pagehelper分页插件的简单实用

结合mybatis实现对pagehelper分页插件的简单使用。

一、创建一个maven项目并导入相关依赖

依赖文件：pom.xml

xml version="1.0" encoding="UTF-8"?>
<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>4.0.0modelVersion>

    <groupId>com.mgygroupId>
    <artifactId>Mybatis_10_pagehelperartifactId>
    <version>1.0-SNAPSHOTversion>

    <dependencies>
        <dependency>
            <groupId>org.mybatisgroupId>
            <artifactId>mybatisartifactId>
            <version>3.4.1version>
        dependency>
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <version>8.0.16version>
        dependency>
        <dependency>
            <groupId>log4jgroupId>
            <artifactId>log4jartifactId>
            <version>1.2.13version>
        dependency>
        <dependency>
            <groupId>junitgroupId>
            <artifactId>junitartifactId>
            <version>4.12version>
            <scope>testscope>
        dependency>
        
        <dependency>
            <groupId>com.github.pagehelpergroupId>
            <artifactId>pagehelperartifactId>
            <version>5.0.0version>
        dependency>

    dependencies>
project>

二、创建一个操作实体：Employee.java

package com.mgy.mybatis.bean;

public class Employee {

    private Integer id;
    private String lastName;
    private String email;
    private String gender;
    private EmpStatus empStatus = EmpStatus.LOGOUT;

    public Employee() {
    }

    public Employee(String lastName, String email, String gender) {
        this.lastName = lastName;
        this.email = email;
        this.gender = gender;
    }

    public EmpStatus getEmpStatus() {
        return empStatus;
    }

    public void setEmpStatus(EmpStatus empStatus) {
        this.empStatus = empStatus;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    @Override
    public String toString() {
        return "Employee{" +
                "id=" + id +
                ", lastName='" + lastName + '\'' +
                ", email='" + email + '\'' +
                ", gender='" + gender + '\'' +
                '}';
    }
}

其他操作可能用到的枚举类：EmpStatus.java

package com.mgy.mybatis.bean;

/**
 * @author MGY
 * @data 2019/11/20 22:00
 */
public enum EmpStatus {

    LOGIN,LOGOUT,REMOVE;
}

 

三、配置全局配置文件：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>

    <typeHandlers>
        <typeHandler handler="org.apache.ibatis.type.EnumOrdinalTypeHandler" javaType="com.mgy.mybatis.bean.EmpStatus" />
    typeHandlers>

    <plugins>
        <plugin interceptor="com.github.pagehelper.PageInterceptor">plugin>
    plugins>

    <environments default="dev_mysql">
        <environment id="dev_mysql">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis?allowMultiQueries = true&useUnicode=true&characterEncoding=UTF-8&userSSL=false&serverTimezone=GMT%2B8" />
                <property name="username" value="root" />
                <property name="password" value="root" />
            dataSource>
        environment>

        <environment id="dev_oracle">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="oracle.jdbc.OracleDriver" />
                <property name="url" value="jdbc:oracle:thin:@localhost:1521:orcl" />
                <property name="username" value="scott" />
                <property name="password" value="123456" />
            dataSource>
        environment>
    environments>

    
    <databaseIdProvider type="DB_VENDOR">
        
        <property name="MySQL" value="mysql"/>
        <property name="Oracle" value="oracle"/>
        <property name="SQL Server" value="sqlserver"/>
    databaseIdProvider>

    
    <mappers>
        <mapper resource="EmployeeMapper.xml" />
    mappers>
configuration>

四、配置一个日志配置文件，方便在控制台查看sql语句的操作：log4j.xml

xml version="1.0" encoding="UTF-8" ?>
DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
 
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
 
 <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
   <param name="Encoding" value="UTF-8" />
   <layout class="org.apache.log4j.PatternLayout">
    <param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS} %m  (%F:%L) \n" />
   layout>
 appender>
 <logger name="java.sql">
   <level value="debug" />
 logger>
 <logger name="org.apache.ibatis">
   <level value="info" />
 logger>
 <root>
   <level value="debug" />
   <appender-ref ref="STDOUT" />
 root>
log4j:configuration>

五、创建一个操作数据库的持久类：EmployeeMapper.java

package com.mgy.mybatis.dao;

import com.mgy.mybatis.bean.Employee;

import java.util.List;

public interface EmployeeMapper {

    Employee getEmpById(Integer id);

    Long addEmps(Employee employee);

    List getMySQLEmployees();

    List getOracleEmployees();
}

六、配置持久类EmployeeMapper.java的mybatis的映射文件：EmployeeMapper.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="com.mgy.mybatis.dao.EmployeeMapper">
    <select id="getEmpById" resultType="com.mgy.mybatis.bean.Employee" >
        select id, last_name lastName, email, gender from tbl_employee where id = #{id}
    select>

    
    <insert id="addEmps" useGeneratedKeys="true" keyProperty="id">
        insert into tbl_employee(last_name, email, gender, empStatus)
        values (#{lastName}, #{email}, #{gender}, #{empStatus})
    insert>

