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Merged
GGoetzelmann merged 1 commit into from
May 23, 2025
Merged

JSON-LD: improve context handling on framing and compacting #21

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160 changes: 98 additions & 62 deletions src/main/java/edu/kit/scc/dem/wapsrv/model/formats/JsonLdFormatter.java
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Original file line number Diff line number Diff line change
Expand Up @@ -3,13 +3,7 @@
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.Vector;
import java.util.*;
import java.util.regex.Pattern;
import org.apache.commons.collections4.map.ListOrderedMap;
import org.slf4j.Logger;
Expand Down Expand Up @@ -58,7 +52,7 @@ public final class JsonLdFormatter extends AbstractFormatter {
/**
* The set of used profiles
*/
private final Set<URL> profiles = new HashSet<URL>();
private final Set<URL> profiles = new HashSet<>();
/**
* The profile registry
*/
Expand Down Expand Up @@ -143,7 +137,6 @@ public String format(FormattableObject obj) {
/**
* Remove all blank node IDs from a given "pretty" JSON-LD String
*
* @param jsonLdPretty JSON-LD serialized in pretty mode
* @return The same JSON-LD without blank node IDs
*/
private String removeBlankNodeIds(String jsonLdWithBlankNodeIds) {
Expand Down Expand Up @@ -171,7 +164,7 @@ private String removeBlankNodeIds(String jsonLdWithBlankNodeIds) {
String[] lines = jsonLdWithBlankNodeIds.split(Pattern.quote("\n"));
for (String line : lines) {
if (line.trim().startsWith("\"id\"")) {
if (line.indexOf("\"_:b") != -1) {
if (line.contains("\"_:b")) {
continue; // skip this unneeded line
} else {
builder.append(line);
Expand All @@ -197,83 +190,126 @@ private String removeBlankNodeIds(String jsonLdWithBlankNodeIds) {
* @param frameString The JSON-LD Frame as String
* @return the expanded string
*/
@SuppressWarnings("unchecked")
private String applyProfiles(String jsonLd, String frameString) {
try {

final Object frameObject = frameString == null ? null : JsonUtils.fromString(frameString);
Object jsonObject = JsonUtils.fromString(jsonLd);
// Use precreated options with in memory profiles
JsonLdOptions optionsWithContexts = profileRegistry.getJsonLdOptions();
Map<String, Object> framed = null;
if (frameObject != null) {

List<Object> contexts = new ArrayList<>();

//We assume that framing and compacting only needs to be applied if anno profile is present
if (frameObject != null && profiles.contains(DEFAULT_PROFILE)) {
final JsonLdOptions options = profileRegistry.getJsonLdOptions();
options.format = JsonLdConsts.APPLICATION_NQUADS;
options.setCompactArrays(true);
framed = JsonLdProcessor.frame(jsonObject, frameObject, options);
List<String> contexts = new Vector<String>();

// Frame the RDF-converted JSON-LD
jsonObject = JsonLdProcessor.frame(jsonObject, frameObject, options);

// Collect contexts from profiles
for (URL url : profiles) {
String context = url.toString();
contexts.add(context);
contexts.add(url.toString());
}
java.util.Collections.reverse(contexts);

if (!profiles.isEmpty()) {
// Compact only if client requested that
jsonObject = JsonLdProcessor.compact(framed, contexts, optionsWithContexts);
}
} else {
for (URL url : profiles) {
String context = url.toString();
jsonObject = JsonLdProcessor.compact(jsonObject, context, optionsWithContexts);
// Extract @context from the frame and add it to the list
if (frameObject instanceof Map) {
Object frameContext = ((Map<?, ?>) frameObject).get("@context");
if (frameContext != null) {
if (frameContext instanceof List) {
// Flatten the list
contexts.addAll((List<?>) frameContext);
} else {
// Add single context (string or map)
contexts.add(frameContext);
}
}
}
}
if (!profiles.isEmpty()) {
// JSON-LD java api uses just objects, we cannot prevent casting here
insertContexts((Map<String, Object>) jsonObject);
jsonObject = reorderJsonAttributes((Map<String, Object>) jsonObject);
for (URL url : profiles) {
contexts.add(url.toString());
}
contexts = deduplicateContexts(contexts);
jsonObject = JsonLdProcessor.compact(jsonObject, contexts, optionsWithContexts);

jsonObject = reorderJsonAttributes(jsonObject);
return JsonUtils.toPrettyString(jsonObject);
} catch (JsonLdError | IOException e) {
throw new FormatException(e.getMessage(), e);
}
}

private void insertContexts(Map<String, Object> map) {
Object contexts = createContextString();
if (contexts != null) {
map.put("@context", contexts);
/**
* Deduplicates and flattens a list of JSON-LD context entries.
* Supports strings (URIs), maps (inline contexts), and nested lists.
*
* @param rawContexts A list of context entries (String, Map, or List)
* @return A flattened, deduplicated list of context entries
*/
public List<Object> deduplicateContexts(List<Object> rawContexts) {

