JSP自定义标签的实现过程

1、编写标签处理类HelloTag（实现javax.servlet.jsp.tagext.Tag类）

package cn.itcast.tag;
import java.io.IOException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.Tag;
public class HelloTag implements Tag {
    private PageContext pageContext;
    private Tag tag;
   
    public int doEndTag() throws JspException {
        try {
            pageContext.getOut().print(\"hello world!\");
        } catch (IOException e) {
            e.printStackTrace();
        }
        return Tag.EVAL_PAGE;
    }
    public int doStartTag() throws JspException {
        return Tag.SKIP_BODY;
    }
    public Tag getParent() {
        return null;
    }
    public void release() {
    }
    public void setPageContext(PageContext arg0) {
        this.pageContext = arg0;
    }
    public void setParent(Tag arg0) {
        this.tag = arg0;
    }
}