Spring Boot Ehcache 3 JSR-107的簡單配置方法如下。
JSR-107(JCache)是Java的快取標準規格,僅提供標準的操作方法及API,並無快取機制的實作;而Ehache 3則是提供JSR-107的實作,又叫做Caching Provider。
範例環境:
- Spring Boot版本2.2.1.RELEASE
- Maven
- Lombok
建立Spring Boot專案(參考IntelliJ IDEA,Eclipse STS)。
把下列快取相關依賴引入專案的pom.xml
:
spring-boot-starter-cache
:Spring Boot對快取的整合。org.ehcache:ehcache
:Ehcachejavax.cache:cache-api
:JSR-107 API
pom.xml
<?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 https://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>2.2.1.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.abc</groupId>
<artifactId>spring-boot-cache-demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>spring-boot-cache-demo</name>
<description>Spring Boot Caching Demo</description>
<packaging>jar</packaging>
<properties>
<java.version>11</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-logging</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-log4j2</artifactId>
</dependency>
<!-- 快取相關依賴 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-cache</artifactId>
</dependency>
<dependency>
<groupId>org.ehcache</groupId>
<artifactId>ehcache</artifactId>
</dependency>
<dependency>
<groupId>javax.cache</groupId>
<artifactId>cache-api</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.10</version>
<scope>provided</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
在application.properties
設定spring.cache.jcache.config=classpath:ehcache.xml
,也就是使用Ehcache配置檔ehcache.xml
作為JCache的配置。
application.properties
#context path
server.servlet.context-path=/demo
#port
server.port=8080
#cache
spring.cache.jcache.config=classpath:ehcache.xml
範例的本機的應用程式路徑為http://localhost:8080/demo
。
在classpath根目錄src/main/resources
新增ehcache.xml
檔設定如下。
ehcache.xml
<config
xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'
xmlns='http://www.ehcache.org/v3'>
<cache alias="employee_cache"> <!-- cache的名稱為"employee_cache" -->
<expiry>
<ttl unit="seconds">5</ttl> <!-- cache建立後只會存在5秒 -->
</expiry>
<resources>
<heap unit="entries">2000</heap> <!-- heap可存2000個快取物件 -->
<offheap unit="MB">100</offheap> <!-- heap外空間可存100MB的快取 -->
</resources>
</cache>
</config>
參考XML配置說明。
在@Configuration
類別名稱前加上@EnableCaching
啟用快取機制。範例是加在@SpringBootApplication
類別DemoApplication
。
DemoApplication
package com.abc.demo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.annotation.EnableCaching;
@EnableCaching // 啟用快取
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
建立DemoController
提供對外API接收外部請求,並轉呼叫EmployeService
取得資源。
DemoController
package com.abc.demo.controller;
import com.abc.demo.model.Employee;
import com.abc.demo.service.EmployeeService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class DemoController {
@Autowired
private EmployeeService employeeService;
@GetMapping("/employee/{id}")
public Employee getEmployee(@PathVariable Long id) {
return employeeService.getEmployeeById(id);
}
}
Employee
為被檢索的資料物件,也就是被快取的對象。注意快取除了放在記憶體中,也可能放在系統外如Redis或硬碟,所以快取對象必須是可序列化的,也就是要實作Serializable
,否則會拋出org.ehcache.spi.resilience.StoreAccessException: org.ehcache.spi.serialization.SerializerException: java.io.NotSerializableException
錯誤。
Employee
package com.abc.demo.model;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.io.Serializable;
@Builder
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Employee implements Serializable { // 序列化
private Long id;
private String name;
private Integer age;
}
EmployeeService.getEmployeeById()
方法用來查詢資料庫的員工資訊,這邊以簡單的Map物件模擬現有的員工資料。加上@Cacheable
對此方法做快取,以相同的查訊條件再次呼叫getEmployeeById()
時會從快取回傳先前的查詢結果。
@Cacheable
的cacheNames
屬性用來指定快取名稱,也就是ehcache.xml
中設定的<cache alias="employee_cache">
。
EmployeeService
package com.abc.demo.service;
import com.abc.demo.model.Employee;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;
import java.util.HashMap;
import java.util.Map;
@Service
public class EmployeeService {
@Cacheable(cacheNames = "employee_cache")
public Employee getEmployeeById(Long id) {
Map<Long, Employee> currentEmployeeMap = getCurrentEmployeeMap();
return currentEmployeeMap.get(id);
}
// 模擬資料庫的資料
private Map<Long, Employee> getCurrentEmployeeMap() {
Map<Long, Employee> currentEmployeeMap = new HashMap<>();
currentEmployeeMap.put(1L, Employee.builder().id(1L).name("alan").age(33).build());
currentEmployeeMap.put(2L, Employee.builder().id(2L).name("bill").age(45).build());
currentEmployeeMap.put(3L, Employee.builder().id(3L).name("carl").age(24).build());
currentEmployeeMap.put(4L, Employee.builder().id(4L).name("dave").age(31).build());
return currentEmployeeMap;
}
}
上面的EmployeeService.getEmployeeById()
使用的@Cacheable
是Spring的快取注釋;此外也可改用JSR-107的@CacheResult
也可達到相同的快取效果(注意屬性名稱不同)。
@CacheResult(cacheName = "employee_cache") // JSR-107 @CacheResult annotation
public Employee getEmployeeById(Long id) {
Map<Long, Employee> currentEmployeeMap = getCurrentEmployeeMap();
return currentEmployeeMap.get(id);
}
完成以上後在EmployeeService.getEmployeeById()
中下中斷點,然後以debug模式啟動。
用Postman呼叫http://localhost:8080/demo/employee/1
,可以發現第一次呼叫時會進入EmployeeService.getEmployeeById()
,但第二次呼叫時就不會進入了,這就是快取的效果。若呼叫的間隔時間超過5秒則快取會被清除,一樣會進入EmployeeService.getEmployeeById()
。
完整程式碼參考github。
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