listtag.java

OA典型例子

/*
 * $Id: ListTag.java,v 1.4 2001/10/26 22:55:55 ro89390 Exp $
 * Copyright 2000 Sun Microsystems, Inc. All rights reserved.
 * Copyright 2000 Sun Microsystems, Inc. Tous droits r?erv?.
 */

package com.sure.taglibs.list;

import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.tagext.BodyTagSupport;
import javax.servlet.jsp.tagext.BodyContent;

import java.io.IOException;
import java.util.Iterator;
import java.util.Collection;

import com.sure.util.tracer.Debug;


/**
 *
 * This class allows you to retrieve a parameter from the request and output it to the page
 * This should allow you to avoid expressions for extracting parameter info.
 *
 */

public class ListTag extends BodyTagSupport {

    private Iterator iterator;
    private int startIndex = -1;
    private int index;
    private int size;
    private String collectionId;
    private String scope;
    private Object currentItem = null;

    public ListTag() {
	super();
    }

    public void setCollectionId(String collectionId){
	this.collectionId = collectionId;
    }

    public void setScope(String scope) {
	this.scope = scope.toLowerCase();
    }

    public void setStartIndex(int startIndex) {
	this.startIndex = startIndex;
    }

    public void setSize(int size) {
	this.size = size;
    }

    public int doStartTag() throws JspTagException {
	Object targetObject = null;
	Collection collection = null;
	if (scope.equals("request")) {
	    targetObject = pageContext.getRequest().getAttribute(collectionId);
	} else if (scope.equals("session")) {
	    targetObject = pageContext.getSession().getAttribute(collectionId);
	} else if (scope.equals("page")) {
	    targetObject = pageContext.getAttribute(collectionId);
	}
	if (targetObject == null) {
	   throw new JspTagException("ListTag: Collection " + collectionId + " not found in " + scope + " scope.");
	} else if (targetObject instanceof java.util.Collection) {
	    collection = (Collection)targetObject;
	} else {
	   throw new JspTagException("ListTag: Iterator " + collectionId + " is not an instance of java.util.Collection.");
	}
	iterator = collection.iterator();
	if (!iterator.hasNext()) return(SKIP_BODY);
	currentItem = iterator.next();
	return(EVAL_BODY_BUFFERED);
    }

  // process the body again until the specified length with the next item if it exists
  public int doAfterBody() {
    if (iterator.hasNext()) {
      currentItem = iterator.next();
      return(EVAL_BODY_BUFFERED);
    } else return(SKIP_BODY);
  }

    /**
     *
     * Meant for use by ListItem tags
     *
     */

    public Object getCurrentItem() {
	return currentItem;
    }

    public int doEndTag() throws JspTagException {
	try {
	    BodyContent body = getBodyContent();
	    if (body != null) {
		JspWriter out = body.getEnclosingWriter();
		out.print(body.getString());
	    }
	} catch(IOException ioe) {
	    System.err.println("Error handling items tag: " + ioe);
	}
	return EVAL_PAGE;
    }
}