How to escape <, >, and & characters to html entities in Oracle PL/SQL

Question

I need to send HTML emails directly from oracle PL/SQL package. This works almost fine.

I have problem with the fact that some of the data fetched from a table contain things like <S>, <L>, and similar fragments, which sometimes ar treated as HTML tags, and even if not, they are always ignored and never displayed.

So, I need to escape this column before inserting into email body.

Is there a function to escape html special chars into entities automaticly? Or do I need to replace('<', '&lt;', string) manually all the special characters?

Answer 1

You can use the htf.escape_sc function:

SQL> select htf.escape_sc('Please escape <this> tag') from dual;

HTF.ESCAPE_SC('PLEASEESCAPE<THIS>TAG')
------------------------------------------------------------------
Please escape &lt;this&gt; tag

Answer 2

Also available is DBMS_XMLGEN.CONVERT which can handle a clob.

Example:

select DBMS_XMLGEN.CONVERT('<foo>') from dual

Details: https://docs.oracle.com/cd/B19306_01/appdev.102/b14258/d_xmlgen.htm

Answer 3

HTF.BDY :
/* SPECIAL FUNCTIONS */
function escape_sc(ctext in varchar2 character set any_cs)
         return varchar2 character set ctext%charset is
begin return(replace(
             replace(
             replace(
             replace(ctext, '&', '&' || 'amp;'),
                            '"', '&' || 'quot;'),
                            '<', '&' || 'lt;'),
                            '>', '&' || 'gt;'));
end;

You can create this function yourself

But better use this variant of function dbms_xmlgen.convert

SQL> select dbms_xmlgen.convert('<test>&''"</test>') from dual
  2  /

DBMS_XMLGEN.CONVERT('<TEST>&''"</TEST>')
--------------------------------------------------------------------------------
&lt;test&gt;&amp;&apos;&quot;&lt;/test&gt;