JSP自定义标签之封装UI组件

1、定义tld文件

2、标签实现

/**
 * Description: 下拉框选择标签
 * Created by Hoscen on 2019/5/20 20:37 with IntelliJ IDEA.
 */
public class SelectTag extends BodyTagSupport {

    private String id;
    private String clasz;
    private String name;
    private String title;

    ... 此处省略一些属性以及set、get方法


    @Override
    public int doStartTag() throws JspException {
        HttpServletRequest request = (HttpServletRequest) this.pageContext.getRequest();
        request.setAttribute("tag", this);
        try {
            startTag(request);
        } catch (Exception e) {
            LOGGER.error("SelectTag exception",e);
        }
        return EVAL_BODY_INCLUDE;
    }

    @Override
    public int doEndTag() throws JspException {
        HttpServletRequest request = (HttpServletRequest) this.pageContext.getRequest();
        try {
            endTag(request);
        } catch (Exception e) {
            LOGGER.error("SelectTag excepion",e);
        }
        return EVAL_PAGE;
    }

    private void startTag(HttpServletRequest request) throws Exception {
        JspWriter out = this.pageContext.getOut();
        SelectTag tag = (SelectTag) request.getAttribute("tag");
        out.write("xxx");   // 后台拼接html输出
        .... // 此处省略
    }

    private void endTag(HttpServletRequest request) throws Exception {
        JspWriter out = this.pageContext.getOut();
        out.write("xxx");
        .... // 此处省略
    }

}

3、web.xml配置jsp-config

4、在jsp中应用

5、效果

6、总结

通过自定义标签我们可以将常用的UI组件做一个封装，好处如下：

1）使用简单清爽，只需一行代码；

2）所有页面统一使用，后期修改组件只需要修改标签体