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Spring Cache框架

杼蛘 人气:0

介绍

Spring Cache是一个框架,实现了基于注解的缓存功能,只需要简单地加一个注解,就能实现缓存功能。

Spring Cache提供了一层抽象,底层可以切换不同的cache实现。具体就是通过CacheManager接口来统一不同的缓存技术。

CacheManager是Spring提供的各种缓存技术抽象接口。

针对不同的缓存技术需要实现不同的CacheManager:

CacheManager描述
EhCacheCacheManager使用EhCache作为缓存技术
GuavaCacheManager使用Google的GuavaCache作为缓存技术
RedisCacheManager使用Redis作为缓存技术

常用注解

注解说明
@EnableCaching开启缓存注解功能
@Cacheable在方法执行前spring先查看缓存中是否有数据,如果有数据,则直接返回缓存数据;若没有数据,调用方法并将方法返回值放到缓存中
@CachePut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

在Spring Boot项目中,使用缓存技术只需在项目中导入相关缓存技术的依赖包,并在启动类上使用@EnableCaching开启缓存支持即可。

例如,使用Redis作为缓存技术,只需要导入spring-boot-starter-data-redis的Maven坐标即可。

实际测试

使用Spring Cache(默认缓存ConcurrentMapCacheManager

创建Spring Boot项目,使用MybatisX插件生成对应的mapper、service、实体类等,导入相关依赖,修改配置文件,创建数据库

pom.xml如下:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.5</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.itheima</groupId>
    <artifactId>cache_demo</artifactId>
    <version>1.0-SNAPSHOT</version>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.20</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.76</version>
        </dependency>
        <dependency>
            <groupId>commons-lang</groupId>
            <artifactId>commons-lang</artifactId>
            <version>2.6</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.4.2</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.23</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>2.4.5</version>
            </plugin>
        </plugins>
    </build>
</project>

application.yml如下:

server:
  port: 8080
spring:
  application:
    #应用的名称,可选
    name: cache_demo
  datasource:
    druid:
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/cache_demo?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&useSSL=false&allowPublicKeyRetrieval=true
      username: root
      password: 123456
mybatis-plus:
  configuration:
    #在映射实体或者属性时,将数据库中表名和字段名中的下划线去掉,按照驼峰命名法映射
    map-underscore-to-camel-case: true
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  global-config:
    db-config:
      id-type: ASSIGN_ID

数据库SQL如下:

/*
 Navicat Premium Data Transfer
 Source Server         : Aiw
 Source Server Type    : MySQL
 Source Server Version : 50528
 Source Host           : localhost:3306
 Source Schema         : cache_demo
 Target Server Type    : MySQL
 Target Server Version : 50528
 File Encoding         : 65001
*/
SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;
-- ----------------------------
-- Table structure for user
-- ----------------------------
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user`  (
  `id` bigint(20) NOT NULL,
  `name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `age` int(11) NULL DEFAULT NULL,
  `address` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Compact;
-- ----------------------------
-- Records of user
-- ----------------------------
INSERT INTO `user` VALUES (1568896554487369729, 'Aiw', 22, '湖北省');
SET FOREIGN_KEY_CHECKS = 1;

在启动类上添加@EnableCaching注解

package com.itheima;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.annotation.EnableCaching;
@Slf4j
@SpringBootApplication
@EnableCaching  // 开启缓存注解功能
public class CacheDemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(CacheDemoApplication.class,args);
        log.info("项目启动成功...");
    }
}

创建UserController

package com.itheima.controller;
import com.itheima.entity.User;
import com.itheima.service.UserService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.CacheEvict;
import org.springframework.cache.annotation.CachePut;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.web.bind.annotation.*;
import java.util.List;
import java.util.Objects;
@RestController
@RequestMapping("/user")
@Slf4j
public class UserController {
    @Autowired
    private CacheManager cacheManager;
    @Autowired
    private UserService userService;
    /**
     * CachePut:将方法返回值放入缓存
     * value:缓存的名称,每个缓存名称下面可以有多个key
     * key:缓存的key
     */
    @CachePut(value = "userCache", key = "#user.id")
    @PostMapping
    public User save(User user) {
        userService.save(user);
        return user;
    }
    /**
     * CacheEvict:清理指定缓存
     * value:缓存的名称,每个缓存名称下面可以有多个key
     * key:缓存的key
     */
    @CacheEvict(value = "userCache", key = "#p0")
    //@CacheEvict(value = "userCache",key = "#root.args[0]")
    //@CacheEvict(value = "userCache",key = "#id")
    @DeleteMapping("/{id}")
    public void delete(@PathVariable Long id) {
        userService.removeById(id);
    }
    //@CacheEvict(value = "userCache",key = "#p0.id")
    //@CacheEvict(value = "userCache",key = "#user.id")
    //@CacheEvict(value = "userCache",key = "#root.args[0].id")
    @CacheEvict(value = "userCache", key = "#result.id")
    @PutMapping
    public User update(User user) {
        userService.updateById(user);
        return user;
    }
    /**
     * Cacheable:在方法执行前spring先查看缓存中是否有数据,如果有数据,则直接返回缓存数据;若没有数据,调用方法并将方法返回值放到缓存中
     * value:缓存的名称,每个缓存名称下面可以有多个key
     * key:缓存的key
     * condition:条件,满足条件时才缓存数据
     * unless:满足条件则不缓存
     */
    @Cacheable(value = "userCache", key = "#id", unless = "#result == null")
    @GetMapping("/{id}")
    public User getById(@PathVariable Long id) {
        return userService.getById(id);
    }
    @Cacheable(value = "userCache", key = "#user.id + '_' + #user.name")
    @GetMapping("/list")
    public List<User> list(User user) {
        return userService.lambdaQuery()
                .eq(Objects.nonNull(user.getId()), User::getId, user.getId())
                .eq(Objects.nonNull(user.getName()), User::getName, user.getName())
                .list();
    }
}

以上不同写法均等价

使用ApiPost进行接口测试

打断点调试,发送请求,可以看到已存入缓存

该缓存底层基于Map实现,默认ConcurrentHashMap基于内存,重启服务会清空缓存数据

使用Spring Cache(redis缓存RedisCacheManager

导入Maven坐标

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

修改配置文件

server:
  port: 8080
spring:
  application:
    #应用的名称,可选
    name: cache_demo
  datasource:
    druid:
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/cache_demo?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&useSSL=false&allowPublicKeyRetrieval=true
      username: root
      password: 123456
  redis:
    host: localhost
    port: 6379
#    password: root@123456
    database: 0
  cache:
    redis:
      time-to-live: 1800000 #设置缓存过期时间(单位:秒),可选
mybatis-plus:
  configuration:
    #在映射实体或者属性时,将数据库中表名和字段名中的下划线去掉,按照驼峰命名法映射
    map-underscore-to-camel-case: true
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  global-config:
    db-config:
      id-type: ASSIGN_ID

启动项目,再次请求接口

启动redis命令行窗口,查看

当请求不存在的id时,不会执行缓存操作(@Cacheable注解的unless条件起作用)

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