Question

I am trying to read from a constants file the key value pair. It works when I directly use the class name and the field name, but does not work when I dynamically construct the Class+field combination. How to negotiate this issue?

The following is my Constants file

Public interface Constants
{
String  DEV_SELECT_STATEMENT  =  “DEV_INT_SQL_SELECT_STATEMENT”
String  INT_SELECT_STATEMENT  =  “DEV_INT_SQL_SELECT_STATEMENT”
}

Query.properties file

DEV_INT_SQL_SELECT_STATEMENT =  “SELECT * FROM SOME TABLE”;

JAVA class file //This works

public someClass
{
public someMethod()  //This works
     {
      String sqlStatement = QueryLoader.getStatement(Constants.DEV_SELECT_STATEMENT);
      System.out.println("The  key is :" + Constants. DEV_SELECT_STATEMENT);
      System.out.println(“SqlStatement is : “ + sqlStatement);
      }
}

The key is : DEV_INT_SQL_SELECT_STATEMENT

SqlStatement is : SELECT * FROM SOME TABLE

 public someClass  //This does not work
 {
public someMethod(String env)  //This does not work
     {
      String queryKey =  “Constants” +env + “_SELECT_STATEMENT “;
      System.out.println(“The Key is :  “ + queryKey);
      String sqlStatement = QueryLoader.getStatement(queryKey);
      System.out.println(“SqlStatement is : “ + sqlStatement);
     }

The Key is :Constants.DEV_SELECT_STATEMENT //This does not give the value but a string

SqlStatement is : null

Answer 1

Use Reflection:

String fieldName = env+"_SELECT_STATEMENT";

String value = String.valueOf(Constants.class.getField(fieldName).get(null));

EDIT: I notice i had done some illegal things (Constants.class.getClass() is not valid)

Any how I have tested the edited code and it Works.