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
最佳答案
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。
关于Java常量通过构建字符串进行实例化,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/10520028/