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 FilesJavajdk1.7.0_79injava.exe" -agentlib:jdwp=transport=dt_socket,address=127.0.0.1:63738,suspend=y,server=n -javaagent:C:UsersweijingliAppDataLocalTempcapture1jarsdebugger-agent.jar=file:/C:/Users/weijingli/AppData/Local/Temp/capture.props -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.7.0_79jrelibcharsets.jar;C:Program FilesJavajdk1.7.0_79jrelibdeploy.jar;C:Program FilesJavajdk1.7.0_79jrelibextaccess-bridge-64.jar;C:Program FilesJavajdk1.7.0_79jrelibextdnsns.jar;C:Program FilesJavajdk1.7.0_79jrelibextjaccess.jar;C:Program FilesJavajdk1.7.0_79jrelibextlocaledata.jar;C:Program FilesJavajdk1.7.0_79jrelibextsunec.jar;C:Program FilesJavajdk1.7.0_79jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.7.0_79jrelibextsunmscapi.jar;C:Program FilesJavajdk1.7.0_79jrelibextzipfs.jar;C:Program FilesJavajdk1.7.0_79jrelibjavaws.jar;C:Program FilesJavajdk1.7.0_79jrelibjce.jar;C:Program FilesJavajdk1.7.0_79jrelibjfr.jar;C:Program FilesJavajdk1.7.0_79jrelibjfxrt.jar;C:Program FilesJavajdk1.7.0_79jrelibjsse.jar;C:Program FilesJavajdk1.7.0_79jrelibmanagement-agent.jar;C:Program FilesJavajdk1.7.0_79jrelibplugin.jar;C:Program FilesJavajdk1.7.0_79jrelib esources.jar;C:Program FilesJavajdk1.7.0_79jrelib t.jar;F:xiangmu3XinIdeadesign_pattern argetclasses;F:xiangmu3XinFuQiangmavencode epoorgapache omcat omcat-servlet-api7.0.64 omcat-servlet-api-7.0.64.jar;F:xiangmu3XinFuQiangmavencode epoorgspringframeworksessionspring-session-core2.1.7.RELEASEspring-session-core-2.1.7.RELEASE.jar;F:xiangmu3XinFuQiangmavencode epoorgspringframeworkspring-webmvc4.0.3.RELEASEspring-webmvc-4.0.3.RELEASE.jar;F:xiangmu3XinFuQiangmavencode epoorgspringframeworkspring-beans4.0.3.RELEASEspring-beans-4.0.3.RELEASE.jar;F:xiangmu3XinFuQiangmavencode epoorgspringframeworkspring-context4.0.3.RELEASEspring-context-4.0.3.RELEASE.jar;F:xiangmu3XinFuQiangmavencode epoorgspringframeworkspring-aop4.0.3.RELEASEspring-aop-4.0.3.RELEASE.jar;F:xiangmu3XinFuQiangmavencode epoaopallianceaopalliance1.0aopalliance-1.0.jar;F:xiangmu3XinFuQiangmavencode epoorgspringframeworkspring-core4.0.3.RELEASEspring-core-4.0.3.RELEASE.jar;F:xiangmu3XinFuQiangmavencode epoorgspringframeworkspring-expression4.0.3.RELEASEspring-expression-4.0.3.RELEASE.jar;F:xiangmu3XinFuQiangmavencode epoorgspringframeworkspring-web4.0.3.RELEASEspring-web-4.0.3.RELEASE.jar;F:xiangmu3XinFuQiangmavencode epoorgspringframeworkspring-oxm4.0.3.RELEASEspring-oxm-4.0.3.RELEASE.jar;F:xiangmu3XinFuQiangmavencode epoorgspringframeworkspring-jdbc4.0.3.RELEASEspring-jdbc-4.0.3.RELEASE.jar;F:xiangmu3XinFuQiangmavencode