一，tag类
1.1 TagMy标签类，格式化当前日期并输出
package com.dkt.tag;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;
/*
* doStartTag() SKIP_BODY执行doEndTag()跳过标签体
* EVAL_BODY_INCLUDE 执行标签体
* doAfterBody() EVAL_BODY_AGAIN 循环执行标签体
* SKIP_BODY 不执行标签体，执行doEndTag()
* doEndTag() SKIP_PAGE 不执行jsp剩余的页面
* EVAL_PAGE 执行剩余的页面
*
*/
public class TagMy extends TagSupport{
private String format;
public int doStartTag() {
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(format);
String nowdate = simpleDateFormat.format(new Date());
JspWriter out = pageContext.getOut();
try {
out.print("Hello 世界！！");
out.print(nowdate);
} catch (IOException e) {
e.printStackTrace();
}
return super.SKIP_BODY;
}
public int doAfterBody() throws JspException {
return super.doAfterBody();
}
public int doEndTag() throws JspException {
return super.doEndTag();
}
public String getFormat() {
return format;
}
public void setFormat(String format) {
this.format = format;
}
}
1.2 ForTag 标签类，自定义<c:foreach>标签，循环输出
package com.dkt.tag;
import javax.servlet.jsp.tagext.TagSupport;
public class FroTag extends TagSupport{
private int start;
private int end;
private String var;
public int doStartTag(){
System.out.println("doStartTag()"+start);
if(start<=end){
pageContext.setAttribute(var, start);
start++;
return super.EVAL_BODY_INCLUDE;
}else {
return super.SKIP_BODY;
}
//执行doAfterBody()
}
public int doAfterBody() {
if(start<=end){
pageContext.setAttribute(var, start);
start++;
System.out.println("doAfterBody()"+start);
return super.EVAL_BODY_AGAIN;
}else {
return super.SKIP_BODY;
}
}
public int doEndTag(){
System.out.println("doEndTag()"+start);
return super.EVAL_PAGE;
}
public int getStart() {
return start;
}
public void setStart(int start) {
this.start = start;
}
public int getEnd() {
return end;
}
public void setEnd(int end) {
this.end = end;
}
public String getVar() {
return var;
}
public void setVar(String var) {
this.var = var;
}
}
1.3 IteratorTag标签类，迭代集合，全部循环输出显示在页面
package com.dkt.tag;
import java.util.ArrayList;
import java.util.Iterator;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class IteratorTag extends TagSupport{
private String scope;
private String var;
private ArrayList list = null;
Iterator it = null;
public int doStartTag() {
/*if (("page").equals(scope)) {
list = (ArrayList)pageContext.getAttribute(list,pageContext.PAGE_SCOPE);
}else if(("request").equals(scope)){
list = (ArrayList)pageContext.getAttribute(list,pageContext.REQUEST_SCOPE);
}else if(("session").equals(scope)){
list = (ArrayList)pageContext.getAttribute(list,pageContext.SESSION_SCOPE);
}else if(("application").equals(scope)){
list = (ArrayList)pageContext.getAttribute(list,pageContext.APPLICATION_SCOPE);
}*/
it = list.iterator();
return super.EVAL_BODY_INCLUDE;
}
public int doAfterBody() {
if (it.hasNext()) {
Object next = it.next();
pageContext.setAttribute(var, next);
return super.EVAL_BODY_AGAIN;
}else {
return super.SKIP_BODY;
}
}
public int doEndTag() throws JspException {
return super.doEndTag();
}
public String getScope() {
return scope;
}
public void setScope(String scope) {
this.scope = scope;
}
public String getVar() {
return var;
}
public void setVar(String var) {
this.var = var;
}
public ArrayList getList() {
return list;
}
public void setList(ArrayList list) {
this.list = list;
}
}
1.4 QueryTag 标签类，根据表名，查询数据库，并由表格输出到页面
package com.dkt.tag;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;
import com.dkt.util.DButil;
public class QueryTag extends TagSupport{
private String tableName;
public int doStartTag() {
DButil dButil = new DButil();
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
