1 享元模式源码解析
1.1 享元模式源码解析1（jdk中的应用）
1.2 享元模式源码解析2（tomcat中的应用）
1 享元模式源码解析
1.1 享元模式源码解析1（jdk中的应用）
测试类：
package com.geely.design.pattern.structural.flyweight; public class Test2 { public static void main(String [] args){ Integer a = 100; Integer b = Integer.valueOf(100); System.out.println("a==b"+ (a==b)); Integer c = 1000; Integer d = Integer.valueOf(1000); System.out.println("c==d"+ (c==d)); } }
Integer类：
public final class Integer extends Number implements Comparable<Integer> { /** * Returns an {@code Integer} instance representing the specified * {@code int} value. If a new {@code Integer} instance is not * required, this method should generally be used in preference to * the constructor {@link #Integer(int)}, as this method is likely * to yield significantly better space and time performance by * caching frequently requested values. * * This method will always cache values in the range -128 to 127, * inclusive, and may cache other values outside of this range. * 如果传入的数值在缓存的-127和128之间，那么都会在cache中，否则的话，会new出新的对象，这也是为什么100==100为true，1000==1000为false * test中a，b，c，d都执行了该方法，一共执行了4次 。
* @param i an {@code int} value. * @return an {@code Integer} instance representing {@code i}. * @since 1.5 */ public static Integer valueOf(int i) { assert IntegerCache.high >= 127; if (i >= IntegerCache.low && i <= IntegerCache.high) return IntegerCache.cache[i + (-IntegerCache.low)]; return new Integer(i); } /** * Cache to support the object identity semantics of autoboxing for values between * -128 and 127 (inclusive) as required by JLS. * * The cache is initialized on first usage. The size of the cache * may be controlled by the -XX:AutoBoxCacheMax=<size> option. * During VM initialization, java.lang.Integer.IntegerCache.high property * may be set and saved in the private system properties in the * sun.misc.VM class. */ private static class IntegerCache { static final int low = -128; static final int high; static final Integer cache[]; static { // high value may be configured by property int h = 127; String integerCacheHighPropValue = sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high"); if (integerCacheHighPropValue != null) { int i = parseInt(integerCacheHighPropValue); i = Math.max(i, 127); // Maximum array size is Integer.MAX_VALUE h = Math.min(i, Integer.MAX_VALUE - (-low) -1); } high = h; cache = new Integer[(high - low) + 1]; int j = low; for(int k = 0; k < cache.length; k++) cache[k] = new Integer(j++); } private IntegerCache() {} } }
打印日志：
"C:\Program Files\Java\jdk1.7.0_79\bin\java.exe" -agentlib:jdwp=transport=dt_socket,address=127.0.0.1:63738,suspend=y,server=n -javaagent:C:\Users\weijingli\AppData\Local\Temp\capture1jars\debugger-agent.jar=file:/C:/Users/weijingli/AppData/Local/Temp/capture.props -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.7.0_79\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jce.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jfxrt.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\resources.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\rt.jar;F:\xiangmu3\Xin\Idea\design_pattern\target\classes;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\apache\tomcat\tomcat-servlet-api\7.0.64\tomcat-servlet-api-7.0.64.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\springframework\session\spring-session-core\2.1.7.RELEASE\spring-session-core-2.1.7.RELEASE.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\springframework\spring-webmvc\4.0.3.RELEASE\spring-webmvc-4.0.3.RELEASE.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\springframework\spring-beans\4.0.3.RELEASE\spring-beans-4.0.3.RELEASE.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\springframework\spring-context\4.0.3.RELEASE\spring-context-4.0.3.RELEASE.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\springframework\spring-aop\4.0.3.RELEASE\spring-aop-4.0.3.RELEASE.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\aopalliance\aopalliance\1.0\aopalliance-1.0.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\springframework\spring-core\4.0.3.RELEASE\spring-core-4.0.3.RELEASE.