MyBatis-Plus分页插件的配置和使用
1.0 MyBatis-Plus分页插件的配置和使用)
MyBatis Plus自带的分页插件，只要简单的配置节课实现分页的功能；
1.1 添加配置类
由于版本的区别更换版本如下：此前版本无法引用MybatisPlusInterceptor 故更换使用3.5.1
<!-- <dependency>-->
<!-- <groupId>com.baomidou</groupId>-->
<!-- <artifactId>mybatis-plus-boot-starter</artifactId>-->
<!-- <version>3.3.1</version>-->
<!-- </dependency>-->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.5.1</version>
</dependency>
package com.example.config;
import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
//地址指向mappe层 持久层也就是Dao接口
@MapperScan("com.example.mapper")
public class MyBatisPlusConfig {
@Bean
public MybatisPlusInterceptor mybatisPlusInterceptor() {
//调用的mybatis的分页拦截器
MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
//我们在此选择数据库的类型，也有其他的参数 我这边选择的mysql
interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
return interceptor;
}
}
查看数据库类型 DbType.（MYSQL）
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//
package com.baomidou.mybatisplus.annotation;
public enum DbType {
MYSQL("mysql", "MySql数据库"),
MARIADB("mariadb", "MariaDB数据库"),
ORACLE("oracle", "Oracle11g及以下数据库(高版本推荐使用ORACLE_NEW)"),
ORACLE_12C("oracle12c", "Oracle12c+数据库"),
DB2("db2", "DB2数据库"),
H2("h2", "H2数据库"),
HSQL("hsql", "HSQL数据库"),
SQLITE("sqlite", "SQLite数据库"),
POSTGRE_SQL("postgresql", "Postgre数据库"),
SQL_SERVER2005("sqlserver2005", "SQLServer2005数据库"),
SQL_SERVER("sqlserver", "SQLServer数据库"),
DM("dm", "达梦数据库"),
XU_GU("xugu", "虚谷数据库"),
KINGBASE_ES("kingbasees", "人大金仓数据库"),
PHOENIX("phoenix", "Phoenix HBase数据库"),
GAUSS("zenith", "Gauss 数据库"),
CLICK_HOUSE("clickhouse", "clickhouse 数据库"),
GBASE("gbase", "南大通用(华库)数据库"),
GBASEDBT("gbasedbt", "南大通用数据库"),
OSCAR("oscar", "神通数据库"),
SYBASE("sybase", "Sybase ASE 数据库"),
OCEAN_BASE("oceanbase", "OceanBase 数据库"),
FIREBIRD("Firebird", "Firebird 数据库"),
HIGH_GO("highgo", "瀚高数据库"),
CUBRID("cubrid", "CUBRID数据库"),
GOLDILOCKS("goldilocks", "GOLDILOCKS数据库"),
CSIIDB("csiidb", "CSIIDB数据库"),
SAP_HANA("hana", "SAP_HANA数据库"),
IMPALA("impala", "impala数据库"),
OTHER("other", "其他数据库");
private final String db;
private final String desc;
public static DbType getDbType(String dbType) {
DbType[] var1 = values();
int var2 = var1.length;
for(int var3 = 0; var3 < var2; ++var3) {
DbType type = var1[var3];
if (type.db.equalsIgnoreCase(dbType)) {
return type;
}
}
return OTHER;
}
public String getDb() {
return this.db;
}
public String getDesc() {
return this.desc;
}
private DbType(final String db, final String desc) {
this.db = db;
this.desc = desc;
}
}
1.2 对分页功能点进行测试
package com.example;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.example.mapper.UserMapper;
import com.example.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
@SpringBootTest
public class MybatisPlusPage {
@Autowired
public UserMapper userMapper;
@Test
public void testpage(){
// 实体类作为对象
//默认参数第几页？每页几行？
Page<User> page = new Page<>(1,3);
userMapper.selectPage(page,null);
System.out.println(page);
}
}
执行结果为：
默认是第一页故我们后端传入的第一页每页3行，后端只验证3行对应 LIMIT ? 故每页3行数据；
==> Preparing: SELECT uid AS id,user_name AS name,age,email,is_delect FROM t_user WHERE is_delect=0 LIMIT ?
==> Parameters: 3(Long)
<== Columns: id, name, age, email, is_delect
<== Row: 4, 我是老王, 18, test4@baomidou.com, 0
<== Row: 5, Billie, 10, test5@baomidou.com, 0
<== Row: 6, 老王, 10, 757631644001, 0
<== Total: 3
当我们更换为第二页，每页3行数据的时候看下图；
LIMIT ? ,? 为2个参数第一个计算规则为 2-1后得出1*3=3；第二数据就是每页3行数据；
结果如下：
<== Columns: total
<== Row: 10
<== Total: 1
==> Preparing: SELECT uid AS id,user_name AS name,age,email,is_delect FROM t_user WHERE is_delect=0 LIMIT ?,?
