How to force Apache POI to create a relations file for my header?

Question

I've got a very simple file generated by Apache POI, that contains an image and a sentence in the page header, nothing else. The image, while embedded, doesn't display under Word.

I have taken a lot of time to compare the same file generated by Word, removing the differences one by one in order to find the root cause.

Here's the Apache POI-generated file structure:

.
├── [Content_Types].xml
├── _rels
├── docProps
│   ├── app.xml
│   └── core.xml
└── word
    ├── _rels
    │   └── document.xml.rels
    ├── document.xml
    ├── footer1.xml
    ├── header1.xml
    ├── media
    │   └── image1.png
    └── settings.xml

Here's the header1.xml file (stripped a little bit):

<?xml version="1.0" encoding="UTF-8" ?>
<w:hdr xmlns:wpc="http://schemas.microsoft.com/office/word/2010/wordprocessingCanvas" xmlns:mo="http://schemas.microsoft.com/office/mac/office/2008/main" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:mv="urn:schemas-microsoft-com:mac:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math" xmlns:v="urn:schemas-microsoft-com:vml" xmlns:wp14="http://schemas.microsoft.com/office/word/2010/wordprocessingDrawing" xmlns:wp="http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawing" xmlns:w10="urn:schemas-microsoft-com:office:word" xmlns:w="http://schemas.openxmlformats.org/wordprocessingml/2006/main" xmlns:w14="http://schemas.microsoft.com/office/word/2010/wordml" xmlns:wpg="http://schemas.microsoft.com/office/word/2010/wordprocessingGroup" xmlns:wpi="http://schemas.microsoft.com/office/word/2010/wordprocessingInk" xmlns:wne="http://schemas.microsoft.com/office/word/2006/wordml" xmlns:wps="http://schemas.microsoft.com/office/word/2010/wordprocessingShape" mc:Ignorable="w14 wp14">
    <w:p>
        <w:pPr>
            <w:jc w:val="left" /></w:pPr>
        <w:r>
            <w:drawing>
                <wp:inline distT="0" distB="0" distL="0" distR="0">
                    <wp:extent cx="1193800" cy="635000" />
                    <wp:docPr id="2" name="Picture 2" descr="Generated" />
                    <a:graphic xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main">
                        <a:graphicData uri="http://schemas.openxmlformats.org/drawingml/2006/picture">
                            <pic:pic xmlns:pic="http://schemas.openxmlformats.org/drawingml/2006/picture">
                                <pic:nvPicPr>
                                    <pic:cNvPr id="2" name="Generated" />
                                    <pic:cNvPicPr/></pic:nvPicPr>
                                <pic:blipFill><a:blip r:embed="rId2" />
                                    <a:stretch><a:fillRect/></a:stretch>
                                </pic:blipFill>
                                <pic:spPr>
                                    <a:xfrm><a:off x="0" y="0" /><a:ext cx="1193800" cy="635000" /></a:xfrm>
                                    <a:prstGeom prst="rect"><a:avLst/></a:prstGeom>
                                </pic:spPr>
                            </pic:pic>
                        </a:graphicData>
                    </a:graphic>
                </wp:inline>
            </w:drawing>
        </w:r>
    </w:p>
</w:hdr>

The image XML code is generated by hand using the solution found here.

The reference ID is relative to what's inside _rels/document.xml.rels:

<?xml version="1.0" encoding="UTF-8"?>

<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">
  <Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/settings" Target="settings.xml"/>
  <Relationship Id="rId2" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/image" Target="media/image1.png"/>
  <Relationship Id="rId3" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/header" Target="header1.xml"/>
  <Relationship Id="rId4" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/footer" Target="footer1.xml"/>
</Relationships>

So basically insert image rId2 => media/image1.png.

