CODEWITHSUNDEEP
exist-db
Honza Hejzl
Honza Hejzl

Reputation: 884

Return type error in eXist-db

I have just realized my logger is very active in the case of a function responsible for generating epubs. The problem is it works as expected. Hence I wonder what is going on here.

The error:

java:org.exist.xquery.XPathException, exerr:ERROR The actual return type does not match the sequence type declared in the function's signature: epub-util:render-epub(node()+, xs:string) xs:base64Binary. Expected cardinality: exactly one, got 0.

… epub is properly served to the client.

As for exerr:ERROR, I checked the general log in $EXIST_HOME/webapp/WEB-INF/logs/exist.log. There are no associated errors caught.

The suspected function:

declare function epub-util:render-epub($entries as node()+, $name as xs:string) as xs:base64Binary {
    let $zip-file    := compression:zip($entries, true())
    let $archiveName := $name
    return
        response:stream-binary($zip-file, 'application/epub+zip', lower-case(replace($archiveName, ' ', '-')) || '.epub')
};

I run eXist on Ubuntu Server 14.04, eXist-db is 3.0.RC1.

Upvotes: 0

Views: 163

Answers (2)

DiZzZz
DiZzZz

Reputation: 656

response:stream-binary() is a very special function, that in essence directly writes bytes to a servlet output stream , hence it can only be used in the REST interface.

It can only write a byte stream to a HTTP agent, that is e.g. your web browser. It is not possible to store this data in a variable.

I agree that even item() is not a good thing, it should be something like void but that does not exist.

The common use-case it to have this expression as the last function call in a xquery script. A similar construct we use in the JFreechart library.

Upvotes: 2

Joe Wicentowski
Joe Wicentowski

Reputation: 5294

According to the eXist-db function documentation for response:stream-binary(), this function returns item(), not xs:base64binary. Replacing the return type with item() should fix the error.

Upvotes: 2

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