一：加入maven依赖

<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>19.0</version>
</dependency>

方法一：

package com.test.guava;

import java.util.concurrent.TimeUnit;

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;

public class UserService
{
private final Cache<String, String> cache;

public UserService()
{
/**
 * 5秒自动过期
 */
cache = CacheBuilder.newBuilder().expireAfterWrite(5, TimeUnit.SECONDS).build();
}

public String getUserName(String id) throws Exception
{
return cache.get(id, () -> {
System.out.println("method invoke2");
//这里执行查询数据库，等其他复杂的逻辑
return "User:" + id;
});
}
}

package com.test.guava;

import java.util.concurrent.TimeUnit;

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

public class UserService
{
private final LoadingCache<String, String> cache;

public UserService()
{
/**
 * 5秒自动过期
 */
cache = CacheBuilder.newBuilder().expireAfterWrite(5, TimeUnit.SECONDS).build(new CacheLoader<String, String>() {
    public String load(String id) throws Exception
    {
    System.out.println("method inovke");
    //这里执行查询数据库，等其他复杂的逻辑
            return "User:" + id;
    }
    });
}

public String getUserName(String id) throws Exception
{
return cache.get(id);
}
}

package com.test.guava;

import java.util.concurrent.TimeUnit;

public class GuavaCacheTest
{
public static void main(String[] args)throws Exception
{
UserService us = new UserService();
for(int i=0;i<20;i++)
{
System.out.println(us.getUserName("1001"));
TimeUnit.SECONDS.sleep(1);
}
}
}