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\springframework\spring-expression\4.0.3.RELEASE\spring-expression-4.0.3.RELEASE.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\springframework\spring-web\4.0.3.RELEASE\spring-web-4.0.3.RELEASE.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\springframework\spring-oxm\4.0.3.RELEASE\spring-oxm-4.0.3.RELEASE.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\springframework\spring-jdbc\4.0.3.RELEASE\spring-jdbc-4.0.3.RELEASE.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\springframework\spring-tx\4.0.3.RELEASE\spring-tx-4.0.3.RELEASE.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\springframework\spring-test\4.0.3.RELEASE\spring-test-4.0.3.RELEASE.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\aspectj\aspectjweaver\1.7.3\aspectjweaver-1.7.3.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\mybatis\mybatis-spring\1.3.0\mybatis-spring-1.3.0.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\mybatis\mybatis\3.4.1\mybatis-3.4.1.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\aspectj\aspectjrt\1.6.11\aspectjrt-1.6.11.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\codehaus\jackson\jackson-mapper-asl\1.9.12\jackson-mapper-asl-1.9.12.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\codehaus\jackson\jackson-core-asl\1.9.12\jackson-core-asl-1.9.12.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\commons-dbcp\commons-dbcp\1.4\commons-dbcp-1.4.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\commons-pool\commons-pool\1.5.4\commons-pool-1.5.4.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\ch\qos\logback\logback-classic\1.1.2\logback-classic-1.1.2.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\slf4j\slf4j-api\1.7.6\slf4j-api-1.7.6.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\ch\qos\logback\logback-core\1.1.2\logback-core-1.1.2.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\mysql\mysql-connector-java\5.1.6\mysql-connector-java-5.1.6.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\com\google\guava\guava\20.0\guava-20.0.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\apache\commons\commons-lang3\3.5\commons-lang3-3.5.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\commons-collections\commons-collections\3.2.1\commons-collections-3.2.1.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\junit\junit\4.12\junit-4.12.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\joda-time\joda-time\2.3\joda-time-2.3.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\hashids\hashids\1.0.1\hashids-1.0.1.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\commons-net\commons-net\3.1\commons-net-3.1.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\commons-fileupload\commons-fileupload\1.2.2\commons-fileupload-1.2.2.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\commons-io\commons-io\2.0.1\commons-io-2.0.1.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\com\github\pagehelper\pagehelper\4.1.0\pagehelper-4.1.0.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\com\github\miemiedev\mybatis-paginator\1.2.17\mybatis-paginator-1.2.17.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\com\github\jsqlparser\jsqlparser\0.9.4\jsqlparser-0.9.4.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\commons-codec\commons-codec\1.10\commons-codec-1.10.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\commons-configuration\commons-configuration\1.10\commons-configuration-1.10.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\commons-lang\commons-lang\2.6\commons-lang-2.6.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\commons-logging\commons-logging\1.1.1\commons-logging-1.1.1.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\com\google\zxing\core\2.1\core-2.1.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\com\google\code\gson\gson\2.3.1\gson-2.3.1.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\hamcrest\hamcrest-core\1.3\hamcrest-core-1.3.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\redis\clients\jedis\2.6.0\jedis-2.6.0.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\apache\commons\commons-pool2\2.0\commons-pool2-2.0.