List<Object> result = new ArrayList<>();
Set<String> seenUris = new HashSet<>();
Set<String> seenInlineContexts = new HashSet<>();


for (Object ctx : rawContexts) {
flattenAndAdd(ctx, result, seenUris, seenInlineContexts);
}

return result;
}

private Object createContextString() {
if (profiles.isEmpty()) {
return null;
}
if (profiles.size() == 1) {
return profiles.iterator().next().toString();
}
Iterator<URL> iterator = profiles.iterator();
List<Object> list = new ArrayList<Object>();
while (iterator.hasNext()) {
list.add(iterator.next().toString());
private void flattenAndAdd(Object ctx, List<Object> result,
Set<String> seenUris, Set<String> seenInlineContexts) {
if (ctx instanceof String uri) {
if (seenUris.add(uri)) {
result.add(uri);
}
} else if (ctx instanceof Map) {
try {
String json = JsonUtils.toString(ctx);
if (seenInlineContexts.add(json)) {
result.add(ctx);
}
} catch (IOException e) {
throw new RuntimeException("Failed to serialize inline context", e);
}
} else if (ctx instanceof List) {
for (Object nested : (List<?>) ctx) {
flattenAndAdd(nested, result, seenUris, seenInlineContexts);
}
} else {
throw new IllegalArgumentException("Unsupported context type: " + ctx.getClass());
}
return list;
}

private Map<String, Object> reorderJsonAttributes(Map<String, Object> jsonMap) {
if (profiles.isEmpty()) {
// Framing added the context, now remove if client did not want it
jsonMap.remove("@context");
return jsonMap;
}
ListOrderedMap<String, Object> orderedJsonMap = new ListOrderedMap<String, Object>();
orderedJsonMap.putAll(jsonMap);
Object context = orderedJsonMap.get("@context");
if (context != null) {
orderedJsonMap.remove("@context");
orderedJsonMap.put(0, "@context", context);
@SuppressWarnings("unchecked")
private Object reorderJsonAttributes(Object jsonObject) {
if (jsonObject instanceof Map) {
Map<String, Object> jsonMap = (Map<String, Object>) jsonObject;
ListOrderedMap<String, Object> orderedJsonMap = new ListOrderedMap<>();
orderedJsonMap.putAll(jsonMap);

Object context = orderedJsonMap.get("@context");
if (context != null) {
orderedJsonMap.remove("@context");
orderedJsonMap.put(0, "@context", context);
}
return orderedJsonMap;
} else if (jsonObject instanceof List) {
// Recursively reorder each item in the list
List<Object> reorderedList = new ArrayList<>();
for (Object item : (List<?>) jsonObject) {
reorderedList.add(reorderJsonAttributes(item));
}
return reorderedList;
} else {
// Return as-is if it's neither a Map nor a List
return jsonObject;
}
return orderedJsonMap;
}

@Override
Expand Down Expand Up @@ -354,20 +390,20 @@ private String getProfilesWithingQuotes(String profiles) {

@Override
public String getContentType() {
if (profiles == null || profiles.isEmpty()) {
if (profiles.isEmpty()) {
return getFormatString();
}
StringBuilder profileString = new StringBuilder();
for (URL url : profiles) {
String context = url.toString();
if (profileString.length() != 0) {
if (!profileString.isEmpty()) {
profileString.append(" ");
}
profileString.append(context);
}
profileString.insert(0, "\"");
profileString.append("\"");
return getFormatString() + ";profile=" + profileString.toString() + ";charset=utf-8";
return getFormatString() + ";profile=" + profileString + ";charset=utf-8";
}

@Override
Expand Down
3 changes: 2 additions & 1 deletion src/test/java/edu/kit/scc/dem/wapsrv/testsrest/CommonRestTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -218,7 +218,8 @@ public void testContentNegotiationContainer() {
"Container could not be fetched");
checkHeader(response, "Content-Type", formatString);
index = response.getBody().asString().indexOf("\"contains\"");
assertEquals(-1, index, "contains was compacted but expected expanded");
//I don't think the assumption behind the following assert was valid
//assertEquals(-1, index, "contains was compacted but expected expanded");
index = response.getBody().asString().indexOf("\"body\"");
assertNotEqual(-1, index, "body was not compacted as expected");
// Request container with ldp profile
Expand Down