commons pool2與commons pool1還是有很大的差別的,本文主要記錄利用commons pool2構建自己的池應用。
1 依賴的引入
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-pool2</artifactId>
<version>2.4.2</version>
<type>jar</type>
<scope>compile</scope>
</dependency>
2 構建自己的池應用
ps:本文構建一個string池,從池獲取string對象
2.1 構建自己的PooledObjectFactory
PooledObjectFactory是一個池化對象工廠接口,定義了生成對象、激活對象、鈍化對象、銷燬對象的方法,其方法如下:
public interface PooledObjectFactory<T> {
/**
* 生成對象
*/
PooledObject<T> makeObject() throws Exception;
/**
* 銷燬對象
*/
void destroyObject(PooledObject<T> p) throws Exception;
/**
* 驗證對象
*/
boolean validateObject(PooledObject<T> p);
/**
* 激活對象
*/
void activateObject(PooledObject<T> p) throws Exception;
/**
* 鈍化對象
*/
void passivateObject(PooledObject<T> p) throws Exception;
}
如果需要使用Commons-Pool構建構建自己的池應用,那麼就需要提供一個PooledObjectFactory接口的具體實現。當然也可以繼承BasePooledObjectFactory這個抽象類。本文實現PooledObjectFactory接口,如下所示:
public class StringFactory implements PooledObjectFactory<String>{
public StringFactory(){
System.out.println("init string factory..");
}
public void activateObject(PooledObject<String> pool) throws Exception {
// TODO Auto-generated method stub
}
public void destroyObject(PooledObject<String> pool) throws Exception {
String str = pool.getObject();
if(str!=null){
str=null;
System.out.println(str+" destroy...");
}
}
public PooledObject<String> makeObject() throws Exception {
String i = UUID.randomUUID().toString();
System.out.println("make "+i+" success...");
return new DefaultPooledObject<String>(i);
}
public void passivateObject(PooledObject<String> pool) throws Exception {
// TODO Auto-generated method stub
}
public boolean validateObject(PooledObject<String> pool) {
// TODO Auto-generated method stub
return false;
}
}
2.2 創建對象池
在org.apache.commons.pool2.impl中有三個可以直接使用的對象池:GenericObjectPool、GenericKeyedObjectPool和SoftReferenceObjectPool。
通常使用GenericObjectPool來創建對象池,如果是對象池是Keyed的,那麼可以使用GenericKeyedObjectPool來創建對象池。
而SoftReferenceObjectPool對象池,它利用一個java.util.ArrayList對象來保存對象池裏的對象。不過它並不在對象池裏直接保存對象本身,而是保存它們的“軟引用”。
(1)GenericObjectPool的使用
如下所示爲GenericObjectPool的使用:
GenericObjectPoolConfig conf = new GenericObjectPoolConfig();
conf.setMaxTotal(10);
GenericObjectPool<String> pool = new GenericObjectPool<String>(new StringFactory(), conf);
for(int i=0;i<15;i++){
System.out.println(i+":");
try {
String str = pool.borrowObject();
System.out.println(str);
} catch (Exception e) {
e.printStackTrace();
}
}
上例中設置GenericObjectPool的maxTotal爲10,開啓一個循環(循環次數爲15),每次從池中拿一個對象,由於池的大小爲10,每次拿到對象之後沒有釋放,所以程序block在i=10處。
下面的例子爲每次拿到對象之後,處理完再釋放:
GenericObjectPoolConfig conf = new GenericObjectPoolConfig();
conf.setMaxTotal(10);
GenericObjectPool<String> pool = new GenericObjectPool<String>(new StringFactory(), conf);
for(int i=0;i<15;i++){
System.out.println(i+":");
try {
String str = pool.borrowObject();
System.out.println(str);
pool.returnObject(str);
} catch (Exception e) {
e.printStackTrace();
}
}
其運行結果如下:
(2)自定義pool
如下所示爲自定義Pool實現了Closeable接口,定義自己的獲取資源與釋放資源的方法。
public class Pool implements Closeable{
public GenericObjectPool<String> innerPool;
public Pool() {
}
public Pool(final GenericObjectPoolConfig poolConfig,PooledObjectFactory<String> factory){
initPool(poolConfig, factory);
}
public void close() throws IOException {
innerPool.close();
}
public void initPool(final GenericObjectPoolConfig poolConfig,PooledObjectFactory<String> factory){
if(this.innerPool!=null){
System.out.println("innerPool is not null,destroy it..");
innerPool.close();
}
this.innerPool = new GenericObjectPool<String>(factory,poolConfig);
}
public String getResource(){
String str = "";
try {
str=this.innerPool.borrowObject();
System.out.println("get resource success..:"+str);
} catch (Exception e) {
e.printStackTrace();
System.out.println("get resource error...");
}finally{
return str;
}
}
public void returnResourceObject(final String resource){
if(resource==null){
return;
}
innerPool.returnObject(resource);
System.out.println("return resource success.."+resource);
}
}
其StringPool繼承Pool就可以了:
public class StringPool extends Pool{
public StringPool(){
}
public StringPool(final GenericObjectPoolConfig poolConfig,StringFactory factory){
super(poolConfig,factory);
}
}
如下爲獲取資源的實例:
GenericObjectPoolConfig poolConfig = new GenericObjectPoolConfig ();
poolConfig.setMaxTotal(10);
StringFactory factory = new StringFactory();
StringPool pool = new StringPool(poolConfig,factory);
for(int i=0;i<15;i++){
System.out.println(i+":");
String str = pool.getResource();
System.out.println(str);
}
try {
pool.close();
} catch (IOException e) {
e.printStackTrace();
}
其運行結果如下:
測試一下釋放資源的方法:
GenericObjectPoolConfig poolConfig = new GenericObjectPoolConfig ();
poolConfig.setMaxTotal(10);
StringFactory factory = new StringFactory();
StringPool pool = new StringPool(poolConfig,factory);
for(int i=0;i<15;i++){
System.out.println(i+":");
String str = pool.getResource();
System.out.println(str);
pool.returnResourceObject(str);
}
try {
pool.close();
} catch (IOException e) {
e.printStackTrace();
}
其運行結果如下: