分页功能的实现(数据库和后端部分)

待我称王封你为后i 2023-10-11 19:51 12阅读 0赞

**目录**

准备数据库

一、创建项目

二、在pom.xml中添加依赖

三、在application.yml中配置数据源

四、在启动类Demo.java中扫描dao

五、实体层

六、创建UserMapper.xml

七、通过ResultMap建立User实体和t\_user表的映射关系

八、在UserMapper中添加查询所有用户的方法

8.1UserMapper.java

8.2UserMapper.xml

十、 在IUserService中添加业务方法

IUserService接口

UserServiceImpl实现类

十一、在UserController中测试

十二、源代码

12.1架构图

12.2依赖pom.xml

12.3配置文件resources/application.yml

12.4 Mapper文件 resources/mappers/UserMapper.xml

12.5 实现类java/demo/Demo.java

12.6 实体类demo/entity/User.java

12.7DAO类 java/demo/dao/UserMapper.java

12.8 服务类 java/demo/service

接口

service类

12.9 controller java/demo/controller/Usercontroller.java

--------------------

## 准备数据库 ##

![d930bf9698f6461fa56d9c84a7aa0967.png][]

![e7be2c0ffb114e878a7eda4d3b6a4fd7.png][] **实行效果如下图所示:**

![3a2139d8eeca475b9d5d61433f52ac68.png][]

## 一、创建项目 ##

1.  添加application.yml配置文件
2.  添加启动类
3.  在resources中添加mappers文件夹
4.  在java中添加entity、dao、service、controller包

**架构如下图所示**

![a891a2d795b64cdf8dac06910261cbc3.png][]

> **添加application.yml配置文件**
> 
> ![9ab8e30b958d427b810c235f3c2eb4c5.png][]

## 二、在pom.xml中添加依赖 ##

![b4731fd8435249058249613e6d889f17.png][]

**依赖源码:**

<dependency>
                <groupId>com.baomidou</groupId>
                <artifactId>mybatis-plus-boot-starter</artifactId>
                <version>3.5.1</version>
            </dependency>
            
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId> <optional>true</optional>
            </dependency>
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <scope>runtime</scope>
            </dependency>

## 三、在application.yml中配置数据源 ##

![beab1327724047afbc802c2d038b577b.png][]

![7d67ad01534b4a3288f022cbed9748fd.png][]

**此处代码代表路径,对应的是**

![389555385c354db2b83e3b4a09951a8d.png][]

> 这里正常写应该是**demo.entity.User**
> 
> 因为配置文件中已经加入了**demo.entity**,所以此处可以不写,只写**User**即可

**配置文件源码:**

server:
      port: 8070
    spring:
      # 配置数据源信息
      datasource:
        # 配置数据源类型
        type: com.zaxxer.hikari.HikariDataSource
        # 配置连接数据库信息
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://localhost:3306/practice?characterEncoding=utf-8&useSSL=false
        username: root
        password: 123456
        #mybatisPlus相关配置
    mybatis-plus:
          mapper-locations: classpath:mappers/*.xml
          type-aliases-package: demo.entity
          configuration:
            # 配置MyBatis日志
            log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

## 四、在启动类Demo.java中扫描dao ##

![912285dae3454254912cf86a7456f350.png][]

package demo;
    
    import org.mybatis.spring.annotation.MapperScan;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    
    @SpringBootApplication
    @MapperScan("demo.dao")
    public class Demo {
        public static void main(String[] args) {
            SpringApplication.run(Demo.class,args);
        }
    }

## 五、实体层 ##

package demo.entity;
    
    import com.baomidou.mybatisplus.annotation.TableId;
    import com.baomidou.mybatisplus.annotation.TableName;
    import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    
    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    public class User {
        private Long id;
        private String userName;
        private String passwd;
        private String createDate;
    }

## 六、创建UserMapper.xml ##

![ca1cac7fd82e4a078ae9caad3209f122.png][]

![7d6ab625593e4772ae5fe7afe662c5c3.png][]

## 七、通过ResultMap建立User实体和t\_user表的映射关系 ##

![1c4673f44376456f81a85a3a2b98c99f.png][]

**代码如下:**

<resultMap id="userResult" type="User">
        <result column="id" property="id"/>
        <result column="user_name" property="userName"/>
        <result column="passwd" property="passwd"/>
        <result column="create_date" property="createDate"/>
    </resultMap>

## 八、在UserMapper中添加查询所有用户的方法 ##

**注意:UserMapp**是为**mappers**文件夹中**UserMapper.xml**服务

### 8.1UserMapper.java ###

![0b3dc43d7d1a45ab8aef0f902ec48a51.png][]

package demo.dao;
    
    import demo.entity.User;
    
    import java.util.List;
    
    public interface UserMapper {
        public List<User> selectAll(int pageIndex,int pageSize);
    
    }

### 8.2UserMapper.xml ###

![c76b2529c94442c38aadc48206f9ec0d.png][]

<sql id="sql_temp">
            select id,user_name,passwd,create_date from  t_user
        </sql>
        <select id="selectAll" resultMap="userResult">
            <include refid="sql_temp"></include>limit #{pageIndex},#{pageSize}
        </select>

## 十、 在IUserService中添加业务方法 ##

### IUserService接口 ###

![64504bc98e4a44eda3e61dd82fac8e26.png][]

