After hitting my head against the wall that is PageContext.pushBody()
and it's near-uselessness, I have finally hacked my Tomcat 4.0.1 and
added one measly method to the servlet API.
And boy is my life getting better fast.
The issues are twofold:
1) pushBody() makes a BodyContent for you, pushes it, and returns it.
This does nothing for folks who want to put some other sort of Writer in
place, like say a PipedJspWriter to be fed from an XSLT Thread, or whatever.
2) even if pushBody() did what you want, it's pointless to invoke it
from a Tag, since the JSP compiler won't set the "out" variable used to
send static content etc.
So I have humbly - humbly! - added pushWriter(JspWriter) to the API and
altered tomcat's TagBeginGenerator and TagEndGenerator to say
out = pageContext.getOut()
when a BodyTag *doesn't* return EVAL_BODY_BUFFERED, and voila I finally
have what I've been needing all this time. Now I can stream between Tags
and take another, more general, and simpler crack at taglibs/io. And
static HTML content just works, and Tags don't have to conspire with
each other or mess with global state. And more, but that's for another post.
I don't know the JSP standards process, but I'm hoping whoever is in
charge will take this modification and the reasoning behind it under
serious consideration.
The attached patches are against jakarta-servletapi-4 as downloaded from
the current CVS, and for jakarta-tomcat-4.0.1-src (the CVS for
tomcat-4.0 seems to be older, and I didn't find a more current one).
Oh, the tomcat patch also includes a fix for TagCache that is more
definite about finding setters for Tag attributes. So you can use
"class=" now and get more predictable behavior for attributes in
general. Apologies for mixing them.
diff -c -r jakarta-servletapi-4-orig/src/share/javax/servlet/jsp/PageContext.java
jakarta-servletapi-4/src/share/javax/servlet/jsp/PageContext.java
*** jakarta-servletapi-4-orig/src/share/javax/servlet/jsp/PageContext.java Fri
Jul 13 16:57:18 2001
--- jakarta-servletapi-4/src/share/javax/servlet/jsp/PageContext.java Sat Feb 2
13:25:29 2002
***************
*** 109,115 ****
*
* <p>
* The following methods enable the <B>management of nested</B> JspWriter streams to
! * implement Tag Extensions: <code>pushBody()</code> and <code>popBody()</code>
*
* <p><B>Methods Intended for JSP authors</B>
* <p>
--- 109,115 ----
*
* <p>
* The following methods enable the <B>management of nested</B> JspWriter streams to
! * implement Tag Extensions: <code>pushBody()</code>, <code>pushWriter()</code>, and
<code>popBody()</code>
*
* <p><B>Methods Intended for JSP authors</B>
* <p>
***************
*** 577,584 ****
/**
* Return the previous JspWriter "out" saved by the matching
! * pushBody(), and update the value of the "out" attribute in
* the page scope attribute namespace of the PageConxtext
*
* @return the saved JspWriter.
--- 577,596 ----
/**
+ * Push a given JspWriter, save the current "out" JspWriter,
+ * and update the value of the "out" attribute in the page scope
+ * attribute namespace of the PageContext
+ *
+ * @param w the jspwriter to use
+ */
+
+ public void pushWriter(JspWriter w) {
+ }
+
+
+ /**
* Return the previous JspWriter "out" saved by the matching
! * pushBody() or pushWriter(), and update the value of the "out" attribute in
* the page scope attribute namespace of the PageConxtext
*
* @return the saved JspWriter.
