframework/web/reactive/result/method/RequestMappingInfoHandlerMapping.java#L169

@Override
protected HandlerMethod handleNoMatch(Set<RequestMappingInfo> infos, ...) throws Exception {
	PartialMatchHelper helper = new PartialMatchHelper(infos, exchange);
	if (helper.isEmpty()) {
		return null;
	}
        ...
}

And this method may allow an empty value in Set<RequestMappingInfo> infos parameter.
(Unfortunately, it happens a lot in the service I am running.)

The constructor code of org.springframework.web.reactive.result.method.RequestMappingInfoHandlerMapping.PartialMatchHelper is shown below.
https://github.com/spring-projects/spring-framework/blob/main/spring-webflux/src/main/java/org/springframework/web/reactive/result/method/RequestMappingInfoHandlerMapping.java#L227

public PartialMatchHelper(Set<RequestMappingInfo> infos, ServerWebExchange exchange) {
	this.partialMatches.addAll(infos.stream().
			filter(info -> info.getPatternsCondition().getMatchingCondition(exchange) != null).
			map(info -> new PartialMatch(info, exchange)).
			collect(Collectors.toList()));
}

This code executes follwoing method even if there is no value in infos
java.util.Collection#stream
java.util.stream.Collectors#toList
java.util.stream.ReferencePipeline#collect(java.util.stream.Collector<? super P_OUT,A,R>)
Unnecessary resources are used via these methods.(create objects and execute operations, so )

Even though parameters have values, it seems better not to use Stream.

It can save resources by changing the constructor like mvc's RequestMappingInfoHandlerMapping.
https://github.com/spring-projects/spring-framework/blob/main/spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/RequestMappingInfoHandlerMapping.java#L300

public PartialMatchHelper(Set<RequestMappingInfo> infos, HttpServletRequest request) {
			for (RequestMappingInfo info : infos) {
				if (info.getActivePatternsCondition().getMatchingCondition(request) != null) {
					this.partialMatches.add(new PartialMatch(info, request));
				}
			}
		}

Below is a test created similar to the code above.

1. style of webflux
2. style of mvc
3. style of reuse object

• test code

public class PartialMatchHelperTest {

    @Test
    public void partialMatchHelperTest() {
        int count = 1000 * 1000 * 100;

        ThreadMXBean mxBean = ManagementFactory.getThreadMXBean();

        // 1)
        long startTime = System.currentTimeMillis();
        final long startCpuTime = mxBean.getCurrentThreadCpuTime();
        for (int i = 0; i < count; i++) {
            new PartialMatchHelper(Collections.emptySet());
        }
        System.out.println(System.currentTimeMillis() - startTime);
        System.out.println(mxBean.getCurrentThreadCpuTime() - startCpuTime);

        // 2)
        long startTime2 = System.currentTimeMillis();
        final long startCpuTime2 = mxBean.getCurrentThreadCpuTime();
        for (int i = 0; i < count; i++) {
            new PartialMatchHelper2(Collections.emptySet());
        }
        System.out.println(System.currentTimeMillis() - startTime2);
        System.out.println(mxBean.getCurrentThreadCpuTime() - startCpuTime2);

        // 3)
        long startTime3 = System.currentTimeMillis();
        final long startCpuTime3 = mxBean.getCurrentThreadCpuTime();
        for (int i = 0; i < count; i++) {
            PartialMatchHelper3.of(Collections.emptySet());
        }
        System.out.println(System.currentTimeMillis() - startTime3);
        System.out.println(mxBean.getCurrentThreadCpuTime() - startCpuTime3);
    }

    private static class PartialMatchHelper {
        private final List<PartialMatch> partialMatches = new ArrayList<>();

        public PartialMatchHelper(Set<RequestMappingInfo> infos) {
            partialMatches.addAll(infos.stream().
                    filter(info -> info.getPatternsCondition().getMatchingCondition(null) != null).
                    map(info -> new PartialMatch(info)).
                    collect(Collectors.toList()));
        }

        public boolean isEmpty() {
            return partialMatches.isEmpty();
        }
    }

    private class PartialMatchHelper2 {
        private final List<PartialMatch> partialMatches = new ArrayList<>();


        public PartialMatchHelper2(Set<RequestMappingInfo> infos) {
            for (RequestMappingInfo info : infos) {
                if (info.getMatchingCondition(null) != null) {
                    this.partialMatches.add(new PartialMatch(info));
                }
            }
        }

        public boolean isEmpty() {
            return partialMatches.isEmpty();
        }
    }

    private static class PartialMatchHelper3 {

        static PartialMatchHelper3 DISALBELD = new PartialMatchHelper3(Collections.emptySet());

        private final List<PartialMatch> partialMatches = new ArrayList<>();


        public static PartialMatchHelper3 of(Set<RequestMappingInfo> infos) {
            if (infos.isEmpty()) {
                return DISALBELD;
            } else {
                return new PartialMatchHelper3(infos);
            }
        }


        public PartialMatchHelper3(Set<RequestMappingInfo> infos) {
            for (RequestMappingInfo info : infos) {
                if (info.getMatchingCondition(null) != null) {
                    this.partialMatches.add(new PartialMatch(info));
                }
            }
        }

        public boolean isEmpty() {
            return partialMatches.isEmpty();
        }
    }

    private static class PartialMatch {

        private final RequestMappingInfo info;

        public PartialMatch(RequestMappingInfo info) {
            this.info = info;
        }


        public RequestMappingInfo getInfo() {
            return this.info;
        }

        @Override
        public String toString() {
            return this.info.toString();
        }
    }
}

Result (from Async Profiler)

    1) samples : CPU   393, Memory allocations      13,474,672
    2) samples : CPU   580, Memory allocations   4,804,133,448
    3) samples : CPU  6,547, Memory allocations 37,581,912,072

In my opinion, the following order seems like a good way.
(Suggested solution (3 + 2) -> 3 -> 2 -> 1)

I will make PR according to your opinion.

Thanks :)

[koo-taejin]

I have worked for Only the initialization part mentioned in the issue.
The performance of Stream itself is not good, so it would be better if other parts were improved.
http://www.angelikalanger.com/Conferences/Videos/Conference-Video-GeeCon-2015-Performance-Model-of-Streams-in-Java-8-Angelika-Langer.html

If you want to change the other parts to the collector's loop as before.
Please let me know, then I am going to work for it.

Thanks :)

[rstoyanchev]

Backported to 5.3.25 with #29667.