conn = dButil.createConn();
String sql = "select * from "+tableName;
try {
ps = conn.prepareStatement(sql);
ResultSetMetaData rsmd = ps.getMetaData();//得到表结构
rs = ps.executeQuery();
JspWriter out = pageContext.getOut();
out.print("<table border='1px' width='60%' align='center'><tr>");
for (int i = 0; i < rsmd.getColumnCount(); i++) {//字段数量
out.print("<th>"+rsmd.getColumnName(i+1)+"</th>");//字段名字
}
out.print("</tr>");
while(rs.next()){
out.print("<tr>");
for (int i = 0; i < rsmd.getColumnCount(); i++) {
out.print("<td>"+rs.getObject(i+1)+"</td>");
}
out.print("</tr>");
}
out.print("</table>");
} catch (SQLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return super.SKIP_BODY;
}
public int doAfterBody() throws JspException {
return super.doAfterBody();
}
public int doEndTag() throws JspException {
return super.doEndTag();
}
public String getTableName() {
return tableName;
}
public void setTableName(String tableName) {
this.tableName = tableName;
}
}
二，hellotag.tld
文件 hellotag.tld 放在WEB-INF目录下，与web.xml同级
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
"http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
<taglib>
<tlib-version>1.0</tlib-version>
<jsp-version>1.2</jsp-version>
<short-name>hello</short-name>
<uri>hello</uri>
<!-- TagMy自定义标签类 -->
<tag>
<name>hello</name> <!-- 标签名 -->
<tag-class>com.dkt.tag.TagMy</tag-class>
<body-content>empty</body-content> <!-- 是否有标签体 jsp/empty -->
<!-- 有属性的标签定义 -->
<attribute>
<name>format</name>
<required>true</required><!-- 表示标签是否必须 -->
<rtexprvalue>true</rtexprvalue><!-- 表示是否可以使用表达式 el/jsp -->
</attribute>
</tag>
<!-- FroTag -->
<tag>
<name>formy</name>
<tag-class>com.dkt.tag.FroTag</tag-class>
<body-content>jsp</body-content>
<attribute>
<name>start</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>end</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>var</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
<!-- IteraterTag -->
<tag>
<name>iteratormy</name>
<tag-class>com.dkt.tag.IteratorTag</tag-class>
<body-content>jsp</body-content>
<attribute>
<name>list</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>scope</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>var</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
<!-- 查询数据库的表并输出 -->
<tag>
<name>query</name>
<tag-class>com.dkt.tag.QueryTag</tag-class>
<body-content>empty</body-content>
<attribute>
<name>tableName</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
三，jsp
index.jsp 开启服务器，直接访问项目下的index.jsp页面即可显示自定义标签
在jsp页面导入自定义标签
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@page import="com.dkt.entity.UserInfo"%>
<%@ taglib uri="hello" prefix="hello" %>
<%
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>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<hello:hello format="yyyy-MM-dd HH:mm:ss a"/><br/>
<hr/>
formy:<hello:formy end="10" var="item1" start="1">
${item1 }----
</hello:formy>
<hr/>
iterator：<%
ArrayList list = new ArrayList();
list.add(new UserInfo(0,"小白","123456","",""));
list.add(new UserInfo(1,"小白111","353456","",""));
list.add(new UserInfo(2,"小白222","532456","",""));
list.add(new UserInfo(3,"小白333","532356","",""));
list.add(new UserInfo(4,"小白444","123536","",""));
request.setAttribute("list",list);
%>
<hello:iteratormy var="item2" scope="request" list="${list}">
${item2.name}+++${item2.password }<br/>
</hello:iteratormy>
<hr/>
<hello:query tableName="goods_table2"/>
<hr>
</body>
</html>
四，web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" 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-app_2_5.xsd"> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>