类图
public Configuration() {
this(true);
}
/** A new configuration where the behavior of reading from the default
* resources can be turned off.
*
* If the parameter {@code loadDefaults} is false, the new instance
* will not load resources from the default files.
* @param loadDefaults specifies whether to load from the default files
*/
public Configuration(boolean loadDefaults) {
this.loadDefaults = loadDefaults;
updatingResource = new HashMap<String, String>();
synchronized(Configuration.class) {
REGISTRY.put(this, null);
}
}
/**
* A new configuration with the same settings cloned from another.
*
* @param other the configuration from which to clone settings.
*/
@SuppressWarnings("unchecked")
public Configuration(Configuration other) {
this.resources = (ArrayList) other.resources.clone();
synchronized (other) {
if (other.properties != null) {
this.properties = (Properties) other.properties.clone();
}
if (other.overlay != null) {
this.overlay = (Properties) other.overlay.clone();
}
this.updatingResource = new HashMap<String, String>(
other.updatingResource);
}
this.finalParameters = new HashSet<String>(other.finalParameters);
synchronized (Configuration.class) {
REGISTRY.put(this, null);
}
}
public int getInt(String name, int defaultValue) {
String valueString = get(name);
if (valueString == null)
return defaultValue;
try {
String hexString = getHexDigits(valueString);
if (hexString != null) {
return Integer.parseInt(hexString, 16);
}
return Integer.parseInt(valueString);
} catch (NumberFormatException e) {
return defaultValue;
}
}
private synchronized Properties getProps() {
if (properties == null) {
properties = new Properties();
loadResources(properties, resources, quietmode);
if (overlay!= null) {
properties.putAll(overlay);
for (Map.Entry<Object,Object> item: overlay.entrySet()) {
updatingResource.put((String) item.getKey(), UNKNOWN_RESOURCE);
}
}
}
return properties;
}
private void loadResources(Properties properties,
ArrayList resources,
boolean quiet) {
if(loadDefaults) {
for (String resource : defaultResources) {
loadResource(properties, resource, quiet);
}
//support the hadoop-site.xml as a deprecated case
if(getResource("hadoop-site.xml")!=null) {
loadResource(properties, "hadoop-site.xml", quiet);
}
}
for (Object resource : resources) {
loadResource(properties, resource, quiet);
}
}
看到了loadDefaults了没有？是不是很开心，在Constructor涉及到的控制默认配置文件加载的loadDefaults终于现身了。defaultResource在loadDefaults为true是才会加载。但是resources中存放的配置文件无论怎么样都会被加载，这里出现了两个存放配置文件的容器defaultResources和resource
/**
* List of configuration resources.
*/
private ArrayList<Object> resources = new ArrayList<Object>();
/**
* List of default Resources. Resources are loaded in the order of the list
* entries
*/
private static final CopyOnWriteArrayList<String> defaultResources =
new CopyOnWriteArrayList<String>();
public static synchronized void addDefaultResource(String name) {
if(!defaultResources.contains(name)) {
defaultResources.add(name);
for(Configuration conf : REGISTRY.keySet()) {
if(conf.loadDefaults) {
conf.reloadConfiguration();
}
}
}
}
addResourceObject(Object object)
private synchronized void addResourceObject(Object resource) {
resources.add(resource); // add to resources
reloadConfiguration();
}
/**
* Reload configuration from previously added resources.
*
* This method will clear all the configuration read from the added
* resources, and final parameters. This will make the resources to
* be read again before accessing the values. Values that are added
* via set methods will overlay values read from the resources.
*/
public synchronized void reloadConfiguration() {
properties = null; // trigger reload
finalParameters.clear(); // clear site-limits
}
public void set(String name, String value) {
getOverlay().setProperty(name, value);
getProps().setProperty(name, value);
this.updatingResource.put(name, UNKNOWN_RESOURCE);
}
private synchronized Properties getProps() {
if (properties == null) {
properties = new Properties();
loadResources(properties, resources, quietmode);
if (overlay!= null) {
properties.putAll(overlay);
for (Map.Entry<Object,Object> item: overlay.entrySet()) {
updatingResource.put((String) item.getKey(), UNKNOWN_RESOURCE);
}
}
}
return properties;
}
原文：http://www.cnblogs.com/wolfblogs/p/4156403.html