Spring框架如何做EhCache缓存？

在Spring框架中，缓存是一种常见的优化手段，用于减少对数据库或其他资源的访问次数，从而提高应用性能。Spring提供了强大的缓存抽象，支持多种缓存实现（如EhCache、Redis、Caffeine等），并可以通过注解或编程方式轻松集成。

本文以EhCache为例，来演示Spring框架如何做缓存。以下是Spring实现EhCache缓存的实现方式和步骤：

1、引入缓存依赖

在pom.xml中添加EhCache相应的依赖：

    org.springframework.boot
    spring-boot-starter-cache


    org.ehcache
    ehcache

2、配置缓存管理器

在Spring Boot中，可以通过配置类来定义缓存管理器。以下是一些EhCache缓存实现的配置示例：

package com.config;

import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cache.ehcache.EhCacheCacheManager;
import org.springframework.cache.ehcache.EhCacheManagerFactoryBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;

@Configuration
@EnableCaching // 启用Spring缓存支持
public class CacheConfig {

    @Bean
    public EhCacheManagerFactoryBean ehCacheManagerFactoryBean() {
        EhCacheManagerFactoryBean bean = new EhCacheManagerFactoryBean();
        bean.setConfigLocation(new ClassPathResource("ehcache.xml")); // 指定配置文件路径
        bean.setShared(true); // 共享EhCache实例
        return bean;
    }

    @Bean
    public CacheManager cacheManager() {
        return new EhCacheCacheManager(ehCacheManagerFactoryBean().getObject());
    }
}

3、配置ehcache.xml文件

需要在src/main/resources目录下创建ehcache.xml配置文件：

 在application.yml中配置EhCache

指定EhCache的XML配置文件路径：

spring:
  cache:
    type: ehcache
    ehcache:
      config: classpath:ehcache.xml

4、使用缓存注解

Spring提供了多个注解来简化缓存的使用，最常用的是@Cacheable、@CachePut和@CacheEvict。

@Cacheable 注解用于方法上，表示该方法的返回值会被缓存。如果缓存中存在值，则不会执行方法体；

@CachePut 注解用于更新缓存。无论缓存中是否存在值，都会执行方法体，并将返回值更新到缓存中；

@CacheEvict 注解用于清除缓存。 

• value：指定缓存的名称，与ehcache.xml中的name保持一致；

• key：指定缓存的键，默认是方法的参数。参考格式：'方法名_' + #参数名

package com.service.cache;

import com.domain.User;
import com.mapstruct.UserMapper;
import com.repository.UserRepository;
import com.web.dto.UserDto;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Optional;

@Slf4j
@Service
@RequiredArgsConstructor
public class UserCacheService {

    private final UserRepository userRepository;
    private final UserMapper userMapper;

    @Cacheable(value = "USER_SESSION", key = "'getUserById_' + #id")
    public User getUserById(Integer id) {
        if (id == null)
            return new User();
        Optional userOptional = userRepository.findById(id);
        return userOptional.isPresent()? userOptional.get() : new User();
    }

    @Cacheable(value = "USER_SESSION", key = "'getUsersByRoleId_' + #roleId")
    public List getUsersByRoleId(Integer roleId) {
        if (roleId == null){
            List optionals = userRepository.findAllByIsDeleteIsFalseOrderByNameAsc();
            return userMapper.toDto(optionals);
        } else {
            List optionals = userRepository.findAllByRoleIdAndIsDeleteIsFalse(roleId);
            return userMapper.toDto(optionals);
        }
    }

    @CachePut(value = "USER_SESSION", key = "#id")
    public String updateDataById(String id, String newData) {
        System.out.println("Updating data in database...");
        return newData;
    }

    @CacheEvict(value = "USER_SESSION", key = "#id")
    public void deleteDataById(String id) {
        System.out.println("Deleting data from database...");
    }

}

5、最后启动ehcache

使用@EnableCaching注解启动缓存：

package com.start;
import io.swagger.v3.oas.annotations.enums.SecuritySchemeIn;
import io.swagger.v3.oas.annotations.enums.SecuritySchemeType;
import io.swagger.v3.oas.annotations.security.SecurityScheme;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.scheduling.annotation.EnableScheduling;

@EnableCaching
@EnableScheduling
@SpringBootApplication
@EntityScan("com.domain")
@SecurityScheme(name = "token", scheme = "Bearer", type = SecuritySchemeType.HTTP, in = SecuritySchemeIn.QUERY)
public class StartDataApplication extends SpringBootServletInitializer {

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

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
        return builder.sources(StartDataApplication.class);
    }
}