Create GroupSummary and ContextListener to cache group information

ace-am/src/main/java/edu/umiacs/ace/monitor/access/GroupSummary.java

+package edu.umiacs.ace.monitor.access;
+
+import java.math.BigDecimal;
+
+/**
+ *
+ * Created by shake on 4/4/17.
+ */
+public final class GroupSummary {
+
+    private final String group;
+    private final BigDecimal size;
+    private final BigDecimal count;
+
+    public GroupSummary(String group, BigDecimal size, BigDecimal count) {
+        this.group = group;
+        this.size = size;
+        this.count = count;
+    }
+
+    public String getGroup() {
+        return group;
+    }
+
+    public BigDecimal getSize() {
+        return size;
+    }
+
+    public BigDecimal getCount() {
+        return count;
+    }
+}

ace-am/src/main/java/edu/umiacs/ace/monitor/access/GroupSummaryContext.java

+package edu.umiacs.ace.monitor.access;
+
+import com.google.common.collect.ImmutableList;
+import edu.umiacs.ace.util.PersistUtil;
+import org.apache.log4j.Logger;
+
+import javax.persistence.EntityManager;
+import javax.persistence.Query;
+import javax.servlet.ServletContextEvent;
+import javax.servlet.ServletContextListener;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ *
+ * Created by shake on 4/4/17.
+ */
+public class GroupSummaryContext implements ServletContextListener {
+    private static final Logger log = Logger.getLogger(GroupSummaryContext.class);
+
+    public static Map<String, GroupSummary> summaries;
+
+    // Main query
+    private static final String SUMMARY_QUERY = "SELECT c.colgroup, sum(m.size) AS size, sum(m.count) AS count " +
+            "FROM collection c " +
+            "JOIN (  " +
+            "SELECT sum(size) AS size, count(id) AS count, parentcollection_id   " +
+            "FROM monitored_item   " +
+            "WHERE directory = 0   " +
+            "GROUP BY parentcollection_id " +
+            ") AS m ON c.id = m.parentcollection_id ";
+
+    // clauses depending on if we're querying on a group or not
+    private static final String SUMMARY_QUERY_NOT_NULL = "WHERE c.colgroup IS NOT NULL ";
+    private static final String SUMMARY_QUERY_PARAM = "WHERE c.colgroup = ? ";
+
+    // and the wrap up
+    private static final String SUMMARY_QUERY_END = "GROUP BY c.colgroup";
+
+    @Override
+    public void contextInitialized(ServletContextEvent servletContextEvent) {
+        summaries = new HashMap<>();
+        updateSummaries(ImmutableList.of(SUMMARY_QUERY, SUMMARY_QUERY_NOT_NULL, SUMMARY_QUERY_END),
+                ImmutableList.<String>of());
+    }
+
+    @Override
+    public void contextDestroyed(ServletContextEvent servletContextEvent) {
+        summaries.clear();
+    }
+
+    /**
+     * Public api method to update a single group
+     *
+     * @param group the group to update
+     */
+    public static void updateGroup(String group) {
+        if (group != null) {
+            updateSummaries(
+                    ImmutableList.of(SUMMARY_QUERY, SUMMARY_QUERY_PARAM, SUMMARY_QUERY_END),
+                    ImmutableList.of(group));
+        }
+    }
+
+    /**
+     * Static method to allow us to update the summary of a group
+     *
+     * @param sql the sql query to build
+     * @param params the parameters to pass along to the query
+     */
+    private static void updateSummaries(List<String> sql, List<String> params) {
+        EntityManager em = PersistUtil.getEntityManager();
+
+        StringBuilder query = new StringBuilder();
+        for (String s : sql) {
+            query.append(s);
+        }
+
+        Query groupSummary = em.createNativeQuery(query.toString(), "GroupSummaryMapping");
+        int i = 1;
+        for (String param : params) {
+            groupSummary.setParameter(i, param);
+            i++;
+        }
+
+        List<GroupSummary> results = (List<GroupSummary>)groupSummary.getResultList();
+        for (GroupSummary result : results) {
+            summaries.put(result.getGroup(), result);
+        }
+    }
+}