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cachehelper java,初识EHCache缓存框架(2.x版本)

發布時間：2023/12/31 编程问答 21 豆豆

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參考文檔:

關于EHCache3.x版本的使用詳見此篇博客:

Maven依賴:

net.sf.ehcache

ehcache

2.10.3

1.獨立使用

在class根目錄下加入配置文件ehcache1.xml.

xsi:noNamespaceSchemaLocation = "http://ehcache.org/ehcache.xsd">

maxEntriesLocalHeap = "10000"

eternal = "false"

timeToIdleSeconds = "120"

timeToLiveSeconds = "120"

maxEntriesLocalDisk = "10000000"

diskExpiryThreadIntervalSeconds = "120"

memoryStoreEvictionPolicy = "LRU" />

maxElementsInMemory = "1000"

eternal = "false"

timeToIdleSeconds = "5"

timeToLiveSeconds = "5"

overflowToDisk = "false"

memoryStoreEvictionPolicy = "LRU" />

Java代碼如下:

public static void main(String[] args) {

// Create a cache manager

final CacheManager cacheManager = CacheManager.newInstance(EHCacheTest.class

.getResource("/ehcache1.xml"));

// create the cache called "hello-world"

final Cache cache = cacheManager.getCache("hello-world1");

// create a key to map the data to

final String key = "greeting";

// Create a data element

final Element putGreeting = new Element(key, "Hello, World!");

// Put the element into the data store

cache.put(putGreeting);

// Retrieve the data element

final Element getGreeting = cache.get(key);

// Print the value

System.out.println(getGreeting.getObjectValue());

}

輸出結果如下(包括日志):

DEBUG 18:15:24,365 [main](ConfigurationFactory.java:98) - Configuring ehcache from URL: file:/D:/WORKSPACE/intelljIdea/SSMProjectMaven/target/test-classes/ehcache1.xml

DEBUG 18:15:24,371 [main](ConfigurationFactory.java:150) - Configuring ehcache from InputStream

DEBUG 18:15:24,466 [main](BeanHandler.java:271) - Ignoring ehcache attribute xmlns:xsi

DEBUG 18:15:24,466 [main](BeanHandler.java:271) - Ignoring ehcache attribute xsi:noNamespaceSchemaLocation

DEBUG 18:15:24,474 [main](DiskStoreConfiguration.java:141) - Disk Store Path: C:\Users\FlyingHe\AppData\Local\Temp\/ehcache

DEBUG 18:15:24,526 [main](CacheManager.java:1102) - Creating new CacheManager with config URL: file:/D:/WORKSPACE/intelljIdea/SSMProjectMaven/target/test-classes/ehcache1.xml

DEBUG 18:15:24,531 [main](PropertyUtil.java:87) - propertiesString is null.

DEBUG 18:15:24,553 [main](ConfigurationHelper.java:189) - No CacheManagerEventListenerFactory class specified. Skipping...

DEBUG 18:15:25,168 [main](Cache.java:1044) - No BootstrapCacheLoaderFactory class specified. Skipping...

DEBUG 18:15:25,169 [main](Cache.java:1017) - CacheWriter factory not configured. Skipping...

DEBUG 18:15:25,169 [main](ConfigurationHelper.java:100) - No CacheExceptionHandlerFactory class specified. Skipping...

DEBUG 18:15:25,189 [main](Cache.java:1044) - No BootstrapCacheLoaderFactory class specified. Skipping...

DEBUG 18:15:25,189 [main](Cache.java:1017) - CacheWriter factory not configured. Skipping...

DEBUG 18:15:25,190 [main](ConfigurationHelper.java:100) - No CacheExceptionHandlerFactory class specified. Skipping...

