/* * To change this license header, choose License Headers in Project Properties. * To change this template file, choose Tools | Templates * and open the template in the editor. */ package le; import javax.servlet.jsp.tagext.*; import javax.servlet.jsp.*; import java.io.*; import java.sql.*; /** * * @author Administrator */ public class QueryTag extends SimpleTagSupport { // 定义成员变量来代表标签的属性 private String driver; private String url; private String user; private String pass; private String sql; // driver的setter和getter方法 public void setDriver(String driver) { this.driver = driver; } public String getDriver() { return this.driver; } // url的setter和getter方法 public void setUrl(String url) { this.url = url; } public String getUrl() { return this.url; } // user的setter和getter方法 public void setUser(String user) { this.user = user; } public String getUser() { return this.user; } // pass的setter和getter方法 public void setPass(String pass) { this.pass = pass; } public String getPass() { return this.pass; } // sql的setter和getter方法 public void setSql(String sql) { this.sql = sql; } public String getSql() { return this.sql; } // conn的setter和getter方法 public void setConn(Connection conn) { this.conn = conn; } public Connection getConn() { return this.conn; } // stmt的setter和getter方法 public void setStmt(Statement stmt) { this.stmt = stmt; } public Statement getStmt() { return this.stmt; } // rs的setter和getter方法 public void setRs(ResultSet rs) { this.rs = rs; } public ResultSet getRs() { return this.rs; } // rsmd的setter和getter方法 public void setRsmd(ResultSetMetaData rsmd) { this.rsmd = rsmd; } public ResultSetMetaData getRsmd() { return this.rsmd; } // 执行数据库访问的对象 private Connection conn = null; private Statement stmt = null; private ResultSet rs = null; private ResultSetMetaData rsmd = null; public void doTag() throws JspException, IOException { try { // 注册驱动 Class.forName(driver); // 获取数据库连接 conn = DriverManager.getConnection(url, user, pass); // 创建Statement对象 stmt = conn.createStatement(); // 执行查询 rs = stmt.executeQuery(sql); rsmd = rs.getMetaData(); // 获取列数目 int columnCount = rsmd.getColumnCount(); // 获取页面输出流 Writer out = getJspContext().getOut(); // 在页面输出表格 out.write("<table border='1' bgColor='#9999cc' width='400'>"); // 遍历结果集 while (rs.next()) { out.write("<tr>"); // 逐列输出查询到的数据 for (int i = 1; i <= columnCount; i++) { out.write("<td>"); out.write(rs.getString(i)); out.write("</td>"); } out.write("</tr>"); } } catch (ClassNotFoundException cnfe) { cnfe.printStackTrace(); throw new JspException("自定义标签错误" + cnfe.getMessage()); } catch (SQLException ex) { ex.printStackTrace(); throw new JspException("自定义标签错误" + ex.getMessage()); } finally { // 关闭结果集 try { if (rs != null) { rs.close(); } if (stmt != null) { stmt.close(); } if (conn != null) { conn.close(); } } catch (SQLException sqle) { sqle.printStackTrace(); } } } }
<?xml version="1.0" encoding="UTF-8"?> <taglib version="2.1" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"> <tlib-version>1.0</tlib-version> <short-name>mytaglib</short-name> <uri>/WEB-INF/tlds/mytaglib</uri> <!-- A validator verifies that the tags are used correctly at JSP translation time. Validator entries look like this: <validator> <validator-class>com.mycompany.TagLibValidator</validator-class> <init-param> <param-name>parameter</param-name> <param-value>value</param-value> </init-param> </validator> --> <!-- A tag library can register Servlet Context event listeners in case it needs to react to such events. Listener entries look like this: <listener> <listener-class>com.mycompany.TagLibListener</listener-class> </listener> --> <!-- 定义第一个标签 --> <tag> <!-- 定义标签名 --> <name>helloWorld</name> <!-- 定义标签处理类 --> <tag-class>le.HelloWorldTag</tag-class> <!-- 定义标签体为空 --> <body-content>empty</body-content> </tag> <!-- 定义第二个标签 --> <tag> <!-- 定义标签名 --> <name>query</name> <!-- 定义标签处理类 --> <tag-class>le.QueryTag</tag-class> <!-- 定义标签体为空 --> <body-content>empty</body-content> <!-- 配置标签属性:driver --> <attribute> <name>driver</name> <required>true</required> <fragment>true</fragment> </attribute> <!-- 配置标签属性:url --> <attribute> <name>url</name> <required>true</required> <fragment>true</fragment> </attribute> <!-- 配置标签属性:user --> <attribute> <name>user</name> <required>true</required> <fragment>true</fragment> </attribute> <!-- 配置标签属性:pass --> <attribute> <name>pass</name> <required>true</required> <fragment>true</fragment> </attribute> <!-- 配置标签属性:sql --> <attribute> <name>sql</name> <required>true</required> <fragment>true</fragment> </attribute> </tag> <!-- 定义第三个标签 --> <tag> <!-- 定义标签名 --> <name>iterator</name> <!-- 定义标签处理类 --> <tag-class>le.IteratorTag</tag-class> <!-- 定义标签体不允许出现JSP脚本 --> <body-content>scriptless</body-content> <!-- 配置标签属性:collection --> <attribute> <name>collection</name> <required>true</required> <fragment>true</fragment> </attribute> <!-- 配置标签属性:item --> <attribute> <name>item</name> <required>true</required> <fragment>true</fragment> </attribute> </tag> <tag> <!-- 定义标签名 --> <name>fragment</name> <!-- 定义标签处理类 --> <tag-class>le.FragmentTag</tag-class> <!-- 指定该标签不支持标签体 --> <body-content>empty</body-content> <!-- 定义标签属性：fragment --> <attribute> <name>fragment</name> <required>true</required> <fragment>true</fragment> </attribute> </tag> <!-- 定义接受动态属性的标签 --> <tag> <name>dynaAttr</name> <tag-class>le.DynaAttributesTag</tag-class> <body-content>empty</body-content> <!-- 指定支持动态属性 --> <dynamic-attributes>true</dynamic-attributes> </tag> </taglib>
<%-- Document : queryTag Created on : 2020-5-4, 21:40:23 Author : Administrator --%> <%@ page contentType="text/html; charset=GBK" language="java" errorPage="" %> <!-- 导入标签库，指定mytag前缀的标签， 由http://www.crazyit.org/mytaglib的标签库处理 --> <%@ taglib uri="/WEB-INF/tlds/mytaglib" prefix="mytag"%> <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>自定义标签示范</title> <meta name="website" content="http://www.crazyit.org" /> </head> <body bgcolor="#ffffc0"> <h2>下面显示的是查询标签的结果</h2> <!-- 使用标签 ，其中mytag是标签前缀，根据taglib的编译指令， mytag前缀将由http://www.crazyit.org/mytaglib的标签库处理 --> <mytag:query driver="com.mysql.cj.jdbc.Driver" url="jdbc:mysql://localhost:3306/taobao" user="root" pass="admin" sql="select * from person"/><br/> </body> </html>
