Java常量通过构建字符串进行实例化

Question

我正在尝试从常量文件中读取键值对。当我直接使用类名和字段名时它可以工作，但是当我动态构造类+字段组合时它不起作用。如何协商这个问题？

以下是我的常量文件

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

查询.properties文件

DEV_INT_SQL_SELECT_STATEMENT =  “SELECT * FROM SOME TABLE”;

JAVA 类文件//这有效

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);
      }
}

关键是:DEV_INT_SQL_SELECT_STATEMENT

SqlStatement 是: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);
     }

关键是:Constants.DEV_SELECT_STATMENT//这不会给出值，而是给出一个字符串

SqlStatement 为:null

Answer 1

使用反射:

String fieldName = env+"_SELECT_STATEMENT";

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

编辑:我注意到我做了一些非法的事情(Constants.class.getClass() 无效)

我如何测试编辑后的代码并且它可以工作。