JSP自己定义标签入门实例具体解释

Posted 2020-09-28 jzdwajue

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JSP自己定义标签主要能用到的两个包

javax.servlet.jsp.*;javax.servlet.jsp.tagext.*;

自己定义标签<userInfo:showUserInfo/>实现对用户的展现。

效果图例如以下

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定义用户累User.java get set就不在赘述。

private String userName;
private Integer age;
private String email;

public User(){
this.userName="张三";
this.email="[email protected]";
this.age=28;
}

创建自己定义标签类UserInfoTag.java

package com.test.tag;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;

import com.test.entity.User;

public class UserInfoTag extends TagSupport {

private User user=new User();

@Override
public int doStartTag() throws JspException {
// TODO Auto-generated method stub

JspWriter out = this.pageContext.getOut();
try {
if (user == null) {
out.print("UserInfo Is Not Found......");
return SKIP_BODY;
}
out.println("<table width=‘500px‘ border=‘1‘ align=‘center‘>");
out.println("<tr>");
out.println("<td width=‘20%‘>Username:</td>");
out.println("<td>" + user.getUserName() + "</td>");
out.println("</tr>");
out.println("<tr>");
out.println("<td>Age:</td>");
out.println("<td>" + user.getAge() + "</td>");
out.println("</tr>");
out.println("<tr>");
out.println("<td>Email:</td>");
out.println("<td>" + user.getEmail() + "</td>");
out.println("</tr>");
out.println("</table>");
} catch (Exception e) {
throw new JspException(e.getMessage());
}
return super.doStartTag();
}

@Override
public int doEndTag() throws JspException {
// TODO Auto-generated method stub
return EVAL_PAGE;
}

@Override
public void release() {
// TODO Auto-generated method stub
super.release();
this.user=null;
}

public User getUser() {
return user;
}

public void setUser(User user) {
this.user = user;
}

}

2在Web-Inf创建标签库描写叙述文件.tdl(Tag Library Description)

xml version="1.0" encoding="UTF-8"?>
<taglib version="2.0" xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee web-jsptaglibrary_2_0.xsd">
<tlib-version>1.0</tlib-version>
<jsp-version>3.0</jsp-version>
<short-name>userInfo</short-name>
<uri>mytaglib</uri>
<tag>
<name>showUserInfo</name>
<tag-class>com.test.tag.UserInfoTag</tag-class>
<body-content>empty</body-content>
<attribute>
<name>user</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>