The document discusses persisting runtime data using Apache Java Caching System (JCS) and Javassist. JCS is used to cache and persist objects to disk. Javassist dynamically sets values for transient fields that are not persisted. The runtime data is cached, persisted to disk, and reloaded to replay in new JVM instances. Javassist injects transient data by dynamically adding setter methods before replaying cached objects.

1. Persist and Replay Runtime Data
Using Apache Java Caching
System and Javassist
https://bitbucket.org/wishcoder/jcs.
marketdata.replay/wiki/Home
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

2. Persist and Replay Runtime Data
• The ability to persist data created at runtime is
useful when application states and data are
required to be replayed multiple times to
investigate application issues.
• This article demonstrates how to persist
runtime data to disk and load disk persisted
data to replay in new JVM instances.
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

3. Apache JCS and Javassist
• JCS is a distributed caching system written in
Java. Indexed Disk Auxiliary Cache is used to
persist data on disk. JCS only persist
Serializable java objects.
• Javassist (Java Programming Assistant) makes
Java bytecode manipulation simple. Javassist
is used to dynamically set values for transient
fields that are not persisted due to transient
nature.
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

4. Maven Dependencies
<properties>
<org.javassist-version>3.19.0-GA</org.javassist-version>
<jcs-version>1.3</jcs-version>
</properties>
<dependencies>
<dependency>
<groupId>org.javassist</groupId>
<artifactId>javassist</artifactId>
<version>${org.javassist-version}</version>
</dependency>
<dependency>
<groupId>jcs</groupId>
<artifactId>jcs</artifactId>
<version>${jcs-version}</version>
</dependency>
</dependencies>
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

5. Log4j Settings for JCS
<appender name="CONSOLE" class="org.apache.log4j.ConsoleAppender">
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%d [%t] %C{1} %p - %m%n"/>
</layout>
</appender>
<logger name="org.apache.jcs">
<!– DEBUG level in dev mode will enable useful logs from JCS jar ->
<!– DON’T PUT THIS IN PRODUCTION ENVIRONMENT ->
<level value="DEBUG"/>
<appender-ref ref="CONSOLE"/>
</logger>
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

6. Setup JCS - DEFAULT CACHE REGION
Properties props = new Properties();
props.put("jcs.default", "DC");
props.put("jcs.default.cacheattributes", "org.apache.jcs.engine.CompositeCacheAttributes");
props.put("jcs.default.cacheattributes.MaxObjects", 1000);
props.put("jcs.default.cacheattributes.MemoryCacheName",
"org.apache.jcs.engine.memory.lru.LRUMemoryCache");
props.put("jcs.default.cacheattributes.DiskUsagePatternName", "UPDATE");
props.put("jcs.default.elementattributes", "org.apache.jcs.engine.ElementAttributes");
props.put("jcs.default.elementattributes.IsSpool", "true");
props.put("jcs.region.elementattributes.IsEternal", "false");
props.put("jcs.default.elementattributes.IsLateral", "false");
props.put("jcs.default.elementattributes.IsRemote", "false");
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

7. Setup JCS - AUXILARY/DISK CACHE
props.put("jcs.auxiliary.DC", "org.apache.jcs.auxiliary.disk.indexed.IndexedDiskCacheFactory");
props.put("jcs.auxiliary.DC.attributes",
"org.apache.jcs.auxiliary.disk.indexed.IndexedDiskCacheAttributes");
props.put("jcs.auxiliary.DC.attributes.DiskPath", “C:TradeCache”);
props.put("jcs.auxiliary.DC.attributes.MaxPurgatorySize", "10000000"); // 10000000
// If the maximum key size is less than 0, no limit will be placed on
// the number of keys. By default, the max key size is 5000.
props.put("jcs.auxiliary.DC.attributes.MaxKeySize", "-1");
// Use Thread Pool for disk operation
props.put("jcs.auxiliary.DC.attributes.EventQueueType", "POOLED");
props.put("jcs.auxiliary.DC.attributes.EventQueuePoolName", "disk_cache_event_queue");
// Disk Cache Event Queue Pool
props.put("thread_pool.disk_cache_event_queue.useBoundary", "false");
props.put("thread_pool.remote_cache_client.maximumPoolSize", "15");
props.put("thread_pool.disk_cache_event_queue.minimumPoolSize", "1");
props.put("thread_pool.disk_cache_event_queue.keepAliveTime", "3500");
props.put("thread_pool.disk_cache_event_queue.startUpSize", "1");
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

