stevesun21 · November 5, 2018 12:24 · May 31, 2015 · May 31, 2015 · May 31, 2015 · May 31, 2015
diff --git a/CassandraPaging b/CassandraPaging
@@ -34,17 +34,29 @@ public class CassandraPaging {
 
     private ResultSet skipRows(Statement statement, int start, int size) {
         ResultSet result = null;
-        int page = getPageNumber(start, size);
+        int skippingPages = getPageNumber(start, size);
         String savingPageState = null;
         statement.setFetchSize(size);
-        for (int i = 0; i < page; i++) {
+        boolean isEnd = false;
+        for (int i = 0; i < skippingPages; i++) {
             if (null != savingPageState) {
                 statement = statement.setPagingState(PagingState.fromString(savingPageState));
             }
             result = session.execute(statement);
-            if (null != result.getExecutionInfo().getPagingState()) {
+            PagingState pagingState = result.getExecutionInfo().getPagingState();
+            if (null != pagingState) {
                 savingPageState = result.getExecutionInfo().getPagingState().toString();
             }
+
+            if (result.isFullyFetched() && null == pagingState) {
+
+                //if hit the end more than once, then nothing to return, otherwise, mark the isEnd to 'true'
+                if (true == isEnd) {
+                    return null;
+                } else {
+                    isEnd = true;
+                }
+            }
         }
         return result;
     }
@@ -62,6 +74,9 @@ public class CassandraPaging {
 
     private List<Row> getRows(ResultSet result, int start, int size) {
         List<Row> rows = new ArrayList<>(size);
+        if (null == result) {
+            return rows;
+        }
         int skippingRows = (start - 1) % size;
         int index = 0;
         for (Iterator<Row> iter = result.iterator(); iter.hasNext() && rows.size() < size;) {
@@ -74,4 +89,4 @@ public class CassandraPaging {
         return rows;
     }
 
-}
+}
diff --git a/CassandraPaging b/CassandraPaging
@@ -1,11 +1,13 @@
+import com.datastax.driver.core.*;
+
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 
 /**
  * This is a helper class for implementing a pagination function based on Cassandra Java Driver (http://datastax.github.io/java-driver/)
  *
- * This solution is that try to skip rows by page state rather than iterator rows one by one.
+ * The solution of skipping rows is that use page state rather than iterator rows one by one.
  *
  */
 public class CassandraPaging {
@@ -72,4 +74,4 @@ public class CassandraPaging {
         return rows;
     }
 
-}
+}
diff --git a/CassandraPaging b/CassandraPaging
@@ -1,13 +1,11 @@
-import com.datastax.driver.core.*;
-
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 
 /**
  * This is a helper class for implementing a pagination function based on Cassandra Java Driver (http://datastax.github.io/java-driver/)
  *
- * This solution utilizes the page state to skip rows rather than iterator rows one by one.
+ * This solution is that try to skip rows by page state rather than iterator rows one by one.
  *
  */
 public class CassandraPaging {

diff --git a/CassandraPaging b/CassandraPaging
@@ -1,6 +1,3 @@
-package com.rewardofclans.base.cassandra;
-
-
 import com.datastax.driver.core.*;
 
 import java.util.ArrayList;
@@ -24,17 +21,22 @@ public class CassandraPaging {
     /**
      * Retrieve rows for the specified page offset.
      *
+     *
      * @param statement
-     * @param start which row start with (>1)
+     * @param start starting row (>1), inclusive
      * @param size the maximum rows need to retrieve.
      * @return List<Row>
      */
     public List<Row> fetchRowsWithPage(Statement statement, int start, int size) {
-        List<Row> rows = new ArrayList<>(size);
-        int page = getPageNumber(start, size);
+        ResultSet result = skipRows(statement, start, size);
+        return getRows(result, start, size);
+    }
+
+    private ResultSet skipRows(Statement statement, int start, int size) {
         ResultSet result = null;
-        statement.setFetchSize(size);
+        int page = getPageNumber(start, size);
         String savingPageState = null;
+        statement.setFetchSize(size);
         for (int i = 0; i < page; i++) {
             if (null != savingPageState) {
                 statement = statement.setPagingState(PagingState.fromString(savingPageState));
@@ -43,14 +45,8 @@ public class CassandraPaging {
             if (null != result.getExecutionInfo().getPagingState()) {
                 savingPageState = result.getExecutionInfo().getPagingState().toString();
             }
-            if (result.isFullyFetched()) {
-                return rows; //no more rows need to fetch.
-            }
         }
-        for (Iterator<Row> iter = result.iterator(); iter.hasNext() && rows.size() < size;) {
-            rows.add(iter.next());
-        }
-        return rows;
+        return result;
     }
 
