Java对象池的简单应用

伊布 — Thu, 10 Dec 2009 09:50:00 GMT

Apache 的commons pool框架为我们提供了对象池封装技术，也就是大家说的缓存技术，个人感觉还是不错的。

以下是一个简单的例子，希望能够起到抛砖引玉的作用，当然如果要应用到实际项目中的话，还需要完善很多内容，比如对象池的参数配置、日志处理、异常解决。。。

需要缓存的对象:

public class Employee {
      static int counter=0;
      private String name;
      private int id;

      public Employee(String name) {
        this.name=name;
        this.id=++counter;
        System.out.println(name+" is created!");
      }

      public String getName() {
        return this.name;
      }

      public void setName(String name) {
        this.name = name;
      }

      public void doWork() {
        System.out.println(this.toString()+" do some thing");
      }

      public String toString() {
        return (" Name: " + this.name+",id:"+this.id);
      }

      public void finalize() {
        System.err.println("Employee " + toString() + " made redundant");
      }
    }

创建缓存对象工厂，由于框架提供了一个基本的BaseKeyedPoolableObjectFactoy创建工厂，可以直接继承并实现makeObject方法，也就是创建缓存对象的具体实现,当然还有其他的创建工厂，这里就不具体讲了，可以查看Apache的相关资料。

import org.apache.commons.pool.BaseKeyedPoolableObjectFactory;

public class EmployeeFactory extends BaseKeyedPoolableObjectFactory {

    @Override
    public Object makeObject(Object key) throws Exception {
        return new Employee((String)key);
    }


}

客户端的调用例子，pool.addObject增加缓存对象，borrowObject从缓存中获取对象，如果没有则会创建一个新对象，returnObject释放对象，即使用完对象后要释放对象到缓存中。

public class TestKeyedObjectPool {
    public static void main(String args[]) throws Exception {

        GenericKeyedObjectPool pool = new GenericKeyedObjectPool();
        pool.setFactory(new EmployeeFactory());

        pool.addObject("Peter");
        pool.addObject("Jerry");
        pool.addObject("Richard");
        pool.addObject("Peter");

      System.out.println("Number of Peter employees in pool: " +
          pool.getNumIdle("Peter") + " out of total employees: " +
          pool.getNumIdle());

        Employee employee = (Employee)pool.borrowObject("Peter");
        employee.doWork();
        pool.returnObject("Peter", employee);

      System.out.println("Number of Peter employees in pool: " +
                  pool.getNumIdle("Peter") + " out of total employees: " +
                  pool.getNumIdle());
      }

}

运行结果：

Peter is created!
Jerry is created!
Richard is created!
Peter is created!
Number of Peter employees in pool: 2 out of total employees: 4
Name: Peter,id:1 do some thing
Number of Peter employees in pool: 2 out of total employees: 4

伊布 2009-12-10 17:50 发表评论

语源科技BlogJava-wanyiwan

Java对象池的简单应用