epoorgspringframeworkspring-tx4.0.3.RELEASEspring-tx-4.0.3.RELEASE.jar;F:xiangmu3XinFuQiangmavencode epoorgspringframeworkspring-test4.0.3.RELEASEspring-test-4.0.3.RELEASE.jar;F:xiangmu3XinFuQiangmavencode epoorgaspectjaspectjweaver1.7.3aspectjweaver-1.7.3.jar;F:xiangmu3XinFuQiangmavencode epoorgmybatismybatis-spring1.3.0mybatis-spring-1.3.0.jar;F:xiangmu3XinFuQiangmavencode epoorgmybatismybatis3.4.1mybatis-3.4.1.jar;F:xiangmu3XinFuQiangmavencode epoorgaspectjaspectjrt1.6.11aspectjrt-1.6.11.jar;F:xiangmu3XinFuQiangmavencode epoorgcodehausjacksonjackson-mapper-asl1.9.12jackson-mapper-asl-1.9.12.jar;F:xiangmu3XinFuQiangmavencode epoorgcodehausjacksonjackson-core-asl1.9.12jackson-core-asl-1.9.12.jar;F:xiangmu3XinFuQiangmavencode epocommons-dbcpcommons-dbcp1.4commons-dbcp-1.4.jar;F:xiangmu3XinFuQiangmavencode epocommons-poolcommons-pool1.5.4commons-pool-1.5.4.jar;F:xiangmu3XinFuQiangmavencode epochqoslogbacklogback-classic1.1.2logback-classic-1.1.2.jar;F:xiangmu3XinFuQiangmavencode epoorgslf4jslf4j-api1.7.6slf4j-api-1.7.6.jar;F:xiangmu3XinFuQiangmavencode epochqoslogbacklogback-core1.1.2logback-core-1.1.2.jar;F:xiangmu3XinFuQiangmavencode epomysqlmysql-connector-java5.1.6mysql-connector-java-5.1.6.jar;F:xiangmu3XinFuQiangmavencode epocomgoogleguavaguava20.0guava-20.0.jar;F:xiangmu3XinFuQiangmavencode epoorgapachecommonscommons-lang33.5commons-lang3-3.5.jar;F:xiangmu3XinFuQiangmavencode epocommons-collectionscommons-collections3.2.1commons-collections-3.2.1.jar;F:xiangmu3XinFuQiangmavencode epojunitjunit4.12junit-4.12.jar;F:xiangmu3XinFuQiangmavencode epojoda-timejoda-time2.3joda-time-2.3.jar;F:xiangmu3XinFuQiangmavencode epoorghashidshashids1.0.1hashids-1.0.1.jar;F:xiangmu3XinFuQiangmavencode epocommons-netcommons-net3.1commons-net-3.1.jar;F:xiangmu3XinFuQiangmavencode epocommons-fileuploadcommons-fileupload1.2.2commons-fileupload-1.2.2.jar;F:xiangmu3XinFuQiangmavencode epocommons-iocommons-io2.0.1commons-io-2.0.1.jar;F:xiangmu3XinFuQiangmavencode epocomgithubpagehelperpagehelper4.1.0pagehelper-4.1.0.jar;F:xiangmu3XinFuQiangmavencode epocomgithubmiemiedevmybatis-paginator1.2.17mybatis-paginator-1.2.17.jar;F:xiangmu3XinFuQiangmavencode epocomgithubjsqlparserjsqlparser .9.4jsqlparser-0.9.4.jar;F:xiangmu3XinFuQiangmavencode epocommons-codeccommons-codec1.10commons-codec-1.10.jar;F:xiangmu3XinFuQiangmavencode epocommons-configurationcommons-configuration1.10commons-configuration-1.10.jar;F:xiangmu3XinFuQiangmavencode epocommons-langcommons-lang2.6commons-lang-2.6.jar;F:xiangmu3XinFuQiangmavencode epocommons-loggingcommons-logging1.1.1commons-logging-1.1.1.jar;F:xiangmu3XinFuQiangmavencode epocomgooglezxingcore2.1core-2.1.jar;F:xiangmu3XinFuQiangmavencode