Now with the document generated by Word, there are a lot more files generated, but once striped, this is what it looks like:

.
├── [Content_Types].xml
├── _rels
├── docProps
│   ├── app.xml
│   └── core.xml
└── word
    ├── _rels
    │   ├── document.xml.rels
    │   └── header1.xml.rels
    ├── document.xml
    ├── header1.xml
    ├── media
    │   └── image1.png
    └── settings.xml

Same files, except for the _rels/header1.xml.rels, which contains:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships>
    <Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/image" Target="media/image1.png"/>
</Relationships>

And the only difference is the relation ID, which is rId1, which is taken from header1.xml.rels, which points to the image.

Now I'm no expert in OOXML nor Apache POI, but I would like POI to put the header's relations in a separate file. Is it possible?

I also noted that these XML namespaces need to be added for the image to be decoded:

xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships"
xmlns:wp="http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawing"
xmlns:w="http://schemas.openxmlformats.org/wordprocessingml/2006/main"

Update: code uploaded to https://gist.github.com/BenoitDuffez/b132d45747ef8c2e9e7c

Processing:

the code calls Exporter#export
the Exporter class calls through POIExporter methods such as #openDocument, #addImage, etc
the order of calls is: createDocument, startHeader, createParagraph, addImage, setParagraphAlignment, endParagraph

I attached a full log to the gist.

How are you adding the image into the file? Normally, POI takes care of adding the relationships between different parts of the document for you — Gagravarr, May 15 '14 at 07:36
You're right, POI does the relationship management. I'm adding the image as described in the linked answer in the middle of my question. I just want the relationship to be added to `_rels/headers.xml.rels` instead of the default `_rels/document.xml.rels`. — Benoit Duffez, May 15 '14 at 07:41
Can you post your code? I think I know what you're doing wrong, but since the question you linked to only deals with pictures in the main document not a header I can't be sure... — Gagravarr, May 15 '14 at 08:26
I'll try and post it. It's kind of complicated because my software is a document writer, with 2 formats for file writing (PDF/OOXML). See my updated question. — Benoit Duffez, May 15 '14 at 08:38
Need the bit where you add the image data to the file, and the bit where you create the paragraph + add the image reference to it, if nothing else. Even better would be a small, self contained unit test! — Gagravarr, May 15 '14 at 08:43
I'll write a unit test if I can't debug this with the full code. Thanks for helping me. — Benoit Duffez, May 15 '14 at 08:44
OK I think I know what's wrong, I use `mXWPFDocument.addPictureData`, so the relation is added to the document. I need to figure out how to do this with the header. — Benoit Duffez, May 16 '14 at 12:39
Call exactly the same thing on the header *as well*, and you should be set. It'll re-use the existing image, but link it to the header. With code I can show you where... — Gagravarr, May 16 '14 at 12:55

score 1 · Accepted Answer · answered May 16 '14 at 15:41

Looking at your code, I can see you adding the image into the main document itself:

// Add the picture data, and get the relationship id
final String blipId = mXWPFDocument.addPictureData(inputStream, pictureType);
// Get the picture number
final int nextPicNameNumber = mXWPFDocument.getNextPicNameNumber(pictureType);
// Add the picture definition
mXWPFDocument.insertPicture(xwpfRun, blipId, nextPicNameNumber, bounds.width, bounds.height);

The problem is that you don't appear to be doing the same thing to the header, so it isn't getting associated. Just as with XWPFDocument, both headers and footers also implement addPictureData

So, what you'll need to do is add a new variable of type XWPFHeaderFooter to your PoiExporter class. Have this populated by the startHeader and startFooter calls, and nulled by the end ones. Finally, when in the addImage method and about to call addPictureData, check if you have a XWPFHeaderFooter object. If you do, add the image data to that. If not, add to the main XWPFDocument as you do now.

With any luck, that ought to solve it!

Thanks a lot. But there's still something that bugs me: how to add paragraphs to a header/footer _after_ it is created? — Benoit Duffez, May 16 '14 at 15:46
Various ways! See the [XWPF Header Unit Tests](http://svn.apache.org/repos/asf/poi/trunk/src/ooxml/testcases/org/apache/poi/xwpf/usermodel/TestXWPFHeader.java) for examples of a few of them :) — Gagravarr, May 16 '14 at 17:34

How to force Apache POI to create a relations file for my header?

1 Answers1