import javax.servlet.jsp.tagext.TagSupport;
import beans.templates.PageParameter;
public class GettagextendstagSupport {
private String name;
// setter method for name attribute
public void setName(String name) {
this.name = name;
}
public int doStartTag() throws JspException {
// obtain reference totemplate stack
Stack stack = (Stack)pageContext.get attribute (
"template-stack"， PageContext.REQUEST_SCOPE);
// stack should not be null
if(stack == null)
throw new JspException("GetTag.doStartTag(): " +
"NO STACK");
// peek at hashtable
Hashtable params = (Hashtable)stack.peek();
// hashtable should not be null
if(params == null)
throw new JspException("GetTag.doStartTag(): " +
"NO HASHTABLE");
// get page parameter from hashtable
PageParameter param = (PageParameter)params.get(name);
if(param != null) {
String content = param.getContent();
if(param.isDirect()) {
// print content if direct attribute is true
try {
pageContext.getOut().print(content);
}
catch(java.io.IOException ex) {
throw new JspException(ex.getMessage());
}
}
else {
// include content if direct attribute is false
try {
pageContext.getOut().flush();
pageContext.include(content);
}
catch(Exception ex) {
throw new JspException(ex.getMessage());
}
}
}
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 = null;
}
}
GetTag.doStartTag从请求区域返回了页面参数bean并从bean中获得了content和direct 属性。然后，内容可以根据direct属性值选择是被包含还是显示。
结论
模板是一种简单而有非常有用的概念。模板的封装布局能够对布局改变的影响达到最小化。而且模板能够根据用户的不同来区分不同的内容，它还能够嵌套到其他的模板和JSP页面中。