epocomgooglecodegsongson2.3.1gson-2.3.1.jar;F:xiangmu3XinFuQiangmavencode epoorghamcresthamcrest-core1.3hamcrest-core-1.3.jar;F:xiangmu3XinFuQiangmavencode epo edisclientsjedis2.6.0jedis-2.6.0.jar;F:xiangmu3XinFuQiangmavencode epoorgapachecommonscommons-pool22.0commons-pool2-2.0.jar;F:xiangmu3XinFuQiangmavencode epoorgprojectlomboklombok1.16.18lombok-1.16.18.jar;F:xiangmu3XinFuQiangmavencode epoorg edisson edisson2.9.0 edisson-2.9.0.jar;F:xiangmu3XinFuQiangmavencode epoio etty etty-common4.1.8.Final etty-common-4.1.8.Final.jar;F:xiangmu3XinFuQiangmavencode epoio etty etty-codec4.1.8.Final etty-codec-4.1.8.Final.jar;F:xiangmu3XinFuQiangmavencode epoio etty etty-buffer4.1.8.Final etty-buffer-4.1.8.Final.jar;F:xiangmu3XinFuQiangmavencode epoio etty etty-transport4.1.8.Final etty-transport-4.1.8.Final.jar;F:xiangmu3XinFuQiangmavencode epoio etty etty-resolver4.1.8.Final etty-resolver-4.1.8.Final.jar;F:xiangmu3XinFuQiangmavencode epoio etty etty-handler4.1.8.Final etty-handler-4.1.8.Final.jar;F:xiangmu3XinFuQiangmavencode epojavaxcachecache-api1.0.0cache-api-1.0.0.jar;F:xiangmu3XinFuQiangmavencode epoioprojectreactor eactor-stream2.0.8.RELEASE eactor-stream-2.0.8.RELEASE.jar;F:xiangmu3XinFuQiangmavencode epoioprojectreactor eactor-core2.0.8.RELEASE eactor-core-2.0.8.RELEASE.jar;F:xiangmu3XinFuQiangmavencode epoorg eactivestreams eactive-streams1.0.0 eactive-streams-1.0.0.jar;F:xiangmu3XinFuQiangmavencode epocomfasterxmljacksondataformatjackson-dataformat-yaml2.6.7jackson-dataformat-yaml-2.6.7.jar;F:xiangmu3XinFuQiangmavencode epoorgyamlsnakeyaml1.15snakeyaml-1.15.jar;F:xiangmu3XinFuQiangmavencode epocomfasterxmljacksoncorejackson-core2.6.7jackson-core-2.6.7.jar;F:xiangmu3XinFuQiangmavencode epocomfasterxmljacksoncorejackson-databind2.6.7jackson-databind-2.6.7.jar;F:xiangmu3XinFuQiangmavencode epocomfasterxmljacksondataformatjackson-dataformat-avro2.9.0jackson-dataformat-avro-2.9.0.jar;F:xiangmu3XinFuQiangmavencode epocomfasterxmljacksoncorejackson-annotations2.9.0jackson-annotations-2.9.0.jar;F:xiangmu3XinFuQiangmavencode epoorgapacheavroavro1.8.1avro-1.8.1.jar;F:xiangmu3XinFuQiangmavencode epocom houghtworksparanamerparanamer2.7paranamer-2.7.jar;F:xiangmu3XinFuQiangmavencode epoorgxerialsnappysnappy-java1.1.1.3snappy-java-1.1.1.3.jar;F:xiangmu3XinFuQiangmavencode epoorgapachecommonscommons-compress1.8.1commons-compress-1.8.1.jar;F:xiangmu3XinFuQiangmavencode epoorg ukaanixz1.5xz-1.5.jar;F:xiangmu3XinFuQiangmavencode epocomsunfacesjsf-api1.2jsf-api-1.2.jar;D:javadevolopKitideaanZhIntelliJ IDEA Community Edition 2018.1.4libidea_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; }