SpringBoot2.x系列教程57--SpringBoot中默认缓存实现方案

作者：一一哥

在上一节中，我带大家学习了在Spring Boot中对缓存的实现方案，尤其是结合Spring Cache的注解的实现方案，接下来在本章节中，我带大家通过代码来实现。

一. Spring Boot实现默认缓存

1. 创建web项目

我们按照之前的经验，创建一个web程序，并将之改造成Spring Boot项目，具体过程略。

2. 添加依赖包

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

<dependency>
   <groupId>mysql</groupId>
   <artifactId>mysql-connector-java</artifactId>
</dependency>

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

3. 创建application.yml配置文件

server:
  port: 8080
spring:
  application:
    name: cache-demo
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    username: root
    password: syc
    url: jdbc:mysql://localhost:3306/spring-security?useUnicode=true&characterEncoding=utf8&characterSetResults=utf8&useSSL=false&serverTimezone=UTC
  #cache:
    #type: generic #由redis进行缓存,一共有10种缓存方案
  jpa:
    database: mysql
    show-sql: true #开发阶段,打印要执行的sql语句.
    hibernate:
      ddl-auto: update

4. 创建一个缓存配置类

主要是在该类上添加@EnableCaching注解，开启缓存功能。

package com.yyg.boot.config;

import org.springframework.cache.annotation.EnableCaching;

/**
 * @Author 一一哥Sun
 * @Date Created in 2020/4/14
 * @Description Description
 * EnableCaching启用缓存
 */ 
@Configuration
@EnableCaching
public class CacheConfig {
}

5. 创建User实体类

package com.yyg.boot.domain;

import lombok.Data;
import lombok.ToString;

import javax.persistence.*;
import java.io.Serializable;

@Entity
@Table(name="user")
@Data
@ToString
public class User implements Serializable {

    //IllegalArgumentException: DefaultSerializer requires a Serializable payload
    // but received an object of type [com.syc.redis.domain.User]

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column
    private String username;

    @Column
    private String password;

}

6. 创建User仓库类

package com.yyg.boot.repository;

import com.yyg.boot.domain.User;
import org.springframework.data.jpa.repository.JpaRepository;

public interface UserRepository extends JpaRepository<User,Long> {
}

7. 创建Service服务类

定义UserService接口

package com.yyg.boot.service;

import com.yyg.boot.domain.User;

public interface UserService {

    User findById(Long id);

    User save(User user);

    void deleteById(Long id);

}

实现UserServiceImpl类

package com.yyg.boot.service.impl;

import com.yyg.boot.domain.User;
import com.yyg.boot.repository.UserRepository;
import com.yyg.boot.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.CacheEvict;
import org.springframework.cache.annotation.CachePut;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserRepository userRepository;

    //普通的缓存+数据库查询代码实现逻辑:
    //User user=RedisUtil.get(key);
    //   if(user==null){
    //        user=userDao.findById(id);
    //        //redis的key="product_item_"+id
    //        RedisUtil.set(key,user);
    //   }
    //   return user;

    /**
     *  注解@Cacheable:查询的时候才使用该注解!
     *  注意:在Cacheable注解中支持EL表达式
     *  redis缓存的key=user_1/2/3....
     *  redis的缓存雪崩,缓存穿透,缓存预热,缓存更新...
     *  condition = "#result ne null",条件表达式,当满足某个条件的时候才进行缓存
     *  unless = "#result eq null":当user对象为空的时候,不进行缓存
     */
    @Cacheable(value = "user", key = "#id", unless = "#result eq null")
    @Override
    public User findById(Long id) {

        return userRepository.findById(id).orElse(null);
    }

    /**
     * 注解@CachePut:一般用在添加和修改方法中
     * 既往数据库中添加一个新的对象,于此同时也往redis缓存中添加一个对应的缓存.
     * 这样可以达到缓存预热的目的.
     */
    @CachePut(value = "user", key = "#result.id", unless = "#result eq null")
    @Override
    public User save(User user) {
        return userRepository.save(user);
    }

    /**
     * CacheEvict:一般用在删除方法中
     */
    @CacheEvict(value = "user", key = "#id")
    @Override
    public void deleteById(Long id) {
        userRepository.deleteById(id);
    }

}

8. 创建Controller接口方法

package com.yyg.boot.web;

import com.yyg.boot.domain.User;
import com.yyg.boot.service.UserService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/user")
@Slf4j
public class UserController {

    @Autowired
    private UserService userService;

    @PostMapping
    public User saveUser(@RequestBody User user) {
        return userService.save(user);
    }

    @GetMapping("/{id}")
    public ResponseEntity<User> getUserById(@PathVariable("id") Long id) {
        User user = userService.findById(id);
        log.warn("user="+user.hashCode());
        HttpStatus status = user == null ? HttpStatus.NOT_FOUND : HttpStatus.OK;
        return new ResponseEntity<>(user, status);
    }

    @DeleteMapping("/{id}")
    public String removeUser(@PathVariable("id") Long id) {
        userService.deleteById(id);
        return "ok";
    }

}

9. 创建入口类

package com.yyg.boot;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class CacheApplication {

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

}