实习18

Java Web应用结构与分页查询优化

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#实习18

本文详细介绍了Java Web应用中删除FindsServlet和FindServlet，优化分页查询功能的过程。通过修改web.xml配置文件，调整UserDaoImpl实现类，实现了更高效的分页查询操作，提升了用户体验。

实习18
分页修改
程序结构
在这里插入图片描述
与上一个程序相比改变
1.删除了FindsServlet和FindServlet
2.修改web

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <servlet>
        <servlet-name>LoginServlet</servlet-name>
        <servlet-class>com.zhongruan.servlet.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LoginServlet</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>DeleteServlet</servlet-name>
        <servlet-class>com.zhongruan.servlet.DeleteServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>DeleteServlet</servlet-name>
        <url-pattern>/delete</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>AddServlet</servlet-name>
        <servlet-class>com.zhongruan.servlet.AddServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>AddServlet</servlet-name>
        <url-pattern>/add</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>UpServlet</servlet-name>
        <servlet-class>com.zhongruan.servlet.UpServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>UpServlet</servlet-name>
        <url-pattern>/up</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>ToUpServlet</servlet-name>
        <servlet-class>com.zhongruan.servlet.ToUpServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ToUpServlet</servlet-name>
        <url-pattern>/toup</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>FindPageServlet</servlet-name>
        <servlet-class>com.zhongruan.servlet.FindPageServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>FindPageServlet</servlet-name>
        <url-pattern>/page</url-pattern>
    </servlet-mapping>
</web-app>

3.修改UserDaoImpl
package com.zhongruan.dao.impl;

import com.zhongruan.dao.UserDao;
import com.zhongruan.model.User;
import com.zhongruan.util.UserUtil;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class UserDaoImpl implements UserDao {

@Override
public User jd(String zh, String mm) {
    ResultSet resultSet = null;
    PreparedStatement statement = null;
    Connection connection = null;
    User user=null;
    try {
        connection = UserUtil.getConnection();
        String sql = "select * from dr where zh=? and mm=?";
        statement = connection.prepareStatement(sql);
        statement.setString(1,zh);
        statement.setString(2,mm);
        resultSet=statement.executeQuery();
        while (resultSet.next()) {
            user = new User();
            user.setId(resultSet.getInt(1));
            user.setZh(resultSet.getString(2));
            user.setMm(resultSet.getString(3));
        }
    } catch (SQLException e) {
        e.printStackTrace();
    }finally {
        UserUtil.closeAll(resultSet, statement, connection);
    }
    return user;
}
@Override
public List<User> findUsers()  {
    ResultSet resultSet = null;
    PreparedStatement statement = null;
    Connection connection = null;
    List<User> users=new ArrayList<>();
    try {
        connection = UserUtil.getConnection();
        String sql = "select * from dr";
        statement = connection.prepareStatement(sql);
        resultSet = statement.executeQuery();
        while (resultSet.next()) {
            User user=new User();
            user.setId(resultSet.getInt(1));
            user.setZh(resultSet.getString(2));
            user.setMm(resultSet.getString(3));
            users.add(user);
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        UserUtil.closeAll(resultSet, statement, connection);
    }
    return users;
}
@Override
public void delete(int id){
    Connection connection = UserUtil.getConnection();
    String sql = "delete from dr where id=?";
    PreparedStatement statement = null;
    try {
        statement = connection.prepareStatement(sql);
        statement.setInt(1,id);
        statement.executeUpdate();
    } catch (SQLException e) {
        e.printStackTrace();
    }finally {
        UserUtil.closeAll(null,statement,connection);
    }
}
@Override
public void zj(String zh,String mm){
    Connection connection = UserUtil.getConnection();
    String sql = "insert into dr(zh,mm) values (?,?)";
    PreparedStatement statement = null;
    try {
        statement = connection.prepareStatement(sql);
        statement.setString(1,zh);
        statement.setString(2,mm);
        statement.executeUpdate();
    } catch (SQLException e) {
        e.printStackTrace();
    }
    finally {
        UserUtil.closeAll(null,statement,connection);
    }
}
@Override
public void xg(int id,String zh,String mm) {
    Connection connection = UserUtil.getConnection();
    String sql = "update dr set zh=?,mm=? where id=?";
    PreparedStatement statement = null;
    try {
        statement = connection.prepareStatement(sql);
        statement.setInt(3,id);
        statement.setString(2,mm);
        statement.setString(1,zh);
        statement.executeUpdate();
    } catch (SQLException e) {
        e.printStackTrace();
    }
    finally {
        UserUtil.closeAll(null,statement,connection);
    }
}
@Override
public User findUserById(int id){
    User user = null;
    Connection connection = null;
    PreparedStatement statement = null;
    ResultSet resultSet = null;
    try {
        connection = UserUtil.getConnection();
        String sql = "select * from dr where id=?";
        statement = connection.prepareStatement(sql);
        statement.setInt(1, id);
        resultSet = statement.executeQuery();
        while (resultSet.next()) {
            user = new User();
            user.setId(resultSet.getInt(1));
            user.setZh(resultSet.getString(2));
            user.setMm(resultSet.getString(3));
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        UserUtil.closeAll(resultSet, statement, connection);
    }
    return user;
}
@Override
public List<User> findsUsers(String text)  {
    ResultSet resultSet = null;
    PreparedStatement statement = null;
    Connection connection = null;
    List<User> users=new ArrayList<>();
    try {
        connection = UserUtil.getConnection();
        String sql = "select * from dr where zh like ?";
        statement = connection.prepareStatement(sql);
        statement.setString(1,"%"+text+"%");
        resultSet = statement.executeQuery();
        while (resultSet.next()) {
            User user=new User();
            user.setId(resultSet.getInt(1));
            user.setZh(resultSet.getString(2));
            user.setMm(resultSet.getString(3));
            users.add(user);
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        UserUtil.closeAll(resultSet, statement, connection);
    }
    return users;
}
@Override
public List<User> findPage(String text,int start, int size)  {
    ResultSet resultSet = null;
    PreparedStatement statement = null;
    Connection connection = null;
    List<User> users=new ArrayList<>();
    String sql=null;
    try {
        connection = UserUtil.getConnection();
        if (text==null){
            sql = "select * from dr limit ?,?";
            statement = connection.prepareStatement(sql);
            statement.setInt(1,start);
            statement.setInt(2,size);
        }else {
            sql = "select * from dr where zh like ? limit ?,?";
            statement = connection.prepareStatement(sql);
            statement.setString(1,"%"+text+"%");
            statement.setInt(2,start);
            statement.setInt(3,size);
        }
        resultSet = statement.executeQuery();
        while (resultSet.next()) {
            User user=new User();
            user.setId(resultSet.getInt(1));
            user.setZh(resultSet.getString(2));
            user.setMm(resultSet.getString(3));
            users.add(user);
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        UserUtil.closeAll(resultSet, statement, connection);
    }
    return users;
}
@Override
public int selectCount(){
    ResultSet resultSet = null;
    PreparedStatement statement = null;
    Connection connection = null;
    List<User> users=new ArrayList<>();
    int count=0;
    try {
        connection = UserUtil.getConnection();
        String sql = "select count(*) from dr";
        statement = connection.prepareStatement(sql);
        resultSet = statement.executeQuery();
        while (resultSet.next()) {
            count=resultSet.getInt(1);
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        UserUtil.closeAll(resultSet, statement, connection);
    }
    return count;
}

}