diff -c -r
jakarta-tomcat-4.0.1-orig/jasper/src/share/org/apache/jasper/compiler/TagBeginGenerator.java
jakarta-tomcat-4.0.1/jasper/src/share/org/apache/jasper/compiler/TagBeginGenerator.java
***
jakarta-tomcat-4.0.1-orig/jasper/src/share/org/apache/jasper/compiler/TagBeginGenerator.java
Mon Nov 12 18:02:50 2001
---
jakarta-tomcat-4.0.1/jasper/src/share/org/apache/jasper/compiler/TagBeginGenerator.java
Fri Feb 1 18:31:53 2002
***************
*** 377,382 ****
--- 377,388 ----
writer.popIndent();
writer.println("}");
+ // a Tag might have pushed something
+ writer.println("else");
+ writer.pushIndent();
+ writer.println("out = pageContext.getOut();");
+ writer.popIndent();
+
writer.println(thVarName+".doInitBody();");
}
diff -c -r
jakarta-tomcat-4.0.1-orig/jasper/src/share/org/apache/jasper/compiler/TagCache.java
jakarta-tomcat-4.0.1/jasper/src/share/org/apache/jasper/compiler/TagCache.java
***
jakarta-tomcat-4.0.1-orig/jasper/src/share/org/apache/jasper/compiler/TagCache.java
Mon Nov 12 18:02:50 2001
--- jakarta-tomcat-4.0.1/jasper/src/share/org/apache/jasper/compiler/TagCache.java
Fri Feb 1 18:32:33 2002
***************
*** 109,114 ****
--- 109,118 ----
return (Class) propertyEditorMaps.get(attrName);
}
+ String setCap(String s) {
+ return "set" + Character.toUpperCase(s.charAt(0)) + s.substring(1);
+ }
+
void setTagHandlerClass(Class tagHandlerClass)
throws JasperException
{
***************
*** 121,129 ****
/*
FIXME: should probably be checking for things like
pageContext, bodyContent, and parent here -akv
- */
if (pd[i].getWriteMethod() != null)
addSetterMethod(pd[i].getName(), pd[i].getWriteMethod());
if (pd[i].getPropertyEditorClass() != null)
addPropertyEditor(pd[i].getName(),
pd[i].getPropertyEditorClass());
}
--- 125,140 ----
/*
FIXME: should probably be checking for things like
pageContext, bodyContent, and parent here -akv
if (pd[i].getWriteMethod() != null)
addSetterMethod(pd[i].getName(), pd[i].getWriteMethod());
+
+ * the right way - check for setters directly, ignore non-setters
+-bnl
+ */
+ try {
+ Method m = tagHandlerClass.getMethod(setCap(pd[i].getName()),
+new Class[] {String.class});
+ addSetterMethod(pd[i].getName(), m);
+ }
+ catch (NoSuchMethodException e) {}
if (pd[i].getPropertyEditorClass() != null)
addPropertyEditor(pd[i].getName(),
pd[i].getPropertyEditorClass());
}
diff -c -r
jakarta-tomcat-4.0.1-orig/jasper/src/share/org/apache/jasper/compiler/TagEndGenerator.java
jakarta-tomcat-4.0.1/jasper/src/share/org/apache/jasper/compiler/TagEndGenerator.java
***
jakarta-tomcat-4.0.1-orig/jasper/src/share/org/apache/jasper/compiler/TagEndGenerator.java
Mon Nov 12 18:02:50 2001
---
jakarta-tomcat-4.0.1/jasper/src/share/org/apache/jasper/compiler/TagEndGenerator.java
Fri Feb 1 18:31:05 2002
***************
*** 167,172 ****
--- 167,173 ----
writer.pushIndent(); writer.println("return;"); writer.popIndent();
writer.popIndent(); // try
+ writer.println("out = pageContext.getOut();"); // doEndTag might have popped
/** FIXME: REMOVE BEGIN */
// writer.println("} catch (Throwable t) {");
diff -c -r
jakarta-tomcat-4.0.1-orig/jasper/src/share/org/apache/jasper/runtime/PageContextImpl.java
jakarta-tomcat-4.0.1/jasper/src/share/org/apache/jasper/runtime/PageContextImpl.java
***
jakarta-tomcat-4.0.1-orig/jasper/src/share/org/apache/jasper/runtime/PageContextImpl.java
Mon Nov 12 18:02:50 2001
---
jakarta-tomcat-4.0.1/jasper/src/share/org/apache/jasper/runtime/PageContextImpl.java
Fri Feb 1 18:09:00 2002
***************
*** 422,427 ****
--- 422,432 ----
return (BodyContent) out;
}
+ public void pushWriter(JspWriter w) {
+ writerStack.push(out);
+ out = w;
+ }
+
public JspWriter popBody() {
out = (JspWriter) writerStack.pop();
return out;
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