Explicit notes on isolation level handling in participating transactions

Issue: SPR-16463

(cherry picked from commit 0ac117f)

spring-tx/src/main/java/org/springframework/transaction/TransactionDefinition.java

@@ -203,21 +203,29 @@ public interface TransactionDefinition {
 
 	/**
 	 * Return the isolation level.
-	 * <p>Must return one of the {@code ISOLATION_XXX} constants
-	 * defined on {@link TransactionDefinition this interface}.
-	 * <p>Only makes sense in combination with {@link #PROPAGATION_REQUIRED}
-	 * or {@link #PROPAGATION_REQUIRES_NEW}.
+	 * <p>Must return one of the {@code ISOLATION_XXX} constants defined on
+	 * {@link TransactionDefinition this interface}. Those constants are designed
+	 * to match the values of the same constants on {@link java.sql.Connection}.
+	 * <p>Exclusively designed for use with {@link #PROPAGATION_REQUIRED} or
+	 * {@link #PROPAGATION_REQUIRES_NEW} since it only applies to newly started
+	 * transactions. Consider switching the "validateExistingTransactions" flag to
+	 * "true" on your transaction manager if you'd like isolation level declarations
+	 * to get rejected when participating in an existing transaction with a different
+	 * isolation level.
 	 * <p>Note that a transaction manager that does not support custom isolation levels
 	 * will throw an exception when given any other level than {@link #ISOLATION_DEFAULT}.
 	 * @return the isolation level
+	 * @see #ISOLATION_DEFAULT
+	 * @see org.springframework.transaction.support.AbstractPlatformTransactionManager#setValidateExistingTransaction
 	 */
 	int getIsolationLevel();
 
 	/**
 	 * Return the transaction timeout.
 	 * <p>Must return a number of seconds, or {@link #TIMEOUT_DEFAULT}.
-	 * <p>Only makes sense in combination with {@link #PROPAGATION_REQUIRED}
-	 * or {@link #PROPAGATION_REQUIRES_NEW}.
+	 * <p>Exclusively designed for use with {@link #PROPAGATION_REQUIRED} or
+	 * {@link #PROPAGATION_REQUIRES_NEW} since it only applies to newly started
+	 * transactions.
 	 * <p>Note that a transaction manager that does not support timeouts will throw
 	 * an exception when given any other timeout than {@link #TIMEOUT_DEFAULT}.
 	 * @return the transaction timeout
@@ -226,13 +234,12 @@ public interface TransactionDefinition {
 
 	/**
 	 * Return whether to optimize as a read-only transaction.
-	 * <p>The read-only flag applies to any transaction context, whether
-	 * backed by an actual resource transaction
-	 * ({@link #PROPAGATION_REQUIRED}/{@link #PROPAGATION_REQUIRES_NEW}) or
-	 * operating non-transactionally at the resource level
-	 * ({@link #PROPAGATION_SUPPORTS}). In the latter case, the flag will
-	 * only apply to managed resources within the application, such as a
-	 * Hibernate {@code Session}.
+	 * <p>The read-only flag applies to any transaction context, whether backed
+	 * by an actual resource transaction ({@link #PROPAGATION_REQUIRED}/
+	 * {@link #PROPAGATION_REQUIRES_NEW}) or operating non-transactionally at
+	 * the resource level ({@link #PROPAGATION_SUPPORTS}). In the latter case,
+	 * the flag will only apply to managed resources within the application,
+	 * such as a Hibernate {@code Session}.
 	 * <p>This just serves as a hint for the actual transaction subsystem;
 	 * it will <i>not necessarily</i> cause failure of write access attempts.
 	 * A transaction manager which cannot interpret the read-only hint will

spring-tx/src/main/java/org/springframework/transaction/annotation/Transactional.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.
@@ -86,19 +86,30 @@ public @interface Transactional {
 	/**
 	 * The transaction isolation level.
 	 * <p>Defaults to {@link Isolation#DEFAULT}.
+	 * <p>Exclusively designed for use with {@link Propagation#REQUIRED} or
+	 * {@link Propagation#REQUIRES_NEW} since it only applies to newly started
+	 * transactions. Consider switching the "validateExistingTransactions" flag to
+	 * "true" on your transaction manager if you'd like isolation level declarations
+	 * to get rejected when participating in an existing transaction with a different
+	 * isolation level.
 	 * @see org.springframework.transaction.interceptor.TransactionAttribute#getIsolationLevel()
+	 * @see org.springframework.transaction.support.AbstractPlatformTransactionManager#setValidateExistingTransaction
 	 */
 	Isolation isolation() default Isolation.DEFAULT;
 
