jsp技术已经是一项很老的技术了，该技术也十分成熟，下面我将对jsp中的自定义标签技术进行一下探讨，并附上本人利用该技术实现的一个分页标签。自定义标签技术的出现也是为了让jsp页面尽量不写java代码，使得数据的显示和业务逻辑相分离，使代码的可读性和维护性更好。
jsp技术流行至今，也是每个java程序员再熟悉不过了，发布本人实现的一个分页标签和大家一起交流，有不足之处，你可以进行修改，但希望你能把修改后的代码贴出来，我将感激不尽！
首先来看一下运行后的效果：
该分页标签由3个标签组成，分别是<d:iterator>,<d:field>,<d:page>
<d:iterator>用于数据的迭代，<d:field>用于输出每一条数据，<d:page>用于数据的分页
下面是每个标签对应的源代码：
1.IteratorTag.java
package org.hnylj.taglib;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import javax.servlet.ServletRequest;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.Tag;
import javax.servlet.jsp.tagext.TagSupport;
public class IteratorTag extends TagSupport {
private static final long serialVersionUID = -3495128280303394359L;
private List<String> fieldList;
private List<String> displayList;
private String list;
private String isTemplate;
public IteratorTag() {
super();
fieldList = new ArrayList<String>();
displayList = new ArrayList<String>();
}
public String getIsTemplate() {
return isTemplate;
}
public void setIsTemplate(String isTemplate) {
this.isTemplate = isTemplate;
}
public String getList() {
return list;
}
public void setList(String list) {
this.list = list;
}
public void addField(String field) {
fieldList.add(field);
}
public void addDisplay(String display) {
displayList.add(display);
}
public int doStartTag() throws JspTagException {
fieldList.clear();
displayList.clear();
return Tag.EVAL_BODY_INCLUDE;
}
public int doEndTag() throws JspTagException {
this.iteratorDisplay();
return Tag.EVAL_PAGE;
}
public void iteratorDisplay () {
JspWriter jspWriter = this.pageContext.getOut();
try {
ServletRequest request = pageContext.getRequest();
List<Map<String,String>> data = (List<Map<String,String>>)request.getAttribute(this.getList());;
jspWriter.write("<table width=100% style='border:1 solid #33CCFF' cellpadding=3><tr>");
for (int i=0; i<displayList.size(); i++) {
jspWriter.write("<td bgcolor=#99CCFF>");
String display = (String) displayList.get(i);
jspWriter.write(display);
jspWriter.write("</td>");
}
jspWriter.write("</tr>");
for (int j=0; j<data.size(); j++) {
Map<String,String> d = (Map<String,String>) data.get(j);
jspWriter.write("<tr>");
for (int k=0; k<fieldList.size(); k++) {
jspWriter.write("<td bgcolor=#CCFFFF>");
String field = (String) fieldList.get(k);
jspWriter.write((String) d.get(field) + " ");
jspWriter.write("</td>");
}
jspWriter.write("</tr>");
}
jspWriter.write("</table>");
jspWriter.flush();
} catch (Exception e) {
e.printStackTrace();
}
}
}2.FieldTag.java
package org.hnylj.taglib;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.tagext.Tag;
import javax.servlet.jsp.tagext.TagSupport;
public class FieldTag extends TagSupport {
private static final long serialVersionUID = -1330092183292977881L;
private String name;
private String display;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDisplay() {
return display;
}
public void setDisplay(String display) {
this.display = display;
}
public int doEndTag() throws JspTagException {
Tag t = findAncestorWithClass(this, IteratorTag.class);
IteratorTag iTag = (IteratorTag) t;
iTag.addDisplay(display);
iTag.addField(name);
return EVAL_PAGE;
}
}
3.PageTag.java
package org.hnylj.taglib;
import java.io.IOException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;
public class PageTag extends TagSupport {
private static final long serialVersionUID = 5824600810852310338L;
private String pageSize;
private String action;
public String getPageSize() {
return pageSize;
}
public void setPageSize(String pageSize) {
this.pageSize = pageSize;
}
public String getAction() {
return action;
}
public void setAction(String action) {
this.action = action;
}
public int doStartTag() throws JspException {
