Mybatis之分页插件pagehelper的简单使用

2022-09-30 13:56:32

最近从家里回来之后一直在想着减肥的事情，一个月都没更新博客了，今天下午没睡午觉就想着把mybatis的分页插件了解一下，由于上个月重新恢复了系统，之前创建的项目都没了，又重新创建了一个项目。

一、创建maven项目

主要创建了User类、UserMapper.xml、database.properties、mybatis-config.xml。

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">

<!-- 为这个mapper指定一个唯一的namespace，namespace的值习惯上设置成包名+sql映射文件名，这样就能够保证namespace的值是唯一的

例如namespace="Cuiyw.MyBatis.DBMapping.UserMapper"就是Cuiyw.MyBatis.DBMapping(包名)+UserMapper(UserMapper.xml文件去除后缀)

 -->

<mapper namespace="Cuiyw.MyBatis.DBMapping.UserMapper">

    <!-- 在select标签中编写查询的SQL语句， 设置select标签的id属性为getUser，id属性值必须是唯一的，不能够重复

    使用parameterType属性指明查询时使用的参数类型，resultType属性指明查询返回的结果集类型

    resultType="Cuiyw.MyBatis.Model.User"就表示将查询结果封装成一个User类的对象返回

    User类就是user表所对应的实体类

    -->

    <!--

        根据id查询得到一个user对象

     -->

    <select id="getUser" parameterType="int"

        resultType="Cuiyw.MyBatis.Model.User">

        select * from user where id=#{id}

    </select>

    <select id="getUserList" resultType="Cuiyw.MyBatis.Model.User">

        select * from user

    </select>

    <insert id="addUser" parameterType="Cuiyw.MyBatis.Model.User">

      <selectKey resultType="java.lang.Integer" order="AFTER" keyProperty="id">

          SELECT LAST_INSERT_ID()

      </selectKey>

        insert into user(name,age) values (#{name},#{age})

    </insert>

    <delete id="deleteUserById" parameterType="int">

        delete from user where id=#{id}

    </delete>

    <update id="updateUser" parameterType="Cuiyw.MyBatis.Model.User">

        update user set name=#{name},age=#{age} where id=#{id}

    </update>

</mapper>

User类

package Cuiyw.MyBatis.Model;

public class User {

    @Override

    public String toString() {

        // TODO Auto-generated method stub

        return  "User [id=" + Id + ", name=" + Name + ", age=" + Age + "]";

    }

    public int getId() {

        return Id;

    }

    public void setId(int id) {

        Id = id;

    }

    public String getName() {

        return Name;

    }

    public void setName(String name) {

        Name = name;

    }

    public int getAge() {

        return Age;

    }

    public void setAge(int age) {

        Age = age;

    }

    private int Id;

    private String Name;

    private int Age;

}

database.properties

driver=com.mysql.jdbc.Driver

url=jdbc:mysql://localhost:3306/mybatis

mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE configuration

  PUBLIC "-//mybatis.org//DTD Config 3.0//EN"

  "http://mybatis.org/dtd/mybatis-3-config.dtd">

    <configuration>

    <properties resource="database.properties">

      <property name="username" value="root"/>

      <property name="password" value="123456"/>

    </properties>

    <typeAliases>

        <typeAlias type="Cuiyw.MyBatis.Model.User" alias="User"/>

    </typeAliases>

    <plugins>

    <!-- com.github.pagehelper为PageHelper类所在包名 -->

    <plugin interceptor="com.github.pagehelper.PageHelper">

        <!-- 方言 -->

        <property name="dialect" value="mysql"/>

        <!-- 该参数默认为false -->

        <!-- 设置为true时，使用RowBounds分页会进行count查询 -->

        <property name="rowBoundsWithCount" value="true"/>

    </plugin>

    </plugins>

    <environments default="development">

        <environment id="development">

            <transactionManager type="JDBC" />

            <!-- 配置数据库连接信息 -->

            <dataSource type="POOLED">

                <property name="driver" value="${driver}" />

                <property name="url" value="${url}" />

                <property name="username" value="${username}" />

                <property name="password" value="${password}" />

            </dataSource>

        </environment>

    </environments>

    <!-- 程序中所用到sql映射文件都在这里列出，这些映射sql都被Mybatis管理 -->

    <mappers>

        <mapper resource="Cuiyw/MyBatis/DBMapping/UserMapper.xml" />

    </mappers>

</configuration>

二、pagehelper插件的配置

pom.xml配置

除了上面mybatis-config.xml中配置的plugin插件com.github.pagehelper.PageHelper.这里还主要使用了org.mybatis、mysql、com.github.pagehelper、com.github.jsqlparser,分页插件的是后面两个。

