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]> > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
