Java Reference
In-Depth Information
We start out by creating the
StringBuffer
object and appending a newline and the indent to it to make
each element start on a new line. This should result in a document we can read comfortably in a text editor.
After saving the name of the current node in
nodeName
, we determine what kind of node we are
dealing with in the
switch
statement. We could have used the
instanceof
operator and
if
statements to do this but here there's a chance to try out the alternative approach that we discussed
earlier. We only identify two cases in the switch, corresponding to the constants
Node.ELEMENT
_
NODE
and
Node.TEXT
_
NODE
. This is because our DTD for Sketcher doesn't provide for any others so we
don't expect to find them.
For a node that is an element we begin appending the start tag for the element, including the element
name. We then check for the presence of attributes for this element. If there are some, we get them as a
NamedNodeMap
object in the same manner as our earlier example. We then just iterate through the
collection of attributes and build the text that corresponds to each, appending the text to the
StringBuffer
object
nodeStr
.
Once we have finished with the attributes for the current node, we determine whether it has child nodes. If it
has no child nodes, it has no content, so we can complete the tag for the current node making it an empty
element. Since the element is now complete we can return it as a
String
. If the current element has child
nodes we obtain those in a
NodeList
object. We then iterate through the nodes in the
NodeList
and call
getDocumentNode()
for each with an extra space appended to
indent
. The
String
that is returned for
each call is appended to
nodeStr
. When all the child nodes have been processed we are done so we can
exit the switch and return the contents of
nodeStr
as a
String
.
The other possibility is that the current node is text. This will arise from an
Element.Text
object in
the sketch. It is also possible that this text may contain double quotes - the delimiter that we are using
for strings in our XML. We therefore call
replaceQuotes()
to replace all occurrence of
QUOTE
in
the text with the
QUOTE
_
ENTITY
constant that we defined in our
Constants
interface, before
appending the string to
nodeStr
.
We can implement the
replaceQuotes()
method in
SketchFrame
as:
public String replaceQuotes(String str) {
StringBuffer buf = new StringBuffer();
for(int i = 0 ; i<str.length() ; i++)
if(str.charAt(i)==QUOTE)
buf.append(QUOTE
_
ENTITY);
else
buf.append(str.charAt(i));
return buf.toString();
}
This just tests each character in the original string. If it's a delimiter for an attribute value, it's replaced
by the entity reference
"
in the output string
buf
.
Well, we are done - almost. We must not forget the extra
import
statements we need in the
SketchFrame.java
file:
