本章阅读收获:可了解Quartz框架中的Scheduler部分源码
继上一节内容
在上一节内容中，我们还是停留在了scheduler初始化过程中（不知道有没有人会觉得有点慢），针对这一点，我觉得阅读源码不应该追求一位的速度，大致了解和深度了解我认为还是不一样的。
instantiate()后续源码讲解
//获取线程池配置，创建线程池
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//PROP_THREAD_POOL_CLASS = org.quartz.threadPool.class
String tpClass = cfg.getStringProperty(PROP_THREAD_POOL_CLASS, SimpleThreadPool.class.getName());
if (tpClass == null) {
initException = new SchedulerException(
"ThreadPool class not specified. ");
throw initException;
}
try {
tp = (ThreadPool) loadHelper.loadClass(tpClass).newInstance();
} catch (Exception e) {
initException = new SchedulerException("ThreadPool class '"
+ tpClass + "' could not be instantiated.", e);
throw initException;
}
这里的内容也很简单。是从配置中获取线程池的类路径，如果没有的话就拿SimpleThreadPool，所以我们可以知道SimpleThreadPool是系统默认实现。
//获取关于线程池的配置组
//PROP_THREAD_POOL_PREFIX = org.quartz.threadPool
tProps = cfg.getPropertyGroup(PROP_THREAD_POOL_PREFIX, true);
try {
//把配置文件中的信息写入到实例中
setBeanProps(tp, tProps);
} catch (Exception e) {
initException = new SchedulerException("ThreadPool class '"
+ tpClass + "' props could not be configured.", e);
throw initException;
}
这块代码简单易懂，就是把如果有线程池配置，就注入进去。下面是一波小高潮，让我们继续观看，不要着急。
//获取任务存储中心配置，创建任务存储中心
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//PROP_JOB_STORE_CLASS = org.quartz.jobStore.class
//默认使用RAMJobStore内存存储
String jsClass = cfg.getStringProperty(PROP_JOB_STORE_CLASS,
RAMJobStore.class.getName());
if (jsClass == null) {
initException = new SchedulerException(
"JobStore class not specified. ");
throw initException;
}
try {
js = (JobStore) loadHelper.loadClass(jsClass).newInstance();
} catch (Exception e) {
initException = new SchedulerException("JobStore class '" + jsClass
+ "' could not be instantiated.", e);
throw initException;
}
这里是加载job存储中心，我们可以看到默认实现是RAMJobStore，也就是内存存储，但是这有个通病也出自内存，就是万一机器挂了，任务内容就没有了，所以如果我们需要改造任务存储中心，可以在这里进行更改。
//反射设置schedName、schedInstId配置
SchedulerDetailsSetter.setDetails(js, schedName, schedInstId);
//PROP_JOB_STORE_PREFIX = org.quartz.jobStore
tProps = cfg.getPropertyGroup(PROP_JOB_STORE_PREFIX, true, new String[] {PROP_JOB_STORE_LOCK_HANDLER_PREFIX});
try {
setBeanProps(js, tProps);
} catch (Exception e) {
initException = new SchedulerException("JobStore class '" + jsClass
+ "' props could not be configured.", e);
throw initException;
}
if (js instanceof JobStoreSupport) {
// Install custom lock handler (Semaphore)
// 获取锁类名
String lockHandlerClass = cfg.getStringProperty(PROP_JOB_STORE_LOCK_HANDLER_CLASS);
if (lockHandlerClass != null) {
try {
Semaphore lockHandler = (Semaphore)loadHelper.loadClass(lockHandlerClass).newInstance();
tProps = cfg.getPropertyGroup(PROP_JOB_STORE_LOCK_HANDLER_PREFIX, true);
// If this lock handler requires the table prefix, add it to its properties.
if (lockHandler instanceof TablePrefixAware) {
tProps.setProperty(
PROP_TABLE_PREFIX, ((JobStoreSupport)js).getTablePrefix());
tProps.setProperty(
PROP_SCHED_NAME, schedName);
}
try {
setBeanProps(lockHandler, tProps);
} catch (Exception e) {
initException = new SchedulerException("JobStore LockHandler class '" + lockHandlerClass
+ "' props could not be configured.", e);
throw initException;
}
((JobStoreSupport)js).setLockHandler(lockHandler);
getLog().info("Using custom data access locking (synchronization): " + lockHandlerClass);
} catch (Exception e) {
initException = new SchedulerException("JobStore LockHandler class '" + lockHandlerClass
+ "' could not be instantiated.", e);
throw initException;
}
}
}
这里先把调度器的名字和标志号注入进去，默认schedName为QuartzScheduler，schedInstId 为NON_CLUSTERED。之后获取锁类名，默认key是
public static final String PROP_JOB_STORE_PREFIX = "org.quartz.jobStore";
public static final String PROP_JOB_STORE_LOCK_HANDLER_PREFIX = PROP_JOB_STORE_PREFIX + ".lockHandler";
public static final String PROP_JOB_STORE_LOCK_HANDLER_CLASS = PROP_JOB_STORE_LOCK_HANDLER_PREFIX + ".class";
实际就是org.quartz.jobStore.lockHandler.class，然后根据这个key从配置查询锁类名。如果有的话，老套路，继续注入配置。这里大家可能会对Semaphore有点疑惑，这是什么？
package org.quartz.impl.jdbcjobstore;
import java.sql.Connection;
/**
* 锁控制器
*/
public interface Semaphore {
/*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Interface.
