https://github.com/lianglliu/cache-sharing
Redis缓存共享探究
https://github.com/lianglliu/cache-sharing
cache cacheable java redis-cache
Last synced: 11 months ago
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Redis缓存共享探究
- Host: GitHub
- URL: https://github.com/lianglliu/cache-sharing
- Owner: LiangLliu
- License: apache-2.0
- Created: 2021-09-09T10:47:29.000Z (almost 5 years ago)
- Default Branch: master
- Last Pushed: 2021-09-16T08:27:35.000Z (over 4 years ago)
- Last Synced: 2025-04-05T11:16:44.307Z (about 1 year ago)
- Topics: cache, cacheable, java, redis-cache
- Language: Java
- Homepage:
- Size: 112 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# cachedemo
* 探究 Redis + Cacheable 的使用
* 不同微服务共享缓存问题
* 探究由于微服务架构划分错误，两个微服务使用了相同的domain时，配置相同的key，redis读取缓存时存在缓存冲突的问题
### 场景
* 两个微服务，对象结构一致，但是包路径不同
* 两个User对象，结构完全一致，包路径不同
* com.edwin.cache.account.User
```java
package com.edwin.cache.account;
import lombok.*;
import java.io.Serializable;
@Setter
@Getter
@AllArgsConstructor
@NoArgsConstructor
@Builder
@ToString
public class User implements Serializable {
private Long id;
private String username;
private String password;
}
```
* com.edwin.cache.user.User
```java
package com.edwin.cache.user;
import lombok.*;
import javax.persistence.*;
import java.io.Serializable;
@Setter
@Getter
@AllArgsConstructor
@NoArgsConstructor
@Entity
@Builder
@Table(name = "user")
@ToString
public class User implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String username;
private String password;
}
```
* 缓存方案
* com.edwin.cache.account.User
```java
@CacheConfig(cacheNames = "user")
@Repository
@RequiredArgsConstructor
public class AccountRepository {
private final AccountJpaRepository accountJpaRepository;
public static final String USER_PEX = "USER_";
@Cacheable(cacheNames = USER_PEX, key = "'user.id:'+#id")
public User findUserById(Long id) {
Optional optionalAccount = accountJpaRepository.findById(id);
if (optionalAccount.isEmpty()) {
return new User();
}
Account account = optionalAccount.get();
return User.builder()
.id(account.getId())
.username(account.getUsername())
.password(account.getPassword())
.build();
}
}
```
* com.edwin.cache.user.UserRepository
```java
@CacheConfig(cacheNames = "user")
@Repository
@RequiredArgsConstructor
public class UserRepository {
private final UserJpaRepository userJpaRepository;
public static final String USER_PEX = "USER_";
@Cacheable(cacheNames = USER_PEX, key = "'user.id:'+#id")
public User findUserById(Long id) {
return userJpaRepository.findById(id).orElse(new User());
}
}
```
* 希望存到Redis后可以做缓存共享
### 方案1
* 配置一个 Map 关系
```java
Map map = new HashMap<>();
map.put("com.edwin.cache.user.User","com.edwin.cache.account.User")
map.put("com.edwin.cache.account.User","com.edwin.cache.user.User")
```
* 当反序列化时，在读取二进制（Json）数据时，进行转换
* 问题：
* 如果redis存入的对象为 com.edwin.cache.user.User，当反序列化为 com.edwin.cache.account.User时，由于反序列化时需要把数据
放进实例化对象中，这时候涉及到类加载，在account上下文中并没有com.edwin.cache.user.User的对象，因此会挂掉。
* 转换时并不知道是哪个对象在获取缓存
### 方案2
* 如同方案1也配置一个map关系
* 对redis存储的数据反序列化时，尝试类加载，如果不能加载该类，那么通过加载 map.get(key)的值，尝试类加载，如果失败，走原来的，如果成功，
替换原来的序列化类加载路径
* RedisSerializer 默认使用 JdkSerializationRedisSerializer
* JdkSerializationRedisSerializer 默认会使用 org.springframework.core.serializer.support.SerializingConverter 和
org.springframework.core.serializer.support.DeserializingConverter, 我们只需要关注反序列化器
* DeserializingConverter 中 会使用 org.springframework.core.ConfigurableObjectInputStream
* ConfigurableObjectInputStream 中有一个 resolveClass方法，我们只需要继承这个类并且把整个方法重写, 就可以按照需求加载对应的类
```java
public class DemoObjectInputStream extends ConfigurableObjectInputStream {
@Override
protected Class> resolveClass(ObjectStreamClass classDesc) throws IOException, ClassNotFoundException {
String name = classDesc.getName();
System.out.println(name);
Map map = new HashMap<>();
map.put("com.edwin.cache.account.User", "com.edwin.cache.user.User");
map.put("com.edwin.cache.user.User", "com.edwin.cache.account.User");
if (!ClassUtils.isPresent(name, classLoader)) {
String className = map.get(name);
if (!ObjectUtils.isEmpty(className) && ClassUtils.isPresent(className, classLoader)) {
return ClassUtils.forName(className, this.classLoader);
}
}
return super.resolveClass(classDesc);
}
}
```
### 测试
分别启动服务 cache-service 和 cache-account
* 通过测试可以拿到相同的结果
* 访问 http://localhost:8080/user
```shell
curl http://localhost:8080/user | python -m json.too
```
```json
[
{
"id": 1,
"password": "111111",
"username": "\u5f20\u4e09"
},
{
"id": 2,
"password": "222222",
"username": "\u674e\u56db"
},
{
"id": 3,
"password": "333333",
"username": "\u738b\u4e94"
},
{
"id": 4,
"password": "444444",
"username": "\u7530\u516d"
}
]
```
* 访问 http://localhost:8090/account
```shell
curl http://localhost:8090/account | python -m json.tool
```
```json
[
{
"id": 1,
"password": "111111",
"username": "\u5f20\u4e09"
},
{
"id": 2,
"password": "222222",
"username": "\u674e\u56db"
},
{
"id": 3,
"password": "333333",
"username": "\u738b\u4e94"
},
{
"id": 4,
"password": "444444",
"username": "\u7530\u516d"
}
]
```