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\projectlombok\lombok\1.16.18\lombok-1.16.18.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\redisson\redisson\2.9.0\redisson-2.9.0.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\io\netty\netty-common\4.1.8.Final\netty-common-4.1.8.Final.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\io\netty\netty-codec\4.1.8.Final\netty-codec-4.1.8.Final.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\io\netty\netty-buffer\4.1.8.Final\netty-buffer-4.1.8.Final.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\io\netty\netty-transport\4.1.8.Final\netty-transport-4.1.8.Final.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\io\netty\netty-resolver\4.1.8.Final\netty-resolver-4.1.8.Final.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\io\netty\netty-handler\4.1.8.Final\netty-handler-4.1.8.Final.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\javax\cache\cache-api\1.0.0\cache-api-1.0.0.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\io\projectreactor\reactor-stream\2.0.8.RELEASE\reactor-stream-2.0.8.RELEASE.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\io\projectreactor\reactor-core\2.0.8.RELEASE\reactor-core-2.0.8.RELEASE.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\reactivestreams\reactive-streams\1.0.0\reactive-streams-1.0.0.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\com\fasterxml\jackson\dataformat\jackson-dataformat-yaml\2.6.7\jackson-dataformat-yaml-2.6.7.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\yaml\snakeyaml\1.15\snakeyaml-1.15.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\com\fasterxml\jackson\core\jackson-core\2.6.7\jackson-core-2.6.7.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\com\fasterxml\jackson\core\jackson-databind\2.6.7\jackson-databind-2.6.7.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\com\fasterxml\jackson\dataformat\jackson-dataformat-avro\2.9.0\jackson-dataformat-avro-2.9.0.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\com\fasterxml\jackson\core\jackson-annotations\2.9.0\jackson-annotations-2.9.0.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\apache\avro\avro\1.8.1\avro-1.8.1.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\com\thoughtworks\paranamer\paranamer\2.7\paranamer-2.7.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\xerial\snappy\snappy-java\1.1.1.3\snappy-java-1.1.1.3.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\apache\commons\commons-compress\1.8.1\commons-compress-1.8.1.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\org\tukaani\xz\1.5\xz-1.5.jar;F:\xiangmu3\Xin\FuQiang\maven\code\repo\com\sun\faces\jsf-api\1.2\jsf-api-1.2.jar;D:\java\devolopKit\idea\anZh\IntelliJ IDEA Community Edition 2018.1.4\lib\idea_rt.jar" com.geely.design.pattern.structural.flyweight.Test2 Connected to the target VM, address: '127.0.0.1:63738', transport: 'socket' a==btrue c==dfalse Disconnected from the target VM, address: '127.0.0.1:63738', transport: 'socket' Process finished with exit code 0
1.2 享元模式源码解析2（tomcat中的应用）
父类（GenericObjectPoolConfig）：添加了一些默认的配置
// // Source code recreated from a .class file by IntelliJ IDEA // (powered by Fernflower decompiler) // package org.apache.commons.pool2.impl; public class GenericObjectPoolConfig extends BaseObjectPoolConfig { public static final int DEFAULT_MAX_TOTAL = 8; public static final int DEFAULT_MAX_IDLE = 8; public static final int DEFAULT_MIN_IDLE = 0; private int maxTotal = 8; private int maxIdle = 8; private int minIdle = 0; public GenericObjectPoolConfig() { } public int getMaxTotal() { return this.maxTotal; } public void setMaxTotal(int maxTotal) { this.maxTotal = maxTotal; } public int getMaxIdle() { return this.maxIdle; } public void setMaxIdle(int maxIdle) { this.maxIdle = maxIdle; } public int getMinIdle() { return this.minIdle; } public void setMinIdle(int minIdle) { this.minIdle = minIdle; } public GenericObjectPoolConfig clone() { try { return (GenericObjectPoolConfig)super.clone(); } catch (CloneNotSupportedException var2) { throw new AssertionError(); } } }
子类（GenericKeyedObjectPoolConfig）（选2版本）：