DEBUG 18:15:25,243 [main](MemoryStore.java:180) - Initialized net.sf.ehcache.store.MemoryStore for hello-world1

DEBUG 18:15:25,406 [main](ExtendedStatisticsImpl.java:224) - Mocking Pass-Through Statistic: LOCAL_OFFHEAP_SIZE

DEBUG 18:15:25,414 [main](ExtendedStatisticsImpl.java:224) - Mocking Pass-Through Statistic: LOCAL_OFFHEAP_SIZE_BYTES

DEBUG 18:15:25,415 [main](ExtendedStatisticsImpl.java:224) - Mocking Pass-Through Statistic: LOCAL_DISK_SIZE

DEBUG 18:15:25,416 [main](ExtendedStatisticsImpl.java:224) - Mocking Pass-Through Statistic: LOCAL_DISK_SIZE_BYTES

DEBUG 18:15:25,417 [main](ExtendedStatisticsImpl.java:224) - Mocking Pass-Through Statistic: WRITER_QUEUE_LENGTH

DEBUG 18:15:25,419 [main](ExtendedStatisticsImpl.java:224) - Mocking Pass-Through Statistic: REMOTE_SIZE

DEBUG 18:15:25,419 [main](ExtendedStatisticsImpl.java:224) - Mocking Pass-Through Statistic: LAST_REJOIN_TIMESTAMP

DEBUG 18:15:25,516 [main](ExtendedStatisticsImpl.java:206) - Mocking Operation Statistic: OFFHEAP_GET

DEBUG 18:15:25,518 [main](ExtendedStatisticsImpl.java:206) - Mocking Operation Statistic: OFFHEAP_PUT

DEBUG 18:15:25,519 [main](ExtendedStatisticsImpl.java:206) - Mocking Operation Statistic: OFFHEAP_REMOVE

DEBUG 18:15:25,522 [main](ExtendedStatisticsImpl.java:206) - Mocking Operation Statistic: DISK_GET

DEBUG 18:15:25,523 [main](ExtendedStatisticsImpl.java:206) - Mocking Operation Statistic: DISK_PUT

DEBUG 18:15:25,524 [main](ExtendedStatisticsImpl.java:206) - Mocking Operation Statistic: DISK_REMOVE

DEBUG 18:15:25,525 [main](ExtendedStatisticsImpl.java:206) - Mocking Operation Statistic: XA_COMMIT

DEBUG 18:15:25,526 [main](ExtendedStatisticsImpl.java:206) - Mocking Operation Statistic: XA_ROLLBACK

DEBUG 18:15:25,556 [main](ExtendedStatisticsImpl.java:206) - Mocking Operation Statistic: XA_RECOVERY

DEBUG 18:15:25,565 [main](ExtendedStatisticsImpl.java:206) - Mocking Operation Statistic: CLUSTER_EVENT

DEBUG 18:15:25,566 [main](ExtendedStatisticsImpl.java:206) - Mocking Operation Statistic: NONSTOP

DEBUG 18:15:25,578 [main](Cache.java:1262) - Initialised cache: hello-world1

DEBUG 18:15:25,578 [main](ConfigurationHelper.java:334) - CacheDecoratorFactory not configured. Skipping for 'hello-world1'.

DEBUG 18:15:25,578 [main](ConfigurationHelper.java:364) - CacheDecoratorFactory not configured for defaultCache. Skipping for 'hello-world1'.

Hello, World!

注:

如果在實例化CacheManager時采用此種方式CacheManager manager = CacheManager.newInstance();則默認加載class根目錄下的ehcache.xml文件。

在官方文檔中已給出多種加載配置文件的方式的解釋:

關于更多配置文件的解釋：

對于配置文件：

xsi:noNamespaceSchemaLocation = "http://ehcache.org/ehcache.xsd">

maxElementsInMemory="10000"

maxElementsOnDisk="0"

eternal="true"

overflowToDisk="true"

diskPersistent="false"

timeToIdleSeconds="0"

timeToLiveSeconds="0"

diskSpoolBufferSizeMB="50"

diskExpiryThreadIntervalSeconds="120"

memoryStoreEvictionPolicy="LFU"

maxElementsInMemory="100"

maxElementsOnDisk="0"

eternal="false"

overflowToDisk="false"

diskPersistent="false"

timeToIdleSeconds="120"

timeToLiveSeconds="120"

diskSpoolBufferSizeMB="50"

diskExpiryThreadIntervalSeconds="120"

memoryStoreEvictionPolicy="FIFO"

