Question

I’m trying to make a query with selected fields for final user from view (JSP) to controller, but I don’t know how.

For example, I have this parameters from view (JSP)

IDUSER,>,2,OR,USERNAME,=,'KURT'

So, I’ll want to have something like this,

SELECT IDUSER, USERNAME FROM TABLE_NAME WHERE IDUSER > 2 OR USERNAME = 'KURT'

but I have next result

SELECT null FROM TABLE_NAME WHERE IDUSER > 2 OR USERNAME = 'KURT'

I’m parsing string with StringTokenizer class, where query is: String query = request.getParameter("data"); and data is IDUSER,>,2,OR,USERNAME,=,'KURT'.

StringTokenizer field = new StringTokenizer(query, ",");
nFields = field.countTokens();
System.out.println("nFields: " + nFields);
String[] fields = new String[nFields];
for(int i = 0; i < fields.length; i++) {
    while(field.hasMoreTokens()) {
         fields[i] = field.nextToken();
    }
    System.out.println("fields[i]: " + fields[i]);
    myQuery = "SELECT " + fields[i] + " FROM "+tableName+ " WHERE ";
    System.out.println("myQuery 1: " + myQuery);
}
StringTokenizer token= new StringTokenizer(query, "|,");
while(token.hasMoreTokens()) {
     myQuery = myQuery + token.nextToken() + " ";
}
System.out.println("QUERY RESOLVED: " + myQuery);

PLEASE HELP ME

Answer 1

Here is the solution after minor tweak in your query (redefined the separators)

public static void main(String[] args) {
        // Redefine the separators as single , separators is difficult to process
        //You would need to define possible operators like this (#OR# , #AND# ) ,surrounded by special characters to identify.
        String query ="IDUSER_>_2#OR#USERNAME_=_'KURT'";
        String tableName="TESTTABLE";
        String operator=null;
        //you can choose operator conditionally
        if(query.contains("#OR#")) operator="#OR#";
//      if(query.contains("#AND#")) operator="#AND#";
        //Used split instead of Tokenizer.
        String cols[]= query.split(operator);
        String myQuery = "SELECT ";
        String select="";
        for(String col:cols){
            if(!select.isEmpty()){
                select+=" , ";
            }
            // Only the first element is retrieved (for select)
            select+=col.split("_")[0];
        }
        myQuery+=select+" FROM "+tableName+ " WHERE ";
        // Removes all special charecters (like,  # and _ with white space)
        String subQuery = query.replaceAll("#", " ");
        subQuery=subQuery.replaceAll("_", "");
        myQuery+=subQuery;
        System.out.println("QUERY RESOLVED: " + myQuery);

    }

Note : ‘,’ is replaced with ‘_’ and operators are surrounded by ‘#’

Cheers!!