springboot缓存抽象例子

• 一
• 新建project

选中Web,cache,mysql,mybatis模块

• 创建数据库表和Javabean(字段\构造器\getter and setter\tostring)
• 配置数据源信息   

application.properties中

spring.datasource.url=jdbc:mysql://localhost:3306/cache
spring.datasource.username=root
spring.datasource.password=123456
#  spring.datasource.driver-class-name=com.mysql.jdbc.Driver

• @MapperScan指定需要扫描的mapper接口所在的包

主程序上

@MapperScan("com.example.springdatacache.mapper")
@SpringBootApplication
public class SpringdataCacheApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringdataCacheApplication.class, args);
    }

}

• 新建mapper包,EmployeeMapper\DepartmentMapper接口类,添加@Mapper注解(也可以不用)

package com.example.springdatacache.mapper;

import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface EmployeeMapper {
}

• 里面添加crud方法

@Select("select * from employee where id=#{id}")
    public Employee getEmpById(Integer id);

    @Update("update employee set lastName=#{lastName},email=#{email},gender=#{gender},d_id=#{dId} where id=#{id}")
    public void updateEmp(Employee employee);

    @Delete("DELETE FROM employee WHERE id=#{id}")
    public void deleteEmpById(Integer id);

    @Insert("insert into employee(lastName,email,gender,d_id) values(#{lastName},#{email},#{gender},#{dId}")
    public void insertEmployee(Employee employee);

• 修改测试类

package com.example.springdatacache;

import com.example.springdatacache.bean.Employee;
import com.example.springdatacache.mapper.EmployeeMapper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
class SpringdataCacheApplicationTests {

    @Autowired
    EmployeeMapper employeeMapper;

    @Test
    void contextLoads() {
        Employee empById = employeeMapper.getEmpById(1);
        System.out.println(empById);
    }

}

运行时报错:java.sql.SQLException: The server time zone value ‘�й���׼ʱ��’ is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.
解决方法:在数据库配置路径上加上     ?serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=utf-8

• 新建service包EmployeeService类

package com.example.springdatacache;

import com.example.springdatacache.bean.Employee;
import com.example.springdatacache.mapper.EmployeeMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class EmployeeService {
    
    @Autowired
    EmployeeMapper employeeMapper;
    
    public Employee getEmp(Integer id){
        System.out.println("查询"+id+"号员工");
        Employee emp = employeeMapper.getEmpById(id);
        return emp;
    }
}

• 新建controller包EmployeeController

package com.example.springdatacache.controller;

import com.example.springdatacache.EmployeeService;
import com.example.springdatacache.bean.Employee;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class EmployeeController {
    
    @Autowired
    EmployeeService employeeService;
    
    @GetMapping("/emp/{id}")
    public Employee getEmployee(@PathVariable("id") Integer id){
        Employee emp = employeeService.getEmp(id);
        return emp;
    }
}

此时数据库中的字段为

javabean中的字段为dId

在application.properties中新增

#开启驼峰命名匹配规则
mybatis.configuration.map-underscore-to-camel-case=true

• 二
• 快速体验缓存

1. 开启基于注解的缓存    @EnableCaching
2. 标注缓存注解即可       @Cacheable ,@CacheEvict, @CachePut

• 主程序类中

@MapperScan("com.example.springdatacache.mapper")
@SpringBootApplication
@EnableCaching
public class SpringdataCacheApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringdataCacheApplication.class, args);
    }

}

• application.properties中开启日志,打印sql语句

logging.level.com.example.springdatacache.mapper = debug

控制台打印

在service中使用@Cacheable

/**
     * 将方法中的运行结果进行缓存,以后再要相同的数据,直接从缓存中获取,不用调用方法
     * CacheManager管理多个Cache组件,对缓存的真正CRUD操作在Cache组件中,每一个缓存组件有自己唯一一个名字
     *
     * 几个属性:
     *     cacheNames/value  :指定缓存组件的名字
     *     key:缓存数据使用的key可以用它来指定.默认是使用方法参数的值  1-方法的返回值
     *           编写Spel    #id,参数id的值    #a0 #p0  #root.arg[0]
     *     (key/keyGenerator二选一使用)keyGenerator:key的生成器;可以自己指定key的生成器的组件id
     *     cacheManager:指定缓存管理器 ;或者用cacheResolver指定获取解析器
     *     condition:指定符合条件的情况下才缓存
     *                 condition="#id>0"
     *     unless:否定缓存;当unless指定的条件为true,方法的返回值就不会缓存,可以获取到结果进行判断
     *                 unless="#result == null"
     *     sync:是否使用异步模式
     *
     * @param id
     * @return
     */
    @Cacheable(cacheNames = {"emp"})
    public Employee getEmp(Integer id){
        System.out.println("查询"+id+"号员工");
        Employee emp = employeeMapper.getEmpById(id);
        return emp;
    }