Servletでのプロパティファイル読み書き

PropertyUtil.java

public class PropertyUtil {

    private static final String PROPERTY_FILE_TEST = "test.properties";

    public static void setTestPropertyValue(ServletContext context, String key, String value) {
        setPropertyValue(context, PROPERTY_FILE_TEST, key, value);
    }

    public static String getTestPropertyValue(ServletContext context, String key) {
        return getPropertyValue(context, PROPERTY_FILE_TEST, key);
    }

    public static void setPropertyValue(ServletContext context, String propertyFileName, String key, String value) {
        String realPath = getPropertyFilePath(context, propertyFileName);
        Properties prop = new Properties();
        try {
            prop.load(new FileInputStream(realPath));
            prop.setProperty(key, value);
            prop.store(new FileOutputStream(realPath), null);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static String getPropertyValue(ServletContext context, String propertyFileName, String key) {
        String realPath = getPropertyFilePath(context, propertyFileName);
        Properties prop = new Properties();
        try {
            prop.load(new FileInputStream(realPath));
            return prop.getProperty(key);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    private static String getPropertyFilePath(ServletContext context, String propertyFileName) {
        String path = String.format("WEB-INF/classes/%s", propertyFileName);
        return context.getRealPath(path);
    }
}