Apache Commons Pool试用小记-阿里云开发者社区

相比众多牛人的自己连接池，Apache的Pool就是牛中的大牛了，这里小试一把。

环境：

commons-pool-1.5.3-bin.zip

jdk1.5

一、基本String对象测试

输出结果：

a
b
c
c
a
8
8

Process finished with exit code 0

当运行到清除最早对象一行，内存状态如下：

初略看看，Apache Commons pool功能还很强大，DBCP数据库连接池就用了它，还可以对其进行参数配置。

二、自定义复杂对象测试

import org.apache.commons.pool.impl.GenericKeyedObjectPool;
import org.apache.commons.pool.BaseKeyedPoolableObjectFactory;

/**
* Created by IntelliJ IDEA.
*
* @author leizhimin 2009-10-27 17:46:18
*/
public class Test {
         public static void main(String[] args) throws Exception {
                 //创建一个对象池
                GenericKeyedObjectPool pool = new GenericKeyedObjectPool( new BaseKeyedPoolableObjectFactory() {
                        @Override
                         public Object makeObject(Object o) throws Exception {
                                 if (o != null && o instanceof User)
                                         return o;
                                 else
                                         return null;
                        }
                });

                 //添加对象到池，重复的不会重复入池
                pool.addObject( "a");
                pool.addObject( "b");
                pool.addObject( "x");
                pool.addObject( null);
                pool.addObject( null);
                pool.addObject( null);
                pool.addObject( new User( "zhangsan", "123"));
                pool.addObject( new User( "lisi", "112"));
                pool.addObject( new User( "lisi", "112", 32));
                pool.addObject( new User( "lisi", "112", 32, "一个烂人！"));

                 //清除最早的对象
                pool.clearOldest();

                 //获取并输出对象
                User u1 = new User( "lisi", "112", 32, "一个烂人！");
                System.out.println(pool.borrowObject(u1));
                pool.returnObject(u1,u1);

                 //获取并输出对象
                User u2 = new User( "lisi", "112", 32, "一个烂人！");
                System.out.println(pool.borrowObject(u2));
                pool.returnObject(u2,u2);

                 //获取并输出对象
                User u3 = new User( "lisi", "112", 32);
                System.out.println(pool.borrowObject(u3));
                pool.returnObject(u3,u3);

                 //获取并输出对象
                User u4 = new User( "lisi", "112");
                System.out.println(pool.borrowObject(u4));
                pool.returnObject(u4,u4);

                System.out.println(pool.borrowObject(u4));
                pool.returnObject(u4,u4);
                System.out.println(pool.borrowObject(u4));
                pool.returnObject(u4,u4);
                System.out.println(pool.borrowObject(u4));
                pool.returnObject(u4,u4);
                System.out.println(pool.borrowObject(u4));
                pool.returnObject(u4,u4);
                System.out.println(pool.borrowObject(u4));
                pool.returnObject(u4,u4);
                System.out.println(pool.borrowObject(u4));
                pool.returnObject(u4,u4);
                System.out.println(pool.borrowObject(u4));
                pool.returnObject(u4,u4);

                System.out.println(pool.borrowObject( new User( "lisi", "112")));
//                System.out.println(pool.borrowObject(new User("lisi", "112")));

                 //输出池状态
                System.out.println(pool.getMaxIdle());
                System.out.println(pool.getMaxActive());
                pool.clearOldest();
                pool.close();

        }
}

class User {
         private String name;
         private String pswd;
         private int age;
         private String reamark;

        User() {
        }

        User(String name, String pswd) {
                 this.name = name;
                 this.pswd = pswd;
        }

        User(String name, String pswd, int age) {
                 this.name = name;
                 this.pswd = pswd;
                 this.age = age;
        }

        User(String name, String pswd, int age, String reamark) {
                 this.name = name;
                 this.pswd = pswd;
                 this.age = age;
                 this.reamark = reamark;
        }

         public String getName() {
                 return name;
        }

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

         public String getPswd() {
                 return pswd;
        }

         public void setPswd(String pswd) {
                 this.pswd = pswd;
        }

         public int getAge() {
                 return age;
        }

         public void setAge( int age) {
                 this.age = age;
        }

         public String getReamark() {
                 return reamark;
        }

         public void setReamark(String reamark) {
                 this.reamark = reamark;
        }

        @Override
         public boolean equals(Object o) {
                 if ( this == o) return true;
                 if (o == null || getClass() != o.getClass()) return false;

                User user = (User) o;

                 if (!name.equals(user.name)) return false;
                 if (!pswd.equals(user.pswd)) return false;

                 return true;
        }

        @Override
         public int hashCode() {
                 int result = name.hashCode();
                result = 31 * result + pswd.hashCode();
                 return result;
        }

