Java tutorial
/* * Copyright 2002-2019 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. * You may obtain a copy of the License at * * https://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.springframework.transaction; import org.springframework.lang.Nullable; /** * Interface that defines Spring-compliant transaction properties. * Based on the propagation behavior definitions analogous to EJB CMT attributes. * * <p>Note that isolation level and timeout settings will not get applied unless * an actual new transaction gets started. As only {@link #PROPAGATION_REQUIRED}, * {@link #PROPAGATION_REQUIRES_NEW} and {@link #PROPAGATION_NESTED} can cause * that, it usually doesn't make sense to specify those settings in other cases. * Furthermore, be aware that not all transaction managers will support those * advanced features and thus might throw corresponding exceptions when given * non-default values. * * <p>The {@link #isReadOnly() read-only flag} applies to any transaction context, * whether backed by an actual resource transaction or operating non-transactionally * at the resource level. In the latter case, the flag will only apply to managed * resources within the application, such as a Hibernate {@code Session}. * * @author Juergen Hoeller * @since 08.05.2003 * @see PlatformTransactionManager#getTransaction(TransactionDefinition) * @see org.springframework.transaction.support.DefaultTransactionDefinition * @see org.springframework.transaction.interceptor.TransactionAttribute */ public interface TransactionDefinition { /** * Support a current transaction; create a new one if none exists. * Analogous to the EJB transaction attribute of the same name. * <p>This is typically the default setting of a transaction definition, * and typically defines a transaction synchronization scope. */ int PROPAGATION_REQUIRED = 0; /** * Support a current transaction; execute non-transactionally if none exists. * Analogous to the EJB transaction attribute of the same name. * <p><b>NOTE:</b> For transaction managers with transaction synchronization, * {@code PROPAGATION_SUPPORTS} is slightly different from no transaction * at all, as it defines a transaction scope that synchronization might apply to. * As a consequence, the same resources (a JDBC {@code Connection}, a * Hibernate {@code Session}, etc) will be shared for the entire specified * scope. Note that the exact behavior depends on the actual synchronization * configuration of the transaction manager! * <p>In general, use {@code PROPAGATION_SUPPORTS} with care! In particular, do * not rely on {@code PROPAGATION_REQUIRED} or {@code PROPAGATION_REQUIRES_NEW} * <i>within</i> a {@code PROPAGATION_SUPPORTS} scope (which may lead to * synchronization conflicts at runtime). If such nesting is unavoidable, make sure * to configure your transaction manager appropriately (typically switching to * "synchronization on actual transaction"). * @see org.springframework.transaction.support.AbstractPlatformTransactionManager#setTransactionSynchronization * @see org.springframework.transaction.support.AbstractPlatformTransactionManager#SYNCHRONIZATION_ON_ACTUAL_TRANSACTION */ int PROPAGATION_SUPPORTS = 1; /** * Support a current transaction; throw an exception if no current transaction * exists. Analogous to the EJB transaction attribute of the same name. * <p>Note that transaction synchronization within a {@code PROPAGATION_MANDATORY} * scope will always be driven by the surrounding transaction. */ int PROPAGATION_MANDATORY = 2; /** * Create a new transaction, suspending the current transaction if one exists. * Analogous to the EJB transaction attribute of the same name. * <p><b>NOTE:</b> Actual transaction suspension will not work out-of-the-box * on all transaction managers. This in particular applies to * {@link org.springframework.transaction.jta.JtaTransactionManager}, * which requires the {@code javax.transaction.TransactionManager} to be * made available it to it (which is server-specific in standard Java EE). * <p>A {@code PROPAGATION_REQUIRES_NEW} scope always defines its own * transaction synchronizations. Existing synchronizations will be suspended * and resumed appropriately. * @see org.springframework.transaction.jta.JtaTransactionManager#setTransactionManager */ int PROPAGATION_REQUIRES_NEW = 3; /** * Do not support a current transaction; rather always execute non-transactionally. * Analogous to the EJB transaction attribute of the same name. * <p><b>NOTE:</b> Actual transaction suspension will not work out-of-the-box * on all transaction managers. This in particular applies to * {@link org.springframework.transaction.jta.JtaTransactionManager}, * which requires the {@code javax.transaction.TransactionManager} to be * made available it to it (which is server-specific in standard Java EE). * <p>Note that transaction synchronization is <i>not</i> available within a * {@code PROPAGATION_NOT_SUPPORTED} scope. Existing synchronizations * will be suspended and resumed appropriately. * @see org.springframework.transaction.jta.JtaTransactionManager#setTransactionManager */ int PROPAGATION_NOT_SUPPORTED = 4; /** * Do not support a current transaction; throw an exception if a current transaction * exists. Analogous to the EJB transaction attribute of the same name. * <p>Note that transaction synchronization is <i>not</i> available within a * {@code PROPAGATION_NEVER} scope. */ int PROPAGATION_NEVER = 5; /** * Execute