 	/**
 	 * The timeout for this transaction.
 	 * <p>Defaults to the default timeout of the underlying transaction system.
+	 * <p>Exclusively designed for use with {@link Propagation#REQUIRED} or
+	 * {@link Propagation#REQUIRES_NEW} since it only applies to newly started
+	 * transactions.
 	 * @see org.springframework.transaction.interceptor.TransactionAttribute#getTimeout()
 	 */
 	int timeout() default TransactionDefinition.TIMEOUT_DEFAULT;
 
 	/**
-	 * {@code true} if the transaction is read-only.
+	 * A boolean flag that can be set to {@code true} if the transaction is
+	 * effectively read-only, allowing for corresponding optimizations at runtime.
 	 * <p>Defaults to {@code false}.
 	 * <p>This just serves as a hint for the actual transaction subsystem;
 	 * it will <i>not necessarily</i> cause failure of write access attempts.
@@ -106,6 +117,7 @@ public @interface Transactional {
 	 * <i>not</i> throw an exception when asked for a read-only transaction
 	 * but rather silently ignore the hint.
 	 * @see org.springframework.transaction.interceptor.TransactionAttribute#isReadOnly()
+	 * @see org.springframework.transaction.support.TransactionSynchronizationManager#isCurrentTransactionReadOnly()
 	 */
 	boolean readOnly() default false;
 

spring-tx/src/main/java/org/springframework/transaction/support/AbstractPlatformTransactionManager.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 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.
@@ -214,6 +214,7 @@ public abstract class AbstractPlatformTransactionManager implements PlatformTran
 	 * <p>Default is "false", leniently ignoring inner transaction settings,
 	 * simply overriding them with the outer transaction's characteristics.
 	 * Switch this flag to "true" in order to enforce strict validation.
+	 * @since 2.5.1
 	 */
 	public final void setValidateExistingTransaction(boolean validateExistingTransaction) {
 		this.validateExistingTransaction = validateExistingTransaction;
@@ -222,6 +223,7 @@ public abstract class AbstractPlatformTransactionManager implements PlatformTran
 	/**
 	 * Return whether existing transactions should be validated before participating
 	 * in them.
+	 * @since 2.5.1
 	 */
 	public final boolean isValidateExistingTransaction() {
 		return this.validateExistingTransaction;
@@ -284,6 +286,7 @@ public abstract class AbstractPlatformTransactionManager implements PlatformTran
 	 * boundary. This allows, for example, to continue unit tests even after an
 	 * operation failed and the transaction will never be completed. All transaction
 	 * managers will only fail earlier if this flag has explicitly been set to "true".
+	 * @since 2.0
 	 * @see org.springframework.transaction.UnexpectedRollbackException
 	 */
 	public final void setFailEarlyOnGlobalRollbackOnly(boolean failEarlyOnGlobalRollbackOnly) {
@@ -293,6 +296,7 @@ public abstract class AbstractPlatformTransactionManager implements PlatformTran
 	/**
 	 * Return whether to fail early in case of the transaction being globally marked
 	 * as rollback-only.
+	 * @since 2.0
 	 */
 	public final boolean isFailEarlyOnGlobalRollbackOnly() {
 		return this.failEarlyOnGlobalRollbackOnly;

