Simplify HibernateJpaAutoConfiguration classes check

This commit removes the now outdated `HibernateEntityManagerCondition`
in favour of a simple check of `SessionImplementor`. As of
Hibernate 5.2, a single `hibernate-core` jar is required so a single
class check is enough.

Closes gh-17288

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaAutoConfiguration.java

@@ -16,29 +16,18 @@
 
 package org.springframework.boot.autoconfigure.orm.jpa;
 
-import java.util.Arrays;
-
 import javax.persistence.EntityManager;
 
+import org.hibernate.engine.spi.SessionImplementor;
+
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
-import org.springframework.boot.autoconfigure.condition.ConditionMessage;
-import org.springframework.boot.autoconfigure.condition.ConditionMessage.Style;
-import org.springframework.boot.autoconfigure.condition.ConditionOutcome;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
-import org.springframework.boot.autoconfigure.condition.SpringBootCondition;
 import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
-import org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration.HibernateEntityManagerCondition;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
-import org.springframework.context.annotation.ConditionContext;
-import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
-import org.springframework.core.Ordered;
-import org.springframework.core.annotation.Order;
-import org.springframework.core.type.AnnotatedTypeMetadata;
 import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
-import org.springframework.util.ClassUtils;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for Hibernate JPA.
@@ -49,31 +38,10 @@ import org.springframework.util.ClassUtils;
  * @author Andy Wilkinson
  */
 @Configuration
-@ConditionalOnClass({ LocalContainerEntityManagerFactoryBean.class, EntityManager.class })
-@Conditional(HibernateEntityManagerCondition.class)
+@ConditionalOnClass({ LocalContainerEntityManagerFactoryBean.class, EntityManager.class, SessionImplementor.class })
 @EnableConfigurationProperties(JpaProperties.class)
 @AutoConfigureAfter({ DataSourceAutoConfiguration.class })
 @Import(HibernateJpaConfiguration.class)
 public class HibernateJpaAutoConfiguration {
 
-	@Order(Ordered.HIGHEST_PRECEDENCE + 20)
-	static class HibernateEntityManagerCondition extends SpringBootCondition {
-
-		private static final String[] CLASS_NAMES = { "org.hibernate.ejb.HibernateEntityManager",
-				"org.hibernate.jpa.HibernateEntityManager" };
-
-		@Override
-		public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
-			ConditionMessage.Builder message = ConditionMessage.forCondition("HibernateEntityManager");
-			for (String className : CLASS_NAMES) {
-				if (ClassUtils.isPresent(className, context.getClassLoader())) {
-					return ConditionOutcome.match(message.found("class").items(Style.QUOTE, className));
-				}
-			}
-			return ConditionOutcome
-					.noMatch(message.didNotFind("class", "classes").items(Style.QUOTE, Arrays.asList(CLASS_NAMES)));
-		}
-
-	}
-
 }