Mybatis之分页插件pagehelper的简单使用

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());
        }
    }
}