调用findExtensions，null在缓存中保存null

privateList<Extension> findExtensions(String scope) {

String[] orders = null;

String orderlist =
conf.get("urlnormalizer.order." +scope);

if (orderlist ==
null)

orderlist = conf.get("urlnormalizer.order");

if (orderlist !=
null&& !orderlist.trim().equals("")) {

orders = orderlist.split("\\s+");

}

String scopelist =
conf.get("urlnormalizer.scope." +scope);

Set<String> impls = null;

if (scopelist !=
null&& !scopelist.trim().equals("")) {

String[] names = scopelist.split("\\s+");

impls = newHashSet<String>(Arrays.asList(names));

}

Extension[] extensions = this.extensionPoint.getExtensions();

HashMap<String, Extension>normalizerExtensions =

newHashMap<String, Extension>();

for (int i =0; i < extensions.length; i++) {

Extension extension = extensions[i];

if(impls !=
null &&!impls.contains(extension.getClazz()))

continue;

normalizerExtensions.put(extension.getClazz(),extension);

}

List<Extension> res = newArrayList<Extension>();

if (orders ==
null) {

res.addAll(normalizerExtensions.values());

} else {

// first add those explicitlynamed in correct order

for (int i =0; i < orders.length; i++) {

Extension e =normalizerExtensions.get(orders[i]);

if (e!=
null) {

res.add(e);

normalizerExtensions.remove(orders[i]);

}

}

// then add all others inrandom order

res.addAll(normalizerExtensions.values());

}

return res;

}

关于scope可以看一下注释You can define a set of contexts (orscopes) in which normalizers may be called. Each scope can have its own list ofnormalizers (defined in "urlnormalizer.scope.<scope_name>"property) and its own order (defined in "urlnormalizer.order.<scope_name>"
property). If any ofthese properties are missing, default settings are used for the global scope.，大意是你可以再定义一个更小的域，处理关于这个子域的特征情况，比如在Injector中调用，可以指定urlnormalizer.order.injector。默认情况下，在injector域中，在配置中使用的是默认的urlnormalizer.order，相应的配置在nutch-default中：

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时间： 2024-11-07 18:40:50

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