简介
Mybatis-Plus是一个Mybatis框架的增强插件。
即可快速进行 CRUD 操作,从而节省大量时间.代码生成,分页,性能分析等功能一应俱全,
官网
1.建student数据表
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(200) COLLATE utf8_bin DEFAULT NULL,
`age` tinyint(3) unsigned DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 COLLATE=utf8_bin;
LOCK TABLES `student` WRITE;
INSERT INTO `student` (`id`, `name`, `age`) VALUES (1,'点点',16),(2,'平平',16),(3,'美美',16),(4,'团团',16);
UNLOCK TABLES;
#COLLATE 表示排序规则
项目目录
项目配置
server.port=8080
## ==============================
## MySQL connection config
## ==============================
spring.datasource.url=jdbc:mysql://localhost:3306/wg_insert?useUnicode=true&characeterEncoding=utf-8&serverTimezone=UTC
spring.datasource.username=root
spring.datasource.password=159682
### ==============================
### Hikari 数据源专用配置
### ==============================
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.hikari.maximum-pool-size=20
spring.datasource.hikari.minimum-idle=5
### ==============================
### mybatis配置
### ==============================
mybatis-plus.mapper-locations=classpath:mapper/*.xml
mybatis-plus.type-aliases-package=com.wg.mybits.entity
#<!--开启驼峰式命名，数据库的列名能够映射到去除下划线驼峰命名后的字段名-->
mybatis-plus.configuration.map-underscore-to-camel-case=true
#<!--全局地开启或关闭配置文件中的所有映射器已经配置的任何缓存-->
mybatis-plus.configuration.local-cache-scope=session
#开启二级缓存
mybatis-plus.configuration.cache-enabled=true
#这个配置会将执行的sql打印出来，在开发或测试的时候可以用
mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl
# ==============================
# Thymeleaf configurations
# ==============================
spring.thymeleaf.mode=HTML
spring.thymeleaf.cache=false
spring.thymeleaf.servlet.content-type=text/html
spring.thymeleaf.encoding=UTF-8
# ==============================
# redis configurations
# ==============================
spring.redis.host=127.0.0.1
spring.redis.port=6379
spring.redis.password=123456
# Redis数据库索引（默认为0）
spring.redis.database=0
# 连接池最大连接数（使用负值表示没有限制）
spring.redis.lettuce.pool.max-active=8
# 连接池最大阻塞等待时间（使用负值表示没有限制）
spring.redis.lettuce.pool.max-wait=-1ms
# 连接池中的最大空闲连接
spring.redis.lettuce.pool.max-idle=8
# 连接池中的最小空闲连接
spring.redis.lettuce.pool.min-idle=0
2.编写实体类 StudentEntity.java
package com.wg.mybits.entity;
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import java.io.Serializable;
@TableName("student")
public class StudentEntity implements Serializable {
// 学号
@TableId(type = IdType.AUTO)
private Integer id;
// 姓名
private String name;
// 年龄
private Integer age;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
final StringBuilder sb = new StringBuilder("StudentEntity{");
sb.append("id=").append(id);
sb.append(", name='").append(name).append('\'');
sb.append(", age=").append(age);
sb.append('}');
return sb.toString();
}
}
3.编写StudentMapper(即Dao层)
继承BaseMapper就自动会有很多基础的CRUD方法具体参考
package com.wg.mybits.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.wg.mybits.entity.StudentEntity;
import org.apache.ibatis.annotations.Param;
import org.springframework.stereotype.Service;
@Service
public interface StudentMapper extends BaseMapper<StudentEntity> {
IPage<StudentEntity> selectPageVo(Page<StudentEntity> param, @Param("age") int age);
}
4.编写StudentService(即service层)
继承IService也会有很多基础方法具体参考
package com.wg.mybits.service;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.IService;
import com.wg.mybits.entity.StudentEntity;
public interface StudentService extends IService<StudentEntity> {
public IPage<StudentEntity> selectUserPage(Page<StudentEntity> page, int age);
}
StudentServiceImpl
package com.wg.mybits.service.impl;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.wg.mybits.entity.StudentEntity;
import com.wg.mybits.mapper.StudentMapper;
import com.wg.mybits.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;
@Service
public class StudentServiceImpl extends ServiceImpl<StudentMapper,StudentEntity> implements StudentService{
@Autowired
private StudentMapper studentMapper;
@Override
@Cacheable(value="user",key="'userList'")
public IPage<StudentEntity> selectUserPage(Page<StudentEntity> page, int age) {
IPage<StudentEntity> pageResult = studentMapper.selectPageVo(page,age);
return pageResult;
}
}
5.配置文件的编写
这里采用redis作为二级缓存
MybatisPlusConfig
package com.wg.mybits.config;
import com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor;
