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package org.glassfish.jersey.message.internal;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Locale;
import java.util.Set;
import javax.ws.rs.core.HttpHeaders;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Variant;
import org.glassfish.jersey.internal.util.collection.Ref;
import com.google.common.base.Function;
import com.google.common.collect.Lists;
/**
* Utility for selecting variant that best matches request from a list of variants.
*
* @author Paul Sandoz
* @author Marek Potociar (marek.potociar at oracle.com)
*/
public final class VariantSelector {
private VariantSelector() {
}
/**
* Interface to get a dimension value from a variant and check if an
* acceptable dimension value is compatible with a dimension value.
*/
private static interface DimensionChecker {
/**
* Get the dimension value from the variant.
*
* @param v the variant.
* @return the dimension value.
*/
U getDimension(VariantHolder v);
/**
* Get the quality source of the dimension.
*
* @return quality source.
*/
int getQualitySource(VariantHolder v, U u);
/**
* Ascertain if the acceptable dimension value is compatible with
* the dimension value.
*
* @param t the acceptable dimension value.
* @param u the dimension value.
* @return {@code true} if the acceptable dimension value is compatible with
* the dimension value.
*/
boolean isCompatible(T t, U u);
/**
* Get the value of the Vary header.
*
* @return the value of the Vary header.
*/
String getVaryHeaderValue();
}
private static final DimensionChecker MEDIA_TYPE_DC =
new DimensionChecker() {
@Override
public MediaType getDimension(VariantHolder v) {
return v.v.getMediaType();
}
@Override
public boolean isCompatible(AcceptableMediaType t, MediaType u) {
return t.isCompatible(u);
}
@Override
public int getQualitySource(VariantHolder v, MediaType u) {
return v.mediaTypeQs;
}
@Override
public String getVaryHeaderValue() {
return HttpHeaders.ACCEPT;
}
};
private static final DimensionChecker LANGUAGE_TAG_DC =
new DimensionChecker() {
@Override
public Locale getDimension(VariantHolder v) {
return v.v.getLanguage();
}
@Override
public boolean isCompatible(AcceptableLanguageTag t, Locale u) {
return t.isCompatible(u);
}
@Override
public int getQualitySource(VariantHolder qsv, Locale u) {
return Quality.MINIMUM_QUALITY;
}
@Override
public String getVaryHeaderValue() {
return HttpHeaders.ACCEPT_LANGUAGE;
}
};
private static final DimensionChecker CHARSET_DC =
new DimensionChecker() {
@Override
public String getDimension(VariantHolder v) {
MediaType m = v.v.getMediaType();
return (m != null) ? m.getParameters().get("charset") : null;
}
@Override
public boolean isCompatible(AcceptableToken t, String u) {
return t.isCompatible(u);
}
@Override
public int getQualitySource(VariantHolder qsv, String u) {
return Quality.MINIMUM_QUALITY;
}
@Override
public String getVaryHeaderValue() {
return HttpHeaders.ACCEPT_CHARSET;
}
};
private static final DimensionChecker ENCODING_DC =
new DimensionChecker() {
@Override
public String getDimension(VariantHolder v) {
return v.v.getEncoding();
}
@Override
public boolean isCompatible(AcceptableToken t, String u) {
return t.isCompatible(u);
}
@Override
public int getQualitySource(VariantHolder qsv, String u) {
return Quality.MINIMUM_QUALITY;
}
@Override
public String getVaryHeaderValue() {
return HttpHeaders.ACCEPT_ENCODING;
}
};
/**
* Select variants for a given dimension.
*
* @param variantHolders collection of variants.
* @param acceptableValues the list of acceptable dimension values, ordered by the quality
* parameter, with the highest quality dimension value occurring
* first.
* @param dimensionChecker the dimension checker
* @param vary output list of generated vary headers.
