今天我分享一个技术点，利用Spring初始化+线程接管进行程序启动后保持会话状态。
先来一段@test单元测试注解，后台开发的很熟悉，这是测试局部代码用的：
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
RunWith和ContextConfiguration的源码和功能就不细解释了，不熟悉的可以去翻翻源码。
1：我来一段@Test单元测试操作数据的代码：
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
public class RunTest {
@Autowired
CustomerServices custServer;//services层，注入了dao层
@Test
public void test(){
Customer customer = new Customer();
customer.setCname("余根海");
customer.setCinfo("我是一条鱼！");
customer.setCage("25");
custServer.insertTest(customer);
}
}
(1) 跑一遍单元测试，INFO日志输出：
16:34:30,296 INFO DefaultTestContextBootstrapper:259 - Loaded default TestExecutionListener class names from location [META-INF/spring.factories]: [org.springframework.test.context.web.ServletTestExecutionListener, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener, org.springframework.test.context.support.DependencyInjectionTestExecutionListener, org.springframework.test.context.support.DirtiesContextTestExecutionListener, org.springframework.test.context.transaction.TransactionalTestExecutionListener, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener]
16:34:30,313 INFO DefaultTestContextBootstrapper:185 - Using TestExecutionListeners: [org.springframework.test.context.web.ServletTestExecutionListener@146ba0ac, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener@4dfa3a9d, org.springframework.test.context.support.DependencyInjectionTestExecutionListener@6eebc39e, org.springframework.test.context.support.DirtiesContextTestExecutionListener@464bee09, org.springframework.test.context.transaction.TransactionalTestExecutionListener@f6c48ac, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener@13deb50e]
16:34:30,390 INFO XmlBeanDefinitionReader:317 - Loading XML bean definitions from class path resource [applicationContext.xml]
16:34:30,685 INFO GenericApplicationContext:578 - Refreshing org.springframework.context.support.GenericApplicationContext@370736d9: startup date [Mon Aug 07 16:34:30 CST 2017]; root of context hierarchy
16:34:30,777 INFO PropertyPlaceholderConfigurer:172 - Loading properties file from class path resource [init.properties]
16:34:30,970 INFO MLog:212 - MLog clients using slf4j logging.
16:34:31,123 INFO C3P0Registry:212 - Initializing c3p0-0.9.5.2 [built 08-December-2015 22:06:04 -0800; debug? true; trace: 10]
16:34:31,296 INFO Version:37 - HHH000412: Hibernate Core {5.0.8.Final}
16:34:31,298 INFO Environment:213 - HHH000206: hibernate.properties not found
16:34:31,299 INFO Environment:317 - HHH000021: Bytecode provider name : javassist
16:34:31,336 INFO Version:66 - HCANN000001: Hibernate Commons Annotations {5.0.1.Final}
16:34:31,416 INFO AbstractPoolBackedDataSource:212 - Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 5, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 30000, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, contextClassLoaderSource -> caller, dataSourceName -> 1bqudj89p1g46yu313x3lsl|41ab013, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver, extensions -> {}, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, forceSynchronousCheckins -> false, forceUseNamedDriverClass -> false, identityToken -> 1bqudj89p1g46yu313x3lsl|41ab013, idleConnectionTestPeriod -> 30, initialPoolSize -> 5, jdbcUrl -> jdbc:mysql://127.0.0.1:3306/yugh?useUnicode=true&characterEncoding=utf-8, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 30, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 20, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 5, numHelperThreads -> 3, preferredTestQuery -> null, privilegeSpawnedThreads -> false, properties -> {user=******, password=******}, propertyCycle -> 0, statementCacheNumDeferredCloseThreads -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, userOverrides -> {}, usesTraditionalReflectiveProxies -> false ]
16:34:31,633 INFO Dialect:156 - HHH000400: Using dialect: org.hibernate.dialect.MySQLDialect
16:34:31,671 INFO LobCreatorBuilderImpl:98 - HHH000423: Disabling contextual LOB creation as JDBC driver reported JDBC version [3] less than 4
16:34:32,027 INFO SchemaUpdate:105 - HHH000228: Running hbm2ddl schema update
16:34:32,120 INFO HibernateTransactionManager:357 - Using DataSource [com.mchange.v2.c3p0.ComboPooledDataSource[ identityToken -> 1bqudj89p1g46yu313x3lsl|41ab013, dataSourceName -> 1bqudj89p1g46yu313x3lsl|41ab013 ]] of Hibernate SessionFactory for HibernateTransactionManager
Hibernate: select next_val as id_val from hibernate_sequence for update
Hibernate: update hibernate_sequence set next_val= ? where next_val=?
