close package parts when closing OPCPackage (#880)

* close package parts when closing OPCPackage

* Update ZipPackagePart.java

poi-ooxml/src/main/java/org/apache/poi/openxml4j/opc/OPCPackage.java

@@ -681,6 +681,9 @@ public abstract class OPCPackage implements RelationshipSource, Closeable {
         // ensure all held resources are freed
         revert();
 
+        // ensure resources associated with package parts are closed
+        closeParts();
+
         // Clear
         this.contentTypeManager.clearAll();
     }
@@ -1870,6 +1873,10 @@ public abstract class OPCPackage implements RelationshipSource, Closeable {
      */
     public abstract boolean isClosed();
 
+    protected void closeParts() {
+        partList.closeParts();
+    }
+
     @Override
     public String toString() {
         return "OPCPackage{" +

poi-ooxml/src/main/java/org/apache/poi/openxml4j/opc/PackagePartCollection.java

@@ -112,8 +112,6 @@ public final class PackagePartCollection implements Serializable {
         return packagePartLookup.size();
     }
 
-
-
     /**
      * Get an unused part index based on the namePattern, which doesn't exist yet
      * and has the lowest positive index
@@ -141,4 +139,11 @@ public final class PackagePartCollection implements Serializable {
             .mapToInt(indexFromName)
             .collect(SparseBitSet::new, SparseBitSet::set, (s1,s2) -> s1.or(s2)).nextClearBit(1);
     }
+
+    // used to ensure resources are closed when they are no longer needed
+    void closeParts() {
+        for (PackagePart part : packagePartLookup.values()) {
+            part.close();
+        }
+    }
 }

poi-ooxml/src/main/java/org/apache/poi/openxml4j/opc/ZipPackage.java

@@ -595,12 +595,15 @@ public final class ZipPackage extends OPCPackage {
                 }
             }
         }
+
+        // ensure resources associated with package parts are closed
+        closeParts();
     }
 
     /**
-     * Create a unique identifier to be use as a temp file name.
+     * Create a unique identifier to be used as a temp file name.
      *
-     * @return A unique identifier use to be use as a temp file name.
+     * @return A unique identifier to be used as a temp file name.
      */
     private synchronized String generateTempFileName(File directory) {
         File tmpFilename;

poi-ooxml/src/main/java/org/apache/poi/openxml4j/opc/ZipPackagePart.java

@@ -134,14 +134,12 @@ public class ZipPackagePart extends PackagePart {
     }
 
     @Override
-    @NotImplemented
     public void close() {
-        throw new InvalidOperationException("Method not implemented !");
+        // do nothing
     }
 
     @Override
-    @NotImplemented
     public void flush() {
-        throw new InvalidOperationException("Method not implemented !");
+        // do nothing
     }
 }