JSP链接数据库操作
调用DAO中search方法返回结果为空
我觉得应该是dao search方法中的问题但是找不到！烦请指点
InformationDAO.java
public Map<String, Object> search(PageBean pb, Information information) throws Exception {
PreparedStatement stmt = null; // 语句对象
ResultSet rs = null; // 数据集
List<Information> list = new ArrayList<Information>(); // 公司资讯集合
// 查询总记录数；设置到pb对象中
int totalCount = this.getTotalCount();
pb.setTotalCount(totalCount);
// 判断（预防当前页为首页或末页时，点击上一页或下一页出错）
if (pb.getCurrentPage() <= 0) {
pb.setCurrentPage(1); // 把当前页设置为1
} else if (pb.getCurrentPage() > pb.getTotalPage()) {
pb.setCurrentPage(pb.getTotalPage()); // 把当前页设置为最大页数
}
// 获取当前页：计算查询的起始行、返回的行数
int currentPage = pb.getCurrentPage(); // 当前页
int index = (currentPage - 1) * pb.getPageCount(); // 查询的起始行
int count = pb.getPageCount(); // 查询返回的行数
try {
String sql = "select * from Information where title like concat('%','?','%') limit ?,?;"; // SQL语句
stmt = DBHelper.getConnection().prepareStatement(sql); // 创建链接对象
stmt.setString(1, information.getTitle()); //设置SQL语句第一个参数标题的值
stmt.setInt(2, index); //设置SQL语句第一个参数初始偏移量
stmt.setInt(3, count); //设置SQL语句第二个参数返回记录行最大数目
rs = stmt.executeQuery(); // 获得数据集
while (rs.next()) {
System.out.println("sdfadfsad");
Information lists = new Information(); //创建一个Information对象
lists.setId(rs.getInt("id")); //将公司资讯ID的值加入lists
lists.setTitle(rs.getString("title")); //将公司资讯标题的值加入lists
lists.setAuthor(rs.getString("author")); //将公司资讯作者的值加入lists
lists.setContent(rs.getString("content")); //将公司资讯内容的值加入lists
lists.setDate(rs.getString("date")); //将公司资讯发布时间的值加入lists
list.add(lists); // 把一个公司资讯加入集合
}
//创建一个hashMap，key是String类型，value是Object类型（任意类型）
Map<String, Object> map = new HashMap<String, Object>();
map.put("PageDate", pb); //将分页对象pb添加到map集合中
map.put("list", list); //将公司资讯集合对象list添加到map集合中
return map; //返回map集合
} catch (Exception ex) {
ex.printStackTrace();
return null;
} finally {
// 释放数据集对象
if (rs != null) {
try {
rs.close();
rs = null;
} catch (Exception ex) {
ex.printStackTrace();
}
}
// 释放语句对象
if (stmt != null) {
try {
stmt.close();
stmt = null;
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
}
public int getTotalCount() throws Exception{
PreparedStatement pStatement = null;
ResultSet rSet = null;
String sql = "select count(*) from information;";
int count = 0;
try {
pStatement = DBHelper.getConnection().prepareStatement(sql);
rSet = pStatement.executeQuery();
rSet.next();
count = rSet.getInt(1);
}catch (SQLException e){
e.printStackTrace();
}finally {
if (rSet != null){
try {
rSet.close();
rSet = null;
}catch (Exception ex){
ex.printStackTrace();
}
}
if (pStatement != null){
try {
pStatement.close();
pStatement = null;
}catch (Exception ex){
ex.printStackTrace();
}
}
}
return count;
}
InformationServlet.java
package servlet;
import dao.InformationDAO;
import entity.Information;
import util.PageBean;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
@WebServlet(name = "InformationServlet", value = "/InformationServlet")
public class InformationServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
//跳转资源
private String uri;
//Costructor of the object.
public InformationServlet(){
super();
}
//Destruction of the servlet
@Override
public void destroy() {
super.destroy(); // Just puts "destroy" string in log //log 日志;
// Put your code here
}
/**
* The doGet method of the servlet.