解釋如下：

1、diskStore ：指定數據(.data and .index)存儲位置，可指定磁盤中的文件夾位置期 The diskStore element is optional. It must be configured if you have overflowToDisk or diskPersistent enabled??? for any cache. If it is not configured, a warning will be issues and java.io.tmpdir will be used.

２、defaultCache ：默認的管理策略

一、以下屬性是必須的：

1、name： Cache的名稱，必須是唯一的(ehcache會把這個cache放到HashMap里)。

2、maxElementsInMemory：在內存中緩存的element的最大數目。

3、maxElementsOnDisk：在磁盤上緩存的element的最大數目，默認值為0，表示不限制。

４、eternal：設定緩存的elements是否永遠不過期。如果為true，則緩存的數據始終有效，如果為false那么還要根據timeToIdleSeconds，timeToLiveSeconds判斷。

５、overflowToDisk：如果內存中數據超過內存限制，是否要緩存到磁盤上。

二、以下屬性是可選的：

１、timeToIdleSeconds：對象空閑時間，指對象在多長時間沒有被訪問就會失效。只對eternal為false的有效。默認值0，表示一直可以訪問。

２、timeToLiveSeconds：對象存活時間，指對象從創建到失效所需要的時間。只對eternal為false的有效。默認值0，表示一直可以訪問。

３、diskPersistent：是否在磁盤上持久化。指重啟jvm后，數據是否有效。默認為false。

４、diskExpiryThreadIntervalSeconds：對象檢測線程運行時間間隔。標識對象狀態的線程多長時間運行一次。

５、diskSpoolBufferSizeMB： DiskStore使用的磁盤大小，默認值30MB。每個cache使用各自的DiskStore。

６、memoryStoreEvictionPolicy：如果內存中數據超過內存限制，向磁盤緩存時的策略。默認值LRU，可選FIFO、LFU。

四、緩存的3 種清空策略：

１、FIFO ，first in first out (先進先出).

２、LFU ， Less Frequently Used (最少使用).意思是一直以來最少被使用的。緩存的元素有一個hit 屬性，hit 值最小的將會被清出緩存。

３、LRU ，Least Recently Used(最近最少使用). (ehcache 默認值).緩存的元素有一個時間戳，當緩存容量滿了，而又需要騰出地方來緩存新的元素的時候，那么現有緩存元素中時間戳離當前時間最遠的元素將被清出緩存。

2.EHCache2.x版本與Spring的整合使用

引入Spring相關的包這里不再詳述。

①創建一個ehcache-spring.xml的文件，配置Spring

xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"

xmlns:cache = "http://www.springframework.org/schema/cache"

xsi:schemaLocation = "

http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd

http://www.springframework.org/schema/cache http://www.springframework.org/schema/cache/spring-cache.xsd">

②創建ehcache1.xml文件，配置EHCache

xsi:noNamespaceSchemaLocation = "http://ehcache.org/ehcache.xsd">

maxEntriesLocalHeap = "10000"

eternal = "false"

timeToIdleSeconds = "120"

timeToLiveSeconds = "120"

maxEntriesLocalDisk = "10000000"

diskExpiryThreadIntervalSeconds = "120"

memoryStoreEvictionPolicy = "LRU" />

maxElementsInMemory = "1000"

eternal = "false"

timeToIdleSeconds = "3"

timeToLiveSeconds = "3"

overflowToDisk = "false"

memoryStoreEvictionPolicy = "LRU" />

③創建一個Person類，需要緩存的對象的所屬類必須實現java.io.Serializable接口

package at.flying.domain;

import java.io.Serializable;

public class Person implements Serializable {

private static final long serialVersionUID = 1L;

private int id;

private String name;

public Person() {}

public Person(int id, String name) {

this.id = id;

this.name = name;

