Spring Boot的缓存之旅（二）

使用Redis

1.引入spring-boot-starter-data-redis依赖

2.进行项目文件配置

使用前先启动redis

#redis配置
#redis服务器地址
spring.redis.host=localhost
#redis服务器端口
spring.redis.port=6379

#数据库配置
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/test?characterEncoding=utf-8&useSSL=false&serverTimezone=GMT%2B8&allowPublicKeyRetrieval=true
spring.datasource.username=root
spring.datasource.password=123456abc

##validate  加载hibernate时，验证创建数据库表结构
##create   每次加载hibernate，重新创建数据库表结构，这就是导致数据库表数据丢失的原因。
##create-drop        加载hibernate时创建，退出是删除表结构
##update                 加载hibernate自动更新数据库结构
##none  启动时不做任何操作
spring.jpa.hibernate.ddl-auto=create

##控制台打印sql
spring.jpa.show-sql=true

3.使用redis的set和get方法

@Service
public class RedisService {
    @Resource
    private RedisTemplate<String, Object> redisTemplate;
    //或者   这时不能有<String, Object>，这个特殊
//    @Autowired
//    private RedisTemplate redisTemplate;
    
    public void set(String key,Object value) {
        redisTemplate.setKeySerializer(new StringRedisSerializer());
        redisTemplate.setValueSerializer(new Jackson2JsonRedisSerializer(Object.class));
        ValueOperations<String, Object> vo=redisTemplate.opsForValue();
        vo.set(key, value);
    }
    
    public void set(String key,Object value,Long time,TimeUnit t) {
        redisTemplate.setKeySerializer(new StringRedisSerializer());
        redisTemplate.setValueSerializer(new Jackson2JsonRedisSerializer(Object.class));
        ValueOperations<String, Object> vo=redisTemplate.opsForValue();
        vo.set(key, value);
    }
    
    public Object get(String key) {
        ValueOperations<String, Object> vo=redisTemplate.opsForValue();
        return vo.get(key);
    }
}

4.编写一个User实体类和repository

5.Controller测试

@RestController
public class UserController {
    @Autowired
    private RedisService redisService;

    @Autowired
    private UserRepository userRepository;

    @GetMapping(value = "saveUser")
    public String saveUser(Long id, String userName, String userPassword) {
        User user = new User(id, userName, userPassword);
        redisService.set(id.toString(), user);
        return "success";
    }

    @GetMapping(value = "getUserById")
    public Object getUserById(Long id) {
        return redisService.get(id.toString());
    }

    @GetMapping("/saveUser2")
    public User saveUser2(Long id, String userName, String userPassword) {
        User user = new User(id, userName, userPassword);
        userRepository.save(user);
        return user;
    }

    @GetMapping(value = "getUser")
    public Object getUser(Long id) {
        Object object = redisService.get(id.toString());
        if (object == null) {
            object = (userRepository.findById(id)).get();
            if (object != null) {
                redisService.set(id.toString(), object, 100L, TimeUnit.SECONDS);
            }
        }
        return object;
    }
}

注意对键和值都要进行序列化。

使用Redis缓存

刚只是把redis当数据库用，而真实环境中一般以传统数据库为主，以redis数据库为辅。redis通常起缓存作用。

1.在RedisService类新增一个设置过期时间的方法：

public void set(String key,Object value,Long time,TimeUnit t) {
        redisTemplate.setKeySerializer(new StringRedisSerializer());
        redisTemplate.setValueSerializer(new Jackson2JsonRedisSerializer(Object.class));
        ValueOperations<String, Object> vo=redisTemplate.opsForValue();
        vo.set(key, value);
    }

2.在Controller类里新增两个方法

@GetMapping("/saveUser2")
    public User saveUser2(Long id, String userName, String userPassword) {
        User user = new User(id, userName, userPassword);
        userRepository.save(user);
        return user;
    }

    @GetMapping(value = "getUser")
    public Object getUser(Long id) {
        Object object = redisService.get(id.toString());
        if (object == null) {
            object = (userRepository.findById(id)).get();
            if (object != null) {
                redisService.set(id.toString(), object, 100L, TimeUnit.SECONDS);
            }
        }
        return object;
    }

测试有效果。