register @RequestMapping and overwrite path

ApiHandlerMapping.java

package com.scienjus;

import org.springframework.core.annotation.AnnotatedElementUtils;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.mvc.condition.RequestCondition;
import org.springframework.web.servlet.mvc.method.RequestMappingInfo;
import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;

import java.lang.annotation.Annotation;
import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Method;
import java.util.Arrays;

/**
 * @author ScienJus
 * @date 16/6/5.
 */
public class ApiHandlerMapping extends RequestMappingHandlerMapping {
    
    /**
     * Uses method and type-level @{@link RequestMapping} annotations to create
     * the RequestMappingInfo.
     * @return the created RequestMappingInfo, or {@code null} if the method
     * does not have a {@code @RequestMapping} annotation.
     * @see #getCustomMethodCondition(Method)
     * @see #getCustomTypeCondition(Class)
     */
    @Override
    protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) {
        RequestMappingInfo info = createRequestMappingInfo(method);
        if (info != null) {
            RequestMappingInfo typeInfo = createRequestMappingInfo(handlerType);
            if (typeInfo != null) {
                info = typeInfo.combine(info);
            }
        }
        return info;
    }

    /**
     * Delegates to {@link #createRequestMappingInfo(RequestMapping, RequestCondition)},
     * supplying the appropriate custom {@link RequestCondition} depending on whether
     * the supplied {@code annotatedElement} is a class or method.
     * @see #getCustomTypeCondition(Class)
     * @see #getCustomMethodCondition(Method)
     */
    private RequestMappingInfo createRequestMappingInfo(AnnotatedElement element) {
        final RequestMapping requestMapping = AnnotatedElementUtils.findMergedAnnotation(element, RequestMapping.class);
        RequestMapping apiMapping = new RequestMapping() {
            @Override
            public boolean equals(Object obj) {
                return requestMapping.equals(obj);
            }

            @Override
            public int hashCode() {
                return requestMapping.hashCode();
            }

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

            @Override
            public Class<? extends Annotation> annotationType() {
                return requestMapping.annotationType();
            }

            @Override
            public String name() {
                return requestMapping.name();
            }

            @Override
            public String[] value() {
                return requestMapping.value();
            }

            @Override
            public String[] path() {
                return Arrays.stream(requestMapping.path()).map(path -> "/api" + path).toArray(String[]::new);
            }

            @Override
            public RequestMethod[] method() {
                return requestMapping.method();
            }

            @Override
            public String[] params() {
                return requestMapping.params();
            }

            @Override
            public String[] headers() {
                return requestMapping.headers();
            }

            @Override
            public String[] consumes() {
                return requestMapping.consumes();
            }

            @Override
            public String[] produces() {
                return requestMapping.produces();
            }
        };
        RequestCondition<?> condition = (element instanceof Class<?> ?
                getCustomTypeCondition((Class<?>) element) : getCustomMethodCondition((Method) element));
        return (requestMapping != null ? createRequestMappingInfo(apiMapping, condition) : null);
    }

}