SpringBoot开发中如何缓存数据, 减少数据库的访问频率？

一：自定义是否开启缓存

方法一：

在不同环境的配置文件中如application-dev.yml、application-test.yml、application-prod.yml，修改 spring.cache.type = none;

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spring:
  cache:
  	type: none

方法二：

自定义配置

application.yml：

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## 开启数据缓存
caching:
  enabled: true

com.scaffold.test.config.CacheConfig

缓存配置文件

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@Configuration
@EnableCaching
//配置文件读取是否启用此配置
@ConditionalOnProperty(prefix = "caching", name = "enabled", havingValue = "true")
public class CacheConfig {

}

二：simpleCacheManage

simpleCacheManage 基于ConcurrentHashMap 实现，不依赖其他库，如果增加了注解@EnableCaching，默认开启缓存，可以通过设置cache-names限制缓存列表

1.设置缓存列表

application.yml

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spring:
  cache:
  	type: simple
  	cache-names: cache1,cache2

2.添加maven依赖：

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<!-- cache 依赖 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-cache</artifactId>
</dependency>

3.使用注解

注意：所有的注解是加到实现类serviceImpl方法上的

|-------------|-------------------------------------------------------------|
| 注解 | 描述 |
| @Cacheable | 在方法执行前 Spring 先查看缓存中是否有数据，若有，则直接返回缓存数据；若无数据，调用方法将方法返回值放入缓存中 |
| @CachePut | 无论怎样，都会将方法的返回值放到缓存中。 |
| @CacheEvict | 将一条或多条数据从缓存中删除 |
| @Caching | 可以通过 @Caching 注解组合多个注解策略在一个方法 |

@Cacheable、@CachePut、@CacheEvict 都有 value 属性，指定的是要使用的缓存名称；key 属性指定的是数据在缓存中存储的键。

4.代码实现：

4.1配置类

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package com.scaffold.test.config;

import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cache.concurrent.ConcurrentMapCacheManager;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.time.Duration;

/**
 * 缓存配置文件
 * 配置文件读取是否启用此配置
 * @author alex
 */
@Configuration
@EnableCaching
@ConditionalOnProperty(prefix = "caching", name = "enabled", havingValue = "true")
public class CacheConfig {

    @Bean
    public CacheManager cacheManager() {
        return new ConcurrentMapCacheManager("cacheData");
    }
  }

4.2实体类

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package com.scaffold.test.entity;

import lombok.Data;
import lombok.EqualsAndHashCode;

import java.io.Serializable;

/**
 * @author alex wong
 */
@Data
@EqualsAndHashCode(callSuper = false)
public class Student implements Serializable {

    private static final long serialVersionUID=1L;

    private int id;

    private String name;

    private Integer age;

}

4.3service层

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package com.scaffold.test.service;

import com.scaffold.test.entity.Student;
import com.baomidou.mybatisplus.extension.service.IService;

import java.util.List;

/**
 * <p>
 * 服务类
 * </p>
 *
 * @author alex wong
 */
public interface StudentService extends IService<Student> {

    List<Student> findAll();

    Student findStudent(Student student);

    Student testStudent(String text);

    void deleteStudent(Student student);

    void saveStudent(Student student);

}

4.4service实现类

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package com.scaffold.test.service.impl;

import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.scaffold.test.entity.Student;
import com.scaffold.test.mapper.StudentMapper;
import com.scaffold.test.service.StudentService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.cache.annotation.CacheEvict;
import org.springframework.cache.annotation.CachePut;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import java.util.List;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author alex wong
 */

@Slf4j
@Service
public class StudentServiceImpl extends ServiceImpl<StudentMapper, Student> implements StudentService {

    @Resource
    private StudentMapper studentMapper;

    @Override
    @Cacheable(value = "cacheData")
    public List<Student> findAll(){
        return studentMapper.selectAll();
    }