*/
private static LinkedList selectVariants(
List variantHolders,
List acceptableValues,
DimensionChecker dimensionChecker,
Set vary) {
int cq = Quality.MINIMUM_QUALITY;
int cqs = Quality.MINIMUM_QUALITY;
final LinkedList selected = new LinkedList();
// Iterate over the acceptable entries
// This assumes the entries are ordered by the quality
for (final T a : acceptableValues) {
final int q = a.getQuality();
final Iterator iv = variantHolders.iterator();
while (iv.hasNext()) {
final VariantHolder v = iv.next();
// Get the dimension value of the variant to check
final U d = dimensionChecker.getDimension(v);
if (d != null) {
vary.add(dimensionChecker.getVaryHeaderValue());
// Check if the acceptable entry is compatable with
// the dimension value
final int qs = dimensionChecker.getQualitySource(v, d);
if (qs >= cqs && dimensionChecker.isCompatible(a, d)) {
if (qs > cqs) {
cqs = qs;
cq = q;
// Remove all entries that were added for qs < cqs
selected.clear();
selected.add(v);
} else if (q > cq) {
cq = q;
// Add variant with higher accept quality at the front
selected.addFirst(v);
} else if (q == cq) {
// Ensure selection is stable with order of variants
// with same quality of source and accept quality
selected.add(v);
}
iv.remove();
}
}
}
}
// Add all variants that are not compatible with this dimension
// to the end
for (VariantHolder v : variantHolders) {
if (dimensionChecker.getDimension(v) == null) {
selected.add(v);
}
}
return selected;
}
private static class VariantHolder {
private final Variant v;
private final int mediaTypeQs;
public VariantHolder(Variant v) {
this(v, Quality.DEFAULT_QUALITY);
}
public VariantHolder(Variant v, int mediaTypeQs) {
this.v = v;
this.mediaTypeQs = mediaTypeQs;
}
}
private static LinkedList getVariantHolderList(final List variants) {
final LinkedList l = new LinkedList();
for (Variant v : variants) {
final MediaType mt = v.getMediaType();
if (mt != null) {
if (mt instanceof QualitySourceMediaType || mt.getParameters().
containsKey(QualitySourceMediaType.QUALITY_SOURCE_PARAMETER_NAME)) {
int qs = QualitySourceMediaType.getQualitySource(mt);
l.add(new VariantHolder(v, qs));
} else {
l.add(new VariantHolder(v));
}
} else {
l.add(new VariantHolder(v));
}
}
return l;
}
/**
* Select the representation variant that best matches the request. More explicit
* variants are chosen ahead of less explicit ones.
*
* @param context inbound message context.
* @param variants list of possible variants.
* @param varyHeaderValue an output reference of vary header value that should be put
* into the response Vary header.
* @return selected variant.
*/
public static Variant selectVariant(InboundMessageContext context, List variants, Ref varyHeaderValue) {
final List selectedVariants = selectVariants(context, variants, varyHeaderValue);
return selectedVariants.isEmpty() ? null : selectedVariants.get(0);
}
/**
* Select possible representation variants in order in which they best matches the request.
*
* @param context inbound message context.
* @param variants list of possible variants.
* @param varyHeaderValue an output reference of vary header value that should be put into the response Vary header.
* @return possible variants.
*/
public static List selectVariants(InboundMessageContext context, List variants, Ref varyHeaderValue) {
LinkedList vhs = getVariantHolderList(variants);
Set vary = new HashSet();
vhs = selectVariants(vhs, context.getQualifiedAcceptableMediaTypes(), MEDIA_TYPE_DC, vary);
vhs = selectVariants(vhs, context.getQualifiedAcceptableLanguages(), LANGUAGE_TAG_DC, vary);
vhs = selectVariants(vhs, context.getQualifiedAcceptCharset(), CHARSET_DC, vary);
vhs = selectVariants(vhs, context.getQualifiedAcceptEncoding(), ENCODING_DC, vary);
if (vhs.isEmpty()) {
return Collections.emptyList();
} else {
StringBuilder varyHeader = new StringBuilder();
for (String v : vary) {
if (varyHeader.length() > 0) {
varyHeader.append(',');
}
varyHeader.append(v);
}
String varyValue = varyHeader.toString();
if (!varyValue.isEmpty()) {
varyHeaderValue.set(varyValue);
}
return Lists.transform(vhs, new Function() {
@Override
public Variant apply(final VariantHolder holder) {
return holder.v;
}
});
}
}
}
