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一、背景
1.在这里不谈什么redis缓存,这里我们主要谈谈java里的缓存工具。
二、项目例子
1.依赖
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>17.0</version>
</dependency>
2.实体类
public class Student {
private String age;
private String name;
public Student(String age, String name) {
this.age = age;
this.name = name;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Student{" +
"age='" + age + '\'' +
", name='" + name + '\'' +
'}';
}
}
3.缓存类
import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import java.util.concurrent.TimeUnit;
public class TestCache {
//设置了最大的缓存数据10,过期策略10秒(10秒内没写入的话)
public static final Cache<String,Student> studentCache=
CacheBuilder.newBuilder()
.maximumSize(10)
.expireAfterWrite(10, TimeUnit.SECONDS)
.build();
}
4.测试类
public class TestCacheDemo {
public static void main(String[] args) {
for (int i=0;i<12;i++){
studentCache.put(i+"",new Student(i+"","诺言"));
}
System.out.println("第一次输出:"+studentCache.getIfPresent("1"));
for (int i=0;i<12;i++){
System.out.println(i+"次输出:"+studentCache.getIfPresent(""+i));
}
System.out.println("缓存总大小:"+studentCache.size());
try{
Thread.sleep(10100L);
} catch (Exception e) {
e.printStackTrace();
}
System.out.println("第三次输出:"+studentCache.getIfPresent("10"));
//获取缓存10,如果null就利用Callable重新计算,所以会输出第四次的结果
try{
studentCache.get("10", new Callable<Student>() {
@Override
public Student call() throws Exception {
return new Student("10","爱你");
}
});
}catch (ExecutionException e){
e.printStackTrace();
}
System.out.println("第四次输出:"+studentCache.getIfPresent("10"));
}
}
5.结果
第一次输出:null //缓存的数量限制
0次输出:null
1次输出:null
2次输出:Student{age='2', name='诺言'}
3次输出:Student{age='3', name='诺言'}
4次输出:Student{age='4', name='诺言'}
5次输出:Student{age='5', name='诺言'}
6次输出:Student{age='6', name='诺言'}
7次输出:Student{age='7', name='诺言'}
8次输出:Student{age='8', name='诺言'}
9次输出:Student{age='9', name='诺言'}
10次输出:Student{age='10', name='诺言'}
11次输出:Student{age='11', name='诺言'}
缓存总大小:10
第三次输出:null //这里因为缓存过期了
第四次输出:Student{age='10', name='爱你'}
三、总结
缓存回收策略
四、结束
Always keep the faith!!!