    /**
     * 缓存查询数据
     * @Cacheable 缓存数据到缓存 student 中
     * 其中缓存名称为 student 数据的 key 是 student 的 id
     * @param student s
     * @return
     */
    @Override
    @Cacheable(value = "cacheData", key = "#student.id")
    public Student findStudent(Student student) {
        log.warn("增加了student为{}的数据缓存", student);
        int id = student.getId();
        if(id == 0){
            return null;
        }
        return studentMapper.findStudent(student);
    }

    /**
     * 删除缓存
     * @CacheEvict 从缓存 student 中删除
     * 其中缓存名称为 student 数据的 key 是 student 的 id
     * @param student s
     */
    @Override
    @CacheEvict(value = "cacheData", key = "#student.id")
    public void deleteStudent(Student student) {
        log.warn("删除了student为{}的数据缓存", student);
    }

    /**
     * @CachePut 缓存新增的或更新的数据到缓存
     * 其中缓存名称为 student 数据的 key 是 student 的 id
     * @param student
     */
    @Override
    @CachePut(value = "cacheData", key = "#student.id")
    public void saveStudent(Student student) {
        log.warn("保存了id、key 为{}的数据缓存", student);
        studentMapper.insertStudent(student);
    }


    @Override
    @Cacheable(value = "cacheData", key = "#text")
    public Student testStudent(String text) {
        System.out.println("test" + text);
        Student student = new Student();
        student.setName(text);
        return student;
    }
}

4.5dao层接口：

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package com.scaffold.test.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.scaffold.test.entity.Student;

import java.util.List;

/**
 * <p>
 * Mapper 接口
 * </p>
 *
 * @author alex wong
 */
public interface StudentMapper extends BaseMapper<Student> {

    List<Student> selectAll();

    Student findStudent(Student student);

    int insertStudent(Student student);
}

4.6Mapper。xml文件

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<?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.scaffold.test.mapper.StudentMapper">

    <!-- 通用查询映射结果 -->
    <resultMap id="BaseResultMap" type="com.scaffold.test.entity.Student">
        <result column="id" property="id"/>
        <result column="name" property="name"/>
        <result column="age" property="age"/>
    </resultMap>

    <!-- 通用查询结果列 -->
    <sql id="Base_Column_List">
        id,
        name, age
    </sql>

    <sql id="Where_Condition">
        <where>
            <if test="id != null and id != ''">
                id=#{id}
            </if>
            <if test="name != null and name != ''">
                and name=#{name}
            </if>
            <if test="age != null and age != ''">
                and age=#{age}
            </if>
        </where>
    </sql>

    <insert id="insertStudent">
        insert student
        (id, name, age)
        values
        (#{id}, #{name}, #{age})
    </insert>

    <select id="selectAll" resultMap="BaseResultMap">
        select * from student
    </select>

    <select id="findStudent" resultType="com.scaffold.test.entity.Student">
        select * from student
        <include refid="Where_Condition"></include>
    </select>
</mapper>

4.7sql

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SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
  `id` int(11) NOT NULL,
  `name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NOT NULL,
  `age` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES (1, '1', 2323);
INSERT INTO `student` VALUES (2, '2', 2323);
INSERT INTO `student` VALUES (3, '3', 2323);

SET FOREIGN_KEY_CHECKS = 1;

4.8Controller层

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package com.scaffold.test.controller;


import com.scaffold.test.entity.Student;
import com.scaffold.test.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

/**
 * <p>
 *  前端控制器
 * </p>
 *
 * @author alex wong
 */
@RestController
@RequestMapping("/student")
public class StudentController {

    @Autowired
    private StudentService studentService;

    @GetMapping("list")
    public List<Student> getAll(){
        return studentService.findAll();
    }

    @GetMapping("add")
    public void addStudent(Student student){
        studentService.saveStudent(student);
    }

    @GetMapping("find")
    public Student findStudent(Student student){
        return studentService.findStudent(student);
    }

    @GetMapping("delete")
    public void deleteStudent(Student student){
        studentService.deleteStudent(student);
    }

    @GetMapping("test")
    public Student test(@RequestParam String text){
        return studentService.testStudent(text);
    }
}