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| author | arved <arved@unknown> | 2002-03-17 17:24:10 +0000 |
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| committer | arved <arved@unknown> | 2002-03-17 17:24:10 +0000 |
| commit | e817266a9f7d1b0579839cc2383fe988ab5c3bc8 (patch) | |
| tree | 01977c8281b32489adbee64edf7125fbe47b0245 /docs/design/understanding/xml_parsing.xml | |
| parent | 63636d3149af05ddc01e8ac38a5d794c36c7af53 (diff) | |
| download | xmlgraphics-fop-e817266a9f7d1b0579839cc2383fe988ab5c3bc8.tar.gz xmlgraphics-fop-e817266a9f7d1b0579839cc2383fe988ab5c3bc8.zip | |
Extra design commentary
git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@194703 13f79535-47bb-0310-9956-ffa450edef68
Diffstat (limited to 'docs/design/understanding/xml_parsing.xml')
| -rw-r--r-- | docs/design/understanding/xml_parsing.xml | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/docs/design/understanding/xml_parsing.xml b/docs/design/understanding/xml_parsing.xml new file mode 100644 index 000000000..a7c8d4a85 --- /dev/null +++ b/docs/design/understanding/xml_parsing.xml @@ -0,0 +1,106 @@ +<?xml version="1.0"?> +<document> + <header> + <title>XML Parsing</title> + <subtitle>All you wanted to know about XML Parsing !</subtitle> + <authors> <person name="Keiron Liddle" email="keiron@aftexsw.com"/> + </authors> + </header> + <body> + +<s1 title="XML Parsing"><p>Since everyone knows the basics we can get + into the various stages starting with the XML handling.</p> + <s2 title="XML Input"><p>FOP can take the input XML in a number of ways: + </p> + <ul> + <li>SAX Events through SAX Handler + <ul> + <li> + <code>FOTreeBuilder</code> is the SAX Handler which is + obtained through <code>getContentHandler</code> on + <code>Driver</code>. + </li> + </ul> + </li> + <li> + DOM which is converted into SAX Events + <ul> + <li> + The conversion of a DOM tree is done via the + <code>render(Document)</code> method on + <code>Driver</code>. + </li> + </ul> + </li> + <li> + data source which is parsed and converted into SAX Events + <ul> + <li> + The <code>Driver</code> can take an + <code>InputSource</code> as input. This can use a + <code>Stream</code>, <code>String</code> etc. + </li> + </ul> + </li> + <li> + XML+XSLT which is transformed using an XSLT Processor and + the result is fired as SAX Events + <ul> + <li> + <code>XSLTInputHandler</code> is used as an + <code>InputSource</code> in the + render(<code>XMLReader</code>, + <code>InputSource</code>) method on + <code>Driver</code> + </li> + </ul> + </li> + </ul> + + <p>The SAX Events which are fired on the SAX Handler, class + <code>FOTreeBuilder</code>, must represent an XSL:FO document. If not there will be an + error. Any problems with the XML being well formed are handled here.</p></s2> + <s2 title="Element Mappings"><p> The element mapping is a hashmap of all + the elements in a particular namespace. This makes it easy to create a + different object for each element. Element mappings are static to save on + memory. </p><p>To add an extension a developer can put in the classpath a jar + that contains the file <code>/META-INF/services/org.apache.fop.fo.ElementMapping</code>. + This must contain a line with the fully qualified name of a class that + implements the <em>org.apache.fop.fo.ElementMapping</em> interface. This will then be + loaded automatically at the start. Internal mappings are: FO, SVG and Extension + (pdf bookmarks)</p></s2> + <s2 title="Tree Building"><p>The SAX Events will fire all the information + for the document with start element, end element, text data etc. This + information is used to build up a representation of the FO document. To do this + for a namespace there is a set of element mappings. When an element + namepsace + mapping is found then it can create an object for that element. If the element + is not found then it creates a dummy object or a generic DOM for unknown + namespaces.</p> + <p>The object is then setup and then given attributes for the element. + For the FO Tree the attributes are converted into properties. The FO objects + use a property list mapping to convert the attributes into a list of properties + for the element. For other XML, for example SVG, a DOM of the XML is + constructed. This DOM can then be passed through to the renderer. Other element + mappings can be used in different ways, for example to create elements that + create areas during the layout process or setup information for the renderer + etc.</p> + <p> + While the tree building is mainly about creating the FO Tree + there are some stages that can propagate to the renderer. At + the end of a page sequence we know that all pages in the + page sequence can be laid out without being effected by any + further XML. The significance of this is that the FO Tree + for the page sequence may be able to be disposed of. The + end of the XML document also tells us that we can finalise + the output document. (The layout of individual pages is + accomplished by the layout managers page at a time; + i.e. they do not need to wait for the end of the page + sequence. The page may not yet be complete, however, + containing forward page number references, for example.) + </p> + </s2> + <s2 title="Associated Tasks"> + <ul><li>Error handling for xml not well formed.</li> + <li>Error handling for other XML parsing errors.</li><li>Developer + info for adding namespace handlers.</li></ul></s2></s1> + </body></document>
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