JSP自定义标签——调用数据库（通过id号搜索相关信息）

一、创建新表(假设在master数据库下新建)

二、连接数据库

开始-->控制面板-->管理工具-->数据源-->系统DSN-->添加-->SQL Server-->名称：userdb-->服务器：(local)\SQLEXPRESS或选择本机名-->下一步-->下一步-->打钩-更改默认的数据库为:master-->下一步-->完成

三、DefinedTagData项目

1、新建Java类：User

package sample.model;
public class User {
    private int id;
    private String name;
    private String phone;
    public void setId(int id){this.id=id;}//setId中的d必须小写
    public void setName(String name){this.name=name;}
    public void setPhone(String phone){this.phone=phone;}
    public int getID(){return id;}
    public String getName(){return name;}
    public String getPhone(){return phone;}
}

2、新建Java类：UserDAO

package sample.model;

import java.sql.*;
public class UserDAO {
    private ResultSet rst;
    private Connection conn;
    private void open()throws Exception{
        String driver="sun.jdbc.odbc.JdbcOdbcDriver";
        String url= "jdbc:odbc:userdb";//test--定义的数据库的名称
        Class.forName(driver);
        conn=DriverManager.getConnection(url);
    }
    private void close()throws SQLException{
        if(rst!=null) rst.close();
        if(conn!=null) conn.close();
    }
    public void save(User user)throws Exception{
        String sql="";
        open();
        Statement stmt=conn.createStatement();
        rst=stmt.executeQuery(sql);
        close();
    }
    public void load(User user)throws Exception{
        String sql="use master    select name,phone from dbo.usera"+" where id = "+user.getID();
        open();
        Statement stmt=conn.createStatement();
        rst=stmt.executeQuery(sql);
        if(rst.next()){
            user.setName(rst.getString(1));
            user.setPhone(rst.getString(2));
        }
        close();
    }
}

3、创建TLD文件
　　新建文件--> Web--> 标记库描述符

　　TLD名称：Data　　前缀：data

4、创建标记处理程序

　　新建文件--> Web-->标记处理程序

　　类名：DataTag　　包：sample.tag　　要扩展的标记支持类：SimpleTagSupport

　　TLD文件：WEB-INF--> tlds--> Data　　新建属性：color和id

package sample.tag;

import javax.servlet.jsp.tagext.*;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.JspException;
import sample.model.*;

public class DataTag extends TagSupport {
    private String id;//添加的属性
    public void setId(String id) {
        this.id = id;
    }
    private String color;//添加的属性
    public void setColor(String color) {
        this.color = color;
    }
    public int doStartTag(){
        User user=new User();
        user.setId(Integer.parseInt(id));
        UserDAO dao=new UserDAO();
        try{
             dao.load(user);
             JspWriter out=pageContext.getOut();
             String html="<br><b style=\"color:"+color+"\">Welcome to Employee Detail Table.</b><br>";
             html+=" <table border=\"1\"><tr><th>员工ID</th><th>员工姓名</th><th>联系电话</th></tr>";
             html+="<tr><td>"+user.getID()+"</td><td>"+user.getName()+"</td><td>"+user.getPhone()+"</td></tr></table>";
             out.println(html);
        }catch(Exception e){
             System.out.println(e.getMessage());
        }
        return SKIP_BODY;
    }

    public int doEndTag() throws JspException{
        return EVAL_PAGE;
    }
}

PS:Data.tld内容

<?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>
  <short-name>data</short-name>
  <uri>/WEB-INF/tlds/Data</uri>

  <tag>
    <name>DataTag</name>
    <tag-class>sample.tag.DataTag</tag-class>
    <body-content>empty</body-content>
    <attribute>
      <name>id</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
      <type>java.lang.String</type>
    </attribute>
    <attribute>
      <name>color</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
      <type>java.lang.String</type>
    </attribute>
  </tag>
  <tag>
    <name>DataTable</name>
    <tag-class>sample.tag.DataTable</tag-class>
    <body-content>JSP</body-content>
    <attribute>
      <name>id</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
      <type>int</type>
    </attribute>
    <attribute>
      <name>color</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
      <type>java.lang.String</type>
    </attribute>
  </tag>
</taglib>

5、index.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>

<%@ taglib uri="/WEB-INF/tlds/Data" prefix="data"%>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>JSP Page</title>
    </head>
    <body>
        <data:DataTag  id="1" color="blue"/>
    </body>
</html>

6、显示结果