package org.springframework.web.servlet.resource;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.ListIterator;
import javax.servlet.http.HttpServletRequest;
import org.springframework.core.io.Resource;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
class DefaultResourceResolverChain implements ResourceResolverChain {
@Nullable
private final ResourceResolver resolver;
@Nullable
private final ResourceResolverChain nextChain;
public DefaultResourceResolverChain(@Nullable List<? extends ResourceResolver> resolvers) {
resolvers = (resolvers != null ? resolvers : Collections.emptyList());
DefaultResourceResolverChain chain = initChain(new ArrayList<>(resolvers));
this.resolver = chain.resolver;
this.nextChain = chain.nextChain;
}
private static DefaultResourceResolverChain initChain(ArrayList<? extends ResourceResolver> resolvers) {
DefaultResourceResolverChain chain = new DefaultResourceResolverChain(null, null);
ListIterator<? extends ResourceResolver> it = resolvers.listIterator(resolvers.size());
while (it.hasPrevious()) {
chain = new DefaultResourceResolverChain(it.previous(), chain);
}
return chain;
}
private DefaultResourceResolverChain(@Nullable ResourceResolver resolver, @Nullable ResourceResolverChain chain) {
Assert.isTrue((resolver == null && chain == null) || (resolver != null && chain != null),
"Both resolver and resolver chain must be null, or neither is");
this.resolver = resolver;
this.nextChain = chain;
}
@Override
@Nullable
public Resource resolveResource(
@Nullable HttpServletRequest request, String requestPath, List<? extends Resource> locations) {
return (this.resolver != null && this.nextChain != null ?
this.resolver.resolveResource(request, requestPath, locations, this.nextChain) : null);
}
@Override
@Nullable
public String resolveUrlPath(String resourcePath, List<? extends Resource> locations) {
return (this.resolver != null && this.nextChain != null ?
this.resolver.resolveUrlPath(resourcePath, locations, this.nextChain) : null);
}
}