Java缓存池代码实例详解

这篇实例中有四个类，分别为

cacheitem  缓存实体类

cachepool  缓存池

student  学生实体类

maintest  主测试类

其中，缓存实体类cacheitem  中存放管理学生实体对象student  ，缓存实体类cacheitem  存放在缓存池cachepool  中，maintest  主要负责整体的测试工作。

缓存实体类

package com.paic.zhangqi.cache;  
import java.util.date; 
 
/** 
 * 缓存实体 
 * @author zhangqi947 
 */ 
public class cacheitem {  
 // 创建缓存时间 
 private date createtime = new date();   
 // 缓存期满时间 
 private long expiretime = 1;   
 // 缓存实体 
 private object entity;    
 public cacheitem(object obj, long expires) { 
  this.entity = obj; 
  this.expiretime = expires; 
 }   
 // 判断缓存是否超时 
 public boolean isexpired() { 
  return (expiretime != -1 && new date().gettime() - createtime.gettime() > expiretime); 
 }  
 public date getcreatetime() { 
  return createtime; 
 }  
 public void setcreatetime(date createtime) { 
  this.createtime = createtime; 
 }  
 public object getentity() { 
  return entity; 
 }  
 public void setentity(object entity) { 
  this.entity = entity; 
 }  
 public long getexpiretime() { 
  return expiretime; 
 }  
 public void setexpiretime(long expiretime) { 
  this.expiretime = expiretime; 
 } 
} 

缓存池cachepool

package com.paic.zhangqi.cache;  
import java.util.date; 
import java.util.hashmap; 
import java.util.map; 
/** 
 * 缓存池 
 * @author administrator 
 */ 
public class cachepool { 
 // 缓存池唯一实例 
 private static cachepool instance; 
 // 缓存map 
 private static map<string, object> cacheitems;   
 private cachepool() { 
  cacheitems = new hashmap<string, object>(); 
 }   
 /** 
  * 获取唯一的实例 
  * @return instance 
  */ 
 public synchronized static cachepool getinstance() { 
  if (instance == null) { 
   instance = new cachepool(); 
  } 
  return instance; 
 }   
 /** 
  * 清除所有的item缓存 
  */ 
 public synchronized void clearallitems() { 
  cacheitems.clear(); 
 }   
 /** 
  * 获取缓存实例 
  * @param name 缓存名称 
  * @return 缓存实例 
  */ 
 public synchronized object getcacheitem(string name) { 
  if (!cacheitems.containskey(name)) { 
   return null; 
  } 
  cacheitem cacheitem = (cacheitem) cacheitems.get(name); 
  if (cacheitem.isexpired()) { 
   return null; 
  } 
  return cacheitem.getentity(); 
 } 
 /** 
  * 存放缓存信息 
  * @param name 名称 
  * @param obj 实例对象 
  * @param expires 超时时长 
  */ 
 public synchronized void putcacheitem(string name, object obj, long expires) { 
  // 判断该对象是否在在缓存池，不在直接put 
  if (!cacheitems.containskey(name)) { 
   cacheitems.put(name, new cacheitem(obj, expires)); 
  } 
  // 获取缓存池中对象，更新对象信息 
  cacheitem cacheitem = (cacheitem) cacheitems.get(name); 
  cacheitem.setcreatetime(new date()); 
  cacheitem.setentity(obj); 
  cacheitem.setexpiretime(expires); 
 } 
 /** 
  * 移除缓存数据 
  * @param name 
  */ 
 public synchronized void removecacheitem(string name) { 
  if (!cacheitems.containskey(name)) { 
   return ; 
  } 
  cacheitems.remove(name); 
 }   
 /** 
  * 获取缓存数据的数量 
  * @return 
  */ 
 public int getsize() { 
  return cacheitems.size(); 
 }  
} 

学生类student

package com.paic.zhangqi.cache; 
/** 
 * 学生类 
 * @author administrator 
 */ 
public class student {  
 private string name; 
 private string id; 
 private int age; 
 private int sal; 
 public student() { 
   
 }   
 public student(string name, string id, int age, int sal) { 
  this.name = name; 
  this.id = id; 
  this.age = age; 
  this.sal = sal; 
 }  
 public string getname() { 
  return name; 
 }  
 public void setname(string name) { 
  this.name = name; 
 }  
 public string getid() { 
  return id; 
 }  
 public void setid(string id) { 
  this.id = id; 
 }  
 public int getage() { 
  return age; 
 }  
 public void setage(int age) { 
  this.age = age; 
 }  
 public int getsal() { 
  return sal; 
 } 
 public void setsal(int sal) { 
  this.sal = sal; 
 } 
}

主测试类maintest

package com.paic.zhangqi.cache; 
/** 
 * 主测试类 
 * @author zhangqi947 
 */ 
public class maintest { 
 
 /** 
  * @param args 
  * @throws interruptedexception 
  */ 
 public static void main(string[] args) throws interruptedexception { 
  // 获取缓存池 
  cachepool cachepool = cachepool.getinstance();    
  student stu1 = new student("l1", "stu001", 25, 40); 
  student stu2 = new student("l2", "stu002", 25, 40); 
  student stu3 = new student("l3", "stu003", 25, 40); 
  student stu4 = new student("l4", "stu004", 25, 40);    
  cachepool.putcacheitem("001", stu1, 122222); 
  cachepool.putcacheitem("002", stu2, 10); 
  cachepool.putcacheitem("003", stu3, 360002); 
  cachepool.putcacheitem("004", stu4, 1222222);    
  // 设置线程休眠，其中002对象会超时 
  thread.sleep(200);    
  student stu001 = (student) cachepool.getcacheitem("001"); 
  if (null != stu001) { 
   system.out.println(stu001.getname()); 
  }    
  // 由于超时，这里取出的002对象为null 
  student stu002 = (student) cachepool.getcacheitem("002"); 
  if (null != stu002) { 
   system.out.println(stu002.getname()); 
  }    
  // 获取打印缓存池中对象数量 
  int cachesize = cachepool.getsize(); 
  system.out.println(cachesize);    
  // 删除对象002 
  cachepool.removecacheitem("002");   
  // 打印缓存池数量 
  cachesize = cachepool.getsize(); 
  system.out.println(cachesize); 
 } 
} 

测试结果

l1 
4 
3

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