f:param converts blanks to '+' in mailto-link

Question

I got a weird problem:

_article.headline is in my database a clob value, in my java entity it is a String value. If I click on the outputlink all whitespaces where replaced by '+'

Example:

Original clob/string: This is a test value.

Result: This+is+a+test+value.

<h:outputLink style="text-decoration: none;" value="mailto:">
     <f:param name="subject" value="#{_article.headline}" />
     <f:param name="body" value="#{informationCenterHandler.articleToMail(_article)}" />
     <i title="Artikel als Mail verschicken" class="fa fa-envelope-o fa-fw" />
</h:outputLink>

Can anyone give me an explanation to me and a solution for this problem?

Thanks LStrike