import com.baomidou.mybatisplus.extension.plugins.PerformanceInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
@MapperScan("com.wg.mybits.mapper")
public class MybatisPlusConfig {
/**
* mybatis-plus SQL执行效率插件【生产环境可以关闭】
*/
@Bean
public PerformanceInterceptor performanceInterceptor() {
return new PerformanceInterceptor();
}
/**
* 分页插件
*/
@Bean
public PaginationInterceptor paginationInterceptor() {
PaginationInterceptor paginationInterceptor = new PaginationInterceptor();
// 设置请求的页面大于最大页后操作， true调回到首页，false 继续请求 默认false
// paginationInterceptor.setOverflow(false);
// 设置最大单页限制数量，默认 500 条，-1 不受限制
// paginationInterceptor.setLimit(500);
return paginationInterceptor;
}
}
RedisConfig
package com.wg.mybits.config;
import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.CachingConfigurerSupport;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.cache.RedisCacheConfiguration;
import org.springframework.data.redis.cache.RedisCacheManager;
import org.springframework.data.redis.cache.RedisCacheWriter;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.serializer.RedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
import java.time.Duration;
@EnableCaching // 开启缓存
@Configuration
public class RedisConfig extends CachingConfigurerSupport {
//缓存管理器
@Bean
public CacheManager cacheManager(RedisConnectionFactory redisConnectionFactory) {
RedisCacheConfiguration redisCacheConfiguration = RedisCacheConfiguration.defaultCacheConfig()
.entryTtl(Duration.ofHours(1)); // 设置缓存有效期一小时
return RedisCacheManager
.builder(RedisCacheWriter.nonLockingRedisCacheWriter(redisConnectionFactory))
.cacheDefaults(redisCacheConfiguration).build();
}
/**
* 配置自定义redisTemplate
*
* @param connectionFactory
* @return
*/
@Bean
public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory connectionFactory) {
RedisTemplate<String, Object> template = new RedisTemplate<>();
template.setConnectionFactory(connectionFactory);
template.setValueSerializer(jackson2JsonRedisSerializer());
//使用StringRedisSerializer来序列化和反序列化redis的key值
template.setKeySerializer(new StringRedisSerializer());
template.setHashKeySerializer(new StringRedisSerializer());
template.setHashValueSerializer(jackson2JsonRedisSerializer());
template.afterPropertiesSet();
return template;
}
/**
* json序列化
* @return
*/
@Bean
public RedisSerializer<Object> jackson2JsonRedisSerializer() {
//使用Jackson2JsonRedisSerializer来序列化和反序列化redis的value值
Jackson2JsonRedisSerializer<Object> serializer = new Jackson2JsonRedisSerializer<Object>(Object.class);
ObjectMapper mapper = new ObjectMapper();
mapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
serializer.setObjectMapper(mapper);
return serializer;
}
}
6.支持自定义的sql
这是分页的sql
StudentMapper.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.wg.mybits.mapper.StudentMapper">
<select id="selectPageVo" resultType="com.wg.mybits.entity.StudentEntity" parameterType="int">
SELECT * FROM student WHERE age = #{age}
</select>
</mapper>
7.测试类StudentMapperTest
包含
- MyBatis-Plus基础CRUD演示
- QueryWrapper条件构造器的条件查询
- 自定义SQL分页查询
package com.wg.mybits;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.wg.mybits.entity.StudentEntity;
import com.wg.mybits.service.impl.StudentServiceImpl;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@SpringBootTest
public class StudentMapperTest {
@Autowired
private StudentServiceImpl studentService;
@Test
public void testGet(){
//条件查询
QueryWrapper<StudentEntity> queryWrapper1 = new QueryWrapper<>();
// queryWrapper1.lambda().eq(StudentEntity::getAge,16);
queryWrapper1.eq("age",16);
System.out.println(studentService.getMap(queryWrapper1).size());
System.out.println(studentService.getById(1).getName());
System.out.println(studentService.getById(1).getName());
System.out.println(studentService.getById(1).getName());
//查询age=16的学生,并且分页
Page<StudentEntity> page = new Page<>(1,2);
System.out.println(studentService.selectUserPage(page,16).getSize());
//检测二级缓存
@System.out.println(studentService.selectUserPage(page,16).getSize());
}
}
mybatis中同一个mapper中的多个查询为什么是启用多个sqlSession来处理的？
因为你的userMapper不是从同一个sqlSession得到，所以不能一级缓存，
SqlSession sqlSession = sqlSessionFactory.openSession();//
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
先通过同一个sqlSeesion获取UserMapper的代理对象，
再使用代理对象调用方法，这样在执行相同sql语句是就不会创建多个SqlSesssion
redis做二级缓存