JspWriter out = pageContext.getOut();
HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();
String pageNow = (String)request.getSession().getAttribute("pageNow");
int pageSize = Integer.parseInt(this.getPageSize());
try {
int first = Integer.parseInt(pageNow);
String count = (String)request.getSession().getAttribute("count");
long countRow = Integer.parseInt(count);
out.println("<style type='text/css'>");
out.println("<a:link{COLOR:#2781c9;TEXT-DECORATION:none}" +
"a:visited{color:blue;TEXT-DECORATION:none}" +
"a:active{color:blue;TEXT-DECORATION:none}" +
"a:hover{color:blue;TEXT-DECORATION:underline}"
+"</style>");
out.println("<div align=right bgcolor=#99CCFF>");
if (first == 0) {
out.println("首页 | ");
} else {
out.println("<a href='"+this.getAction()+"?pageNow=0'>首页 | </a>");
}
if ((first-1) < 0) {
out.println(" 上一页 | ");
} else {
out.println("<a href='"+this.getAction()+"?pageNow="+String.valueOf(first-1)+"'> 上一页 | </a>");
}
if (countRow%pageSize == 0) {
if ((first+1) >= (countRow/pageSize)) {
out.println(" 下一页 | ");
} else {
out.println("<a href='"+this.getAction()+"?pageNow="+String.valueOf(first+1)+"'> 下一页 | </a>");
}
if ((first+1) >= countRow/pageSize) {
out.println(" 尾页");
} else {
if (countRow%pageSize == 0) {
out.println("<a href='"+this.getAction()+"?pageNow="+String.valueOf(countRow/pageSize-1)+"'> 尾页</a>");
} else {
out.println("<a href='"+this.getAction()+"?pageNow="+String.valueOf(countRow/pageSize)+"'> 尾页</a>");
}
}
}
if (countRow%pageSize != 0) {
if ((first+1) > (countRow/pageSize)) {
out.println(" 下一页 | ");
} else {
out.println("<a href='"+this.getAction()+"?pageNow="+String.valueOf(first+1)+"'> 下一页 | </a>");
}
if ((first+1) > countRow/pageSize) {
out.println(" 尾页");
} else {
if (countRow%pageSize == 0) {
out.println("<a href='"+this.getAction()+"?pageNow="+String.valueOf(countRow/pageSize-1)+"'> 尾页</a>");
} else {
out.println("<a href='"+this.getAction()+"?pageNow="+String.valueOf(countRow/pageSize)+"'> 尾页</a>");
}
}
}
out.println("</div>");
out.flush();
} catch (IOException e) {
e.printStackTrace();
}
return super.doStartTag();
}
}
下面是每个标签处理类的标签描述文件
iteratorTag.tld
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd"> <taglib> <tlibversion>1.2</tlibversion> <jspversion>1.1</jspversion> <shortname>d</shortname> <uri>http://hnylj.iteye.com</uri> <tag> <name>iterator</name> <tagclass>org.hnylj.taglib.IteratorTag</tagclass> <bodycontent>JSP</bodycontent> <attribute> <name>list</name> <required>true</required> <rtexprvalue>false</rtexprvalue> </attribute> </tag> <tag> <name>field</name> <tagclass>org.hnylj.taglib.FieldTag</tagclass> <bodycontent>JSP</bodycontent> <attribute> <name>name</name> <required>true</required> <rtexprvalue>false</rtexprvalue> </attribute> <attribute> <name>display</name> <required>true</required> <rtexprvalue>false</rtexprvalue> </attribute> </tag> <tag> <name>page</name> <tagclass>org.hnylj.taglib.PageTag</tagclass> <bodycontent>JSP</bodycontent> <attribute> <name>action</name> <required>true</required> <rtexprvalue>false</rtexprvalue> </attribute> <attribute> <name>pageSize</name> <required>true</required> <rtexprvalue>false</rtexprvalue> </attribute> </tag> </taglib>
********
接下来是对该标签的使用实例,使用非常简单！
我使用的是struts1.2,所以要正确运行，你需要新建web工程,加入struts1.2所需的jar包。
1.jsp页面如下：
data.jsp:
<%@ page language="java" pageEncoding="utf-8"%>
<%@ taglib uri="/WEB-INF/iteratorTag.tld" prefix="d" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>自定义漂亮的分页标签</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
</head>
<body>
<d:iterator list="data">
<d:field name="cid" display="序号"></d:field>
<d:field name="name" display="姓名"></d:field>
<d:field name="sex" display="性别"></d:field>
