Re: HashMap and dynamic JDBC update

Lew <>
Fri, 07 Aug 2009 09:04:36 -0400
Please *DO NOT* multipost.
(Reply cross-posted to rectify.)

Alessandro wrote:

I have an HashMap<String, Object> used to save names and values of
fields to be updated via JDBC update in a table. The type of data is
variable according to field name , so I'm using Object ... the idea to
produce update query is as follows but I believe there is a better
method to do it.

public void updateQuery(Session session, String table,
HashMap<String,Object> updateH, String condition) throws Throwable{

Your indentation is far too wide for Usenet. Do not use TAB characters to
indent Usenet posts; use a maximum of four spaces per indent level.

                        String sQuery="UPDATE " + table + " SET ";
                        String keys="";

                        Iterator iterator = updateH.keySet().iterator
(); //key set
                        while(iterator.hasNext()) //got the key
and then remove first char,
ie ","
                                keys= keys + "," + +
"= ?";

                        PreparedStatement ps = session.connection
+ keys.substring(1) + " WHERE " + condition);

                                Object myObj=updateH.get(
                                if(myObj instanceof String){

Anytime you are checking type with 'instanceof' to support varied behavior,
suspect that you've erred.

                                else if (myObj.instanceof Date){
                               //etc also for Double, Integer, ..
                catch(Throwable ex){
                        throw ex;


I've built up queries and corresponding set logic, polymorphically, using tiny
little setters similar to

   interface ParmSetter <T>
     void setValue( PreparedStatement ps, T value );
   class StringSetter implements ParmSetter <String>
     public void setValue( PreparedStatement ps, String value )
       ps.setString( value );

Then you build up a list of SQL WHERE clause pieces and corresponding
ParmSetters as you receive criteria. Then you iterate through, calling

   nextSetter.setValue( ps, nextValue );

Yet another way is to skip 'PreparedStatement#setString()' and the rest and
just use 'setObject()'.


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