springBoot整合redis(做緩存)

時間 2020-07-03

原文原文鏈接

springBoot整合Redis

1，配置Redis配置類

package org.redislearn.configuration;

import java.lang.reflect.Method;

import org.springframework.cache.annotation.CachingConfigurerSupport;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cache.interceptor.KeyGenerator;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.HashOperations;
import org.springframework.data.redis.core.ListOperations;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.SetOperations;
import org.springframework.data.redis.core.ValueOperations;
import org.springframework.data.redis.core.ZSetOperations;
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;

@EnableCaching
@Configuration
public class RedisConfiguration extends CachingConfigurerSupport{
    /*
     * key的生成策略(根據目標對象，本例是service實現類，以及其中的方法，參數拼接成一個key)
     * 能夠根據業務需求更改策略
     */
    @Override
    public KeyGenerator keyGenerator() {
        return new KeyGenerator() {
            /*
             * 參數1：要操做的目標對象
             * 參數2：要操做的方法
             * 參數3：執行方法時的參數
             */
            @Override
            public Object generate(Object target, Method method, Object... params) {
                StringBuilder sBuilder = new StringBuilder();
                sBuilder.append(target.getClass().getName());
                sBuilder.append(".");
                sBuilder.append(method.getName());    //生成key
                for(Object object:params){
                    sBuilder.append(".");
                    sBuilder.append(object.toString());
                }
                return sBuilder.toString();
            }
        };
    }
    /**
     * redisTemplate相關配置  RedisTemplate操做Redis
     * @param factory
     * @return
     */
    @Bean
    @SuppressWarnings("all")
    public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory factory) {
        RedisTemplate<String, Object> template  = new RedisTemplate<>();
        //設置工廠
        template.setConnectionFactory(factory);
        //使用Jackson2JsonRedisSerializer來序列化和反序列化redis的value值
//（默認使用JDK的序列化方式）
        Jackson2JsonRedisSerializer jackson2JsonRedisSerializer =
                new Jackson2JsonRedisSerializer<>(Object.class);
        //建立對象映射
        ObjectMapper mapper = new ObjectMapper();
        //指定要序列化的域，field,get和set,以及修飾符範圍，ANY是都有包括private和public
        mapper.setVisibility(PropertyAccessor.ALL,JsonAutoDetect.Visibility.ANY);
        //指定序列化輸入的類型，類必須是非final修飾的，final修飾的類，好比String,Integer
//等會拋出異常
        mapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        //
        jackson2JsonRedisSerializer.setObjectMapper(mapper);
        //字符串序列化器
        StringRedisSerializer stringRedisSerializer = new StringRedisSerializer();
        //key採用String的序列化方式
        template.setKeySerializer(stringRedisSerializer);
        //hash的key也採用String的方式
        template.setHashKeySerializer(stringRedisSerializer);
        //value採用jackson的方式
        template.setValueSerializer(jackson2JsonRedisSerializer);
        //hash的value也採用Jackson
        template.setHashValueSerializer(jackson2JsonRedisSerializer);

        template.afterPropertiesSet();
        return template;
    }
}

2，配置application.yml配置文件

server:
  port: 8080
mybatis:
  config-location: classpath:mybatis-config.xml
  type-aliases-package: org.xxxx.entity
  mapper-locations:
    - classpath:mapper/*.xml
spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/test?serverTimezone=UTC
    username: root
    password: 123456
  redis:
    host: 127.0.0.1
    port: 6379
    jedis:
      pool:
        max-active: 10
        max-idle: 5
        min-idle: 2
        max-wait: -1

3，操做Redis數據庫

RedisTemplate<String,Object> :相似於Mybatis的SqlSession，用來操做數據庫的對象

//在須要使用的地方利用spring注入RedisTemplate對象
@Autowired
private RedisTemplate<String,Object> redisTemplate;

4，使用Redis做緩存

新建一個實體類

ps：存入redis的實體類數據須要實現序列化接口，否則會報org.springframework.data.redis.serializer.SerializationException: Cannot deserialize; 至於原理，能夠看看我看過的這篇文章瞭解一下
Redis爲何須要序列化https://www.zhihu.com/question/277363840/answer/392945240java

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Product implements Serializable {//redis need to serialize
    private int pid;
    private String pname;
    private double price;
    private int store;
    private List<String> images;
    private String detail;
}

（默認已經寫好了mapper，service等接口和相關配置）

在service實現類中的方法加註解

@Cacheable("xxx") //數據以xxx開頭存入緩存
@CacheEvict(value = {"xxx","xxx"},allEntries = true) //清除緩存中的xxx開頭的數據

@Service
public class ProductServiceImpl implements ProductService {

    @Autowired
    private ProductMapper productMapper;

    @Cacheable("findAll")
    @Override
    public List<Product> all() {
        return productMapper.all();
    }

    @Cacheable("findById")
    @Override
    public Product findProductByPid(int pid) {
        return productMapper.findProductByPid(pid);
    }

    //把跟這個id有關的數據都要刪除，這裏是"findAll"和"findById"
    @CacheEvict(value = {"findAll","findById"},allEntries = true)
    @Override
    public int deleteProductByPid(int pid) {
        return productMapper.deleteProductByPid(pid);
    }
}

這裏的清除緩存的數據配置有問題，當執行刪除方法的時候會將以"findAll","findById"開頭的key的其餘數據都清除掉，這樣以後的查詢又是從數據庫查，性能再次降低
解決方案：
寫一個工具類，生成對應的key，用來精準刪除

public class RedisUtil {
    public static String generate(String namespace,Object target, String method, Object... params) {
        StringBuilder sBuilder = new StringBuilder();
        sBuilder.append(namespace);
        sBuilder.append("::");  //自動生成的key會有雙冒號
        sBuilder.append(target.getClass().getName());
        sBuilder.append(".");
        sBuilder.append(method);    //生成key
        for(Object object:params){
        sBuilder.append(".");
        sBuilder.append(object.toString());
        }
        return sBuilder.toString();
    }
}

改進service實現類的方法

//定義一個須要的命名空間
private static final String NAMESPACE = "findProductByPid";

//刪除指定的key
@CacheEvict(value = "findAll",allEntries = true)
@Override
public int deleteProductByPid(int pid){
    //前綴 this method 參數
    String key = RedisUtil.generate(NAMESPACE,this,"findProductByPid",pid);
    System.out.println(key);
    //操做刪除指令
    redisTemplate.delete(key);
    return productMapper.deleteProductByPid(pid);
}