hi,
if you look at the source code of the join method then you will find
that it is doing exactly what struts is currently doing, ie using
StringBuffer for concatenation and finally returning a string.
as far as the packaging of the StringHolder class is concerned, it is
not great a concern. only thing i wished to point out was that all the
html tags need a change in this direction. this will make them much
faster and this is really needed as these tags are quite often used.
thanks,
nishant.
On Sun, 2004-02-15 at 07:41, Martin Cooper wrote:
> Rather than add a new string utility class to Struts, which isn't really
> where it should belong, I think we'd be better off just using this:
>
> http://jakarta.apache.org/commons/lang/api/org/apache/commons/lang/StringUti
> ls.html#join(java.lang.Object[])
>
> Alternatively, you could suggest (on the commons-dev list) adding a
> variation of your StringHolder class, based on the join() method above, to
> Commons Lang.
>
> --
> Martin Cooper
>
>
> > -----Original Message-----
> > From: nishant kumar [mailto:[EMAIL PROTECTED]
> > Sent: Saturday, February 14, 2004 5:46 PM
> > To: [EMAIL PROTECTED]
> > Subject: string concatenation
> >
> >
> > hi,
> > I have a performance tuning suggestion which i think will greatly
> > impact the performance of struts html tags.
> > String concatenation using StringBuffer is definitely much
> > better than
> > using the plus operator but there are scenarios where there are much
> > better ways than using StringBuffers. Actually struts html tags fall in
> > those scenarios.
> > So let me give you an example. this is the code from
> > renderFormStartElement method of FormTag.
> >
> > StringBuffer results = new StringBuffer();
> > results.append("<form");
> > results.append(" name=\"");
> > results.append(beanName);
> > results.append("\"");
> > results.append(" method=\"");
> > results.append(method == null ? "post" : method);
> > results.append("\" action=\"");
> > ....
> > str = results.toString();
> >
> > pageContext.getOut().write(str);
> >
> > Now lets list the issues with this.
> > 1. first presizing this buffer is quite difficult (avoided in this
> > case). here the buffer starts with size 16 and doubles each time the
> > size is exceeded. This causes unnecessary creation of new char arrays
> > and redundant copy of data whenever resizing happens.
> > 2. whenever append is called data is copied from the passed string to
> > the end of stringbuffer.
> > 3. finally the whole concatenated data is again copied into another
> > string.
> > 4. and then in the end this string is written to a writer, another copy,
> > which is the only copy required.
> >
> > so even if you had presized the stringbuffer correctly, you have copied
> > the same data thrice instead of just once. And you also create two NOT
> > needed objects.
> >
> > so here is the solution i propose. have a class holding an array of
> > Strings and keep appending strings to this array and finally print this
> > array to the writer. something like this.
> >
> > private String[] data = new String[256];
> > private int size = 0;
> >
> > public StringHolder append(String str){
> > ensureCapacity(this.size + 1);
> > this.data[this.size++] = str;
> > return this;
> > }
> >
> > public void writeTo(Writer out) throws IOException{
> > for (int i = 0; i < this.size; i++){
> > if (this.data[i] != null){
> > out.write(this.data[i]);
> > }
> > }
> > }
> >
> > this way only the last copy takes place and you also avoid creating so
> > much garbage.
> >
> > i have attached StringHolder class which does the above task and also
> > the FormTag after making necessary modification to fit in this class.
> > >From the code of FormTag you can see that you need to make quite few
> > changes to get great benefit.
> >
> > i have also attached a better implementation of
> > ResponseUtils.filter(String) method. the logic is on the same lines as
> > above.
> >
> > thanks,
> > nishant
> >
> > --
> > nishant kumar <[EMAIL PROTECTED]>
> >
>
>
>
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