Chapter 2

陈辉煌

1. XmlConfiguration的value方法
读取某个节点的值，并进行相应处理：修剪空字符串，解析并拼接结果

private Object value(Object obj, XmlParser.Node node) throws Exception
{
Object value = null;
// Get the type
String type = node.getAttribute("type");
// Try a ref lookup
String ref = node.getAttribute("ref");
if (ref != null)
{
value = _idMap.get(ref);
}
else
{
// handle trivial case
if (node.size() == 0)
{
if ("String".equals(type)) return "";
return null;
}
// Trim values
int first = 0;
int last = node.size() - 1;
// Handle default trim type
if (type == null || !"String".equals(type))
{
// Skip leading white
Object item = null;
while (first <= last)
{
item = node.get(first);
if (!(item instanceof String)) break;
item = ((String) item).trim();
if (((String) item).length() > 0) break;
first++;
}
// Skip trailing white
while (first < last)
{
item = node.get(last);
if (!(item instanceof String)) break;
item = ((String) item).trim();
if (((String) item).length() > 0) break;
last--;
}
// All white, so return null
if (first > last) return null;
}
if (first == last)
//  Single Item value
value = itemValue(obj, node.get(first));
else
{
// Get the multiple items as a single string
StringBuffer buf = new StringBuffer();
synchronized (buf)
{
for (int i = first; i <= last; i++)
{
Object item = node.get(i);
buf.append(itemValue(obj, item));
}
value = buf.toString();
}
}
}
// Untyped or unknown
if (value == null)
{
if ("String".equals(type)) return "";
return null;
}
// Try to type the object
if (type == null)
{
if (value != null && value instanceof String) return ((String) value).trim();
return value;
}
if ("String".equals(type) || "java.lang.String".equals(type)) return value.toString();
Class pClass = TypeUtil.fromName(type);
if (pClass != null) return TypeUtil.valueOf(pClass, value.toString());
if ("URL".equals(type) || "java.net.URL".equals(type))
{
if (value instanceof URL) return value;
try
{
return new URL(value.toString());
}
catch (MalformedURLException e)
{
throw new InvocationTargetException(e);
}
}
if ("InetAddress".equals(type) || "java.net.InetAddress".equals(type))
{
if (value instanceof InetAddress) return value;
try
{
return InetAddress.getByName(value.toString());
}
catch (UnknownHostException e)
{
throw new InvocationTargetException(e);
}
}
throw new IllegalStateException("Unknown type " + type);
}


2. XmlConfiguration的itemValue方法
读取单个节点的值，如果item是String类型，直接返回
如果是其它的tag，还需要调用对应的处理方法

private Object itemValue(Object obj, Object item) throws Exception
{
// String value
if (item instanceof String) return item;
XmlParser.Node node = (XmlParser.Node) item;
String tag = node.getTag();
if ("Call".equals(tag)) return call(obj, node);
if ("Get".equals(tag)) return get(obj, node);
if ("New".equals(tag)) return newObj(obj, node);
if ("Ref".equals(tag)) return refObj(obj, node);
if ("Array".equals(tag)) return newArray(obj, node);
if ("Map".equals(tag)) return newMap(obj, node);
if ("Property".equals(tag)) return propertyObj(obj,node);
if ("SystemProperty".equals(tag))
{
String name = node.getAttribute("name");
String defaultValue = node.getAttribute("default");
return System.getProperty(name, defaultValue);
}
Log.warn("Unknown value tag: " + node, new Throwable());
return null;
}