自定义JSP标签入门

1、编写一个实现Tag接口的java类

package TagDemo;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.Tag;
import java.io.IOException;

public class ViewIPTag implements Tag {

    private PageContext pageContext;

    @Override
    public void setPageContext(PageContext pageContext) {
        this.pageContext = pageContext;
    }

    @Override
    public void setParent(Tag tag) {

    }

    @Override
    public Tag getParent() {
        return null;
    }

    @Override
    public int doStartTag() throws JspException {
        System.out.println("调用doStartTag方法");
        HttpServletRequest request= (HttpServletRequest) pageContext.getRequest();
        JspWriter writer=pageContext.getOut();
        String ip=request.getRemoteAddr();
        try {
            writer.write(ip);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return 0;
    }

    @Override
    public int doEndTag() throws JspException {
        System.out.println("调用doEndTag方法");
        return 0;
    }

    @Override
    public void release() {
        System.out.println("调用release方法");
    }
}

ViewIPTag