JSP自定义标签实例---从数据库读取数据放在下拉列表中
JSP自定义标签实例---从数据库读取数据放在下拉列表中
Myselect.java
package com.xiefei.mytag;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.tagext.BodyTagSupport;
import com.xiefei.db.DBConn;
import com.xiefei.vo.Users;
public class MySelect extends BodyTagSupport {
@Override
public void setBodyContent(BodyContent b) {
super.setBodyContent(b);
}
@Override
public int doStartTag() throws JspException {
try {
List
list = getUserList();
JspWriter out = pageContext.getOut();
out.print(" "+list.get(i).getName()); out.print("");
} catch (IOException e) {
System.out.println("发生错误!");
e.printStackTrace();
}
return SKIP_BODY;
}
@Override
public int doEndTag() throws JspException {
return EVAL_PAGE;
}
/**
* 返回用户列表
*
* @return
*/
public List
getUserList() {
List
list = new ArrayList();
DBConn dbconn = new DBConn();
Connection conn = dbconn.getConnection();
String mysql = "select name from users";
PreparedStatement statement = null;
ResultSet rs = null;
try {
statement = conn.prepareStatement(mysql);
rs = statement.executeQuery();
while (rs.next()) {
Users user = new Users();
user.setName(rs.getString(1));
list.add(user);
}
} catch (SQLException e) {
e.printStackTrace();
return null;
} finally {
try {
rs.close();
statement.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
return list;
}
}
DBconn.java
package com.xiefei.db;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class DBConn {
static{
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
/**
* 得到数据库连接
* @return 一个数据库连接
*/
public Connection getConnection(){
Connection conn=null;
try{
conn=DriverManager.getConnection("jdbc:mysql://localhost/userinformation","root","123");
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}
}
Users.java
package com.xiefei.vo;
public class Users {
private int id;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
myselect.tld
<?xml version="1.0" encoding="GBK" ?>
<!DOCTYPE taglib
PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
"http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
<!-- 描述 -->
<taglib>
<tlib-version>1.0</tlib-version>
<jsp-version>1.2</jsp-version>
<short-name>myselect</short-name>
<tag>
<name>myselect</name>
<tag-class>com.xiefei.mytag.MySelect</tag-class>
<body-content>jsp</body-content>
</tag>
</taglib>
index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="gb2312"%>
<%@ taglib uri="WEB-INF/myselect.tld" prefix="m"%>
<%
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>
<base href="<%=basePath%>">
<title>My JSP 'index.jsp' starting page</title>
</head>
<body>
<m:myselect/>
</body>
</html>
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