package org.springframework.web.servlet.resource;
import java.io.IOException;
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 DefaultResourceTransformerChain implements ResourceTransformerChain {
private final ResourceResolverChain resolverChain;
@Nullable
private final ResourceTransformer transformer;
@Nullable
private final ResourceTransformerChain nextChain;
public DefaultResourceTransformerChain(
ResourceResolverChain resolverChain, @Nullable List<ResourceTransformer> transformers) {
Assert.notNull(resolverChain, "ResourceResolverChain is required");
this.resolverChain = resolverChain;
transformers = (transformers != null ? transformers : Collections.emptyList());
DefaultResourceTransformerChain chain = initTransformerChain(resolverChain, new ArrayList<>(transformers));
this.transformer = chain.transformer;
this.nextChain = chain.nextChain;
}
private DefaultResourceTransformerChain initTransformerChain(ResourceResolverChain resolverChain,
ArrayList<ResourceTransformer> transformers) {
DefaultResourceTransformerChain chain = new DefaultResourceTransformerChain(resolverChain, null, null);
ListIterator<? extends ResourceTransformer> it = transformers.listIterator(transformers.size());
while (it.hasPrevious()) {
chain = new DefaultResourceTransformerChain(resolverChain, it.previous(), chain);
}
return chain;
}
public DefaultResourceTransformerChain(ResourceResolverChain resolverChain,
@Nullable ResourceTransformer transformer, @Nullable ResourceTransformerChain chain) {
Assert.isTrue((transformer == null && chain == null) || (transformer != null && chain != null),
"Both transformer and transformer chain must be null, or neither is");
this.resolverChain = resolverChain;
this.transformer = transformer;
this.nextChain = chain;
}
@Override
public ResourceResolverChain getResolverChain() {
return this.resolverChain;
}
@Override
public Resource transform(HttpServletRequest request, Resource resource) throws IOException {
return (this.transformer != null && this.nextChain != null ?
this.transformer.transform(request, resource, this.nextChain) : resource);
}
}