*
* This method is called when a form has its tag value method equals to get.
*
* @param request
* the request send by the client to the server
* @param response
* the response send by the server to the client
* @throws ServletException
* if an error occurred
* @throws IOException
* if an error occurred
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//设置编码
request.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
//获取操作类型
String method = request.getParameter("method");
//判断
if ("add".equals(method))
add(request, response);
else if ("list".equals(method))
list(request, response);
else if ("search".equals(method))
search(request, response);
else if ("delete".equals(method))
delete(request, response);
else if ("jumpup".equals(method))
jumpup(request, response);
else if ("update".equals(method))
update(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
// d.查找单个公司资讯
public void search(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
// 获取“当前页”参数；（当第一次访问当前页为null）
String currPage = request.getParameter("currentPage");
// 获取查找的标题
String InformationTitle = request.getParameter("title");
// 判断
if (currPage == null || "".equals(currPage.trim())) {
currPage = "1"; // 第一次访问，设置当前页为1；
}
// 转换页参数为int类型
int currentPage = Integer.parseInt(currPage);
// 创建PageBean对象，设置当前页参数；
PageBean pageBean = new PageBean();
pageBean.setCurrentPage(currentPage);
// 创建Information对象，将标题的值加入title
Information title = new Information();
title.setTitle(InformationTitle);
// 调用dao对象的search方法，得到结果
InformationDAO dao = new InformationDAO();
Map<String, Object> result = dao.search(pageBean, title);
if (result==null)
response.getWriter().println("232323223");
// 保存
request.setAttribute("result", result);
// 跳转路径
uri = "/sys/information/information.jsp";
} catch (Exception e) {
e.printStackTrace();
}
// 转发
//request.getRequestDispatcher(uri).forward(request, response);
}
/**
* Initialization of the servlet.
*
* @throws ServletException
* if an error occurs
*/
@Override
public void init() throws ServletException {
// Put your code here
}
}
```java
package entity; //entity实体
//公司资讯类
public class Information {
private int id; //ID
private String title; //标题
private String author; //作者
private String content; //内容
private String date; //发布时间
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
public String getDate() {
return date;
}
public void setDate(String date) {
this.date = date;
}
}
entity.Information.java Inforamtion实体
util.DBHelper和util.PageBean（这俩个应该没有问题，其他功能都调用过都正常运行)
package util;
import java.sql.Connection;
import java.sql.DriverManager;
public class DBHelper {
private static final String driver = "com.mysql.jdbc.Driver";
private static final String url = "jdbc:mysql://localhost:3306/red_wine?useSSL=false&useUnicode=true&characterEncoding=UTF-8";
private static final String username = "root";
private static final String password = "newpassword";
private static Connection conn = null;
static {
try {
Class.forName(driver);
}catch (Exception ex){
ex.printStackTrace();
}
}
public static Connection getConnection() throws Exception{
if (conn==null){
conn = DriverManager.getConnection(url,username,password);
return conn;
}
return conn;
}
}
package util;
public class PageBean {
private int currentPage = 1; //current现在的;当前的 //当前页，默认显示第一页
private int pageCount = 6; //每页显示的行数（查询返回的行数），默认每页显示6行
private int totalCount; //总记录数
private int totalPage; //总页数=总记录数/每页显示的行数（+1）
public int getTotalPage() {
if (totalCount % pageCount == 0){
totalPage = totalCount / pageCount;
}else {
totalPage = totalCount / pageCount + 1;
}
return totalPage;
}
public int getCurrentPage() {
return currentPage;
}
public void setCurrentPage(int currentPage) {
this.currentPage = currentPage;
}
public int getPageCount() {
return pageCount;
}
public void setPageCount(int pageCount) {
this.pageCount = pageCount;
}
public int getTotalCount() {
return totalCount;
}
public void setTotalCount(int totalCount) {
this.totalCount = totalCount;
}
public void setTotalPage(int totalPage) {
this.totalPage = totalPage;
}
}
数据库
报错信息
