[Guava] CacheBuilder, CachLoader 예제

Guava의 CacheBuilder와 CacheLoader 예제이다. 

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;

import org.apache.commons.collections.MapUtils;
import org.junit.Test;

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.cache.RemovalListener;
import com.google.common.cache.RemovalNotification;

public class GuavaTest {
CacheLoader<String, String> loader = new CacheLoader<String, String>() {
@Override
public String load(String key) {
return key.toUpperCase();
}
};

@Test
public void simpleTest() {
System.out.println("--- simple ---");
LoadingCache<String, String> cache = CacheBuilder.newBuilder().build(loader);

cache.getUnchecked("hello");
cache.getUnchecked("world");

MapUtils.debugPrint(System.out, "map", cache.asMap());
System.out.println(cache.size());
}

@Test
public void sizeLimitTest() {
System.out.println("--- size limit test ---");
LoadingCache<String, String> cache = CacheBuilder.newBuilder().maximumSize(3).build(loader);

cache.getUnchecked("a");
cache.getUnchecked("b");
cache.getUnchecked("c");
cache.getUnchecked("d");

MapUtils.debugPrint(System.out, "map", cache.asMap());
System.out.println(cache.size());
System.out.println(cache.getIfPresent("a")); // a는 evit 되었다.
System.out.println(cache.getIfPresent("d"));
}

@Test
public void timeLimitTest() throws InterruptedException {
System.out.println("--- time limit test ---");
LoadingCache<String, String> cache = CacheBuilder.newBuilder().expireAfterAccess(1, TimeUnit.SECONDS).build(loader);

cache.getUnchecked("Samuel");
System.out.println(cache.getIfPresent("Samuel"));
Thread.sleep(800);
System.out.println(cache.getIfPresent("Samuel")); // a는 evit되었다.
}

@Test
public void preloadTest() {
System.out.println("-- preload test ---");
Map<String, String> map = new HashMap<String, String>();
    map.put("samuel", "SAMUEL");
    map.put("jason", "JASON");
    LoadingCache<String, String> cache = CacheBuilder.newBuilder().build(loader);
    cache.putAll(map);
    MapUtils.debugPrint(System.out, "map", cache.asMap());
}

@Test
public void removeNotiTest() {
System.out.println("-- remove test ---");
RemovalListener<String, String> listener = new RemovalListener<String, String>() {
        @Override
        public void onRemoval(RemovalNotification<String, String> n){
            if (n.wasEvicted()) {
                String cause = n.getCause().name();
                System.out.println("[removed] cause : " + cause + ", key : " + n.getKey());
            }
        }
    };

    LoadingCache<String, String> cache = CacheBuilder.newBuilder().maximumSize(2).removalListener(listener).build(loader);

    cache.getUnchecked("samuel");
    cache.getUnchecked("jason");
    cache.getUnchecked("kalley");
}

@Test
public void etc() {
// LoadingCache<String, String> cache = CacheBuilder.newBuilder().refreshAfterWrite(1,TimeUnit.MINUTES).build(loader);
// LoadingCache<String, String> cache = CacheBuilder.newBuilder().weakKeys().build(loader);
// LoadingCache<String, String> cache = CacheBuilder.newBuilder().softKeys().build(loader);
}
}

결과

--- size limit test ---

map = 

{

    c = C java.lang.String

    b = B java.lang.String

    d = D java.lang.String

} com.google.common.cache.LocalCache

3

null

D

--- simple ---

map = 

{

    hello = HELLO java.lang.String

    world = WORLD java.lang.String

} com.google.common.cache.LocalCache

2

-- preload test ---

map = 

{

    jason = JASON java.lang.String

    samuel = SAMUEL java.lang.String

} com.google.common.cache.LocalCache

--- time limit test ---

SAMUEL

SAMUEL

-- remove test ---

[removed] cause : SIZE, key : samuel