8. Setup JCS – CUSTOM DATA CACHE REGION
props.put("jcs.region.marketdata_cache", "DC");
props.put("jcs.region.marketdata_cache.cacheattributes",
"org.apache.jcs.engine.CompositeCacheAttributes");
props.put("jcs.region.marketdata_cache.cacheattributes.MaxObjects", maxObjectInMemory);
props.put("jcs.region.marketdata_cache.cacheattributes.MemoryCacheName",
"org.apache.jcs.engine.memory.lru.LRUMemoryCache");
props.put("jcs.region.marketdata_cache.cacheattributes.DiskUsagePatternName", "UPDATE");
props.put("jcs.region.marketdata_cache.elementattributes",
"org.apache.jcs.engine.ElementAttributes");
props.put("jcs.region.marketdata_cache.elementattributes.IsEternal", "false");
props.put("jcs.region.marketdata_cache.elementattributes.IsLateral", "false");
props.put("jcs.region.marketdata_cache.elementattributes.IsRemote", "false");
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

9. Initialize and use JCS
CompositeCacheManager ccm = CompositeCacheManager.getUnconfiguredInstance();
ccm.configure(props )
CacheAccess cCache = JCS.getInstance(“marketdata_cache”);
• Write
cCache.put(Object name, Object obj);
• Read
Object obj = cCache.get(name);
• Persist Cache To Disk
// marketdata_cache.data and marketdata_cache.key files generated
cCache.dispose();
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

10. JCS - Load Data From Cache
CompositeCacheManager ccm = CompositeCacheManager.getUnconfiguredInstance();
ccm.configure(props )
CacheAccess cCache = JCS.getInstance(“marketdata_cache”);
• Read
Object obj = cCache.get(name);
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

11. Javassist – Inject Transient Data
Javassist (Java Programming Assistant) makes
Java bytecode manipulation simple. Javassist is
used to dynamically set values for transient
fields that are not persisted due to transient
nature.
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

12. Javassist – Helper Class
CacheReplayHelper .java
https://bitbucket.org/wishcoder/jcs.marketdata.replay/raw/de77eb8afaa818d21b1ac4bd1f0c
90bc99521cd4/jcs.marketdata.replay/trade.common/src/main/java/com/wishcoder/samples/j
cs/trade/common/cache/CacheReplayHelper.java
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

13. Javassist – Dynamically Add Setter Method
List<CtMethod> setterMethods = new ArrayList<CtMethod>();
CtClass sourceClass =
ClassPool.getDefault().get("com.wishcoder.samples.jcs.trade.common.data.TickEvent");
CtMethod setSourceMethod = getCacheManager().getMethod(sourceClass,
"setSource", "source",
"com.wishcoder.samples.jcs.trade.common.data.User");
setterMethods.add(setTickBookMethod);
CacheReplayHelper.addSetterMethods(sourceClass, setterMethods);
Class<?>[] userObject = new Class[1];
userObject[0] =
Class.forName("com.wishcoder.samples.jcs.trade.common.data.User");
HashMap<String, Class<?>[]> parameterMap = new HashMap<String,
Class<?>[]>();
parameterMap.put("setSource", userObject);
CacheReplayHelper.prepareNonSerializeSetters("com.wishcoder.samples.jcs.trade.common.data.TickEv
ent",
parameterMap);
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

14. Javassist – Set Transient Data
• Read object from JCS Cache:
CompositeCacheManager ccm = CompositeCacheManager.getUnconfiguredInstance();
ccm.configure(props )
CacheAccess cCache = JCS.getInstance(“marketdata_cache”);
Object cachedObject = cCache.get(name);
• Initialize object that need to be injected in cached object
User user = new User(‘1’, ‘Name’);
• Inject Transient data in cached object
cachedObject = CacheReplayHelper.setNonSerializeSetter(cachedObject ,
"setSource", user );
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

15. Wiki and Source Repository
https://bitbucket.org/wishcoder/jcs.marketdata.replay/wiki/Home
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

16. Useful Links
• Log4J
• Java
• Java MigLayout
• Javassist
• Apache Java Caching System - JCS
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder

17. Questions?
Ajay Singh | message4ajay@gmail.com
LinkedIn - https://www.linkedin.com/in/ajaysinghonline
Bitbucket - https://bitbucket.org/wishcoder
Slideshare - http://www.slideshare.net/ajaysingh672
Ajay Singh | message4ajay@gmail.com | LinkedIn - https://www.linkedin.com/in/ajaysinghonline | Bitbucket - https://bitbucket.org/wishcoder