spring boot JPA 和 数据库连接
Posted 二奎
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当JPA获取数据库数据连接时，如果连接数超过最大连接数的配置，系统就会报错：
Unable to acquire JDBC Connection
和：
Caused by: java.sql.SQLTransientConnectionException: HikariPool-1 - Connection is not available, request timed out after 30002ms. at com.zaxxer.hikari.pool.HikariPool.createTimeoutException(HikariPool.java:676) ~[HikariCP-3.2.0.jar:?] at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:190) ~[HikariCP-3.2.0.jar:?] at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:155) ~[HikariCP-3.2.0.jar:?] at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:128) ~[HikariCP-3.2.0.jar:?] at com.zaxxer.hikari.HikariDataSource$$FastClassBySpringCGLIB$$eeb1ae86.invoke(<generated>) ~[HikariCP-3.2.0.jar:?] at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) ~[spring-core-5.1.8.RELEASE.jar:5.1.8.RELEASE] at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:749) ~[spring-aop-5.1.8.RELEASE.jar:5.1.8.RELEASE] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.1.8.RELEASE.jar:5.1.8.RELEASE] at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:136) ~[spring-aop-5.1.8.RELEASE.jar:5.1.8.RELEASE] at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:124) ~[spring-aop-5.1.8.RELEASE.jar:5.1.8.RELEASE] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.8.RELEASE.jar:5.1.8.RELEASE] at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:688) ~[spring-aop-5.1.8.RELEASE.jar:5.1.8.RELEASE] at com.zaxxer.hikari.HikariDataSource$$EnhancerBySpringCGLIB$$5e528ef9.getConnection(<generated>) ~[HikariCP-3.2.0.jar:?] at org.hibernate.engine.jdbc.connections.internal.DatasourceConnectionProviderImpl.getConnection(DatasourceConnectionProviderImpl.java:122) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.internal.NonContextualJdbcConnectionAccess.obtainConnection(NonContextualJdbcConnectionAccess.java:35) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.acquireConnectionIfNeeded(LogicalConnectionManagedImpl.java:106) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.getPhysicalConnection(LogicalConnectionManagedImpl.java:136) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.engine.jdbc.internal.StatementPreparerImpl.connection(StatementPreparerImpl.java:47) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$5.doPrepare(StatementPreparerImpl.java:146) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$StatementPreparationTemplate.prepareStatement(StatementPreparerImpl.java:172) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.engine.jdbc.internal.StatementPreparerImpl.prepareQueryStatement(StatementPreparerImpl.java:148) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1984) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1914) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1892) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.loader.Loader.doQuery(Loader.java:937) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:340) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.loader.Loader.doList(Loader.java:2689) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.loader.Loader.doList(Loader.java:2672) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2506) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.loader.Loader.list(Loader.java:2501) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:504) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:395) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:220) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1508) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.query.internal.AbstractProducedQuery.doList(AbstractProducedQuery.java:1537) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] at org.hibernate.query.internal.AbstractProducedQuery.list(AbstractProducedQuery.java:1505) ~[hibernate-core-5.3.10.Final.jar:5.3.10.Final] ... 64 more
连接数的配置：
spring:
datasource:
hikari:
minimum-idle: 1
maximum-pool-size: 5
如果不配置的话，默认都是10.
我们使用entitymanager进行查询和其他操作时，调用这个方法org.springframework.orm.jpa.SharedEntityManagerCreator.DeferredQueryInvocationHandler#invoke，红色代码是会数据库连接池进行进行释放。SharedEntityManagerCreator这个类是这个关键，有兴趣可以重点看一下。
@Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { // Invocation on Query interface coming in... if (method.getName().equals("equals")) { // Only consider equal when proxies are identical. return (proxy == args[0]); } else if (method.getName().equals("hashCode")) { // Use hashCode of EntityManager proxy. return hashCode(); } else if (method.getName().equals("unwrap")) { // Handle JPA 2.0 unwrap method - could be a proxy match. Class<?> targetClass = (Class<?>) args[0]; if (targetClass == null) { return this.target; } else if (targetClass.isInstance(proxy)) { return proxy; } } else if (method.getName().equals("getOutputParameterValue")) { if (this.entityManager == null) { Object key = args[0]; if (this.outputParameters == null || !this.outputParameters.containsKey(key)) { throw new IllegalArgumentException("OUT/INOUT parameter not available: " + key); } Object value = this.outputParameters.get(key); if (value instanceof IllegalArgumentException) { throw (IllegalArgumentException) value; } return value; } } // Invoke method on actual Query object. try { Object retVal = method.invoke(this.target, args); if (method.getName().equals("registerStoredProcedureParameter") && args.length == 3 && (args[2] == ParameterMode.OUT || args[2] == ParameterMode.INOUT)) { if (this.outputParameters == null) { this.outputParameters = new LinkedHashMap<>(); } this.outputParameters.put(args[0], null); } return (retVal == this.target ? proxy : retVal); } catch (InvocationTargetException ex) { throw ex.getTargetException(); } finally { if (queryTerminatingMethods.contains(method.getName())) { // Actual execution of the query: close the EntityManager right // afterwards, since that was the only reason we kept it open. if (this.outputParameters != null && this.target instanceof StoredProcedureQuery) { StoredProcedureQuery storedProc = (StoredProcedureQuery) this.target; for (Map.Entry<Object, Object> entry : this.outputParameters.entrySet()) { try { Object key = entry.getKey(); if (key instanceof Integer) { entry.setValue(storedProc.getOutputParameterValue((Integer) key)); } else { entry.setValue(storedProc.getOutputParameterValue(key.toString())); } } catch (IllegalArgumentException ex) { entry.setValue(ex); } } } EntityManagerFactoryUtils.closeEntityManager(this.entityManager); this.entityManager = null; } } }
如果我们使用@Transactional注解时，就不是上会的代码来释放连接池的，是下面的代码：
org.springframework.orm.jpa.JpaTransactionManager#doCleanupAfterCompletion
@Override protected void doCleanupAfterCompletion(Object transaction) { JpaTransactionObject txObject = (JpaTransactionObject) transaction; // Remove the entity manager holder from the thread, if still there. // (Could have been removed by EntityManagerFactoryUtils in order // to replace it with an unsynchronized EntityManager). if (txObject.isNewEntityManagerHolder()) { TransactionSynchronizationManager.unbindResourceIfPossible(obtainEntityManagerFactory()); } txObject.getEntityManagerHolder().clear(); // Remove the JDBC connection holder from the thread, if exposed. if (getDataSource() != null && txObject.hasConnectionHolder()) { TransactionSynchronizationManager.unbindResource(getDataSource()); ConnectionHandle conHandle = txObject.getConnectionHolder().getConnectionHandle(); if (conHandle != null) { try { getJpaDialect().releaseJdbcConnection(conHandle, txObject.getEntityManagerHolder().getEntityManager()); } catch (Exception ex) { // Just log it, to keep a transaction-related exception. logger.error("Could not close JDBC connection after transaction", ex); } } } getJpaDialect().cleanupTransaction(txObject.getTransactionData()); // Remove the entity manager holder from the thread. if (txObject.isNewEntityManagerHolder()) { EntityManager em = txObject.getEntityManagerHolder().getEntityManager(); if (logger.isDebugEnabled()) { logger.debug("Closing JPA EntityManager [" + em + "] after transaction"); } EntityManagerFactoryUtils.closeEntityManager(em); } else { logger.debug("Not closing pre-bound JPA EntityManager after transaction"); } }
这是两种逻辑，如果我们在@Transactional注解的方法会使用em的方法进行数据库的操作的话，会采用第二种方式来释放，
如果不加@Transactional注解的话，采用第一种方法来释放。
所以为了避免发现特殊情况，出现不释放连接池的情况，可以采用加@Transactional注解的方式 处理，如下面的代码：
@Transactional @RequestMapping("/search") public List search() { CriteriaBuilder cb = entityManager.getCriteriaBuilder(); CriteriaQuery<Tuple> query = cb.createTupleQuery(); Root<BillDO> root = query.from(BillDO.class); List<Predicate> predicates = new ArrayList<>(); predicates.add(cb.equal(root.get(BillDO.Fields.hisId),"3035-M6748091-1695675075-1")); query.where(Iterables.toArray(predicates, Predicate.class)); query.multiselect(Arrays.asList( root.get(BillDO.Fields.hisId), root.get(BillDO.Fields.hospitalName), root.get(BillDO.Fields.hospitalId), root.get(BillDO.Fields.id), root.get(BillDO.Fields.diseaseName) )); TypedQuery<Tuple> typedQuery = entityManager.createQuery(query); // Query unwrap = typedQuery.unwrap(Query.class); QueryImpl unwrap = typedQuery.unwrap(QueryImpl.class); Query query1 = unwrap.setResultTransformer( new CisAliasToBeanResultTransformer(BillDO.class, query.getSelection())); List resultList = query1.list(); return resultList; }
如果不加@Transactional注解的话，那么连接池将不会释放，连接数会一直增加，直到超过最大连接数的配置。
可以通过下面的配置，来观察hikari数据库连接连接池的变化：
logging:
level:
root: warn
com:
zaxxer:
hikari: trace
这个代码是Hikari回收连接的：com.zaxxer.hikari.pool.HikariPool#recycle
@Override void recycle(final PoolEntry poolEntry) { metricsTracker.recordConnectionUsage(poolEntry); connectionBag.requite(poolEntry); }
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