#919 - io.ebean package initial

src/main/java/io/ebeaninternal/server/query/CQueryIteratorWithBuffer.java

@@ -0,0 +1,66 @@
+package io.ebeaninternal.server.query;
+
+import io.ebean.QueryIterator;
+import io.ebeaninternal.server.core.OrmQueryRequest;
+
+import javax.persistence.PersistenceException;
+import java.sql.SQLException;
+import java.util.ArrayList;
+
+/**
+ * A QueryIterator that uses a buffer to execute secondary queries periodically.
+ */
+class CQueryIteratorWithBuffer<T> implements QueryIterator<T> {
+
+  private final CQuery<T> cquery;
+  private final int bufferSize;
+  private final OrmQueryRequest<T> request;
+  private final ArrayList<T> buffer;
+
+  private boolean moreToLoad = true;
+
+  CQueryIteratorWithBuffer(CQuery<T> cquery, OrmQueryRequest<T> request, int bufferSize) {
+    this.cquery = cquery;
+    this.request = request;
+    this.bufferSize = bufferSize;
+    this.buffer = new ArrayList<>(bufferSize);
+  }
+
+  @SuppressWarnings("unchecked")
+  public boolean hasNext() {
+    try {
+      if (buffer.isEmpty() && moreToLoad) {
+        // load buffer
+        request.flushPersistenceContextOnIterate();
+
+        int i = -1;
+        while (moreToLoad && ++i < bufferSize) {
+          if (cquery.hasNext()) {
+            buffer.add((T) cquery.next());
+          } else {
+            moreToLoad = false;
+          }
+        }
+        request.executeSecondaryQueries(true);
+      }
+      return !buffer.isEmpty();
+
+    } catch (SQLException e) {
+      throw cquery.createPersistenceException(e);
+    }
+  }
+
+  public T next() {
+    return buffer.remove(0);
+  }
+
+  public void close() {
+    cquery.updateExecutionStatistics();
+    cquery.close();
+    request.endTransIfRequired();
+  }
+
+  public void remove() {
+    throw new PersistenceException("Remove not allowed");
+  }
+}