<d:field name="address" display="住址"></d:field>
<d:field name="phone" display="电话"></d:field>
<d:field name="job" display="职业"></d:field>
</d:iterator>
<d:page action="data.do" pageSize="7"/>
</body>
</html>对该页面的3个标签作一个简单说明：
<d:iterator list="data"> 用于数据的迭代，list属性为request范围里的一个List对象，List对性封装了从数据库查询出的数据，这个List需要你在struts或servlet里设置。
<d:field name="cid" display="序号">用于输出每一个字段数据，name属性为数据库表的字段，display属性为在页面上要显示的字段表头
<d:page action="data.do" pageSize="7"/>用于数据的分页，action属性为分页请求的的处理器，如jsp，servlet，action等都可以。pageSize属性为每页要显示的数据条数。
2.后台处理的action如下：
PageAction.java
package org.hnylj.action;
import java.util.List;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.hnylj.db.DbManager;
/**
* 分页处理的action
* @编写者：hnylj
*
*/
public class PageAction extends Action {
private int pageSize = 7;
private DbManager dbManager;
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception {
dbManager = new DbManager();
int pageNow = 0;
String s = request.getParameter("pageNow");
if (s == null || "".equals(s)) {
} else {
pageNow = Integer.parseInt(s);
}
List<Map<String,String>> list = dbManager.pageQuery(pageNow, pageSize);
int count = dbManager.getCount();
request.getSession().setAttribute("count", String.valueOf(count));
request.getSession().setAttribute("pageNow", String.valueOf(pageNow));
request.setAttribute("data", list);
return mapping.findForward("success");
}
}
这个action就不必说明了，很简单。
这个action还调用了一个DbManager类，其代码如下：
package org.hnylj.db;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* 数据库管理与操作
* @编写者：hnylj
*
*/
public class DbManager {
private Connection conn;
private Statement stmt;
private ResultSet rs;
private static final String DRIVER = "oracle.jdbc.driver.OracleDriver";
private static final String URL = "jdbc:oracle:thin:@localhost:1521:orcl";
private static final String USERNAME = "scott";
private static final String PASSWORD = "tiger";
// 数据库连接
public synchronized Connection getConnection() {
try {
Class.forName(DRIVER);
conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
} catch (ClassNotFoundException e) {
e.printStackTrace();
return null;
} catch (SQLException e) {
e.printStackTrace();
return null;
}
return conn;
}
/**
* 根据pageNow和pageSize查询数据
* @param pageNow
* @param pageSize
* @return
*/
public List<Map<String,String>> pageQuery (int pageNow,int pageSize) {
String sql = "SELECT * FROM (SELECT AA.*, ROWNUM RN FROM (SELECT * FROM CUSTOMER ORDER BY CID ASC) AA WHERE ROWNUM <= "+((pageNow+1)*pageSize)+") WHERE RN > "+(pageNow*pageSize)+" ";
Map<String,String> data = null;
List<Map<String,String>> list = new ArrayList<Map<String,String>>();
try {
conn = this.getConnection();
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
while (rs.next()) {
data = new HashMap<String,String>();
data.put("cid", new Integer(rs.getInt("cid")).toString());
data.put("name", rs.getString("name"));
data.put("sex", rs.getString("sex"));
data.put("address", rs.getString("address"));
data.put("phone", rs.getString("phone"));
data.put("job", rs.getString("job"));
list.add(data);
}
} catch (SQLException e) {
e.printStackTrace();
return null;
}
return list;
}
/**
* 获取总记录数
* @param conn
* @param sql
* @return
*/
public int getCount() {
int count = 0;
String sql = "SELECT COUNT(*) AS COUNT FROM CUSTOMER";
try {
conn = this.getConnection();
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
while (rs.next()) {
count = Integer.parseInt(rs.getString("count"));
}
} catch (SQLException e) {
e.printStackTrace();
return 0;
}
return count;
}
}
另外要正确运行，你需要配置web.xml,struts-config.xml文件并建立一张数据库表customer（本人使用的是oracle），相信大家知道怎么做！
整个标签代码及使用实例代码如上，与大家交流！我的博客地址:http://hnylj.iteye.com
一个Java技术交流群，一起交流，共同进步，扣扣群号：513086638
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