Add RowFilter contributed by Patricia Donaldson

git-svn-id: https://svn.code.sf.net/p/jackcess/code/jackcess/trunk@378 f203690c-595d-4dc9-a70b-905162fa7fd2

1 files changed, 203 insertions, 0 deletions

diff --git a/src/java/com/healthmarketscience/jackcess/RowFilter.java b/src/java/com/healthmarketscience/jackcess/RowFilter.java
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+/*
+Copyright (c) 2007 Health Market Science, Inc.
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 2.1 of the License, or (at your option) any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
+USA
+
+You can contact Health Market Science at info@healthmarketscience.com
+or at the following address:
+
+Health Market Science
+2700 Horizon Drive
+Suite 200
+King of Prussia, PA 19406
+*/
+
+package com.healthmarketscience.jackcess;
+
+import java.util.Iterator;
+import java.util.Map;
+
+import org.apache.commons.lang.ObjectUtils;
+
+
+/**
+ * The RowFilter class encapsulates a filter test for a table row.  This can
+ * be used by the {@link #apply(Iterable)} method to create an Iterable over a
+ * table which returns only rows matching some criteria.
+ * 
+ * @author Patricia Donaldson, Xerox Corporation
+ */
+public abstract class RowFilter
+{
+
+  /**
+   * Returns {@code true} if the given table row matches the Filter criteria,
+   * {@code false} otherwise.
+   * @param row current row to test for inclusion in the filter
+   */
+  public abstract boolean matches(Map<String, Object> row);
+
+  /**
+   * Returns an iterable which filters the given iterable based on this
+   * filter.
+   *
+   * @param iterable row iterable to filter
+   *
+   * @return a filtering iterable
+   */
+  public Iterable<Map<String, Object>> apply(
+      Iterable<Map<String, Object>> iterable)
+  {
+    return new FilterIterable(iterable);
+  }
+
+
+  /**
+   * Creates a filter based on a row pattern.
+   * 
+   * @param rowPattern Map from column names to the values to be matched.
+   *                   A table row will match the target if
+   *                   {@code ObjectUtil.equals(rowPattern.get(s), row.get(s))}
+   *                   for all column names in the pattern map.
+   * @return a filter which matches table rows which match the values in the
+   *         row pattern
+   */
+  public static RowFilter matchPattern(final Map<String, Object> rowPattern) 
+  {
+    return new RowFilter() {
+        @Override
+        public boolean matches(Map<String, Object> row) 
+        {
+          for(Map.Entry<String,Object> e : rowPattern.entrySet()) {
+            if(!ObjectUtils.equals(e.getValue(), row.get(e.getKey()))) {
+              return false;
+            }
+          }
+          return true;
+        }
+      };
+  }
+
+  /**
+   * Creates a filter based on a single value row pattern.
+   *
+   * @param columnPattern column to be matched
+   * @param valuePattern value to be matched.
+   *                     A table row will match the target if
+   *                     {@code ObjectUtil.equals(valuePattern, row.get(columnPattern.getName()))}.
+   * @return a filter which matches table rows which match the value in the
+   *         row pattern
+   */
+  public static RowFilter matchPattern(final Column columnPattern, final Object valuePattern) 
+  {
+    return new RowFilter() {
+        @Override
+        public boolean matches(Map<String, Object> row) 
+        {
+          return ObjectUtils.equals(valuePattern, row.get(columnPattern.getName()));
+        }
+      };
+  }
+
+  /**
+   * Creates a filter which inverts the sense of the given filter (rows which
+   * are matched by the given filter will not be matched by the returned
+   * filter, and vice versa).
+   *
+   * @param filter filter which to invert
+   *
+   * @return a RowFilter which matches rows not matched by the given filter
+   */
+  public static RowFilter invert(final RowFilter filter)
+  {
+    return new RowFilter() {
+        @Override
+        public boolean matches(Map<String, Object> row) 
+        {
+          return !filter.matches(row);
+        }
+      };
+  }
+
+
+  /**
+   * Returns an iterable which filters the given iterable based on the given
+   * rowFilter.
+   *
+   * @param rowFilter the filter criteria, may be {@code null}
+   * @param iterable row iterable to filter
+   *
+   * @return a filtering iterable (or the given iterable if a {@code null}
+   *         filter was given)
+   */
+  public static Iterable<Map<String, Object>> apply(
+      RowFilter rowFilter,
+      Iterable<Map<String, Object>> iterable)
+  {
+    return((rowFilter != null) ? rowFilter.apply(iterable) : iterable);
+  }
+
+
+  /**
+   * Iterable which creates a filtered view of a another row iterable.
+   */
+  private class FilterIterable implements Iterable<Map<String, Object>>
+  {
+    private final Iterable<Map<String, Object>> _iterable;
+
+    private FilterIterable(Iterable<Map<String, Object>> iterable) 
+    {
+      _iterable = iterable;
+    }
+
+
+    /**
+     * Returns an iterator which iterates through the rows of the underlying
+     * iterable, returning only rows for which the {@link RowFilter#matches}
+     * method returns {@code true}
+     */
+    public Iterator<Map<String, Object>> iterator() 
+    {
+      return new Iterator<Map<String, Object>>() {
+        private final Iterator<Map<String, Object>> _iter =
+          _iterable.iterator();
+        private Map<String, Object> _next;
+
+        public boolean hasNext() {
+          while(_iter.hasNext()) {
+            _next = _iter.next();
+            if(RowFilter.this.matches(_next)) {
+              return true;
+            }
+          }
+          _next = null;
+          return false;
+        }
+
+        public Map<String, Object> next() {
+          return _next;
+        }
+
+        public void remove() {
+          throw new UnsupportedOperationException();
+        }
+
+      };
+    }
+
+  }
+
+}