如何使用google guava cache创建缓存?

x33g5p2x  于12天前 转载在 Go  
字(3.5k)|赞(0)|评价(0)|浏览(15)

创建普通缓存很简单,但是如果数据的数据结构很复杂,我们需要一个Cache来缓存。

在云原生应用开发中,微服务对于某些主数据是相互依赖的。获取信息意味着发送HTTP请求,当客户端微服务非常频繁地需要数据并且数据源是另一个微服务时,必须进行非常频繁的HTTP请求。这会导致客户端微服务中的处理延迟。由于这些原因,将主数据缓存在不经常更改的客户端微服务中是有意义的。虽然这种实现不仅适用于云原生开发中的微服务,而且可以用于任何类型的应用程序。

在这篇文章中,我将展示如何实现缓存的缓存。缓存的缓存是一个通用的番石榴缓存,其中键是字符串,值是其他番石榴缓存。这些作为值的番石榴缓存也有键值对。键和值可以是任何类型。这里缓存的缓存是 CacheManager 中的 cacheMap。内部缓存定义为 Cache<K,V>。这就是为什么缓存管理器是通用的,可以用来保存任何类型的键值对。 CacheManager 中的 getEntityCache() 方法从 cacheMap 中检索缓存。如果给定 entityId 的缓存不存在,则创建它并将其添加到 cacheMap 然后返回。

CacheManager<K,V> 类

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

/** manages a set of caches where each instance of cache belongs to exactly one entity=manager
*   @param <K> - type of key
*   @param <V> - type of cache object
*/
public class **CacheManager****<****K****,****V****>** {
  public static final int maxSize = 1024;
  protected final Cache<String , Cache<K,V>> cacheMap;
  private boolean isWeekKeys;

  public CacheManager() { this(false);}
  public CacheManager(boolean isWeekKeys) { this. isWeekKeys = isWeekKeys ;}

  /** returns a user/manager specific instance of cache
  *  @param entityId user/manager
  */
  public Cache<K,V> getEntityCache(String entityId) {
    Cache<K,V> entityCache = cacheMap.getIfpresent( entityId );
    if( entityCache == null) {
       entityId =  entityId.intern() //do not remove inturn()
       synchronized(entityId) {
           entityCache = cacheMap.getIfPresent(entityId);
           if( entityCache == null ) {
              final CacheBuilder builder =  CacheBuilder.newbuilder().maximumsize(256);
              if(isWeekKeys) {
                  builder.weakKeys();
              }
              entityCache = builder.build();
              cacheMap.put(entityId, entityCache); 
           }
       }
    }
    return  entityCache;
  } 
}

现在我们将使用这个通用的 CacheManager 来实现一个 EmployeeCacheManager。 EmployeeCacheManager 代表组织中的经理列表。缓存中的每个经理都拥有为他们工作的员工列表。管理者由缓存的缓存的键表示,它是字符串,员工是缓存的缓存的值。内部缓存(员工)中的每个元素都由一个 Sting 键表示,该键是employeeId,内部缓存的值是员工对象。

EmployeeCacheManager

import com.google.common.cache.Cache;
import EmployeeCacheManager.Employee;
public class **EmployeeCacheManager** extends CacheManager<String, Employee> {
 
  public String getEmployeeAddress(String managerId, String employeeId) {
 
    Cache< String, Employee > employeeCache = getEntityCache(managerId);
    Employee employee = getEmployee(employeeCache, employeeId);
    String address = getEmployeeAddress(employee);
    return address; 
  }
  public void setEmployeeAddress(String managerId, String employeeId, String address) {
 
    Cache< String, Employee > employeeCache = getEntityCache(managerId);
    Employee employee = getEmployee(employeeCache, employeeId);
    setEmployeeAddress(employee, address);
  }
  public Employee getEmployee(Cache< String, Employee > employeeCache, 
     String employeeId) {
    Employee employee =  employeeCache.getIfPresent( employeeId );
    if( employee == null) {
      synchronized( employee ) {
         employee =  employeeCache.getIfPresent( employeeId );
          if( employee == null) {
            employee = new Employee(employeeId);
            employeeCache.put( employeeId , employee);
         }
      }
     }
     return employee;
  } 
  public String getEmployeeAddress(Employee employee) { 
return employee.getAddress();
  }
  public void setEmployeeAddress( Employee employee, String address ) {
employee.setAddress(address);
}
 
  public class **Employee** {
    String name;
    String address;
    String id;
    public class Employee(id) { this.id = id;}
     public String getName() {return this.name;}
     public String getAddress() {return this.address;}
     public String getId() {this.id;}
     public void setName(String name) {this.name = name;}
     public void setAddress(String address) {this.address = address;}
  }
}

EmployeeCachecreator

此类创建 EmployeeCacheManager 的一个实例。

public class **EmployeeCachecreator** {
 
  public static void main(String[] args) {
 
    EmployeeCacheManager  cacheManager = new  EmployeeCacheManager();
    cacheManager.setEmployeeAddres("M111", "E111", "adress");
    String address =  cacheManager.getEmployeeAddres("M111", "E111");
  }
}

相关文章