缓存（Cache，Redis）

1.pom

<?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 https://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>2.7.4</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.example</groupId>
   <artifactId>springboot_01_cache</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <name>springboot_01_cache</name>
   <description>Demo project for Spring Boot</description>
   <properties>
      <java.version>1.8</java.version>
   </properties>
   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-cache</artifactId>
         <version>2.4.4</version>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-data-redis</artifactId>
         <version>2.4.4</version>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
      </dependency>
      <dependency>
         <groupId>mysql</groupId>
         <artifactId>mysql-connector-java</artifactId>
      </dependency>
      <dependency>
         <groupId>org.mybatis.spring.boot</groupId>
         <artifactId>mybatis-spring-boot-starter</artifactId>
         <version>2.1.3</version>
      </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

   <build>
      <plugins>
         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>
      </plugins>
   </build>

</project>

2.peoperties

spring.datasource.url=jdbc:mysql://localhost:3306/mysql2
spring.datasource.username=root
spring.datasource.password=123456
#spring.datasource.driver-class-name=com.mysql.jdbc.Driver

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

# 打印sql语句日志
logging.level.com.example.cache.mapper=debug

#自动配置的报告
#debug=true

#redis配置
spring.redis.host=192.168.45.128
spring.redis.password=123456

3.启动类

package com.example.cache;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.annotation.EnableCaching;

/**
 * 一、 搭建基本环境
 * 1、导入数据库文件，创建department和employee表
 * 2、创建JavaBean封装数据
 * 3、整合MyBatis操作数据
 *       1.配置数据源信息
 *       2.使用注解版MyBatis;
 *        1). @MapperScan指定需要扫描的mapper接口所在的包
 * 二、 快速体验缓存
 *        步骤
 *           1、开启基于注解的缓存 @EnableCaching
 *           2、标注缓存注解即可
 *              @Cacheable
 *              @CacheEvict
 *              @CachePut
 *默认使用的是ConcurrentMapCacheManager==ConcurrentMapCache：将数据保存在ConcurrentMap<Object,Object>
 *在开发中使用缓存中间件：redis、memcached、ehcache;
 *
 * 三、整合redis作为缓存
 * Redis是一个开源（BSD）的，内存中的数据结构存储系统，它可以用作数据库、缓存和消息中间件。
 *     在bin目录中执行 redis-server /usr/local/redis/redis-5.0.2/etc/redis.conf
 *     再执行 redis-cli 即可启动。
 *     引入redis的starter
 *     配置redis
 *     测试缓存
 *        原理：CacheManager===Cache 缓存组件来实际给缓存中存取数据
 *        1）、引入redis的starter，容器中保存的是RedisCacheManager；
 *        2）、RedisCacheManager帮我们创建RedisCache来作为缓存组件；RedisCache通过操作redis缓存数据
 *        3）、默认保存数据 k-v 都是Object；利用序列化保存；如何保存为json?
 *           1.引入redis的starter，cacheManager变为RedisCacheManager；
 *           2.默认创建的RedisCacheManager 操作redis的时候使用的是RedisTemplate<Object,Object> </>
 *           3.RedisTemplate<Object,Object>是默认使用jdk的序列化机制
 *        4）、自定义CacheManager；
 *
 */
@MapperScan("com.example.cache.mapper")
@SpringBootApplication
@EnableCaching //开启缓存
public class Springboot01CacheApplication {

   public static void main(String[] args) {
      SpringApplication.run(Springboot01CacheApplication.class, args);
   }

}

4.两个实体类

package com.example.cache.bean;

import java.io.Serializable;

/**
 * @PackageName: com.example.cache.bean
 * @ClassName: Department
 * @author: zhangpan
 * @data: 2022/11/7 16:16
 */
public class Department implements Serializable {
    private Integer id;
    private String departmentName;

    public Department(Integer id, String departmentName) {
        this.id = id;
        this.departmentName = departmentName;
    }

    public Department() {
    }

    @Override
    public String toString() {
        return "Department{" +
                "id=" + id +
                ", departmentName='" + departmentName + '\'' +
                '}';
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getDepartmentName() {
        return departmentName;
    }

    public void setDepartmentName(String departmentName) {
        this.departmentName = departmentName;
    }
}

package com.example.cache.bean;

import java.io.Serializable;

/**
 * @PackageName: com.example.cache.bean
 * @ClassName: Employee
 * @author: zhangpan
 * @data: 2022/11/7 16:16
 */
public class Employee implements Serializable {
    private Integer id;
    private String lastName;
    private String email;
    private Integer gender;
    private Integer dId;

