java：方括号的属性文件转义序列

Question

Need to escape the [ at the starting of a value.

I am using PropertyResourceBundle to read the properties file and i have a property whose value is starting with a square bracket like

myapp.add.user.email.selfRegistration.subject=[MYAPP] Welcome to MYAPP

when i try to read this file i get following exception

java.lang.ClassCastException: [Ljava.lang.String; cannot be cast to
java.lang.String    at
java.util.ResourceBundle.getString(ResourceBundle.java:355)

i am using jdk7

Answer 1

java.util.PropertyResourceBundle is based on the java.util.Properties . Technically java.util.Properties implements Map<Object,Object> but when you load properties from a file the keys and values are restricted to String only (check the source of the java.util.Properties.load() methods). And the '[' character has no special meaning in the properties file format.

Hence it is impossible to get ClassCastException due to attempted cast of String[] to String if all your resource bundles are indeed based on property files.

Most likely you have a ListResourceBundle -based bundle (or a custom subclass of ResourceBundle ) which can contain values of any type, arrays included.

And it is possible to mix property-based and class-based resources bundles with the same base name, for example the default resource bundle can be properties file while locale-specific child bundles are ListResourceBundle -based.

Answer 2

I tried the same with the below program and i am able to get the output from my program without any exception

can you check it and let me know if any other issues

package com.kb;

import java.util.Enumeration;
import java.util.ResourceBundle;

public class ResourceBundleTest {
    public static void main(String[] args) {

        ResourceBundle rb = ResourceBundle.getBundle("mybundle");
        Enumeration <String> keys = rb.getKeys();
        while (keys.hasMoreElements()) {
            String key = keys.nextElement();
            String value = rb.getString(key);
            System.out.println(key + ": " + value);
        }
    }

}