valuetag.java

一个javaweb开的小例子

package cn.com.pkusoft.tag;

import java.io.IOException;
import java.util.Collection;
import java.util.Map;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyTagSupport;
import javax.servlet.jsp.tagext.Tag;

/**
 * <p>Title: </p>
 * <p>Description: </p>
 * <p>Copyright: Copyright (c) 2003</p>
 * <p>Company: pku-soft</p>
 * @author weiming
 * @version 1.0
 */

public class ValueTag
    extends BodyTagSupport
{
    private String name = null;
    private String source = null;
    private String filter = null;

    public ValueTag()
    {
    }

    public void setName(String name)
    {
        this.name = name;
    }

    public void setSource(String source)
    {
        this.source = source;
    }

    public Tag getParent()
    {
        /**@todo Implement this javax.servlet.jsp.tagext.Tag abstract method*/
        throw new java.lang.UnsupportedOperationException(
            "Method getParent() not yet implemented.");
    }

    public int doStartTag() throws JspException
    {
        return 0;
    }

    public int doEndTag() throws JspException
    {
        String bodyValue = "";

        try
        {
            if (this.source != null)
            {
                Object contains = pageContext.getSession().getAttribute(this.
                    source);

                if (contains instanceof Map)
                {
                    Map containMap = (Map) contains;
                    Object bodyObject = containMap.get(this.name);
                    if (bodyObject == null)
                    {
                        bodyValue = "";
                    }
                    else
                    {
                        bodyValue = (String) bodyObject;
                    }
                }
                else if (contains instanceof Collection)
                {
                    System.out.println("this not a Map!");
                }

                if (this.filter != null && this.filter.equals("true"))
                {
                    bodyValue = this.filter(bodyValue);
                }

                pageContext.getOut().write(bodyValue);
            }
        }
        catch (IOException ex)
        {
            throw new JspException(ex.getMessage());
        }

        return EVAL_PAGE;
    }

    private String filter(String strSrc)
    {
        StringBuffer buff = new StringBuffer(strSrc.length());

        int length = strSrc.length();

        for (int i = 0; i < length; i++)
        {
            char ch = strSrc.charAt(i);

            switch (ch)
            {
                case '<':
                    buff.append("&lt;");
                    break;
                case '>':
                    buff.append("&gt;");
                    break;
                case '&':
                    buff.append("&amp;");
                    break;
                default:
                    buff.append(ch);
            }
        }

        return buff.toString();
    }

    public void setFilter(String filter)
    {
        this.filter = filter;
    }

}