        @Override
         public String toString() {
                 return "User{" +
                                 "name='" + name + '\'' +
                                 ", pswd='" + pswd + '\'' +
                                 ", age=" + age +
                                 ", reamark='" + reamark + '\'' +
                                '}';
        }
}

测试结果：

User{name='lisi', pswd='112', age=32, reamark=' null'}
User{name='lisi', pswd='112', age=32, reamark='一个烂人！'}
User{name='lisi', pswd='112', age=32, reamark='一个烂人！'}
User{name='lisi', pswd='112', age=32, reamark=' null'}
User{name='lisi', pswd='112', age=0, reamark=' null'}
User{name='lisi', pswd='112', age=0, reamark=' null'}
User{name='lisi', pswd='112', age=0, reamark=' null'}
User{name='lisi', pswd='112', age=0, reamark=' null'}
User{name='lisi', pswd='112', age=0, reamark=' null'}
User{name='lisi', pswd='112', age=0, reamark=' null'}
User{name='lisi', pswd='112', age=0, reamark=' null'}
User{name='lisi', pswd='112', age=0, reamark=' null'}
8
8

Process finished with exit code 0

内存状态：

这次测试得出一些有用的结论：

1、复杂对象应该实现equals() 、hashCode()方法，以便不重复入池。

2、对于非入池的目标对象，比如a、b、x字符串，目前没有有效的办法过滤掉，不让其入池，虽然在工厂方法里做了努力。

3、试图将null入池，不会成功的，但也不抛异常。

4、对于池对象，使用应该遵循“接而有还，再借不难”-----从池中获取，不用时候归池，否则当池中没有空闲可用的对象时候，程序会处于等待状态，如果没有显式的调用归还方法，则造成程序死锁。

三、使用GenericObjectPool

import org.apache.commons.pool.impl.GenericObjectPool;
import org.apache.commons.pool.BasePoolableObjectFactory;

import java.util.Random;

/**
* Created by IntelliJ IDEA.
*
* @author leizhimin 2009-10-28 10:51:11
*/
public class Test2 {
         public static void main(String[] args) throws Exception {
                GenericObjectPool pool = new GenericObjectPool( new BasePoolableObjectFactory() {
                         public Object makeObject() throws Exception {
                                 return new Random().nextFloat();
                        }
                });

                pool.addObject();
                pool.addObject();
                pool.addObject();
                pool.addObject();
                pool.addObject();
                pool.addObject();
                pool.addObject();
                pool.addObject();
                pool.addObject();
                pool.addObject();
                pool.addObject();
                pool.addObject();

                Object o = pool.borrowObject();
                System.out.println(o);
                pool.returnObject(o);

                Object o1 = pool.borrowObject();
                System.out.println(o1);

                Object o2 = pool.borrowObject();
                System.out.println(o2);

                Object o3 = pool.borrowObject();
                System.out.println(o3);

                Object o4 = pool.borrowObject();
                System.out.println(o4);

                Object o5 = pool.borrowObject();
                System.out.println(o5);

                Object o6 = pool.borrowObject();
                System.out.println(o6);

                Object o7 = pool.borrowObject();
                System.out.println(o7);

                Object o8 = pool.borrowObject();
                System.out.println(o8);

                pool.returnObject(o1);
                pool.returnObject(o2);
                pool.returnObject(o3);
                pool.returnObject(o4);
                pool.returnObject(o5);
                pool.returnObject(o6);
                pool.returnObject(o7);
                pool.returnObject(o8);

                Object o9 = pool.borrowObject();
                System.out.println(o9);
                pool.returnObject(o9);

                Object o10 = pool.borrowObject();
                System.out.println(o10);
                pool.returnObject(o10);

                Object o11 = pool.borrowObject();
                System.out.println(o11);
                pool.returnObject(o11);

                Object o12 = pool.borrowObject();
                System.out.println(o12);
                pool.returnObject(o12);

                Object o13 = pool.borrowObject();
                System.out.println(o13);
                pool.returnObject(o13);

        }
}

输出：

0.7358789
0.7358789
0.15324193
0.7465391
0.7198403
0.7477861
0.37906575
0.049714446
0.9650687
0.9650687
0.9650687
0.9650687
0.9650687
0.9650687

Process finished with exit code 0

从内存状态看到，这种对象池，没法将指定的对象入池，只能通过工厂生成对象入池，而且无法给工厂传递参数。

这种池适合数据库连接池等，所有的池对象拿出来都一样用。

经过上面三个例子综合测试得知，池的大小是初始化配置的，在没有显式配置指定的情况下，池大小默认为8.可以通过 GenericKeyedObjectPool.Config来配置。

本文转自 leizhimin 51CTO博客，原文链接：http://blog.51cto.com/lavasoft/217547，如需转载请自行联系原作者

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