Jsp&Servlet入门级项目全程实录第3讲

1、建立数据表及数据（略）

2、装载驱动，建立数据表
<link rel="stylesheet" type="text/css" href="jquery-easyui-1.3.3/themes/default/easyui.css">
<link rel="stylesheet" type="text/css" href="jquery-easyui-1.3.3/themes/icon.css">
<script type="text/javascript" src="jquery-easyui-1.3.3/jquery.min.js"></script>
<script type="text/javascript" src="jquery-easyui-1.3.3/jquery.easyui.min.js"></script>
<script type="text/javascript" src="jquery-easyui-1.3.3/locale/easyui-lang-zh_CN.js"></script>

<table id="dg" title="班级信息" class="easyui-datagrid" fitColumns="true" pagination="true" rownumbers="true" fit="true" url="gradeList">
<thead>
<tr>
<th field="id" width="50" >编号</th>
<th field="gradeName" width="100" >班级名称</th>
<th field="gradeDesc" width="250" >班级描述</th>
</tr>
</thead>
</table>
field：与数据库名称相同
fitColumns：自适应
pagination：分页
rownumbers：行号
fit：最大化
url：请求的地址

3、model
package com.java1234.model;

public class Grade {
private int id;
private String gradeName;
private String gradeDesc;

public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getGradeName() {
return gradeName;
}
public void setGradeName(String gradeName) {
this.gradeName = gradeName;
}
public String getGradeDesc() {
return gradeDesc;
}
public void setGradeDesc(String gradeDesc) {
this.gradeDesc = gradeDesc;
}
}

4、创建GradeListServlet及配置web.xml、填写url请求
package com.java1234.web;

import java.io.IOException;
import java.sql.Connection;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

import com.java1234.dao.GradeDao;
import com.java1234.model.PageBean;
import com.java1234.util.DbUtil;
import com.java1234.util.JsonUtil;
import com.java1234.util.ResponseUtil;

public class GradeListServlet extends HttpServlet{

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//转换doPost
this.doPost(request, response);
}

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

}
}

<servlet>
<servlet-name>gradeListServlet</servlet-name>
<servlet-class>com.java1234.web.GradeListServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>gradeListServlet</servlet-name>
<url-pattern>/gradeList</url-pattern>
</servlet-mapping>

<table id="dg" title="班级信息" class="easyui-datagrid" fitColumns="true" pagination="true" rownumbers="true"  url="gradeList">

5、分页
String * from table limie start,size
start起始页
size每页大小

算法
start=(page-1)*rows;

封装page对象
package com.java1234.model;

public class PageBean {

private int page;//第几页
private int rows;//每页记录数
private int start;//起始页

public PageBean(int page, int rows) {
super();
this.page = page;
this.rows = rows;
}

public int getPage() {
return page;
}
public void setPage(int page) {
this.page = page;
}
public int getRows() {
return rows;
}
public void setRows(int rows) {
this.rows = rows;
}
public int getStart() {
return (page-1)*rows;
}

}

6、取数据
public ResultSet gradeList(Connection con,PageBean pageBean)throws Exception{
StringBuffer sb=new StringBuffer("select * from t_grade");
if(pageBean!=null){
sb.append(" limit "+pageBean.getStart()+","+pageBean.getRows());
}
PreparedStatement pstmt=con.prepareStatement(sb.toString());
return pstmt.executeQuery();
}

7、创建jsonUtil并导入json-lib包（将rs转换成List）
public static JSONArray formatRsToJsonArray(ResultSet rs)throws Exception{
ResultSetMetaData md=rs.getMetaData();
int num=md.getColumnCount();
JSONArray array=new JSONArray();
while(rs.next()){
JSONObject mapOfColValues=new JSONObject();
for(int i=1;i<=num;i++){
mapOfColValues.put(md.getColumnName(i),rs.getObject(i));
}
array.add(mapOfColValues);
}
return null;
}
ResultSetMetaData得到结果集(rs)的结构信息，比如字段数、字段名等。
int num=md.getColumnCount();取得列数

8、封闭PageBean加构造方法
//封装
PageBean pageBean=new PageBean(Integer.parseInt(page),Integer.parseInt(rows));

public PageBean(int page, int rows) {
super();
this.page = page;
this.rows = rows;
}

9、获取总记录数
public int gradeCount(Connection con)throws Exception{
String sql="select count(*) as total from t_grade";
PreparedStatement pstmt=con.prepareStatement(sql);
ResultSet rs=pstmt.executeQuery();
if(rs.next()){
return rs.getInt("total");
}else{
return 0;
}
}

10、封装向页面输出数据
public static void write(HttpServletResponse response,JSONObject jsonObject)throws Exception{
response.setContentType("text/html;charset=utf-8");
PrintWriter out=response.getWriter();
out.println(jsonObject.toString());
out.flush();
out.close();
}