"No Inserttagancestor");
// gettemplate stack from insert tag
Stacktemplate_stack = parent.getStack();
//template stack should never be null
if(template_stack == null)
throw new JspException("PutTag: notemplate stack");
// peek at hashtable on the stack
Hashtable params = (Hashtable)template_stack.peek();
// hashtable should never be null either
if(params == null)
throw new JspException("PutTag: no hashtable");
// put a new PageParameter in the hashtable
params.put(name， new PageParameter(content， direct));
return SKIP_BODY; // not interested in tagbody， if present
}
// taghandlers should always implement release() because
// handlers can be reused by the JSP container
public void release() {
name = content = direct = null;
}
// convenience method for finding ancestor names with
// a specific class name
privatetagSupport getAncestor(String className)
throws JspException {
Class klass = null; // can't name variable "class"
try {
klass = Class.forName(className);
}
catch(ClassNotFoundException ex) {
throw new JspException(ex.getMessage());
}
return (TagSupport)findAncestorWithClass(this， klass);
}
}
PutTag.doStarttag建立了一个 PageParameter bean – 在例 3.c中列出——然后存储到请求区域。
例 3.c. PageParameter.java
package beans.templates;
public class PageParameter {
private String content， direct;
public void setContent(String s) {content = s; }
public void setDirect(String s) { direct = s; }
public String getContent() { return content;}
public boolean isDirect() { return Boolean.valueOf(direct).booleanValue(); }
public PageParameter(String content， String direct) {
this.content = content;
this.direct = direct;
}
}
PageParameter将作为简单的占位符使用。我们来看一看例 3.d中的Gettag类和tag handler:
例 3.d. GetTag.java
packagetags.templates;
import java.util.Hashtable;
import java.util.Stack;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
