I wrote the simple tag to handle and show the nested beans. May be it will be
good idea to add this tag to the JSTL standard tags repository?
--
Eugene N Dzhurinsky
/*
* Created on 19.08.2005
* @author Eugene N. Dzhurinsky,
* JDevelop Software
* [EMAIL PROTECTED]
*/
import java.io.IOException;
import java.io.Writer;
import java.lang.reflect.Method;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyTagSupport;
import org.apache.log4j.Logger;
/**
* Tag to make recursive lists from the nested beans
*/
public class RecursiveTag extends BodyTagSupport {
private static Logger log = Logger.getLogger(RecursiveTag.class.getName());
/**
* The name of method, which returns the java.util.List
*/
private String method;
/**
* The root object
*/
private Object object;
/**
* The name of object to store in the JSP page context
*/
private String name;
/**
* The HTML code to place before the item
*/
private String start;
/**
* The HTML code to palce after the item
*/
private String stop;
/**
* Internal stack to keep the bean (required to emulate the recursive behavior)
*/
private LinkedList list;
/**
* The writer used to write out the tag body
*/
private Writer writer;
public RecursiveTag() {
super();
list = new LinkedList();
}
/**
* @param methodName The methodName to set.
*/
public void setMethod(String methodName) {
this.method = methodName;
}
/**
* @param object The object to set.
*/
public void setObject(Object object) {
this.object = object;
}
/**
* @param objectName The objectName to set.
*/
public void setName(String objectName) {
this.name = objectName;
}
/**
* @param start The start to set.
*/
public void setStart(String start) {
this.start = start;
}
/**
* @param stop The stop to set.
*/
public void setStop(String stop) {
this.stop = stop;
}
/**
* The main routine to build recursive list. It takes the current
* iterator from the top of the stack and process the bean referenced by the iterator.
* If the bean contains the list of nested beans, the iterator of this list is pushed
* to the top of the stack, and it will be processed at the next step.
*/
public int doAfterBody() throws JspException {
// if list is empty - do nothing
if (list.isEmpty()) {
log.info("List is empty");
return SKIP_BODY;
}
Iterator it = (Iterator) list.getFirst();
// the sequence of the iterators which don't have
// items to process will be removed from the top of stack
while (!it.hasNext()) {
try {
// we need to print stop item here, to close the current level of recursion
bodyContent.print(stop);
} catch (IOException e1) {
log.error(e1);
}
list.removeFirst();
if (!list.isEmpty())
it = (Iterator) list.getFirst();
else
return SKIP_BODY;
}
Object o = it.next();
pageContext.setAttribute(name, o);
Iterator newIt = getIterator(o);
if (newIt != null)
list.addFirst(newIt);
log.debug("Current size " + list.size());
try {
bodyContent.print(start);
} catch (IOException e) {
log.error(e);
}
return EVAL_BODY_AGAIN;
}
/**
* Printing out the contents of the processed tag body
*/
public int doEndTag() throws JspException {
try {
if (object == null || getMethod(object) == null)
throw new Exception();
if (bodyContent != null) {
writer.write(bodyContent.getString());
bodyContent.clearBody();
}
} catch (Exception e) {
log.error(e, e);
}
return EVAL_PAGE;
}
/**
* The initial (root) object is placed in the JSP page context here
*/
public void doInitBody() throws JspException {
pageContext.setAttribute(name, object);
list.add(getIterator(object));
writer = bodyContent.getEnclosingWriter();
try {
bodyContent.print(start);
} catch (IOException e) {
log.error(e, e);
}
}
/**
* The passed bean is examined to have declared method here
*/
public int doStartTag() throws JspException {
int retval = SKIP_BODY;
try {
log.debug(object);
if (object == null || getMethod(object) == null)
throw new Exception();
retval = EVAL_BODY_BUFFERED;
} catch (Exception e) {
log.error(e);
}
return retval;
}
/**
* Helper method - getting the iterafor of the bean's internal list
*/
private Iterator getIterator(Object obj) {
Iterator it = null;
try {
Method method = getMethod(obj);
List klist = (List) method.invoke(obj, null);
if (klist != null)
it = klist.iterator();
} catch (Exception e) {
log.error(e, e);
}
return it;
}
/**
* Helper method to get the reference to bean method
*/
private Method getMethod(Object obj) throws NoSuchMethodException {
return obj.getClass().getMethod(method, null);
}
}
<?xml version="1.0" encoding="UTF-8" ?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee";
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd";
version="2.0">
<tlibversion>1.1</tlibversion>
<shortname>test</shortname>
<info>
</info>
<tag>
<name>recursive</name>
<tagclass>
RecursiveTag</tagclass>
<body-content>JSP</body-content>
<attribute>
<name>method</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>name</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>object</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>start</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>stop</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
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