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

  <modelVersion>4.0.0</modelVersion>

  <groupId>Cuiyw</groupId>

  <artifactId>MyBatisDemo</artifactId>

  <version>0.0.1-SNAPSHOT</version>

  <packaging>jar</packaging>

  <name>MyBatisDemo</name>

  <url>http://maven.apache.org</url>

  <properties>

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

  </properties>

  <dependencies>

  <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->

    <dependency>

        <groupId>org.mybatis</groupId>

        <artifactId>mybatis</artifactId>

        <version>3.2.1</version>

    </dependency>

  <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->

    <dependency>

        <groupId>mysql</groupId>

        <artifactId>mysql-connector-java</artifactId>

        <version>5.1.6</version>

    </dependency>

    <dependency>

    <groupId>com.github.pagehelper</groupId>

    <artifactId>pagehelper</artifactId>

    <version>3.4.2</version>

    </dependency>

    <dependency>

    <groupId>com.github.jsqlparser</groupId>

    <artifactId>jsqlparser</artifactId>

    <version>0.9.1</version>

</dependency>

    <dependency>

      <groupId>junit</groupId>

      <artifactId>junit</artifactId>

      <version>3.8.1</version>

      <scope>test</scope>

    </dependency>

  </dependencies>

</project>

三、数据库配置

这里我事先在user表准备了一个几条数据。

四、插件的使用

PageHelper.startPage(1, 5, true)用来设置分页,PageInfo用来显示分页信息。

package Cuiyw.MyBatisDemo;

import java.io.IOException;

import java.io.Reader;

import java.util.List;

import org.apache.ibatis.io.Resources;

import org.apache.ibatis.session.SqlSession;

import org.apache.ibatis.session.SqlSessionFactory;

import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import com.github.pagehelper.PageHelper;

import com.github.pagehelper.PageInfo;

import Cuiyw.MyBatis.Model.User;

public class App

{

    public static void main( String[] args ) throws IOException

    {

        //mybatis的配置文件

        String resource = "mybatis-config.xml";

        //使用MyBatis提供的Resources类加载mybatis的配置文件（它也加载关联的映射文件）

        Reader reader = Resources.getResourceAsReader(resource);

        //构建sqlSession的工厂

        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);

        //创建能执行映射文件中sql的sqlSession

        SqlSession session = sessionFactory.openSession();

//        String statement="Cuiyw.MyBatis.DBMapping.UserMapper.addUser";

//        User user=new User();

//        user.setName("Cuiyw");

//        user.setAge(27);

//        int result=session.insert(statement, user);

//        session.commit();

//        session.close();

//        System.out.println(user.getId());

        System.out.println("------所有记录----------");

        String statement="Cuiyw.MyBatis.DBMapping.UserMapper.getUserList";

        List<User>users=session.selectList(statement);

        for (User u: users) {

          System.out.println(u.toString());

        }

        System.out.println("------分页----------");

        PageHelper.startPage(1, 5, true);

        statement="Cuiyw.MyBatis.DBMapping.UserMapper.getUserList";

        users=session.selectList(statement);

        for (User u: users) {

          System.out.println(u.toString());

        } 

        PageInfo<User> pageInfo = new PageInfo<User>(users);

        System.out.println("数据总数：" + pageInfo.getTotal());

        System.out.println("数据总页数：" + pageInfo.getPages());

        System.out.println("最后一页：" + pageInfo.getLastPage());  

        for (User u: pageInfo.getList()) {

            System.out.println(u.toString());

        }

    }

}

码农公寓

相关文章