[client] Add classes for caching of data fetched via thrift

(could be used for other things too, code is fairly generic)

2 files changed, 163 insertions, 0 deletions

diff --git a/dozentenmodul/src/main/java/org/openslx/bwlp/dozmod/thrift/ACache.java b/dozentenmodul/src/main/java/org/openslx/bwlp/dozmod/thrift/ACache.java
new file mode 100644
index 00000000..7c7d927e
--- /dev/null
+++ b/dozentenmodul/src/main/java/org/openslx/bwlp/dozmod/thrift/ACache.java
@@ -0,0 +1,94 @@
+package org.openslx.bwlp.dozmod.thrift;
+
+import java.util.concurrent.atomic.AtomicReference;
+
+import org.apache.log4j.Logger;
+
+public abstract class ACache<T> {
+	
+	private static final Logger LOGGER = Logger.getLogger(ACache.class);
+	
+	/**
+	 * How long the cached data is valid after fetching
+	 */
+	private final int validMs;
+	
+	/**
+	 * Deadline when the cache goes invalid
+	 */
+	private long validUntil = 0;
+	
+	/**
+	 * The data being held
+	 */
+	private final AtomicReference<T> item = new AtomicReference<>();
+	
+	public ACache(int validMs) {
+		this.validMs = validMs;
+	}
+	
+	/**
+	 * Get the cached object, but refresh the cache first if
+	 * the cached instance is too old.
+	 * 
+	 * @return
+	 */
+	public T get() {
+		return get(CacheMode.DEFAULT);
+	}
+	
+	/**
+	 * Get the cached object, using the given cache access strategy.
+	 * ALWAYS_CACHED: Never refresh the cache, except if it has never been fetched before
+	 * DEFAULT: Only fetch from remote if the cached value is too old
+	 * NEVER_CACHED: Always fetch from remote. If it fails, return null
+	 *
+	 * @param mode Cache access strategy as described above 
+	 * @return T
+	 */
+	public T get(CacheMode mode) {
+		switch (mode) {
+		case ALWAYS_CACHED:
+			if (validUntil == 0)
+				ensureUpToDate(true);
+			break;
+		case DEFAULT:
+			ensureUpToDate(false);
+			break;
+		case NEVER_CACHED:
+			if (!ensureUpToDate(true))
+				return null;
+			break;
+		}
+		return item.get();
+	}
+	
+	private synchronized boolean ensureUpToDate(boolean force) {
+		final long now = System.currentTimeMillis();
+		if (!force && now < validUntil)
+			return true;
+		T fetched;
+		try {
+			fetched = update();
+			if (fetched == null)
+				return false;
+		} catch (Exception e) {
+			LOGGER.warn("Could not fetch fresh data", e);
+			return false;
+		}
+		item.set(fetched);
+		validUntil = now + validMs;
+		return true;
+	}
+	
+	public abstract T update() throws Exception;
+	
+	//
+	
+	public static enum CacheMode {
+		ALWAYS_CACHED,
+		DEFAULT,
+		NEVER_CACHED
+	}
+
+}
diff --git a/dozentenmodul/src/main/java/org/openslx/bwlp/dozmod/thrift/OrganizationList.java b/dozentenmodul/src/main/java/org/openslx/bwlp/dozmod/thrift/OrganizationList.java
new file mode 100644
index 00000000..d13da1b3
--- /dev/null
+++ b/dozentenmodul/src/main/java/org/openslx/bwlp/dozmod/thrift/OrganizationList.java
@@ -0,0 +1,69 @@
+package org.openslx.bwlp.dozmod.thrift;
+
+import java.util.List;
+
+import org.openslx.bwlp.thrift.iface.Organization;
+import org.openslx.bwlp.thrift.iface.UserInfo;
+import org.openslx.thrifthelper.ThriftManager;
+
+public class OrganizationList extends ACache<List<Organization>> {
+
+	/**
+	 * How long should the list be cached?
+	 */
+	private static final int CACHE_TIME_MS = 20 * 60 * 1000;
+
+	private static final OrganizationList instance = new OrganizationList();
+
+	private OrganizationList() {
+		super(CACHE_TIME_MS);
+	}
+
+	@Override
+	public List<Organization> update() throws Exception {
+		try {
+			return ThriftManager.getMasterClient().getOrganizations();
+		} catch (Exception e) {
+			// Swallow exception, then try satellite
+		}
+		return ThriftManager.getSatClient().getAllOrganizations();
+		// TODO: Sort list by display name?
+	}
+
+	/**
+	 * Get all known organizations
+	 * 
+	 * @return list of organizations
+	 */
+	public static List<Organization> getAll() {
+		return instance.get();
+	}
+
+	/**
+	 * Find the organization the given user belongs to
+	 * 
+	 * @param user
+	 * @return matching organization, or <code>null</code> if not found
+	 */
+	public static Organization find(UserInfo user) {
+		return find(user.organizationId);
+	}
+	
+	/**
+	 * Find the organization with the given id
+	 * 
+	 * @param organization id
+	 * @return matching organization, or <code>null</code> if not found
+	 */
+	public static Organization find(String organizationId) {
+		List<Organization> list = instance.get();
+		if (list == null)
+			return null;
+		for (Organization org : list) {
+			if (org.organizationId.equals(organizationId))
+				return org;
+		}
+		return null;
+	}
+
+}