    @Override
    public String toString() {
        return "Employee{" +
                "id=" + id +
                ", lastName='" + lastName + '\'' +
                ", email='" + email + '\'' +
                ", gender=" + gender +
                ", dId=" + dId +
                '}';
    }

    public Employee(Integer id, String lastName, String email, Integer gender, Integer dId) {
        this.id = id;
        this.lastName = lastName;
        this.email = email;
        this.gender = gender;
        this.dId = dId;
    }

    public Employee() {
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public Integer getGender() {
        return gender;
    }

    public void setGender(Integer gender) {
        this.gender = gender;
    }

    public Integer getdId() {
        return dId;
    }

    public void setdId(Integer dId) {
        this.dId = dId;
    }
}

5.两个mapper接口

package com.example.cache.mapper;

import com.example.cache.bean.Department;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;

@Mapper
public interface DepartmentMapper {
    @Select("select * from department where id = #{id}")
    Department getDeptById(Integer id);
}

package com.example.cache.mapper;

import org.apache.ibatis.annotations.*;
import com.example.cache.bean.Employee;

@Mapper
public interface EmployeeMapper {

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

    @Select("select * from employee where lastName = #{lastName}")
    public Employee getEmpByLastName(String lastName);

    @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 deleteEmp(Integer id);

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

}

6.两个配置类

6.1 Cache注解配置类

package com.example.cache.config;

import org.springframework.cache.interceptor.KeyGenerator;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.lang.reflect.Method;
import java.util.Arrays;

/**
 * @PackageName: com.example.cache.config
 * @ClassName: MyCacheConfig
 * @author: zhangpan
 * @data: 2022/11/8 14:54
 */
@Configuration
public class MyCacheConfig {

    @Bean("myKeyGenerator")
    public KeyGenerator keyGenerator() {
        return new KeyGenerator(){
            @Override
            public Object generate(Object target, Method method, Object... params) {
                return method.getName()+"["+ Arrays.asList(params).toString() +"]";
            }
        };
    }
}

6.2redis配置类

package com.example.cache.config;

import com.example.cache.bean.Department;
import com.example.cache.bean.Employee;
import org.springframework.cache.CacheManager;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.data.redis.cache.RedisCacheConfiguration;
import org.springframework.data.redis.cache.RedisCacheManager;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.serializer.GenericJackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializationContext;

import java.time.Duration;
import java.util.Map;


/**
 * @PackageName: com.example.cache.config
 * @ClassName: MyRedisConfig
 * @author: zhangpan
 * @data: 2022/11/8 19:23
 */
@Configuration
public class MyRedisConfig {

    @Bean
    public RedisTemplate<Object, Employee> employeeRedisTemplate(RedisConnectionFactory redisConnectionFactory) throws Exception {
        RedisTemplate<Object, Employee> template = new RedisTemplate<>();
        template.setConnectionFactory(redisConnectionFactory);
        Jackson2JsonRedisSerializer<Employee> serializer = new Jackson2JsonRedisSerializer<Employee>(Employee.class);
        template.setDefaultSerializer(serializer);
        return template;
    }
    @Bean
    public CacheManager employeeCacheManager(RedisConnectionFactory factory){
        RedisCacheConfiguration cacheConfiguration =
                RedisCacheConfiguration.defaultCacheConfig()
                        .entryTtl(Duration.ofDays(1))
                        .disableCachingNullValues()
                        .serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(new
                                GenericJackson2JsonRedisSerializer()));
        return RedisCacheManager.builder(factory).cacheDefaults(cacheConfiguration).build();
    }


    @Bean
    public RedisTemplate<Object, Department> depRedisTemplate(RedisConnectionFactory redisConnectionFactory) throws Exception {
        RedisTemplate<Object, Department> template = new RedisTemplate<>();
        template.setConnectionFactory(redisConnectionFactory);
        Jackson2JsonRedisSerializer<Department> serializer = new Jackson2JsonRedisSerializer<Department>(Department.class);
        template.setDefaultSerializer(serializer);
        return template;
    }
    @Primary //@Primary作用 指定默认的CacheManager
    @Bean
    public RedisCacheManager departmentCacheManager(RedisConnectionFactory factory){
        RedisCacheConfiguration cacheConfiguration =
                RedisCacheConfiguration.defaultCacheConfig()
                        .entryTtl(Duration.ofDays(1))
                        .disableCachingNullValues()
                        .serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(new
                                GenericJackson2JsonRedisSerializer()));
        return RedisCacheManager.builder(factory).cacheDefaults(cacheConfiguration).build();
    }


//    @Bean
//    public RedisCacheManager employeeCacheManager(RedisTemplate<Object, Employee> empRedisTemplate){
//        RedisCacheManager cacheManager = new RedisCacheManager(empRedisTemplate);
//        //key多了一个前缀
//        //使用前缀，默认会将CacheName作为key的前缀
//        cacheManager.setUsePrefix(true);
//        return cacheManager;
//    }


}

7.service层

7.1使用cache注解做缓存

package com.example.cache.service;

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

/**
 * @PackageName: com.example.cache
 * @ClassName: EmployeeService
 * @author: zhangpan
 * @data: 2022/11/7 16:48
 */
//@CacheConfig(cacheNames="emp") //下面的注解中不需要写emp了 (抽取缓存的公共配置)
@Service
public class EmployeeService {
    @Autowired(required = false)
    public EmployeeMapper employeeMapper;

    /**
     * @Cacheable注解的作用：
     *      将方法运行结果进行缓存，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组件的，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;将方法的返回结果放在哪个缓存中，是数组的方式，可以指定多个缓存。
     *      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SqEl； #id;参数id的值  #a0  #p0  #root.args[0]
     *      keyGenerator：key的生成器；可以自己指定key的生成器的组件id
     *                  key/keyGenerator: 二选一使用
     *      cacheManager：指定缓存管理器，获取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"
     *                  condition = "#a0>1"：第一个参数的值 > 1 的时候才进行缓存
     *      unless：否定缓存，当unless指定的条件为true，方法的返回值就不会被缓存，可以获取到的结果进行判断
     *             unless = "#result == null"
     *             例如：,unless = "#a0==2"：如果第一个参数的值是2，结果不缓存
     *      sync：是否使用异步模式
     *
     * 原理：
     *    1、自动配置类：CacheAutoConfiguration
     *    2、缓存配置类（一共有10个） 【默认使用SimpleCacheConfiguration】
     *    3、那个配置默认生效：SimpleCacheConfiguration;
     *    4、给容器中注册一个CacheManager：ConcurrentMapCacheManager
     *    5、可以获取和创建ConcurrentMapCache类型的缓存组件，他的作用将数据保存在ConcurrentMap中。
     *
     * 运行流程：
     *    @Cacheable:
     *    1、方法运行之前，先去查询Cache(缓存组件)，按照cacheNames指定的名字获取；
     *      （CacheManage先获取相应的缓存），第一次获取缓存如果没有Cache组件会自动创建。
     *    2、去Cache中查找缓存的内容，使用一个key，默认就是方法的参数；
     *      key是按照某种策略生成的；默认是使用keyGenerator生成的，默认使用keyGenerator生成key;
     *          SimpleKeyGenerator生成key的默认策略；
     *              如果没有参数：key = new SimpleKey();
     *              如果有一个参数：key = 参数的值
     *              如果有多个参数：key = new SimpleKey(params);
     *    3、没有查到缓存就调用目标方法；
     *    4、没有目标方法返回的结果，放进缓存中
     *
     * @Cacheable标注的方法执行之前先来检查缓存中有没有这个数据，默认按照参数的值作为key去查询缓存。
     * 如果没有就运行方法并将结果放入缓存：以后再来调用就可以直接使用缓存中的数据。
     *
     * 核心：
     *      1）、使用CacheManager【ConcurrentMapCacheManager】按照名字得到Cache【ConcurrentMapCache】组件
     *      2）、key使用keyGenerator生成的，默认是SimpleKeyGenerator
     * @param id
     * @return
     *///注解的作用就是将方法的运行结果进行缓存
    @Cacheable(cacheNames = "emp"/*,keyGenerator = "myKeyGenerator",condition = "#a0>1",unless = "#a0==2"*/)
    public Employee getEmp(Integer id) {
        System.out.println("查询"+id+"号员工");
        Employee emp = employeeMapper.getEmpById(id);
        return emp;
    }

    /**
     * @CachePut：即调用方法，又更新缓存数据；同步更新缓存(更新数据库同时更新缓存)
     * 修改了数据库的某个数据，同时更新缓存；
     * 运行时机：
     *    1、先调用目标方法
     *    2、将目标方法的结果缓存起来
     *
     * 测试步骤：
     *    1、查询1号员工，查到的结果会放在缓存中
     *          key: 1  value: lastName:张三
     *    2、以后查询还是之前的结果
     *    3、更新1号员工：【lastName:zhangsan; gender:0】
     *          将方法的返回值也放进缓存了；
     *          key：传入的employee对象。值：返回的employee对象；
     *    4、查询1号员工？
     *         应该是更新后的员工；
     *              key = "#employee.id" :使用传入的参数的员工id；
     *              key = “#result.id” :使用返回后的id
     *                  @Cacheable的key是不能用#result
     *         为什么是没更新前的？【1号员工没有在缓存中更新】
     *
     */
    @CachePut(value = "emp",key = "#result.id")
    public Employee updateEmp(Employee employee) {
        System.out.println("updateEmp:"+employee);
        employeeMapper.updateEmp(employee);
        return employee;
    }

