SpringBoot中默认缓存实现方案的示例代码_java

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);
 }
 
}

10. 完整项目结构