within a nested transaction if a current transaction exists, * behave like {@link #PROPAGATION_REQUIRED} otherwise. There is no * analogous feature in EJB. * <p><b>NOTE:</b> Actual creation of a nested transaction will only work on * specific transaction managers. Out of the box, this only applies to the JDBC * {@link org.springframework.jdbc.datasource.DataSourceTransactionManager} * when working on a JDBC 3.0 driver. Some JTA providers might support * nested transactions as well. * @see org.springframework.jdbc.datasource.DataSourceTransactionManager */ int PROPAGATION_NESTED = 6; /** * Use the default isolation level of the underlying datastore. * All other levels correspond to the JDBC isolation levels. * @see java.sql.Connection */ int ISOLATION_DEFAULT = -1; /** * Indicates that dirty reads, non-repeatable reads and phantom reads * can occur. * <p>This level allows a row changed by one transaction to be read by another * transaction before any changes in that row have been committed (a "dirty read"). * If any of the changes are rolled back, the second transaction will have * retrieved an invalid row. * @see java.sql.Connection#TRANSACTION_READ_UNCOMMITTED */ int ISOLATION_READ_UNCOMMITTED = 1; // same as java.sql.Connection.TRANSACTION_READ_UNCOMMITTED; /** * Indicates that dirty reads are prevented; non-repeatable reads and * phantom reads can occur. * <p>This level only prohibits a transaction from reading a row * with uncommitted changes in it. * @see java.sql.Connection#TRANSACTION_READ_COMMITTED */ int ISOLATION_READ_COMMITTED = 2; // same as java.sql.Connection.TRANSACTION_READ_COMMITTED; /** * Indicates that dirty reads and non-repeatable reads are prevented; * phantom reads can occur. * <p>This level prohibits a transaction from reading a row with uncommitted changes * in it, and it also prohibits the situation where one transaction reads a row, * a second transaction alters the row, and the first transaction re-reads the row, * getting different values the second time (a "non-repeatable read"). * @see java.sql.Connection#TRANSACTION_REPEATABLE_READ */ int ISOLATION_REPEATABLE_READ = 4; // same as java.sql.Connection.TRANSACTION_REPEATABLE_READ; /** * Indicates that dirty reads, non-repeatable reads and phantom reads * are prevented. * <p>This level includes the prohibitions in {@link #ISOLATION_REPEATABLE_READ} * and further prohibits the situation where one transaction reads all rows that * satisfy a {@code WHERE} condition, a second transaction inserts a row * that satisfies that {@code WHERE} condition, and the first transaction * re-reads for the same condition, retrieving the additional "phantom" row * in the second read. * @see java.sql.Connection#TRANSACTION_SERIALIZABLE */ int ISOLATION_SERIALIZABLE = 8; // same as java.sql.Connection.TRANSACTION_SERIALIZABLE; /** * Use the default timeout of the underlying transaction system, * or none if timeouts are not supported. */ int TIMEOUT_DEFAULT = -1; /** * Return the propagation behavior. * <p>Must return one of the {@code PROPAGATION_XXX} constants * defined on {@link TransactionDefinition this interface}. * <p>The default is {@link #PROPAGATION_REQUIRED}. * @return the propagation behavior * @see #PROPAGATION_REQUIRED * @see org.springframework.transaction.support.TransactionSynchronizationManager#isActualTransactionActive() */ default int getPropagationBehavior() { return PROPAGATION_REQUIRED; } /** * Return the isolation level. * <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>The default is {@link #ISOLATION_DEFAULT}. 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 */ default int getIsolationLevel() { return ISOLATION_DEFAULT; } /** * Return the transaction timeout. * <p>Must return a number of seconds, or {@link #TIMEOUT_DEFAULT}. * <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}. * <p>The default is {@link #TIMEOUT_DEFAULT}. * @return the transaction timeout */ default int getTimeout() { return TIMEOUT_DEFAULT; } /** * 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>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. * @return {@code true} if the transaction is to be optimized as read-only * ({@code false} by default) * @see org.springframework.transaction.support.TransactionSynchronization#beforeCommit(boolean) * @see org.springframework.transaction.support.TransactionSynchronizationManager#isCurrentTransactionReadOnly() */ default boolean isReadOnly() { return false; } /** * Return the name of this transaction. Can be {@code null}. * <p>This will be used as the transaction name to be shown in a * transaction monitor, if applicable (for example, WebLogic's). * <p>In case of Spring's declarative transactions, the exposed name will be * the {@code fully-qualified class name + "." + method name} (by default). * @return the name of this transaction ({@code null} by default} * @see org.springframework.transaction.interceptor.TransactionAspectSupport * @see org.springframework.transaction.support.TransactionSynchronizationManager#getCurrentTransactionName() */ @Nullable default String getName() { return null; } // Static builder methods /** * Return an unmodifiable {@code TransactionDefinition} with defaults. * <p>For customization purposes, use the modifiable * {@link org.springframework.transaction.support.DefaultTransactionDefinition} * instead. * @since 5.2 */ static TransactionDefinition withDefaults() { return StaticTransactionDefinition.INSTANCE; } }