guava缓存的使用及与spring的集成

一、guava缓存简介

guava是google为java开发的库，对jdk进行了扩展。在此我们只介绍guava的缓存。

guava缓存是内存缓存，也就是数据存在内存中的。

二、guava基本使用

1、添加maven依赖

<dependency>    <groupId>com.google.guava</groupId>    <artifactId>guava</artifactId>    <version>23.0</version></dependency>

2、自定义guava工具类

public class GuavaCacheUtil {    public static LoadingCache<String, String> strCache = CacheBuilder            .newBuilder()            .maximumSize(1000)            .expireAfterAccess(5, TimeUnit.MINUTES)            .build(                    new CacheLoader<String, String>() {                        @Override                        public String load(String s) throws Exception { //当缓存中不存在时，自动加载新数据到缓存                            return null;                        }                    }            );    /**     * 将值存入缓存     *     * @param key     * @param val     */    public static void setStr(String key, String val) {        strCache.put(key, val);    }    /**     * 从缓存中取值     *     * @param key     * @return     */    public static String getStr(String key) {        String val = "";        try {            val = strCache.get(key);        } catch (ExecutionException e) {        }        return val;    }}

3、使用

public class GuavaCacheMain {    public static void main(String[] args) {        String key = "k1";        String val = "v1";        GuavaCacheUtil.setStr(key, val);        String v1 = GuavaCacheUtil.getStr(key);        System.out.println("k1 : " + v1);        String v2 = GuavaCacheUtil.getStr(key);        System.out.println("k2 : " + v2);    }}

输出：

k1 : v1
k1 : v1

三、guava缓存与spring的集成

1、添加maven依赖

<dependency>    <groupId>com.google.guava</groupId>    <artifactId>guava</artifactId>    <version>23.0</version></dependency>

2、在spring中配置guava缓存

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xmlns:context="http://www.springframework.org/schema/context"       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/context       http://www.springframework.org/schema/context/spring-context.xsd       http://www.springframework.org/schema/cache       http://www.springframework.org/schema/cache/spring-cache.xsd        ">    <context:component-scan base-package="com.dragon.study" />    <cache:annotation-driven />    <bean id="cacheManager" class="org.springframework.cache.guava.GuavaCacheManager">        <property name="cacheSpecification" value="concurrencyLevel=4,expireAfterAccess=100s,expireAfterWrite=100s" />        <property name="cacheNames">            <list>                <value>guavaCache</value>            </list>        </property>    </bean></beans>

3、在服务中使用guava缓存

public interface StudentService {    public Student getStudent(Integer id);    public Student updateStudent(Student stu);    public void deleteStudent(Integer id);    public void deleteAllStudent();    public void myDelete(Integer id);}

@Service("studentGuavaCache")public class StudentGuavaCacheImpl implements StudentService {    @Cacheable(value = "guavaCache",key="'id_'+#id",condition = "#id<3")    public Student getStudent(Integer id) {        Student stu = new Student();        stu.setId(id);        stu.setName("apple");        return stu;    }    @CachePut(value = "guavaCache",key="'id_'+#stu.getId()")    public Student updateStudent(Student stu){        System.out.println("update stu");        return stu;    }    @CacheEvict(value = "guavaCache",key="'id_'+#id")    public void deleteStudent(Integer id){        System.out.println("delete student "+id);    }    public void myDelete(Integer id){        try {            StudentService ss = (StudentService) AopContext.currentProxy();            ss.deleteStudent(id);            return ;        }catch (Exception e){            e.printStackTrace();        }        this.deleteStudent(id);    }    @CacheEvict(value = "guavaCache",allEntries = true)    public void deleteAllStudent(){        System.out.println("delete all student ");    }}

4、测试

public class SpringGuavaCacheMain {    public static void main(String[] args) {        ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("classpath:spring-guava-cache.xml");        StudentService studentService = (StudentService) ac.getBean("studentGuavaCache");        Integer id =1;        Student stu = studentService.getStudent(id);  //新建缓存        stu = studentService.getStudent(id);   //从缓存中取        studentService.myDelete(id);        stu = studentService.getStudent(id);   //从缓存中取        stu.setName("banana");  //重新设置值        studentService.updateStudent(stu); //更新缓存        stu = studentService.getStudent(id); //从缓存中取出新值        stu = new Student();  //新实例        stu.setId(0);        studentService.updateStudent(stu);  //用新建的实例进行更新，会新建缓存        stu = studentService.getStudent(0);  //从缓存中取        studentService.deleteStudent(id);  // 删除缓存        stu = studentService.getStudent(id);  //再次新建缓存        id=2;        stu = studentService.getStudent(id); //新建缓存        studentService.deleteAllStudent(); //删除所有缓存        id=1;        stu = studentService.getStudent(id); //因所有缓存被前一步清除，会新建缓存        id=5;        stu = studentService.getStudent(id); //不会新建缓存 因为设置了缓存条件必须小于3        stu = studentService.getStudent(id); //因没有缓存，不会从缓存中取        Assert.notNull(stu);    }}

输出：

delete student 1
update stu
update stu
delete student 1
delete all student

四、guava缓存与其它形式缓存共存

除了guava缓存，在还有其它如redis等缓存，使用方法类似，在此仅列出其spring的配置文件

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xmlns:context="http://www.springframework.org/schema/context"       xmlns:cache="http://www.springframework.org/schema/cache"       xmlns:p="http://www.springframework.org/schema/p"       xsi:schemaLocation="http://www.springframework.org/schema/beans       http://www.springframework.org/schema/beans/spring-beans.xsd       http://www.springframework.org/schema/context       http://www.springframework.org/schema/context/spring-context.xsd       http://www.springframework.org/schema/cache       http://www.springframework.org/schema/cache/spring-cache.xsd        ">    <context:component-scan base-package="com.dragon.study" />    <cache:annotation-driven />    <bean id="cacheManager" class="org.springframework.cache.support.CompositeCacheManager">        <property name="cacheManagers">            <list>                <ref bean="simpleCacheManager" />                <ref bean="guavaCacheManager" />            </list>        </property>        <property name="fallbackToNoOpCache" value="true" />    </bean>    <bean id="simpleCacheManager" class="org.springframework.cache.support.SimpleCacheManager">        <property name="caches">            <set>                <bean class="org.springframework.cache.concurrent.ConcurrentMapCacheFactoryBean" p:name="default" />                <bean class="org.springframework.cache.concurrent.ConcurrentMapCacheFactoryBean" p:name="mycache" />                <bean class="com.dragon.tbscheduleStudy.cache.RedisCache" p:name="redisCache" p:timeout="60000" />            </set>        </property>    </bean>    <bean id="guavaCacheManager" class="org.springframework.cache.guava.GuavaCacheManager">        <property name="cacheSpecification" value="concurrencyLevel=4,expireAfterAccess=100s,expireAfterWrite=100s" />        <property name="cacheNames">            <list>                <value>guavaCache</value>            </list>        </property>    </bean></beans>