}

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

@Override

public String toString() {

return "id=" + this.id + ", name=" + this.name;

}

④創建一個PersonService類，用于模擬對數據庫操作的業務邏輯

package at.flying.service;

import at.flying.domain.Person;

import org.springframework.cache.annotation.CacheEvict;

import org.springframework.cache.annotation.CachePut;

import org.springframework.cache.annotation.Cacheable;

import org.springframework.stereotype.Service;

import java.util.HashSet;

import java.util.Set;

public class PersonService {

private Set people;

public PersonService() {

people = new HashSet<>();

Person person1 = new Person(1, "張三");

Person person2 = new Person(2, "趙四");

Person person3 = new Person(3, "王五");

people.add(person1);

people.add(person2);

people.add(person3);

}

@Cacheable({"Person"})

public Person findUser(Person person) {

return findUserInDB(person.getId());

}

@Cacheable(value = "Person", condition = "#person.getId() <= 2")

public Person findUserInLimit(Person person) {

return findUserInDB(person.getId());

}

@CachePut(value = "Person")

public Person updateUser(Person person) {

updateUserInDB(person);

return person;

}

@CacheEvict(value = "Person")

public void removeUser(Person person) {

removeUserInDB(person.getId());

}

@CacheEvict(value = "Person", allEntries = true)

public void clear() {

removeAllInDB();

}

/**

* 模擬查找數據庫

private Person findUserInDB(int id) {

for (Person u : people) {

if (id == u.getId()) {

System.out.println("查找數據庫 id = " + id + " 成功");

return u;

}

return null;

}

/**

* 模擬更新數據庫

private void updateUserInDB(Person person) {

for (Person u : people) {

if (person.getId() == u.getId()) {

System.out.println("更新數據庫" + u + " -> " + person);

u.setName(person.getName());

}

private void removeUserInDB(int id) {

for (Person u : people) {

if (id == u.getId()) {

System.out.println("從數據庫移除 id = " + id + " 的數據");

people.remove(u);

break;

}

private void removeAllInDB() {

people.clear();

}

⑤測試類EHCacheSpringTest

package at.flying.test;

import at.flying.domain.Person;

import at.flying.service.PersonService;

import net.sf.ehcache.Element;

import org.junit.Test;

import org.junit.runner.RunWith;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.cache.ehcache.EhCacheCacheManager;

import org.springframework.test.context.ContextConfiguration;

import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import java.util.List;

@RunWith(SpringJUnit4ClassRunner.class)

@ContextConfiguration(locations = {"classpath:at/flying/ehcache/spring/xml/ehcache-spring.xml"})

public class EHCacheSpringTest {

@Autowired

PersonService personService;

@Autowired

EhCacheCacheManager cacheManager;

/**

* 測試@Cacheable

@Test

public void testFindUser() throws InterruptedException {

// 設置查詢條件

Person person1 = new Person(1, null);

Person person2 = new Person(2, null);

Person person3 = new Person(3, null);

System.out.println("第一次查詢");

System.out.println(personService.findUser(person1));

System.out.println(personService.findUser(person2));

System.out.println(personService.findUser(person3));

this.printCacheStatus();

System.out.println("\n第二次查詢");

System.out.println(personService.findUser(person1));

System.out.println(personService.findUser(person2));

System.out.println(personService.findUser(person3));

// 在classpath:ehcache/ehcache.xml中，設置了userCache的緩存時間為3000 ms, 這里設置等待

Thread.sleep(3000);

System.out.println("\n緩存過期，再次查詢");

System.out.println(personService.findUser(person1));

