Java事务分为：JDBC事务、JTA事务，容器事务。
JDBC事务
利用JDBC定义的java.sql.Connection接口中setAutoCommit(boolean)来达到自动提交和手动提交，只能局限在同一个数据库连接，不能跨库。
切记：MySQL只有InnoDB才有事务效果，其他引擎设置了autoCommit无效。
不用JDBC事务的DEMO
SQL
CREATE TABLE `test1` (
`id` bigint(1) NOT NULL DEFAULT 0 ,
`name` varchar(1) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL ,
PRIMARY KEY (`id`)
)
CREATE TABLE `test2` (
`id` bigint(1) NOT NULL DEFAULT 0 ,
`name` varchar(1) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL ,
PRIMARY KEY (`id`)
)Java
package com.mousycoder.server.jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
public class JdbcNoTransaction {
public final static String DB_DRIVER_CLASS = "com.mysql.jdbc.Driver";
public final static String DB_URL = "jdbc:mysql://xxx.mysql.rds.aliyuncs.com/xxx";
public final static String DB_USERNAME = "xx";
public final static String DB_PASSWORD = "xxx";
public static final String INSERT_TEST1 = "INSERT INTO test1(id,name) VALUES(?,?)";
public static final String INSERT_TEST2 = "INSERT INTO test2(id,name) VALUES(?,?)";
public static void main(String[] args) {
Connection con = null;
try {
con = getConnection();
insertTest1(con);
insertTest2(con);
} catch (ClassNotFoundException|SQLException e ) {
e.printStackTrace();
} finally {
if (con != null) {
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
public static Connection getConnection() throws ClassNotFoundException,
SQLException {
Connection conn = null;
Class.forName(DB_DRIVER_CLASS);
conn = DriverManager.getConnection(DB_URL, DB_USERNAME, DB_PASSWORD);
return conn;
}
public static void insertTest1(Connection conn) throws SQLException {
PreparedStatement stmt;
stmt = conn.prepareStatement("INSERT INTO test1(id,name) VALUES(?,?)");
stmt.setInt(1, 1);
stmt.setString(2, "1");
stmt.executeUpdate();
System.out.println("======insert into test1 successfully======");
stmt.close();
}
public static void insertTest2(Connection conn) throws SQLException {
PreparedStatement stmt;
stmt = conn.prepareStatement("INSERT INTO test2(id,name) VALUES(?,?)");
stmt.setInt(1, 1);
stmt.setString(2, "11"); // 故意长度超出
stmt.executeUpdate();
System.out.println("======insert into test2 successfully========");
stmt.close();
}
}控制台输出
======insert into test1 successfully======
com.mysql.jdbc.MysqlDataTruncation: Data truncation: Data too long for column 'name' at row 1
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3885)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3823)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2435)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2582)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2530)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1907)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2141)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2077)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2062)
at com.mousycoder.server.jdbc.JdbcNoTransaction.insertTest2(JdbcNoTransaction.java:61)
at com.mousycoder.server.jdbc.JdbcNoTransaction.main(JdbcNoTransaction.java:22)结果：
表test1有数据，表test2里没有数据，但是我们想让test1,test2 要么同时插入数据，要么都不插数据，这个时候就需要用到事务了。
顺便提一下，如果让test1抛异常，那么直接异常处理，结果是test1没数据,test2也没数据，但是这里并不是用到了事务，而是异常处理改变了程序走向。
利用JDBC事务的DEMO
Java
package com.mousycoder.server.jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
public class JdbcTransaction {
public final static String DB_DRIVER_CLASS = "com.mysql.jdbc.Driver";
public final static String DB_URL = "jdbc:mysql://xx.mysql.rds.aliyuncs.com/xxx";
public final static String DB_USERNAME = "xxx";
public final static String DB_PASSWORD = "xxx";
public static final String INSERT_TEST1 = "INSERT INTO test1(id,name) VALUES(?,?)";
public static final String INSERT_TEST2 = "INSERT INTO test2(id,name) VALUES(?,?)";
public static void main(String[] args) {
Connection con = null;
try {
con = getConnection();
con.setAutoCommit(false);
insertTest1(con);
insertTest2(con);
con.commit();
System.out.println("=======JDBC Transaction commit===========");
