HibernateTransactionManager lazily acquires JDBC Connection

Aligned with HibernateJpaDialect, using ConnectionHandle as functional interface now. Also, LazyConnectionDataSourceProxy supports Connection holdability as applied by HibernateTransactionManager, for use with prepareConnection=true.

Issue: SPR-17216

spring-jdbc/src/main/java/org/springframework/jdbc/datasource/ConnectionHandle.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -27,6 +27,7 @@ import java.sql.Connection;
  * @see SimpleConnectionHandle
  * @see ConnectionHolder
  */
+@FunctionalInterface
 public interface ConnectionHandle {
 
 	/**
@@ -36,8 +37,11 @@ public interface ConnectionHandle {
 
 	/**
 	 * Release the JDBC Connection that this handle refers to.
+	 * <p>The default implementation is empty, assuming that the lifecycle
+	 * of the connection is managed externally.
 	 * @param con the JDBC Connection to release
 	 */
-	void releaseConnection(Connection con);
+	default void releaseConnection(Connection con) {
+	}
 
 }

spring-jdbc/src/main/java/org/springframework/jdbc/datasource/LazyConnectionDataSourceProxy.java

@@ -21,6 +21,7 @@ import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.Proxy;
 import java.sql.Connection;
+import java.sql.ResultSet;
 import java.sql.SQLException;
 import javax.sql.DataSource;
 
@@ -256,14 +257,16 @@ public class LazyConnectionDataSourceProxy extends DelegatingDataSource {
 		@Nullable
 		private String password;
 
-		private Boolean readOnly = Boolean.FALSE;
-
 		@Nullable
 		private Boolean autoCommit;
 
 		@Nullable
 		private Integer transactionIsolation;
 
+		private boolean readOnly = false;
+
+		private int holdability = ResultSet.CLOSE_CURSORS_AT_COMMIT;
+
 		private boolean closed = false;
 
 		@Nullable
@@ -319,11 +322,15 @@ public class LazyConnectionDataSourceProxy extends DelegatingDataSource {
 				if (method.getName().equals("toString")) {
 					return "Lazy Connection proxy for target DataSource [" + getTargetDataSource() + "]";
 				}
-				else if (method.getName().equals("isReadOnly")) {
-					return this.readOnly;
+				else if (method.getName().equals("getAutoCommit")) {
+					if (this.autoCommit != null) {
+						return this.autoCommit;
+					}
+					// Else fetch actual Connection and check there,
+					// because we didn't have a default specified.
 				}
-				else if (method.getName().equals("setReadOnly")) {
-					this.readOnly = (Boolean) args[0];
+				else if (method.getName().equals("setAutoCommit")) {
+					this.autoCommit = (Boolean) args[0];
 					return null;
 				}
 				else if (method.getName().equals("getTransactionIsolation")) {
@@ -337,15 +344,18 @@ public class LazyConnectionDataSourceProxy extends DelegatingDataSource {
 					this.transactionIsolation = (Integer) args[0];
 					return null;
 				}
-				else if (method.getName().equals("getAutoCommit")) {
-					if (this.autoCommit != null) {
-						return this.autoCommit;
-					}
-					// Else fetch actual Connection and check there,
-					// because we didn't have a default specified.
+				else if (method.getName().equals("isReadOnly")) {
+					return this.readOnly;
 				}
-				else if (method.getName().equals("setAutoCommit")) {
-					this.autoCommit = (Boolean) args[0];
+				else if (method.getName().equals("setReadOnly")) {
+					this.readOnly = (Boolean) args[0];
+					return null;
+				}
+				else if (method.getName().equals("getHoldability")) {
+					return this.holdability;
+				}
+				else if (method.getName().equals("setHoldability")) {
+					this.holdability = (Integer) args[0];
 					return null;
 				}
 				else if (method.getName().equals("commit")) {

spring-jdbc/src/main/java/org/springframework/jdbc/datasource/SimpleConnectionHandle.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -49,14 +49,6 @@ public class SimpleConnectionHandle implements ConnectionHandle {
 		return this.connection;
 	}
 
-	/**
-	 * This implementation is empty, as we're using a standard
-	 * Connection handle that does not have to be released.
-	 */
-	@Override
-	public void releaseConnection(Connection con) {
-	}
-
 
 	@Override
 	public String toString() {