Describe AEM assets and their relationships

AssetRelationshipServlet.java

package com.chrisp.core.servlets;

import java.io.IOException;
import java.util.Iterator;

import javax.jcr.Node;
import javax.jcr.RepositoryException;
import javax.jcr.Session;
import javax.servlet.Servlet;

import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.SlingHttpServletResponse;
import org.apache.sling.api.resource.Resource;
import org.apache.sling.api.resource.ResourceResolver;
import org.apache.sling.api.servlets.HttpConstants;
import org.apache.sling.api.servlets.SlingSafeMethodsServlet;
import org.osgi.framework.Constants;
import org.osgi.service.component.annotations.Component;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.day.cq.dam.api.Asset;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonArray;
import com.google.gson.JsonObject;

/**
 * Servlet that lists assets and their relationships under a specific path
 * Usage: /bin/assets/relationships?path=/content/dam/path
 */
@Component(
    service = Servlet.class,
    property = {
        Constants.SERVICE_DESCRIPTION + "=Asset Relationship Servlet",
        "sling.servlet.methods=" + HttpConstants.METHOD_GET,
        "sling.servlet.paths=" + "/bin/assets/relationships",
        "sling.servlet.extensions=" + "json"
    }
)
public class AssetRelationshipServlet extends SlingSafeMethodsServlet {
    private static final long serialVersionUID = 1L;
    private static final Logger log = LoggerFactory.getLogger(AssetRelationshipServlet.class);
    
    @Override
    protected void doGet(SlingHttpServletRequest request, SlingHttpServletResponse response)
            throws IOException {
        
        response.setContentType("application/json");
        ResourceResolver resolver = request.getResourceResolver();

        String path = request.getParameter("path");
        if (path == null || path.isEmpty()) {
            response.getWriter().write("{\"error\": \"Please provide a path parameter\"}");
            return;
        }
        
        Resource resource = resolver.getResource(path);
        if (resource == null) {
            response.getWriter().write("{\"error\": \"Path not found: " + path + "\"}");
            return;
        }
        
        try {
            JsonArray resultArray = findAssetsWithRelationships(resource, resolver);
            Gson gson = new GsonBuilder().setPrettyPrinting().create();
            String jsonOutput = gson.toJson(resultArray);
            response.getWriter().write(jsonOutput);
        } catch (Exception e) {
            log.error("Error processing assets", e);
            response.getWriter().write("{\"error\": \"" + e.getMessage() + "\"}");
        }
    }
    
    /**
     * Recursively find all assets under the given resource
     */
    private JsonArray findAssetsWithRelationships(Resource resource, ResourceResolver resolver) 
            throws RepositoryException {
        JsonArray results = new JsonArray();
        
        // Process current resource if it's an asset
        Asset asset = resource.adaptTo(Asset.class);
        if (asset != null) {
            JsonObject assetJson = processAsset(asset, resolver);
            results.add(assetJson);
        }
        
        // Process children recursively
        Iterator<Resource> children = resource.listChildren();
        while (children.hasNext()) {
            Resource child = children.next();
            JsonArray childResults = findAssetsWithRelationships(child, resolver);
            for (int i = 0; i < childResults.size(); i++) {
                results.add(childResults.get(i));
            }
        }
        
        return results;
    }
    
    /**
     * Process a single asset and find its relationships
     */
    private JsonObject processAsset(Asset asset, ResourceResolver resolver) throws RepositoryException {
        JsonObject assetJson = new JsonObject();
        Resource assetResource = asset.adaptTo(Resource.class);
        
        // Get the JCR node
        Node assetNode = assetResource.adaptTo(Node.class);
        String uuid = "";
        
        if (assetNode != null && assetNode.hasProperty("jcr:uuid")) {
            uuid = assetNode.getProperty("jcr:uuid").getString();
        }
        
        assetJson.addProperty("path", asset.getPath());
        assetJson.addProperty("name", asset.getName());
        assetJson.addProperty("uuid", uuid);
        
        // Find all types of related assets based on the specified structure
        JsonArray derivedAssets = findRelatedAssets(asset, "derived", resolver);
        assetJson.add("derivedAssets", derivedAssets);
        
        JsonArray sourceAssets = findRelatedAssets(asset, "sources", resolver);
        assetJson.add("sourceAssets", sourceAssets);
        
        JsonArray otherAssets = findRelatedAssets(asset, "others", resolver);
        assetJson.add("otherAssets", otherAssets);
        
        return assetJson;
    }
    
    /**
     * Find related assets of a specific type using the structure:
     * ./jcr:content/related/{relation-type}/sling:members/{asset-name}
     * 
     * @param asset The asset to find relationships for
     * @param relationType The type of relation ("derived", "source", or "other")
     * @param resolver The resource resolver
     * @return JsonArray containing related assets
     */
    private JsonArray findRelatedAssets(Asset asset, String relationType, ResourceResolver resolver) {
        JsonArray relatedAssets = new JsonArray();
        Resource assetResource = asset.adaptTo(Resource.class);
        
        try {
            if (assetResource != null) {
                // Path to the related assets based on the specified structure
                String relatedPath = assetResource.getPath() + "/jcr:content/related/" + relationType + "/sling:members";
                Resource relatedResource = resolver.getResource(relatedPath);
                
                if (relatedResource != null) {
                    // Iterate through all children (asset-name nodes)
                    Iterator<Resource> relatedMembers = relatedResource.listChildren();
                    while (relatedMembers.hasNext()) {
                        Resource memberResource = relatedMembers.next();
                        Node memberNode = memberResource.adaptTo(Node.class);
                        
                        if (memberNode != null && memberNode.hasProperty("sling:resource")) {
                            // Get the path of the related asset
                            String linkedAssetPath = memberNode.getProperty("sling:resource").getString();
                            Resource linkedResource = resolver.getResource(linkedAssetPath);
                            
                            if (linkedResource != null) {
                                Asset linkedAsset = linkedResource.adaptTo(Asset.class);
                                if (linkedAsset != null) {
                                    JsonObject relatedJson = new JsonObject();
                                    relatedJson.addProperty("path", linkedAsset.getPath());
                                    relatedJson.addProperty("name", linkedAsset.getName());
                                    
                                    // Get the UUID of the linked asset
                                    Node linkedNode = linkedResource.adaptTo(Node.class);
                                    if (linkedNode != null && linkedNode.hasProperty("jcr:uuid")) {
                                        relatedJson.addProperty("uuid", linkedNode.getProperty("jcr:uuid").getString());
                                    }
                                    
                                    relatedAssets.add(relatedJson);
                                }
                            }
                        }
                    }
                }
            }
        } catch (RepositoryException e) {
            log.error("Error finding " + relationType + " related assets", e);
        }
        
        return relatedAssets;
    }
}