Hibernate: insert into customer (cage, cinfo, cname, id) values (?, ?, ?, ?)
16:34:32,487 INFO GenericApplicationContext:960 - Closing org.springframework.context.support.GenericApplicationContext@370736d9: startup date [Mon Aug 07 16:34:30 CST 2017]; root of context hierarchy
(2) 可以看到@Test单元测试初始化了一遍Spring和Spring文件里的所有配置，因为要操作数据对象，在大部分后台单元测试中，目的都是数据交互。
@Test总结：通过@Test单元测试可以得到初始化Spring以及加载完毕已经配置到Spring文件中所有正确的配置参数，虽然它运行是短暂的。
请忽略上面的Hibernate，虽然上面测试是hibernate作为持久层，但本文所有知识点都是Spring，包括用Spring的数据控制替换其他持久层。
2：得到了初始化的目的，下面就得用线程接管初始化后的操作，几个关键点：(1)初始化spring文件 (2)事务用谁，怎么用，能否成功？(3)线程何时去接管？
静态对象是保持对象唯一，保持初始化的唯一，因为用@TEST单元测试时候，注解RunWith是把测试类和方法名都反射了，已经得到了真实的功能类入口，而我们自己初始化Spring启动程序不用@TEST注解就要定义全局静态对象。
(1)：初始化Spring文件，文件加载方式是我常用的：
public static final ApplicationContext context= new ClassPathXmlApplicationContext("applicationContext.xml");
(2)：事务采用Spring的：dataSource是数据库的bean
<bean id="transactionManager"
class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource">
<ref bean="dataSource" />
</property>
</bean>
写下获取事务的静态对象：
static final PlatformTransactionManager manager= (PlatformTransactionManager)context.getBean("transactionManager");
(3)：数据控制对象jdbctemplate，前身jdbcAccessor，源码用的基于sql的DataSource：
public static final JdbcTemplate jdbcTemplate= (JdbcTemplate)context.getBean("jdbcTemplate");
<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
<property name="dataSource">
<ref bean="dataSource" />
</property>
</bean>
(4) 到这里的配置菜单有：初始化Spring文件 + 事务 + 数据控制对象，虽然全部依赖Spring，但已经是一个很优秀的纯后台项目架构了，虽然在持久层没有hibernate那么强大各种操作方式。
最后来一段Spring初始化日志：
09:43:35,326 INFO ClassPathXmlApplicationContext:578 - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@7ce6a65d: startup date [Tue Aug 08 09:43:35 CST 2017]; root of context hierarchy
09:43:35,368 INFO XmlBeanDefinitionReader:317 - Loading XML bean definitions from class path resource [applicationContext.xml]
09:44:21,994 INFO PropertyPlaceholderConfigurer:172 - Loading properties file from class path resource [init.properties]
09:44:24,847 INFO MLog:212 - MLog clients using slf4j logging.
09:44:25,007 INFO C3P0Registry:212 - Initializing c3p0-0.9.5.2 [built 08-December-2015 22:06:04 -0800; debug? true; trace: 10]
09:44:33,517 INFO AbstractPoolBackedDataSource:212 - Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 5, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 30000, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, contextClassLoaderSource -> caller, dataSourceName -> 1bqudj89p1h4zfam1rricvn|62e8f862, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver, extensions -> {}, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, forceSynchronousCheckins -> false, forceUseNamedDriverClass -> false, identityToken -> 1bqudj89p1h4zfam1rricvn|62e8f862, idleConnectionTestPeriod -> 30, initialPoolSize -> 5, jdbcUrl -> jdbc:mysql://127.0.0.1:3306/yugh?useUnicode=true&characterEncoding=utf-8, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 30, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 20, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 5, numHelperThreads -> 3, preferredTestQuery -> null, privilegeSpawnedThreads -> false, properties -> {user=******, password=******}, propertyCycle -> 0, statementCacheNumDeferredCloseThreads -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, userOverrides -> {}, usesTraditionalReflectiveProxies -> false ]
总结构思：(1)利用代码初始加载Spring文件 ——> (2)主入口定义一个main方法，各种校验运行后，运行 ——> (3)调用静态的初始化代码，开始初始 ——> (4) 初始完毕后调用数据控制 ——> (5)通过一系列后台操作后，线程开始接管 ——> (6)代码控制它保持后台运行会话状态。