jengebr opened a new pull request, #842:
URL: https://github.com/apache/tomcat/pull/842
Enables optimized, non-standard behavior for the most common JSP tags, when
configured to do so.
**Unit tests pending**
**Off by default.**
When activated, the code generation to call `c:set` and/or `c:remove` is
drastically reduced (samples follow). When not activated or when the specific
case is not supported, code generation falls back to the existing standard
behavior. Value comes from:
1. Reduced Object allocation and eventual GC
2. Fewer method calls (setters, start and end tag, recycle tag)
3. Elimination of try/finally
4. No branching by the caller
5. Smaller .java and .class files
So far this supports only basic cases, but they are approximately 25% of of
the tags in my application.
1. `c:set` with `var` and `value`, optional `scope`, no body
7. `c:remove` with `var`, optional `scope`, no body
The nonstandard generated code looks like this:
```
private void _jspx_meth_c_005fset_005f125(javax.servlet.jsp.PageContext
_jspx_page_context)
throws java.lang.Throwable {
_jspx_page_context.setAttribute("groupName", new
org.apache.jasper.el.JspValueExpression("/WEB-INF/views/jsp/features/buybox/offerDisplayGroupLayout.jsp(235,12)
'${tabContents.keySet().toArray()[0]}'",_jsp_getExpressionFactory().createValueExpression(_jspx_page_context.getELContext(),"${tabContents.keySet().toArray()[0]}",java.lang.Object.class)).getValue(_jspx_page_context.getELContext()),
javax.servlet.jsp.PageContext.PAGE_SCOPE);
}
```
The standard generated code looks like this:
```
private boolean
_jspx_meth_c_005fset_005f39(javax.servlet.jsp.tagext.JspTag
_jspx_th_c_005fwhen_005f11, javax.servlet.jsp.PageContext _jspx_page_context)
throws java.lang.Throwable {
javax.servlet.jsp.PageContext pageContext = _jspx_page_context;
javax.servlet.jsp.JspWriter out = _jspx_page_context.getOut();
// c:set
org.apache.taglibs.standard.tag.rt.core.SetTag _jspx_th_c_005fset_005f39
= new org.apache.taglibs.standard.tag.rt.core.SetTag();
_jsp_getInstanceManager().newInstance(_jspx_th_c_005fset_005f39);
try {
_jspx_th_c_005fset_005f39.setPageContext(_jspx_page_context);
_jspx_th_c_005fset_005f39.setParent((javax.servlet.jsp.tagext.Tag)
_jspx_th_c_005fwhen_005f11);
//
/WEB-INF/views/jsp/features/buybox/offerDisplayGroupLayout.jsp(230,12) name =
var type = java.lang.String reqTime = false required = false fragment = false
deferredValue = false expectedTypeName = null deferredMethod = false
methodSignature = null
_jspx_th_c_005fset_005f39.setVar("groupName");
//
/WEB-INF/views/jsp/features/buybox/offerDisplayGroupLayout.jsp(230,12) name =
value type = javax.el.ValueExpression reqTime = true required = false fragment
= false deferredValue = true expectedTypeName = java.lang.Object deferredMethod
= false methodSignature = null
_jspx_th_c_005fset_005f39.setValue(new
org.apache.jasper.el.JspValueExpression("/WEB-INF/views/jsp/features/buybox/offerDisplayGroupLayout.jsp(230,12)
'${tabContents.keySet().toArray()[0]}'",_jsp_getExpressionFactory().createValueExpression(_jspx_page_context.getELContext(),"${tabContents.keySet().toArray()[0]}",java.lang.Object.class)).getValue(_jspx_page_context.getELContext()));
int _jspx_eval_c_005fset_005f39 =
_jspx_th_c_005fset_005f39.doStartTag();
if (_jspx_th_c_005fset_005f39.doEndTag() ==
javax.servlet.jsp.tagext.Tag.SKIP_PAGE) {
return true;
}
} finally {
org.apache.jasper.runtime.JspRuntimeLibrary.releaseTag(_jspx_th_c_005fset_005f39,
_jsp_getInstanceManager(), false);
}
return false;
}
```
Caller code is also modified to eliminate the boolean check:
```
if (_jspx_meth_c_005fset_005f39(_jspx_th_c_005fwhen_005f11,
_jspx_page_context))
return true;
```
```
_jspx_meth_c_005fset_005f125(_jspx_page_context);
```
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