3步輕松搞定Spring Boot緩存

作者:譚朝紅

前言

本次內容主要介紹基于Ehcache 3.0來快速實現Spring Boot應用程序的數據緩存功能。在Spring Boot應用程序中，我們可以通過Spring Caching來快速搞定數據緩存。

接下來我們將介紹如何在三步之內搞定 Spring Boot 緩存。

1. 創建一個Spring Boot工程

你所創建的Spring Boot應用程序的maven依賴文件至少應該是下面的樣子：

<?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?http://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>2.1.3.RELEASE</version>
????????<relativePath/>?<!--?lookup?parent?from?repository?-->
????</parent>
????<groupId>com.ramostear</groupId>
????<artifactId>cache</artifactId>
????<version>0.0.1-SNAPSHOT</version>
????<name>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>
????????</dependency>
????????<dependency>
????????????<groupId>org.springframework.boot</groupId>
????????????<artifactId>spring-boot-starter-web</artifactId>
????????</dependency>
????????<dependency>
????????????<groupId>org.ehcache</groupId>
????????????<artifactId>ehcache</artifactId>
????????</dependency>
????????<dependency>
????????????<groupId>javax.cache</groupId>
????????????<artifactId>cache-api</artifactId>
????????</dependency>
????????<dependency>
????????????<groupId>org.springframework.boot</groupId>
????????????<artifactId>spring-boot-starter-test</artifactId>
????????????<scope>test</scope>
????????</dependency>
????????<dependency>
????????????<groupId>org.projectlombok</groupId>
????????????<artifactId>lombok</artifactId>
????????</dependency>
????</dependencies>
????<build>
????????<plugins>
????????????<plugin>
????????????????<groupId>org.springframework.boot</groupId>
????????????????<artifactId>spring-boot-maven-plugin</artifactId>
????????????</plugin>
????????</plugins>
????</build>
</project>

依賴說明：

• spring-boot-starter-cache為Spring Boot應用程序提供緩存支持

• ehcache提供了Ehcache的緩存實現

• cache-api 提供了基于JSR-107的緩存規范

2. 配置Ehcache緩存

現在，需要告訴Spring Boot去那里找緩存配置文件，這需要在Spring Boot配置文件中進行設置：

spring.cache.jcache.config=classpath:ehcache.xml

然后使用@EnableCaching注解開啟Spring Boot應用程序緩存功能，你可以在應用主類中進行操作：

package?com.ramostear.cache;
import?org.springframework.boot.SpringApplication;
import?org.springframework.boot.autoconfigure.SpringBootApplication;
import?org.springframework.cache.annotation.EnableCaching;
@SpringBootApplication
@EnableCaching
public?class?CacheApplication?{
????public?static?void?main(String[]?args)?{
????????SpringApplication.run(CacheApplication.class,?args);
????}
}

接下來，需要創建一個 ehcache 的配置文件，該文件放置在類路徑下，如resources目錄下：

<config?xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
????????xmlns="http://www.ehcache.org/v3"
????????xmlns:jsr107="http://www.ehcache.org/v3/jsr107"
????????xsi:schemaLocation="
????????????http://www.ehcache.org/v3?http://www.ehcache.org/schema/ehcache-core-3.0.xsd
????????????http://www.ehcache.org/v3/jsr107?http://www.ehcache.org/schema/ehcache-107-ext-3.0.xsd">
????<service>
????????<jsr107:defaults?enable-statistics="true"/>
????</service>
????<cache?alias="person">
????????<key-type>java.lang.Long</key-type>
????????<value-type>com.ramostear.cache.entity.Person</value-type>
????????<expiry>
????????????<ttl?unit="minutes">1</ttl>
????????</expiry>
????????<listeners>
????????????<listener>
????????????????<class>com.ramostear.cache.config.PersonCacheEventLogger</class>
????????????????<event-firing-mode>ASYNCHRONOUS</event-firing-mode>
????????????????<event-ordering-mode>UNORDERED</event-ordering-mode>
????????????????<events-to-fire-on>CREATED</events-to-fire-on>
????????????????<events-to-fire-on>UPDATED</events-to-fire-on>
????????????????<events-to-fire-on>EXPIRED</events-to-fire-on>
????????????????<events-to-fire-on>REMOVED</events-to-fire-on>
????????????????<events-to-fire-on>EVICTED</events-to-fire-on>
????????????</listener>
????????</listeners>
????????<resources>
????????????????<heap?unit="entries">2000</heap>
????????????????<offheap?unit="MB">100</offheap>
????????</resources>
????</cache>
</config>

最后，還需要定義個緩存事件監聽器，用于記錄系統操作緩存數據的情況，最快的方法是實現CacheEventListener接口：

package?com.ramostear.cache.config;
import?org.ehcache.event.CacheEvent;
import?org.ehcache.event.CacheEventListener;
import?org.slf4j.Logger;
import?org.slf4j.LoggerFactory;
/**
?*?@author?ramostear
?*?@create-time?2019/4/7?0007-0:48
?*?@modify?by?:
?*?@since:
?*/
public?class?PersonCacheEventLogger?implements?CacheEventListener<Object,Object>{
????private?static?final?Logger?logger?=?LoggerFactory.getLogger(PersonCacheEventLogger.class);
????@Override
????public?void?onEvent(CacheEvent?cacheEvent)?{
????????logger.info("person?caching?event?{}?{}?{}?{}",
????????????????cacheEvent.getType(),
????????????????cacheEvent.getKey(),
????????????????cacheEvent.getOldValue(),
????????????????cacheEvent.getNewValue());
????}
}