通过object的双端队列来保存对象池的对象，重点看p是怎么给值的。
/** * 借 */ public T borrowObject(K key, long borrowMaxWaitMillis) throws Exception { this.assertOpen(); PooledObject<T> p = null; boolean blockWhenExhausted = this.getBlockWhenExhausted(); long waitTime = 0L; GenericKeyedObjectPool.ObjectDeque objectDeque = this.register(key); try { while(p == null) { boolean create = false; if (blockWhenExhausted) { p = (PooledObject)objectDeque.getIdleObjects().pollFirst(); if (p == null) { create = true; p = this.create(key); } if (p == null) { if (borrowMaxWaitMillis < 0L) { p = (PooledObject)objectDeque.getIdleObjects().takeFirst(); } else { waitTime = System.currentTimeMillis(); p = (PooledObject)objectDeque.getIdleObjects().pollFirst(borrowMaxWaitMillis, TimeUnit.MILLISECONDS); waitTime = System.currentTimeMillis() - waitTime; } } if (p == null) { throw new NoSuchElementException("Timeout waiting for idle object"); } if (!p.allocate()) { p = null; } } else { p = (PooledObject)objectDeque.getIdleObjects().pollFirst(); if (p == null) { create = true; p = this.create(key); } if (p == null) { throw new NoSuchElementException("Pool exhausted"); } if (!p.allocate()) { p = null; } } if (p != null) { try { this.factory.activateObject(key, p); } catch (Exception var22) { try { this.destroy(key, p, true); } catch (Exception var21) { ; } p = null; if (create) { NoSuchElementException nsee = new NoSuchElementException("Unable to activate object"); nsee.initCause(var22); throw nsee; } } if (p != null && this.getTestOnBorrow()) { boolean validate = false; Throwable validationThrowable = null; try { validate = this.factory.validateObject(key, p); } catch (Throwable var20) { PoolUtils.checkRethrow(var20); validationThrowable = var20; } if (!validate) { try { this.destroy(key, p, true); this.destroyedByBorrowValidationCount.incrementAndGet(); } catch (Exception var19) { ; } p = null; if (create) { NoSuchElementException nsee = new NoSuchElementException("Unable to validate object"); nsee.initCause(validationThrowable); throw nsee; } } } } } } finally { this.deregister(key); } this.updateStatsBorrow(p, waitTime); return p.getObject(); } /** * 还 */ public void returnObject(K key, T obj) { GenericKeyedObjectPool<K, T>.ObjectDeque<T> objectDeque = (GenericKeyedObjectPool.ObjectDeque)this.poolMap.get(key); PooledObject<T> p = (PooledObject)objectDeque.getAllObjects().get(obj); if (p == null) { throw new IllegalStateException("Returned object not currently part of this pool"); } else { long activeTime = p.getActiveTimeMillis(); if (this.getTestOnReturn() && !this.factory.validateObject(key, p)) { try { this.destroy(key, p, true); } catch (Exception var11) { this.swallowException(var11); } this.updateStatsReturn(activeTime); } else { try { this.factory.passivateObject(key, p); } catch (Exception var13) { this.swallowException(var13); try { this.destroy(key, p, true); } catch (Exception var10) { this.swallowException(var10); } this.updateStatsReturn(activeTime); return; } if (!p.deallocate()) { throw new IllegalStateException("Object has already been retured to this pool"); } else { int maxIdle = this.getMaxIdlePerKey(); LinkedBlockingDeque<PooledObject<T>> idleObjects = objectDeque.getIdleObjects(); if (this.isClosed() || maxIdle > -1 && maxIdle <= idleObjects.size()) { try { this.destroy(key, p, true); } catch (Exception var12) { this.swallowException(var12); } } else if (this.getLifo()) { idleObjects.addFirst(p); } else { idleObjects.addLast(p); } if (this.hasBorrowWaiters()) { this.reuseCapacity(); } this.updateStatsReturn(activeTime); } } } }
工厂类：
// // Source code recreated from a .class file by IntelliJ IDEA // (powered by Fernflower decompiler) // package org.apache.commons.pool2; public interface KeyedPooledObjectFactory<K, V> { //创建对象方法 PooledObject<V> makeObject(K var1) throws Exception; //销毁对象方法 void destroyObject(K var1, PooledObject<V> var2) throws Exception; //验证对象方法 boolean validateObject(K var1, PooledObject<V> var2); //激活对象方法，用的时候激活 void activateObject(K var1, PooledObject<V> var2) throws Exception; //钝化对象方法，不用的钝化 void passivateObject(K var1, PooledObject<V> var2) throws Exception; }
诸葛