     private int getPageNumber(int start, int size) {
@@ -64,4 +60,18 @@ public class CassandraPaging {
         return page;
     }
 
-}
+    private List<Row> getRows(ResultSet result, int start, int size) {
+        List<Row> rows = new ArrayList<>(size);
+        int skippingRows = (start - 1) % size;
+        int index = 0;
+        for (Iterator<Row> iter = result.iterator(); iter.hasNext() && rows.size() < size;) {
+            Row row = iter.next();
+            if (index >= skippingRows) {
+                rows.add(row);
+            }
+            index ++;
+        }
+        return rows;
+    }
+
+}
diff --git a/CassandraPaging b/CassandraPaging
@@ -1,11 +1,14 @@
+package com.rewardofclans.base.cassandra;
+
+
 import com.datastax.driver.core.*;
 
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 
 /**
- * This is a helper class for implementing a pagination function for Cassandra Java Driver (http://datastax.github.io/java-driver/)
+ * This is a helper class for implementing a pagination function based on Cassandra Java Driver (http://datastax.github.io/java-driver/)
  *
  * This solution utilizes the page state to skip rows rather than iterator rows one by one.
  *
@@ -61,4 +64,4 @@ public class CassandraPaging {
         return page;
     }
 
-}
+}
diff --git a/CassandraPaging b/CassandraPaging
@@ -0,0 +1,64 @@
+import com.datastax.driver.core.*;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+/**
+ * This is a helper class for implementing a pagination function for Cassandra Java Driver (http://datastax.github.io/java-driver/)
+ *
+ * This solution utilizes the page state to skip rows rather than iterator rows one by one.
+ *
+ */
+public class CassandraPaging {
+
+    private Session session;
+
+    public CassandraPaging(Session session) {
+        this.session = session;
+    }
+
+    /**
+     * Retrieve rows for the specified page offset.
+     *
+     * @param statement
+     * @param start which row start with (>1)
+     * @param size the maximum rows need to retrieve.
+     * @return List<Row>
+     */
+    public List<Row> fetchRowsWithPage(Statement statement, int start, int size) {
+        List<Row> rows = new ArrayList<>(size);
+        int page = getPageNumber(start, size);
+        ResultSet result = null;
+        statement.setFetchSize(size);
+        String savingPageState = null;
+        for (int i = 0; i < page; i++) {
+            if (null != savingPageState) {
+                statement = statement.setPagingState(PagingState.fromString(savingPageState));
+            }
+            result = session.execute(statement);
+            if (null != result.getExecutionInfo().getPagingState()) {
+                savingPageState = result.getExecutionInfo().getPagingState().toString();
+            }
+            if (result.isFullyFetched()) {
+                return rows; //no more rows need to fetch.
+            }
+        }
+        for (Iterator<Row> iter = result.iterator(); iter.hasNext() && rows.size() < size;) {
+            rows.add(iter.next());
+        }
+        return rows;
+    }
+
+    private int getPageNumber(int start, int size) {
+        if (start < 1) {
+            throw new IllegalArgumentException("Starting row need to be larger than 1");
+        }
+        int page = 1;
+        if (start > size) {
+            page = (start - 1) / size + 1;
+        }
+        return page;
+    }
+
+}
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