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
/**
* 获取锁
*/
boolean obtainLock(Connection conn, String lockName) throws LockException;
/**
* 释放锁
*/
void releaseLock(String lockName) throws LockException;
/**
* 是否连接
*/
boolean requiresConnection();
}
这个接口是这样的，默认实现类是StdRowLockSemaphore，是用来做什么的呢？
主要是用来针对集群的同步操作，默认实现是通过数据库行锁来进行操作（个人感觉应该不怎么用得到，这部分也是扩展点）。
// Set up any DataSources
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// PROP_DATASOURCE_PREFIX = org.quartz.dataSource
String[] dsNames = cfg.getPropertyGroups(PROP_DATASOURCE_PREFIX);
for (int i = 0; i < dsNames.length; i++) {
PropertiesParser pp = new PropertiesParser(cfg.getPropertyGroup(
PROP_DATASOURCE_PREFIX + "." + dsNames[i], true));
//PROP_CONNECTION_PROVIDER_CLASS = connectionProvider.class
String cpClass = pp.getStringProperty(PROP_CONNECTION_PROVIDER_CLASS, null);
// custom connectionProvider...
if(cpClass != null) {
ConnectionProvider cp = null;
try {
cp = (ConnectionProvider) loadHelper.loadClass(cpClass).newInstance();
} catch (Exception e) {
initException = new SchedulerException("ConnectionProvider class '" + cpClass
+ "' could not be instantiated.", e);
throw initException;
}
try {
// remove the class name, so it isn't attempted to be set
pp.getUnderlyingProperties().remove(
PROP_CONNECTION_PROVIDER_CLASS);
if (cp instanceof PoolingConnectionProvider) {
populateProviderWithExtraProps((PoolingConnectionProvider)cp, pp.getUnderlyingProperties());
} else {
setBeanProps(cp, pp.getUnderlyingProperties());
}
cp.initialize();
} catch (Exception e) {
initException = new SchedulerException("ConnectionProvider class '" + cpClass
+ "' props could not be configured.", e);
throw initException;
}
dbMgr = DBConnectionManager.getInstance();
dbMgr.addConnectionProvider(dsNames[i], cp);
} else {
String dsJndi = pp.getStringProperty(PROP_DATASOURCE_JNDI_URL, null);
if (dsJndi != null) {
boolean dsAlwaysLookup = pp.getBooleanProperty(
PROP_DATASOURCE_JNDI_ALWAYS_LOOKUP);
String dsJndiInitial = pp.getStringProperty(
PROP_DATASOURCE_JNDI_INITIAL);
String dsJndiProvider = pp.getStringProperty(
PROP_DATASOURCE_JNDI_PROVDER);
String dsJndiPrincipal = pp.getStringProperty(
PROP_DATASOURCE_JNDI_PRINCIPAL);
String dsJndiCredentials = pp.getStringProperty(
PROP_DATASOURCE_JNDI_CREDENTIALS);
Properties props = null;
if (null != dsJndiInitial || null != dsJndiProvider
|| null != dsJndiPrincipal || null != dsJndiCredentials) {
props = new Properties();
if (dsJndiInitial != null) {
props.put(PROP_DATASOURCE_JNDI_INITIAL,
dsJndiInitial);
}
if (dsJndiProvider != null) {
props.put(PROP_DATASOURCE_JNDI_PROVDER,
dsJndiProvider);
}
if (dsJndiPrincipal != null) {
props.put(PROP_DATASOURCE_JNDI_PRINCIPAL,
dsJndiPrincipal);
}
if (dsJndiCredentials != null) {
props.put(PROP_DATASOURCE_JNDI_CREDENTIALS,
dsJndiCredentials);
}
}
JNDIConnectionProvider cp = new JNDIConnectionProvider(dsJndi,
props, dsAlwaysLookup);
dbMgr = DBConnectionManager.getInstance();
dbMgr.addConnectionProvider(dsNames[i], cp);
} else {
String dsDriver = pp.getStringProperty(PoolingConnectionProvider.DB_DRIVER);
String dsURL = pp.getStringProperty(PoolingConnectionProvider.DB_URL);
if (dsDriver == null) {
initException = new SchedulerException(
"Driver not specified for DataSource: "
+ dsNames[i]);
throw initException;
}
if (dsURL == null) {
initException = new SchedulerException(
"DB URL not specified for DataSource: "
+ dsNames[i]);
throw initException;
}
try {
PoolingConnectionProvider cp = new PoolingConnectionProvider(pp.getUnderlyingProperties());
dbMgr = DBConnectionManager.getInstance();
dbMgr.addConnectionProvider(dsNames[i], cp);
// Populate the underlying C3P0 data source pool properties
populateProviderWithExtraProps(cp, pp.getUnderlyingProperties());
} catch (Exception sqle) {
initException = new SchedulerException(
"Could not initialize DataSource: " + dsNames[i],
sqle);
throw initException;
}
}
}
}
这部分代码大家可以大致看懂应该是跟连接数据库有关，这里提供了很多种连接方式，有Driver、JNDI或者自定义的。这部分个人感觉深度下去对我目前帮助不是特别大，所以我在这先跳过了。有兴趣的朋友可以深入继续看下去。但是这里的扩展性，我们可以学习一下，考虑到多种连接方式。
结束语
本节又这么结束了，我们继续深入的了解了jobStore的初始化过程等等，黎明前的黑暗即将结束，加油~~~~~