3. 使用@Cacheable注解

要讓Spring Boot能夠緩存我們的數據，還需要使用@Cacheable注解對業務方法進行注釋，告訴Spring Boot該方法中產生的數據需要加入到緩存中：

package?com.ramostear.cache.service;
import?com.ramostear.cache.entity.Person;
import?org.springframework.cache.annotation.Cacheable;
import?org.springframework.stereotype.Service;
/**
?*?@author?ramostear
?*?@create-time?2019/4/7?0007-0:51
?*?@modify?by?:
?*?@since:
?*/
@Service(value?=?"personService")
public?class?PersonService?{
????@Cacheable(cacheNames?=?"person",key?=?"#id")
????public?Person?getPerson(Long?id){
????????Person?person?=?new?Person(id,"ramostear","ramostear@163.com");
????????return?person;
????}
}

通過以上三個步驟，我們就完成了Spring Boot的緩存功能。接下來，我們將測試一下緩存的實際情況。

歡迎大家關注我的公種浩【程序員追風】，文章都會在里面更新，整理的資料也會放在里面。

4. 緩存測試

為了測試我們的應用程序，創建一個簡單的Restful端點，它將調用PersonService返回一個Person對象：

package?com.ramostear.cache.controller;
import?com.ramostear.cache.entity.Person;
import?com.ramostear.cache.service.PersonService;
import?org.springframework.beans.factory.annotation.Autowired;
import?org.springframework.http.HttpStatus;
import?org.springframework.http.ResponseEntity;
import?org.springframework.web.bind.annotation.GetMapping;
import?org.springframework.web.bind.annotation.PathVariable;
import?org.springframework.web.bind.annotation.RequestMapping;
import?org.springframework.web.bind.annotation.RestController;
/**
?*?@author?ramostear
?*?@create-time?2019/4/7?0007-0:54
?*?@modify?by?:
?*?@since:
?*/
@RestController
@RequestMapping("/persons")
public?class?PersonController?{
????@Autowired
????private?PersonService?personService;
????@GetMapping("/{id}")
????public?ResponseEntity<Person>?person(@PathVariable(value?=?"id")?Long?id){
????????return?new?ResponseEntity<>(personService.getPerson(id),?HttpStatus.OK);
????}
}

Person是一個簡單的POJO類：

package?com.ramostear.cache.entity;
import?lombok.AllArgsConstructor;
import?lombok.Getter;
import?lombok.NoArgsConstructor;
import?lombok.Setter;
import?java.io.Serializable;
/**
?*?@author?ramostear
?*?@create-time?2019/4/7?0007-0:45
?*?@modify?by?:
?*?@since:
?*/
@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
public?class?Person?implements?Serializable{
????private?Long?id;
????private?String?username;
????private?String?email;
}

以上準備工作都完成后，讓我們編譯并運行應用程序。項目成功啟動后，使用瀏覽器打開：http://localhost:8080/persons/1 ,你將在瀏覽器頁面中看到如下的信息：

{"id":1,"username":"ramostear","email":"ramostear@163.com"}

此時在觀察控制臺輸出的日志信息：

2019-04-07?01:08:01.001??INFO?6704?---?[nio-8080-exec-1]?
o.s.web.servlet.DispatcherServlet????????:?Completed?initialization?in?5?ms
2019-04-07?01:08:01.054??INFO?6704?---?[e?[_default_]-0]?
c.r.cache.config.PersonCacheEventLogger??:?person?caching?event?CREATED?1?
null?com.ramostear.cache.entity.Person@ba8a729

由于我們是第一次請求API，沒有任何緩存數據。因此，Ehcache創建了一條緩存數據，可以通過CREATED看一了解到。

我們在ehcache.xml文件中將緩存過期時間設置成了1分鐘（1），因此在一分鐘之內我們刷新瀏覽器，不會看到有新的日志輸出，一分鐘之后，緩存過期，我們再次刷新瀏覽器，將看到如下的日志輸出：

2019-04-07?01:09:28.612??INFO?6704?---?[e?[_default_]-1]
c.r.cache.config.PersonCacheEventLogger??:?person?caching?event?EXPIRED?1
com.ramostear.cache.entity.Person@a9f3c57?null
2019-04-07?01:09:28.612??INFO?6704?---?[e?[_default_]-1]?
c.r.cache.config.PersonCacheEventLogger??:?person?caching?event?CREATED?1
null?com.ramostear.cache.entity.Person@416900ce

第一條日志提示緩存已經過期，第二條日志提示Ehcache重新創建了一條緩存數據。

總結

在本次案例中，通過簡單的三個步驟，講解了基于 Ehcache 的 Spring Boot 應用程序緩存實現。文章內容重在緩存實現的基本步驟與方法，簡化了具體的業務代碼，有興趣的朋友可以自行擴展。

最后

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