Uregent help needed StoredProcedure call with paramater Map

[bala r]

I  am using ParameterMap to map StoredProcedure IN parameters.
If all parameter have value then storedproeceure is executed fine.
But if one of the parameter is empty then getting exception
"PL/SQL: numeric or value error: character to number conversion error"
getting error.
here are teh sqlmap details.
<parameterMap id="product_map" class="java.util.HashMap" >
       <parameter         property="item_type_id"
jdbcType="VARCHAR2"    javaType="java.lang.String" mode="IN"/>
        <parameter         property="item_id"
jdbcType="VARCHAR2"    javaType="java.lang.String" mode="IN"/>
        <parameter         property="web_display_name"
jdbcType="VARCHAR2"    javaType="java.lang.String" mode="IN"/>
        <parameter         property="url"
jdbcType="VARCHAR2"    javaType="java.lang.String" mode="IN"/>
        <parameter         property="uri"
jdbcType="VARCHAR2"    javaType="java.lang.String" mode="IN"/>
</parameter>
<procedure id="product" parameterMap="product_map">
        {call product.load (?,?,?,?,?)}
    </procedure>

Thanks in Advance.

Thanks
Bala.