Spring DSL: Use message header in transformer - spring

Question

I have xml like below, in the runtime i want to dynamically process . First time first then etc
<tag1>
<tag2>
.
.
.
</tag2>
<tag2>
.
.
.
</tag2>
</tag1>
CASE1: Working code sending static xslt parameter:
.transform(Transformers.xslt(this.config.getSome().getXslt(), xsltParameters(1 or 2)))
public Tuple2[] xsltParameters(int number)
{
final SpelExpressionParser parser = new SpelExpressionParser();
final List<Tuple2<String,Expression>> parameters = new ArrayList<>();
parameters.add(Tuples.of("Id1", parser.parseRaw(String.format("headers['%s']",ID1))));
parameters.add(Tuples.of("Id2", parser.parseRaw(String.format("headers['%s']",ID2))));
parameters.add(Tuples.of("tagNumber", parser.parseRaw(String.format("%d",number))));
return parameters.toArray(new Tuple2[]{});
}
Above is working and transformer can trasnform xslt.
CASE2: Getting error when i want to pass dynamic number:
.transform(Message.class, m-> Transformers.xslt(this.config.getSome().getXslt(), xsltParameters())
xsltparametr(){
parameters.add(Tuples.of("tagNumber",
parser.parseRaw(String.format("headers['%s']",COUNT))));
}
ERROR while transforming:
Error on line 158 of test.xslt(Prior to line 158 is working fine)
XPTY0004: A sequence of more than one item is not allowed as the first argument of starts-with() ("xxmmyty", "xxmmyty")
My xslt at line 158
<xsl:if test="starts-with(xc:tag1/xc:tag2[$count]/xc:trade/xcml:header/xcml:Identifier/xcml:tradeId[#IdScheme='urn:abcd.something'], 'XYZ')" >
<xsl:value-of select="tag" />
</xsl:if>
In CASE1 with same xslt file i can pass above code but in case of dynamic passing(CASE2) it is failing.

Answer 1

First of all it looks like you use old enough Spring version.
Would be grate to upgrade at least to 5.0.x.
Secondly it isn't clear what is your xsltParameters(). You hide it from us and we fully don't know what you do over there. Although we can assume that you are fully based on this method:
#SafeVarargs
public static XsltPayloadTransformer xslt(Resource xsltTemplate,
Tuple2<String, Expression>... xslParameterMappings) {
So, you build in that xsltParameters() an array of Tuple2. OK. So, get access to the header in the param you need to build an appropriate expression.
I'm rally sure that it can be a FunctionExpression:
.transform(Transformers.xslt(this.config.getSome().getXslt(),
Tuples.of("foo", new FunctionExpression<Message<?>>(m -> m.getHeader.get("int_val"))))).
What you do with the lambda can't be combined with a transformer from that factory.
UPDATE
You need to modify your xsltParameters() to accept a String instead. Which is going to be just raw expression representation.
So, your CASE1 is going to be like this:
.transform(Transformers.xslt(this.config.getSome().getXslt(), xsltParameters("'1'")))
With meaning as literal expression.
The CASE2 is going to be like this:
.transform(Transformers.xslt(this.config.getSome().getXslt(), xsltParameters("headers.int_val")))