SET DEFINE OFF
CREATE OR REPLACE AND compile JAVA source named XmlNumericEncoder AS
PUBLIC class XmlNumericEncoder {
    PUBLIC static String encode(String xmlstring) {
        String xmlstring_out = "";
        FOR (int i = 0; i < xmlstring.LENGTH(); i++){
            CHAR ch = xmlstring.charAt(i);

            IF ((int)ch  >=  192 && (int)ch <= 255){
               xmlstring_out += "&#" + (int)ch + ";";
            } ELSE {
               xmlstring_out += ch;
            }
        }
        RETURN xmlstring_out;
    }
};
/

CREATE OR REPLACE FUNCTION XmlNumericEncoder(xmlstring VARCHAR2)
        RETURN String
        AS LANGUAGE JAVA
        NAME 'XmlNumericEncoder.encode(java.lang.String) return java.lang.String';
/

SELECT XmlNumericEncoder('Böhmer') FROM dual;
SELECT XmlNumericEncoder('Böhmer') FROM dual;

CREATE OR REPLACE FUNCTION plXmlNumericEncoder(xmlstring VARCHAR2) RETURN VARCHAR2 IS
   l_result LONG;
   l_char   VARCHAR2(1);
BEGIN
   FOR i IN 1 .. LENGTH(xmlstring) LOOP
      l_char   := SUBSTR(xmlstring, i, 1);
      l_result := l_result
                  || CASE WHEN ASCII(l_char) BETWEEN 192 AND 255 THEN '&#' || ASCII(l_char) || ';' ELSE l_char END;
   END LOOP;
   RETURN l_result;
END;
/
SELECT plXmlNumericEncoder('Böhmer') FROM dual;

SET SERVEROUTPUT ON
DECLARE
   l_ts_start TIMESTAMP;
   TYPE tab_varchar2 IS TABLE OF VARCHAR2(2000) INDEX BY PLS_INTEGER;
   l_random    tab_varchar2;
   l_converted LONG;
BEGIN
   SELECT DBMS_RANDOM.STRING('p', 2000) BULK COLLECT INTO l_random FROM dual CONNECT BY LEVEL <= 1e3;
   -- method 1
   l_ts_start := SYSTIMESTAMP;
   FOR i IN 1 .. l_random.COUNT LOOP
      l_converted := plXmlNumericEncoder(l_random(i));
   END LOOP;
   DBMS_OUTPUT.put_line('method 1:' || (SYSTIMESTAMP - l_ts_start));
   -- method 2
   l_ts_start := SYSTIMESTAMP;
   FOR i IN 1 .. l_random.COUNT LOOP
      l_converted := XmlNumericEncoder(l_random(i));
   END LOOP;
   DBMS_OUTPUT.put_line('method 2:' || (SYSTIMESTAMP - l_ts_start));
END;
/