    /**
     * @CacheEvict：缓存清除
     * key:指定要清除的数据
     *    allEntries = true : 指定清除这个缓存中所有的数据
     *    beforeInvocation = false : 缓存的清除是否在方法之前执行
     *       默认代表缓存清除操作是在方法之后执行；如果出现异常缓存就不会清除
     *
     *    beforeInvocation = true:
     *       代表清除缓存操作是在方法运行之前执行，无论方法是否出现异常，缓存都清除
     */
    @CacheEvict(value = "emp"/*, key = "#id"*//*, allEntries = true*/,beforeInvocation = true)
    public void deleteEmp(Integer id) {
        System.out.println("deleteEmp:"+id);
//        employeeMapper.deleteEmp(id);
//        int i = 10/0;
    }

    /**
     * 定义复杂的缓存规则
     * @param lastName
     * @return
     */
    @Caching(
         cacheable = {
             @Cacheable(value = "emp",key = "#lastName")
         },
         put = {
                 @CachePut(value = "emp",key = "#result.id"),
                 @CachePut(value = "emp",key = "#result.email")
         }
    )
    public Employee getEmpLastName(String lastName) {
        return employeeMapper.getEmpByLastName(lastName);
    }
}

7.2使用redis做缓存

package com.example.cache.service;

import com.example.cache.bean.Department;
import com.example.cache.mapper.DepartmentMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.cache.Cache;
import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.data.redis.cache.RedisCacheManager;
import org.springframework.stereotype.Service;

/**
 * @PackageName: com.example.cache.service
 * @ClassName: DeptService
 * @author: zhangpan
 * @data: 2022/11/10 17:11
 */
@Service
public class DeptService {
    @Autowired(required = false)
    DepartmentMapper departmentMapper;

//    @Qualifier("departmentCacheManager")
//    @Autowired
//    RedisCacheManager departmentCacheManager; //注入缓存管理器 （使用编码的方式操作缓存）

    /**
     * 缓存
     * @param id
     * @return
     */
    @Cacheable(cacheNames = "dept")
    public Department getDeptById(Integer id) {
        System.out.println("查询部门的id为："+id);
        Department department = departmentMapper.getDeptById(id);
        return department;
    }

    /**
     * 使用编码操作缓存数据
     * @param id
     * @return
     */
//    public Department getDeptByIdCache(Integer id) {
//        System.out.println("查询部门的id为："+id);
//        Department department = departmentMapper.getDeptById(id);
//        //获取某个缓存
//        Cache dept = departmentCacheManager.getCache("dept");
//        dept.put("dept:1",department);
//        return department;
//    }
}

8.controller

8.1注解controller

package com.example.cache.controller;

import com.example.cache.bean.Employee;
import com.example.cache.service.EmployeeService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

/**
 * @PackageName: com.example.cache.controller
 * @ClassName: EmployeeController
 * @author: zhangpan
 * @data: 2022/11/7 16:52
 */
@Controller
public class EmployeeController {

    @Autowired(required = false)
    public EmployeeService employeeService;

    @RequestMapping(value = "/emp/{id}",method = RequestMethod.GET)
    @ResponseBody
    public Employee getEmp(@PathVariable("id") Integer id) {
        Employee emp = employeeService.getEmp(id);
        return emp;
    }

//    @RequestMapping(value = "/emp/{id}",method = RequestMethod.PUT)
//    @ResponseBody
//    public Employee updateEmp(@RequestBody Employee employee,@PathVariable("id")Integer id) {
//        Employee emp = employeeService.updateEmp(employee);
//        return emp;
//    }

//    @ResponseBody
//    @RequestMapping(value = "emp/{id}", method = RequestMethod.DELETE)
//    public String deleteEmp(@PathVariable("id") Integer id) {
//        employeeService.deleteEmp(id);
//        return "success";
//    }

//    @ResponseBody
//    @RequestMapping(value = "emp/{lastName}", method = RequestMethod.GET)
//    public String getEmpLastName(@PathVariable("lastName") String lastName){
//        employeeService.getEmpLastName(lastName);
//        return "success";
//    }
}

8.2redis controller

package com.example.cache.controller;

import com.example.cache.bean.Department;
import com.example.cache.service.DeptService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

/**
 * @PackageName: com.example.cache.controller
 * @ClassName: DeptController
 * @author: zhangpan
 * @data: 2022/11/10 17:20
 */
@RestController
public class DeptController {
    @Autowired
    private DeptService deptService;

    @RequestMapping(value = "/dept/{id}", method = RequestMethod.GET)
    public Department getDeptById(@PathVariable("id") Integer id) {
        Department dept = deptService.getDeptById(id);
        return dept;
    }


}