spring-tx/src/main/java/org/springframework/transaction/support/DefaultTransactionDefinition.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.
@@ -108,7 +108,7 @@ public class DefaultTransactionDefinition implements TransactionDefinition, Seri
 	 * Set the propagation behavior by the name of the corresponding constant in
 	 * TransactionDefinition, e.g. "PROPAGATION_REQUIRED".
 	 * @param constantName name of the constant
-	 * @exception IllegalArgumentException if the supplied value is not resolvable
+	 * @throws IllegalArgumentException if the supplied value is not resolvable
 	 * to one of the {@code PROPAGATION_} constants or is {@code null}
 	 * @see #setPropagationBehavior
 	 * @see #PROPAGATION_REQUIRED
@@ -123,8 +123,16 @@ public class DefaultTransactionDefinition implements TransactionDefinition, Seri
 	/**
 	 * Set the propagation behavior. Must be one of the propagation constants
 	 * in the TransactionDefinition interface. Default is PROPAGATION_REQUIRED.
-	 * @exception IllegalArgumentException if the supplied value is not
-	 * one of the {@code PROPAGATION_} constants
+	 * <p>Exclusively designed for use with {@link #PROPAGATION_REQUIRED} or
+	 * {@link #PROPAGATION_REQUIRES_NEW} since it only applies to newly started
+	 * transactions. Consider switching the "validateExistingTransactions" flag to
+	 * "true" on your transaction manager if you'd like isolation level declarations
+	 * to get rejected when participating in an existing transaction with a different
+	 * isolation level.
+	 * <p>Note that a transaction manager that does not support custom isolation levels
+	 * will throw an exception when given any other level than {@link #ISOLATION_DEFAULT}.
+	 * @throws IllegalArgumentException if the supplied value is not one of the
+	 * {@code PROPAGATION_} constants
 	 * @see #PROPAGATION_REQUIRED
 	 */
 	public final void setPropagationBehavior(int propagationBehavior) {
@@ -143,7 +151,7 @@ public class DefaultTransactionDefinition implements TransactionDefinition, Seri
 	 * Set the isolation level by the name of the corresponding constant in
 	 * TransactionDefinition, e.g. "ISOLATION_DEFAULT".
 	 * @param constantName name of the constant
-	 * @exception IllegalArgumentException if the supplied value is not resolvable
+	 * @throws IllegalArgumentException if the supplied value is not resolvable
 	 * to one of the {@code ISOLATION_} constants or is {@code null}
 	 * @see #setIsolationLevel
 	 * @see #ISOLATION_DEFAULT
@@ -158,8 +166,16 @@ public class DefaultTransactionDefinition implements TransactionDefinition, Seri
 	/**
 	 * Set the isolation level. Must be one of the isolation constants
 	 * in the TransactionDefinition interface. Default is ISOLATION_DEFAULT.
-	 * @exception IllegalArgumentException if the supplied value is not
-	 * one of the {@code ISOLATION_} constants
+	 * <p>Exclusively designed for use with {@link #PROPAGATION_REQUIRED} or
+	 * {@link #PROPAGATION_REQUIRES_NEW} since it only applies to newly started
+	 * transactions. Consider switching the "validateExistingTransactions" flag to
+	 * "true" on your transaction manager if you'd like isolation level declarations
+	 * to get rejected when participating in an existing transaction with a different
+	 * isolation level.
+	 * <p>Note that a transaction manager that does not support custom isolation levels
+	 * will throw an exception when given any other level than {@link #ISOLATION_DEFAULT}.
+	 * @throws IllegalArgumentException if the supplied value is not one of the
+	 * {@code ISOLATION_} constants
 	 * @see #ISOLATION_DEFAULT
 	 */
 	public final void setIsolationLevel(int isolationLevel) {
@@ -177,6 +193,11 @@ public class DefaultTransactionDefinition implements TransactionDefinition, Seri
 	/**
 	 * Set the timeout to apply, as number of seconds.
 	 * Default is TIMEOUT_DEFAULT (-1).
+	 * <p>Exclusively designed for use with {@link #PROPAGATION_REQUIRED} or
+	 * {@link #PROPAGATION_REQUIRES_NEW} since it only applies to newly started
+	 * transactions.
+	 * <p>Note that a transaction manager that does not support timeouts will throw
+	 * an exception when given any other timeout than {@link #TIMEOUT_DEFAULT}.
 	 * @see #TIMEOUT_DEFAULT
 	 */
 	public final void setTimeout(int timeout) {
@@ -194,6 +215,16 @@ public class DefaultTransactionDefinition implements TransactionDefinition, Seri
 	/**
 	 * Set whether to optimize as read-only transaction.
 	 * Default is "false".
+	 * <p>The read-only flag applies to any transaction context, whether backed
+	 * by an actual resource transaction ({@link #PROPAGATION_REQUIRED}/
+	 * {@link #PROPAGATION_REQUIRES_NEW}) or operating non-transactionally at
+	 * the resource level ({@link #PROPAGATION_SUPPORTS}). In the latter case,
+	 * the flag will only apply to managed resources within the application,
+	 * such as a Hibernate {@code Session}.
+	 * <p>This just serves as a hint for the actual transaction subsystem;
+	 * it will <i>not necessarily</i> cause failure of write access attempts.
+	 * A transaction manager which cannot interpret the read-only hint will
+	 * <i>not</i> throw an exception when asked for a read-only transaction.
 	 */
 	public final void setReadOnly(boolean readOnly) {
 		this.readOnly = readOnly;