I want to
build a ApplicationSetting for my application. The ApplicationSetting can be stored in a properties file or in a database table. The
settings are stored in key-value pairs. E.g.
ftp.host = blade
ftp.username = dummy
ftp.pass = pass
content.row_pagination = 20
content.title = How to train your dragon.
I have designed it as follows:
Application
settings reader:
interface IApplicationSettingReader {
read();
}
DatabaseApplicationSettingReader {
dao appSettingDao;
AppSettings read() {
List<AppSettingEntity> listEntity = appSettingsDao.findAll();
Map<String, String> map = new HaspMap<String, String>();
foreach (AppSettingEntity entity : listEntity) {
map.put(entity.getConfigName(), entity.getConfigValue());
}
return new AppSettings(map);
}
}
DatabaseApplicationSettingReader {
dao appSettingDao;
AppSettings read() {
//read from some properties file
return new AppSettings(map);
}
}
Application
settings class:
AppSettings {
private static AppSettings instance;
private Map map;
Public AppSettings(Map map) {
this.map = map;
}
public static AppSettings getInstance() {
if (instance == null) {
throw new RuntimeException("Object not configure yet");
}
return instance;
}
public static configure(IApplicationSettingReader reader) {
instance = reader.read();
}
public String getFtpSetting(String param) {
return map.get("ftp." + param);
}
public String getContentSetting(String param) {
return map.get("content." + param);
}
}
Test class:
AppSettingsTest {
IApplicationSettingReader reader;
@Before
public void setUp() throws Exception {
reader = new DatabaseApplicationSettingReader();
}
@Test
public void getContentSetting_should_get_content_title() {
AppSettings.configure(reader);
Instance
settings = AppSettings.getInstance();
String title =
settings.getContentSetting("title");
assertNotNull(title);
Sysout(title);
}
}
My questions are:
Can you give your opinion about my code, is there something wrong?
I configure my application setting once, while the application start, I configure the application setting with appropriate reader (DbReader or PropertiesReader), I make it singleton. The problem is, when some user edit the database or file directly to database or file, I can't get the changed values. Now, I want to implement something like ApplicationSettingChangeListener. So if the data changes, I will refresh my application
settings. Do you have any suggestions how this can be implemented?