    
    <select id="getMySQLEmployees" resultMap="PageEmp" databaseId="oracle">
        select * from tbl_employee
    select>

    
    <select id="getOracleEmployees" resultMap="PageEmp" databaseId="oracle">
        select * from employees
    select>

    <resultMap id="PageEmp" type="com.mgy.mybatis.bean.Employee">
        <id column="employee_id" property="id" />
        <result column="last_name" property="lastName" />
        <result column="email" property="email" />
        <result column="gender" property="gender" />
    resultMap>
mapper>

七、编写测试类：MyBatisTest.java

package com.mgy.mybatis.test;

import com.github.pagehelper.Page;
import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.mgy.mybatis.bean.EmpStatus;
import com.mgy.mybatis.bean.Employee;
import com.mgy.mybatis.dao.EmployeeMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.ExecutorType;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.UUID;

/**
 * 1、接口式编程
 *    原生：         Dao       ===========>    DaoImpl
 *    mybatis:       Mapper    ===========>    xxMapper.xml
 * 2、SqlSession 代表和数据库的一次会话；用完必须关闭
 * 3、SqlSession 和 connection 一样，它们都是非线程安全。每次使用都应该去获取新的对象
 * 4、mapper 接口没有实现类，但是 mybatis 会为这个接口生成一个代理对象
 *     （将接口和 xml 进行绑定）
 *     EmployeeMapper empMapper = sqlSession.getMapper(EmployeeMapper.class);
 * 5、两个重要的配置文件：
 *      mybatis 的全局配置文件：包含数据库连接池信息，事务处理器信息等....系统运行环境信息
 *      sql 映射文件：保存了每一个 sql 语句的映射信息：
 *                    将 sql 抽取出来
 */
public class MyBatisTest {

    public SqlSessionFactory getSqlSessionFactory() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        return new SqlSessionFactoryBuilder().build(inputStream);
    }

    /**
     * 1、根据 xml 配置文件（全局配置文件）创建一个 SqlSessionFactory 对象  有数据源一些运行环境信息
     * 2、sql 映射文件；配置了每一个 sql，以及 sql 的封装规则等。
     * 3、将 sql 映射文件注册在全局配置文件中
     * 4、写代码：
     *      1）、根据全局配置文件得到 SqlSessionFactory
     *      2）、使用 sqlSessionFactory 获取到 sqlSession 对象，使用它来执行增删改查
     *           一个 sqlSession 就是代表和数据库的一次会话，用完关闭
     *      3）、使用 sql 的唯一标识来告诉 MyBatis 执行哪个 sql。sql 都是保存在 sql 映射文件中的
     * @throws IOException
     */
    @Test
    public void test() throws IOException {

        // 2、获取sqlSession实例，能直接执行已经映射的sql语句
        SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
        SqlSession sqlSession = sqlSessionFactory.openSession();

        try {
            // selectOne 的参数
            // 参数1  sql的唯一标识：statement Unique identifier matching the statement to use.
            // 参数2  执行sql要用的参数：parameter A parameter object to pass to the statement.
            Employee employee = sqlSession.selectOne("com.mgy.mybatis.dao.EmployeeMapper.getEmpById", 1);
            System.out.println(employee);
        } finally {
            sqlSession.close();
        }
    }

    @Test
    public void test01() throws IOException {

        // 1、获取 sqlSessionFactory 对象
        SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
        // 2、获取 sqlSession 对象
        SqlSession sqlSession = sqlSessionFactory.openSession();

        try {
            // 3、获取接口的实现类对象
            // MyBatis 会为接口自动的创建一个代理对象，代理对象去执行增删改查方法
            EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
            Employee empById = mapper.getEmpById(1);
            System.out.println(mapper.getClass());
            System.out.println(empById);
        } finally {
            sqlSession.close();
        }
    }

    @Test
    public void testBatch() throws IOException {
        SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();

        // 可以执行批量操作的 sqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession(ExecutorType.BATCH);

        long start = System.currentTimeMillis();
        try {
            EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
            for (int i = 0; i < 10000; i++) {
                mapper.addEmps(new Employee(UUID.randomUUID().toString().substring(0, 5), "b", "1"));
            }
            sqlSession.commit();
            long end = System.currentTimeMillis();

            /*
             * 批量：（预编译 sql 一次 ==> 设置参数 10000 次 ===> 执行一次） 执行时长：12394
             * Parameters: 09c31(String), b(String), 1(String)  (BaseJdbcLogger.java:145)
             *
             * 非批量： （预编译 sql = 设置参数 = 执行 = 10000 次） 执行时长：21923
             * Preparing: insert into tbl_employee(last_name, email, gender) values (?, ?, ?)   (BaseJdbcLogger.java:145)
             * Parameters: 48154(String), b(String), 1(String)  (BaseJdbcLogger.java:145)
            * */
            System.out.println("执行时长："+ (end - start));

        } finally {
            sqlSession.close();
        }
    }

    /**
     * MySQL 的测试
     * @throws IOException
     */
    @Test
    public void testMySQLPageHelper() throws IOException {
        SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
        SqlSession sqlSession = sqlSessionFactory.openSession();

        try {
            EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
            Page