代码如下:

package demo.service;
    
    import demo.entity.User;
    
    import java.util.List;
    
    public interface IUserService {
    //pageIndex为页码,pageSize为一页的个数
        public List<User> queryUserList(int pageIndex,int pageSize);
    }

### UserServiceImpl实现类 ###

![e50fe2194acb44f3b6ca07bd3db5f4ba.png][] **代码如下:**

package demo.service.Impl;
    
    import demo.dao.UserMapper;
    import demo.entity.User;
    import demo.service.IUserService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    
    import java.util.List;
    @Service
    public class UserServiceImpl implements IUserService {
        @Autowired(required = false)
        private UserMapper userMapper;
        @Override
        public List<User> queryUserList(int pageIndex,int pageSize) {
            List<User> list = userMapper.selectAll((pageIndex-1)*pageSize,pageSize);
            return list;
        }
    }

## 十一、在UserController中测试 ##

![71c0114391f64444a407649ff33b1f10.png][]

**代码如下:**

package demo.controller;
    import demo.dao.UserMapper;
    import demo.entity.User;
    import demo.service.IUserService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    import java.util.List;
    @RestController
    @RequestMapping("/user")
    public class Usercontroller {
        @Autowired
        private IUserService userService;
    
        @RequestMapping("/list")
        public List<User> findUserList(int pageIndex,int pageSize) {
            return userService.queryUserList(pageIndex,pageSize);
        }
    }

## 十二、源代码 ##

### 12.1架构图 ###

![75480dd8c5f743a0907d4284d772be8f.png][]

### 12.2依赖pom.xml ###

### 12.3配置文件resources/application.yml ###

server:
      port: 8080
    spring:
      # 配置数据源信息
        datasource:
        # 配置数据源类型
        type: com.zaxxer.hikari.HikariDataSource
        # 配置连接数据库信息
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://localhost:3306/practice?characterEncoding=utf-8&useSSL=false
        username: root
        password: 123456
        #mybatisPlus相关配置
    mybatis-plus:
      mapper-locations: classpath:mappers/*.xml
      type-aliases-package: demo.entity
      configuration:
        # 配置MyBatis日志
        log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

### 12.4 Mapper文件 resources/mappers/UserMapper.xml ###

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    <mapper namespace="demo.dao.UserMapper">
        
        <resultMap id="userResult" type="User">
            
            <result column="id" property="id"></result>
            <result column="user_name" property="userName"></result>
            <result column="passwd" property="passwd"></result>
            <result column="create_date" property="createDate"></result>
        </resultMap>
        <sql id="sql_temp">
            select id,user_name,passwd,create_date from  t_user
        </sql>
        <select id="selectAll" resultMap="userResult">
            <include refid="sql_temp"></include>limit #{pageIndex},#{pageSize}
        </select>
    </mapper>

### 12.5 实现类java/demo/Demo.java ###

### 12.6 实体类demo/entity/User.java ###

### 12.7DAO类 java/demo/dao/UserMapper.java ###

package demo.dao;
    
    import demo.entity.User;
    
    import java.util.List;
    
    public interface UserMapper {
        public List<User> selectAll(int pageIndex,int pageSize);
    
    }

### 12.8 服务类 java/demo/service ###

#### 接口 ####

#### service类 ####

### 12.9 controller java/demo/controller/Usercontroller.java ###

[d930bf9698f6461fa56d9c84a7aa0967.png]: https://img-blog.csdnimg.cn/d930bf9698f6461fa56d9c84a7aa0967.png
[e7be2c0ffb114e878a7eda4d3b6a4fd7.png]: https://img-blog.csdnimg.cn/e7be2c0ffb114e878a7eda4d3b6a4fd7.png
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[7d67ad01534b4a3288f022cbed9748fd.png]: https://img-blog.csdnimg.cn/7d67ad01534b4a3288f022cbed9748fd.png
[389555385c354db2b83e3b4a09951a8d.png]: https://img-blog.csdnimg.cn/389555385c354db2b83e3b4a09951a8d.png
[912285dae3454254912cf86a7456f350.png]: https://img-blog.csdnimg.cn/912285dae3454254912cf86a7456f350.png
[ca1cac7fd82e4a078ae9caad3209f122.png]: https://img-blog.csdnimg.cn/ca1cac7fd82e4a078ae9caad3209f122.png
[7d6ab625593e4772ae5fe7afe662c5c3.png]: https://img-blog.csdnimg.cn/7d6ab625593e4772ae5fe7afe662c5c3.png
[1c4673f44376456f81a85a3a2b98c99f.png]: https://img-blog.csdnimg.cn/1c4673f44376456f81a85a3a2b98c99f.png
[0b3dc43d7d1a45ab8aef0f902ec48a51.png]: https://img-blog.csdnimg.cn/0b3dc43d7d1a45ab8aef0f902ec48a51.png
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[e50fe2194acb44f3b6ca07bd3db5f4ba.png]: https://img-blog.csdnimg.cn/e50fe2194acb44f3b6ca07bd3db5f4ba.png
[71c0114391f64444a407649ff33b1f10.png]: https://img-blog.csdnimg.cn/71c0114391f64444a407649ff33b1f10.png
[75480dd8c5f743a0907d4284d772be8f.png]: https://img-blog.csdnimg.cn/75480dd8c5f743a0907d4284d772be8f.png