7種事務的傳播機制

事務的傳播機制定義在TransactionDefinition介面中，我們也可以通過枚舉類Propagation類調用，下面我也附上兩個類的源碼供參考。 REQUIRED（預設）：支援使用當前事務，如果當前事務不存在，建立一個新事務。 SUPPORTS：支援使用當前事務，如果當前事務不存在，則不使用事務。 MANDATORY：中文翻譯為強制，支援使用當前事務，如果當前事務不存在，則拋出Exception。 REQUIRES_NEW：建立一個新事務，如果當前事務不存在，把當前事務掛起。 NOT_SUPPORTED：無事務執行，如果當前事務不存在，把當前事務掛起。 NEVER：無事務執行，如果當前有事務則拋出Exception。 NESTED：嵌套事務，如果當前事務存在，那麼在嵌套的事務中執行。如果當前事務不存在，則表現跟REQUIRED一樣。

重點講一下requires_new和nested的區別，requires_new完全是一個新事務，nested是一個外部事務的子事務，是外部事務的一部分，如果嵌套事務發生異常復原，則只復原嵌套事務部分。而外部事務的提交和復原均會提交/復原嵌套事務。requires這是兩個事務互不干擾，如果內部事務發生異常且異常拋到了外部調用方法，那麼兩個事務都復原，如果內部事務提交成功，外部事務提交失敗，外部事務不影響內部事務，或者外部事務提交成功，但內部事務失敗的異常被外部事務catch住，則不影響外部事務。

package org.springframework.transaction.annotation;import org.springframework.transaction.TransactionDefinition;public enum Propagation {    /**     * Support a current transaction, create a new one if none exists.     * Analogous to EJB transaction attribute of the same name.     * <p>This is the default setting of a transaction annotation.     */    REQUIRED(TransactionDefinition.PROPAGATION_REQUIRED),    /**     * Support a current transaction, execute non-transactionally if none exists.     * Analogous to EJB transaction attribute of the same name.     * <p>Note: For transaction managers with transaction synchronization,     * PROPAGATION_SUPPORTS is slightly different from no transaction at all,     * as it defines a transaction scope that synchronization will apply for.     * As a consequence, the same resources (JDBC Connection, Hibernate Session, etc)     * will be shared for the entire specified scope. Note that this depends on     * the actual synchronization configuration of the transaction manager.     * @see org.springframework.transaction.support.AbstractPlatformTransactionManager#setTransactionSynchronization     */    SUPPORTS(TransactionDefinition.PROPAGATION_SUPPORTS),    /**     * Support a current transaction, throw an exception if none exists.     * Analogous to EJB transaction attribute of the same name.     */    MANDATORY(TransactionDefinition.PROPAGATION_MANDATORY),    /**     * Create a new transaction, suspend the current transaction if one exists.     * Analogous to EJB transaction attribute of the same name.     * <p>Note: Actual transaction suspension will not work on out-of-the-box     * on all transaction managers. This in particular applies to JtaTransactionManager,     * which requires the {@code javax.transaction.TransactionManager} to be     * made available it to it (which is server-specific in standard J2EE).     * @see org.springframework.transaction.jta.JtaTransactionManager#setTransactionManager     */    REQUIRES_NEW(TransactionDefinition.PROPAGATION_REQUIRES_NEW),    /**     * Execute non-transactionally, suspend the current transaction if one exists.     * Analogous to EJB transaction attribute of the same name.     * <p>Note: Actual transaction suspension will not work on out-of-the-box     * on all transaction managers. This in particular applies to JtaTransactionManager,     * which requires the {@code javax.transaction.TransactionManager} to be     * made available it to it (which is server-specific in standard J2EE).     * @see org.springframework.transaction.jta.JtaTransactionManager#setTransactionManager     */    NOT_SUPPORTED(TransactionDefinition.PROPAGATION_NOT_SUPPORTED),    /**     * Execute non-transactionally, throw an exception if a transaction exists.     * Analogous to EJB transaction attribute of the same name.     */    NEVER(TransactionDefinition.PROPAGATION_NEVER),    /**     * Execute within a nested transaction if a current transaction exists,     * behave like PROPAGATION_REQUIRED else. There is no analogous feature in EJB.     * <p>Note: Actual creation of a nested transaction will only work on specific     * transaction managers. Out of the box, this only applies to the JDBC     * DataSourceTransactionManager when working on a JDBC 3.0 driver.     * Some JTA providers might support nested transactions as well.     * @see org.springframework.jdbc.datasource.DataSourceTransactionManager     */    NESTED(TransactionDefinition.PROPAGATION_NESTED);    private final int value;    Propagation(int value) { this.value = value; }    public int value() { return this.value; }}

package org.springframework.transaction;import java.sql.Connection;public interface TransactionDefinition {    int PROPAGATION_REQUIRED = 0;    int PROPAGATION_SUPPORTS = 1;    int PROPAGATION_MANDATORY = 2;    int PROPAGATION_REQUIRES_NEW = 3;    int PROPAGATION_NOT_SUPPORTED = 4;    int PROPAGATION_NEVER = 5;    int PROPAGATION_NESTED = 6;    int ISOLATION_DEFAULT = -1;    int ISOLATION_READ_UNCOMMITTED = Connection.TRANSACTION_READ_UNCOMMITTED;    int ISOLATION_READ_COMMITTED = Connection.TRANSACTION_READ_COMMITTED;    int ISOLATION_REPEATABLE_READ = Connection.TRANSACTION_REPEATABLE_READ;    int ISOLATION_SERIALIZABLE = Connection.TRANSACTION_SERIALIZABLE;    int TIMEOUT_DEFAULT = -1;    //事務的傳播行為    int getPropagationBehavior();    //事務的隔離等級    int getIsolationLevel();    //事務的到期時間    int getTimeout();    //事務的讀寫特性    boolean isReadOnly();    //事務名    String getName();}