jsp自定义标签
jsp自定义标签的用途非常重要，其开发业很简单，具体的开发步骤简介为：
1，创建标签处理类，该类应该继承 javax.servlet.jsp.tagext.SimpleTagSupport类
2，创建标签的说明xml文件 tld文件，该文件需要放到WEB-INF下面
3，在页面上引入标签包，使用标签。
实例：创建一个jsp标签，该标签接收5个属性值，查询数据库的值显示在页面上
1，创建标签处理类
2，创建标签说明的xml文件 my-taglib.xml,注意该文件必须放在WEB-INF下面
3，页面引用标签及使用标签
1，创建标签处理类，该类应该继承 javax.servlet.jsp.tagext.SimpleTagSupport类
2，创建标签的说明xml文件 tld文件，该文件需要放到WEB-INF下面
3，在页面上引入标签包，使用标签。
实例：创建一个jsp标签，该标签接收5个属性值，查询数据库的值显示在页面上
1，创建标签处理类
package com.supan.tag;
import java.io.IOException;
import java.io.Writer;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.SimpleTagSupport;
public class QueryTag extends SimpleTagSupport {
private String driver;
private String url;
private String user;
private String pass;
private String sql;
private Connection conn = null;
private Statement stmt = null;
private ResultSet rs = null;
private ResultSetMetaData rsmd = null;
public String getDriver() {
return driver;
}
public void setDriver(String driver) {
this.driver = driver;
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public String getUser() {
return user;
}
public void setUser(String user) {
this.user = user;
}
public String getPass() {
return pass;
}
public void setPass(String pass) {
this.pass = pass;
}
public String getSql() {
return sql;
}
public void setSql(String sql) {
this.sql = sql;
}
@Override
public void doTag() throws JspException, IOException {
try {
Class.forName(driver);
conn = DriverManager.getConnection(url,user,pass);
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
rsmd = rs.getMetaData();
int columnCount = rsmd.getColumnCount();
Writer out = getJspContext().getOut();
out.write("<table border='1' bgColor='#9999cc' width='400px'>");
while(rs.next()){
out.write("<tr>");
for(int i = 1; i <= columnCount; i++){
out.write("<td>");
out.write(rs.getString(i));
out.write("</td>");
}
out.write("</tr>");
}
} catch (Exception e) {
e.printStackTrace();
}finally{
try {
if(rs != null){
rs.close();
}
if(stmt != null){
stmt.close();
}
if(conn != null){
conn.close();
}
} catch (Exception e2) {
e2.printStackTrace();
}
}
}
}
2，创建标签说明的xml文件 my-taglib.xml,注意该文件必须放在WEB-INF下面
<?xml version="1.0" encoding="UTF-8" ?>
<taglib 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 http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
version="2.0">
<description>A tag library exercising SimpleTag handlers.</description>
<tlib-version>1.0</tlib-version>
<short-name>mytaglib</short-name>
<uri>/mytaglib</uri>
<!-- 定义标签 -->
<tag>
<name>query</name>
<tag-class>com.supan.tag.QueryTag</tag-class>
<body-content>empty</body-content>
<attribute>
<name>driver</name>
<required>true</required>
<fragment>true</fragment>
</attribute>
<attribute>
<name>url</name>
<required>true</required>
<fragment>true</fragment>
</attribute>
<attribute>
<name>user</name>
<required>true</required>
<fragment>true</fragment>
</attribute>
<attribute>
<name>pass</name>
<required>true</required>
<fragment>true</fragment>
</attribute>
<attribute>
<name>sql</name>
<required>true</required>
<fragment>true</fragment>
</attribute>
</tag>
</taglib>
3，页面引用标签及使用标签
<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
<%@ taglib prefix="my" uri="/mytaglib" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
</head>
<body>
<my:query user="emg" url="jdbc:oracle:thin:@127.0.0.1:1521:ORCL" pass="root" driver="oracle.jdbc.driver.OracleDriver" sql="select * from department"/>
</body>
</html>