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Java > Open Source Codes > com > etymon > pjx > PdfObjectFilter


1 /*
2   Copyright (C) Etymon Systems, Inc. <http://www.etymon.com/>
3 */
4
5 package com.etymon.pjx;
6
7 /**
8    A filtering function that allows examining and modifying PDF
9    objects recursively. {@link PdfObject#filter(PdfObjectFilter)
10    PdfObject.filter(PdfObjectFilter)} passes each object through
11    {@link #preFilter(PdfObject) preFilter(PdfObject)} before
12    descending recursively into the object's contents (if it is a
13    container such as {@link PdfArray PdfArray} or {@link PdfDictionary
14    PdfDictionary}). It then passes the (possibly modified) object
15    through {@link #postFilter(PdfObject) postFilter(PdfObject)} for a
16    second opportunity to examine or modify the object. The modified
17    object is not required to be of the same type as the original
18    object.
19    @author Nassib Nassar
20 */
21 public interface PdfObjectFilter {
22
23     /**
24        Examines a PDF object and optionally returns a modified
25        object. This method should return the original object or a
26        modified replacement. If no modifications are desired, it
27        should return the original object. This method may also
28        return <code>null</code> in order to discard the object;
29        however, this will cause {@link #postFilter(PdfObject)
30        postFilter(PdfObject)} to be called with a
31        <code>null</code> value as its parameter. A {@link
32        PdfArray PdfArray} or {@link PdfDictionary PdfDictionary}
33        object is considered to be a container, and this method
34        filters the container as a whole before filtering each
35        element within it (assuming the elements are still present
36        in the modified object). When this method receives a
37        container, that container's contents will not yet have been
38        filtered by this method.
39        @param obj the object to examine.
40        @return the "filtered" object.
41        @throws PdfFormatException
42      */
43     public PdfObject preFilter(PdfObject obj) throws PdfFormatException;
44
45     /**
46        Examines a PDF object and optionally returns a modified
47        object. This method should return the original object or a
48        modified replacement. If no modifications are desired, it
49        should return the original object. This method may also
50        return <code>null</code> in order to discard the object. A
51        {@link PdfArray PdfArray} or {@link PdfDictionary
52        PdfDictionary} object is considered to be a container, and
53        this method filters each element within it before filtering
54        the container as a whole. When this method receives a
55        container, that container's contents will have already been
56        filtered by this method.
57        @param obj the object to examine.
58        @return the "filtered" object.
59        @throws PdfFormatException
60      */
61     public PdfObject postFilter(PdfObject obj) throws PdfFormatException;
62
63 }
64
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