System.out.println(personService.findUser(person2));

System.out.println(personService.findUser(person3));

}

/**

* 輸出當前Person緩存的緩存信息

public void printCacheStatus() {

net.sf.ehcache.CacheManager cacheManager = this.cacheManager.getCacheManager();

net.sf.ehcache.Cache cache = cacheManager.getCache("Person");

System.out.println("緩存對象數:" + cache.getSize());

System.out.println("各元素的Key-Value如下:");

List keys = cache.getKeys();

for (Object o : keys) {

Element e = cache.get(o);

System.out.println(o + " -> " + e.getObjectValue());

}

/**

* 測試@Cacheable設置Spring SpEL條件限制

@Test

public void testFindUserInLimit() throws InterruptedException {

// 設置查詢條件

Person person1 = new Person(1, null);

Person person2 = new Person(2, null);

Person person3 = new Person(3, null);

System.out.println("第一次查詢user info");

System.out.println(personService.findUserInLimit(person1));

System.out.println(personService.findUserInLimit(person2));

System.out.println(personService.findUserInLimit(person3));

System.out.println("\n第二次查詢user info");

System.out.println(personService.findUserInLimit(person1));

System.out.println(personService.findUserInLimit(person2));

System.out.println(personService.findUserInLimit(person3)); // 超過限制條件，不會從緩存中讀數據

// 在classpath:ehcache/ehcache.xml中，設置了userCache的緩存時間為3000 ms, 這里設置等待

Thread.sleep(3000);

System.out.println("\n緩存過期，再次查詢");

System.out.println(personService.findUserInLimit(person1));

System.out.println(personService.findUserInLimit(person2));

System.out.println(personService.findUserInLimit(person3));

}

/**

* 測試@CachePut

@Test

public void testUpdateUser() {

// 設置查詢條件

Person person2 = new Person(2, null);

System.out.println(personService.findUser(person2));

this.printCacheStatus();

personService.updateUser(new Person(2, "尼古拉斯.趙四"));

this.printCacheStatus();

System.out.println(personService.findUser(person2));

}

/**

* 測試@CacheEvict刪除指定緩存

@Test

public void testRemoveUser() {

// 設置查詢條件

Person person1 = new Person(1, null);

System.out.println("數據刪除前：");

System.out.println(personService.findUser(person1));

personService.removeUser(person1);

System.out.println("數據刪除后：");

System.out.println(personService.findUser(person1));

}

/**

* 測試@CacheEvict刪除所有緩存

@Test

public void testClear() {

System.out.println("數據清空前：");

System.out.println(personService.findUser(new Person(1, null)));

System.out.println(personService.findUser(new Person(2, null)));

System.out.println(personService.findUser(new Person(3, null)));

personService.clear();

System.out.println("\n數據清空后：");

System.out.println(personService.findUser(new Person(1, null)));

System.out.println(personService.findUser(new Person(2, null)));

System.out.println(personService.findUser(new Person(3, null)));

}

測試結果不再貼出。

注意：

注解Cacheable與Cacheput的區別:

cacheable一般用于查詢數據，cacheput一般用于修改數據。兩者都會對修飾的方法的返回值做緩存，如果在注解中沒有指定緩存時的key并且也沒有指定keyGenerator參數的話，那么默認key將會是直接調用緩存對象的toString()方法的返回值作為key，如果被修飾的方法沒有返回值，那么緩存值value將會是null。

并且對于Cacheable如果在查詢時發現緩存中存在，則不再執行被修飾的方法體，也就是說不會取數據庫中查詢數據，而對于CachePut的話，不管怎樣被修飾的方法體都會執行，所以說，Cacheable一般用于查詢數據，而CachePut一般用于修改數據。

結果可測試得到，這里不再貼出測試結果。

關于這三個注解的詳細解釋可以參考此篇博客:

關于EHCache配置文件中diskStore的解釋可參看此篇博客:

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