Currently, Yarfraw's writer and reader implementation uses JAXB to read from and write to xml files. Most of these JAXB codes are generated automatically from a few xsd schemas. It's a good idea to take a look at these schema files, you will find a lot of insights on how things work internally in Yarfraw.
The default implementation of ValidationEventHandler in JAXB will fail as soon as the first error or fatal error is encountered. The FeedReader class overrides this default implementation to make the validation only fail when a 'fatal error' is encountered. This lets FeedReader to be able to read as many different feeds as possible. The DefaultValidationEventHandler will output some error messages when it encounters an event, so this handler in Yarfraw will also output these messages.
//ONLY FeedReader uses this handler, writer uses Default handler
private static class WarningHandler implements ValidationEventHandler{
public boolean handleEvent(ValidationEvent event) {
DefaultValidationEventHandler d = new DefaultValidationEventHandler();
d.handleEvent(event);
return event.getSeverity()== ValidationEvent.FATAL_ERROR;
}
}
You can pass in your own implementation of ValidationEventHandler to the IO classes in case you need to handler these validations events differently.
FeedReader r = new FeedReader("rss20.xml");
//Note: null handler will be promptly ignored
r.readChannel(new ValidationEventHandler(){
public boolean handleEvent(ValidationEvent event) {
//Process the event
return false;
}
});
Similarly, you can add your own event handler to FeedWriter:
ChannelFeed c = new ChannelFeed();
FeedWriter w = new FeedWriter(File.createTempFile("yarfraw", ".xml"));
w.writeChannel(c);
w.writeChannel(c, new ValidationEventHandler(){
public boolean handleEvent(ValidationEvent event) {
System.out.println(event);
return false;
}
});
In Atom 1.0, there is a <content> element under <entry> where you can put any text and xhtml as the content of the entry. This element is mapped to the Content class in Yarfraw. There is no support for such element in RSS 2.0, you are supposed to simply use the <description> element for any text (html or non-html). In RSS 1.0, there is a 'content' extension module you can use to add encoded content to your feed. see <content:encoded> . Yarfraw does not support this <encoded> element directly, but I have seen a few places where this element <encoded> element is being used. If a RSS 1.0 or RSS 2.0 feed has this <encoded> element, the FeedReader will add this element as an 'otherElements' under the ItemEntry. Although this element is not in the RSS 2.0 specs, you might want to look for it explicitly because I have seen some RSS 2.0 feeds use this element.
The following snippet shows you how to get the text content of this element.
FeedReader r = new FeedReader("content.xml", FeedFormat.RSS10);
ChannelFeed c = r.readChannel();
ItemEntry i = c.getItems().get(0);
System.out.println(i.getElementByLocalName("encoded").getTextContent());
content.xml
<?xml version="1.0" encoding="utf-8"?>
<rdf:RDF
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:content="http://purl.org/rss/1.0/modules/content/"
xmlns="http://purl.org/rss/1.0/"
>
<channel rdf:about="http://example.org/rss.rdf">
<title>Example Feed</title>
<link>http://www.example.org</link>
<description>Simply for the purpose of demonstration.</description>
<items>
<rdf:Seq>
<rdf:li resource="http://example.org/item/" />
</rdf:Seq>
</items>
</channel>
<item rdf:about="http://example.org/item/">
<title>The Example Item</title>
<link>http://example.org/item/</link>
<content:encoded><![CDATA[<p>What a <em>beautiful</em> day!</p>]]></content:encoded>
</item>
</rdf:RDF>
According to the Atom 1.0 specs , The <content> element can have a single xhtmlDiv element. When FeedReader reads such an element, it will automatically parse it into an DOM element object. For example, for the following feed:
<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
<title type="text">dive into mark</title>
<link rel="alternate" type="text/html"
hreflang="en" href="http://example.org/"/>
<entry>
<title>Atom draft-07 snapshot</title>
<content type="xhtml" xml:lang="en"
xml:base="http://diveintomark.org/">
<div xmlns="http://www.w3.org/1999/xhtml">
<p><i>[Update: The Atom draft is finished.]</i></p>
</div>
</content>
</entry>
</feed>
You can use the following code to get the div element.
FeedReader r = new FeedReader("atomXhtml.xml", FeedFormat.ATOM10);
ChannelFeed c = r.readChannel();
ItemEntry i1 = c.getItems().get(0);
if(i1.getContent().getType().equals("xhtml")){//only content that is of type 'xhtml' will has div element
DOMSerializer serializer = new DOMSerializer();
Element div = i1.getContent().getElementByNS("http://www.w3.org/1999/xhtml", "div");
StringWriter writer = new StringWriter();
serializer.serializeNode((Node)div, writer, "");
System.out.println(writer.toString());
}else{//the rest will be interpreted as simple text content
System.out.println(i1.getContent().getContentText());
}
Content will be automatically encoded, so you can put any strings you want in the <description> element and the <content> element (and all other text elements). For example:
ChannelFeed c = new ChannelFeed()
.setDescriptionOrSubtitle("<div xmlns=\"http://www.w3.org/1999/xhtml\">"+
"<p><i>[Update: The Atom draft is finished.]</i></p>"+
"</div>");
FeedWriter w = new FeedWriter("test.xml");
w.writeChannel(c);
resulting feed:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<rss version="2.0">
<channel>
<description><div xmlns="http://www.w3.org/1999/xhtml"><p><i>
[Update: The Atom draft is finished.]</i></p></div></description>
</channel>
</rss>
use org.apache.common.lang.StringEscapeUtils if you want decode it:
System.out.println(StringEscapeUtils.unescapeXml(
"<div xmlns="http://www.w3.org/1999/xhtml"><p><i>"+
"[Update: The Atom draft is finished.]</i></p></div>"));
For more details, I encourage to take a look at the Javadoc . Also check out the FAQ section for more insights about this API.