==> Parameters: 3(Long), 3(Long)
<== Columns: id, name, age, email, is_delect
<== Row: 7, 老王超1, 10, 757631644111, 0
<== Row: 8, 闫文超2, 10, 757631644221, 0
<== Row: 9, 闫文超3, 10, 757631644331, 0
<== Total: 3
1.3 对分页功能点进行测试
在这里插入图片描述
@Test
public void testpage(){
// 实体类作为对象
//默认参数第几页？每页几行？
Page<User> page = new Page<>(3,2);
userMapper.selectPage(page,null);
System.out.println("获取当前页数据"+page.getRecords());
System.out.println("获取总页数"+page.getPages());
System.out.println("获取数据总条数"+page.getTotal());
System.out.println("是否有上一页"+page.hasNext());
System.out.println("是否有下一页"+page.hasPrevious());
System.out.println("---");
System.out.println("返回: 此对象的哈希码值"+page.hashCode());
System.out.println("当前是第几页"+page.getCurrent());
System.out.println("每页几条数据"+page.getSize());
}
测试数据如下：
<== Columns: total
<== Row: 10
<== Total: 1
==> Preparing: SELECT uid AS id,user_name AS name,age,email,is_delect FROM t_user WHERE is_delect=0 LIMIT ?,?
==> Parameters: 4(Long), 2(Long)
<== Columns: id, name, age, email, is_delect
<== Row: 8, 闫文超2, 10, 757631644221, 0
<== Row: 9, 闫文超3, 10, 757631644331, 0
<== Total: 2
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@76db540e]
获取当前页数据[User(id=8, name=闫文超2, age=10, email=757631644221, isDelect=0), User(id=9, name=闫文超3, age=10, email=757631644331, isDelect=0)]
获取总页数5
获取数据总条数10
是否有上一页true
是否有下一页true
---
返回: 此对象的哈希码值722321959
当前是第几页3
每页几条数据2
2.0 自定义分页Demo
package com.example.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.example.pojo.User;
import org.apache.ibatis.annotations.Param;
import org.springframework.stereotype.Repository;
//继承 BaseMapper<实体类> 即可调用crud方法
//标记持久层组件
@Repository
public interface UserMapper extends BaseMapper<User> {
/**
* 根据年龄查询用户列表，分页显示
* @param page 分页对象,xml中可以从里面进行取值,传递参数 Page 即自动分页,必须放在第一位
* @param age 年龄
* @return
*/
Page<User> selectpageVo(@Param("page") Page<User> page,@Param("age") Integer age);
}
<?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.example.mapper.UserMapper">
<sql id="File_Column_List" >
uid,user_name,age,email
</sql>
<select id="selectpageVo" resultType="User">
select <include refid="File_Column_List"/>
from t_user where age >#{age}
</select>
</mapper>
下面这个配置是对应xml中resultType 返回对象的值；就行配置
spring:
# 配置数据源信息
datasource:
#配置数据源类型
type: com.zaxxer.hikari.HikariDataSource
#配置连接数据的信息
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/mybatis_plus?characterEncoding=utf-8&userSSL=false
username: root
password: root
mybatis-plus:
configuration:
#加入mybatis 日志查看执行语句sql语句
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
global-config:
db-config:
table-prefix: t_
#设置统一的主键生成策略
id-type: auto
#配置实体类类型别名对应的包(也就是实体类和mapper.xml的返回的对象对应)
type-aliases-package: com.example.pojo
测试类
@Test
public void testpage01(){
// 实体类作为对象
//默认参数第几页？每页几行？
Page<User> page = new Page<>(2,2);
userMapper.selectpageVo(page,10);
System.out.println("page"+page);
}
执行结果如下
==> Preparing: SELECT COUNT(*) AS total FROM t_user WHERE age > ?
==> Parameters: 10(Integer)
<== Columns: total
<== Row: 9
<== Total: 1
==> Preparing: select uid,user_name,age,email from t_user where age >? LIMIT ?,?
==> Parameters: 10(Integer), 2(Long), 2(Long)
<== Columns: uid, user_name, age, email
<== Row: 4, 我是老王, 18, test4@baomidou.com
<== Row: 10, 闫文超4, 14, 757631644441
<== Total: 2
MyBatis-Plus分页插件的配置和使用到这里就暂时结束了；