} catch (ClassNotFoundException|SQLException e ) {
try {
con.rollback();
System.out
.println("=======JDBC Transaction rolled back successfully=======");
} catch (SQLException e1) {
System.out.println("=======SQL Exception in rollback"
+ e1.getMessage()); // 回滚必要条件：1.同一个transaction
// 2.connection未关，所以这里要加异常处理
}
e.printStackTrace();
} finally {
if (con != null) {
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
public static Connection getConnection() throws ClassNotFoundException,
SQLException {
Connection conn = null;
Class.forName(DB_DRIVER_CLASS);
conn = DriverManager.getConnection(DB_URL, DB_USERNAME, DB_PASSWORD);
return conn;
}
public static void insertTest1(Connection conn) throws SQLException {
PreparedStatement stmt;
stmt = conn.prepareStatement("INSERT INTO test1(id,name) VALUES(?,?)");
stmt.setInt(1, 1);
stmt.setString(2, "1");
stmt.executeUpdate();
System.out.println("======insert into test1 successfully======");
stmt.close();
}
public static void insertTest2(Connection conn) throws SQLException {
PreparedStatement stmt;
stmt = conn.prepareStatement("INSERT INTO test2(id,name) VALUES(?,?)");
stmt.setInt(1, 1);
stmt.setString(2, "11"); // 故意长度超出
stmt.executeUpdate();
System.out.println("======insert into test2 successfully========");
stmt.close();
}
}控制台输出
======insert into test1 successfully======
=======JDBC Transaction rolled back successfully=======
com.mysql.jdbc.MysqlDataTruncation: Data truncation: Data too long for column 'name' at row 1
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3885)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3823)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2435)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2582)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2530)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1907)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2141)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2077)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2062)
at com.mousycoder.server.jdbc.JdbcTransaction.insertTest2(JdbcTransaction.java:73)
at com.mousycoder.server.jdbc.JdbcTransaction.main(JdbcTransaction.java:23)结果：
表test1和表test2是没有数据的，因为insertTest2方法抛出了异常，直接到异常处理，进行了手动的rollback(结束事务，回滚先前操作，释放掉锁),如果insertTest1()和insertTest2()都正常插入，则调用commit()方法(结束事务，提交先前改变，释放掉锁)
源码分析
com.mysql.jdbc.ConnectionImpl.rollback()
/**
* The method rollback() drops all changes made since the previous
* commit/rollback and releases any database locks currently held by the
* Connection.
*
* @exception SQLException
* if a database access error occurs
* @see commit
*/
public void rollback() throws SQLException {
synchronized (getConnectionMutex()) {
checkClosed();
try {
if (this.connectionLifecycleInterceptors != null) {
IterateBlock iter = new IterateBlock(this.connectionLifecycleInterceptors.iterator()) {
@Override
void forEach(Extension each) throws SQLException {
if (!((ConnectionLifecycleInterceptor) each).rollback()) {
this.stopIterating = true;
}
}
};
iter.doForAll();
if (!iter.fullIteration()) {
return;
}
}
// no-op if _relaxAutoCommit == true
if (this.autoCommit && !getRelaxAutoCommit()) {
throw SQLError.createSQLException("Can't call rollback when autocommit=true", SQLError.SQL_STATE_CONNECTION_NOT_OPEN,
getExceptionInterceptor());
} else if (this.transactionsSupported) {
try {
rollbackNoChecks(); //真正执行rollback地方，发送rollback指令到数据库
} catch (SQLException sqlEx) {
// We ignore non-transactional tables if told to do so
if (getIgnoreNonTxTables() && (sqlEx.getErrorCode() == SQLError.ER_WARNING_NOT_COMPLETE_ROLLBACK)) {
return;
}
throw sqlEx;
}
}
} catch (SQLException sqlException) {
if (SQLError.SQL_STATE_COMMUNICATION_LINK_FAILURE.equals(sqlException.getSQLState())) {
throw SQLError.createSQLException("Communications link failure during rollback(). Transaction resolution unknown.",
SQLError.SQL_STATE_TRANSACTION_RESOLUTION_UNKNOWN, getExceptionInterceptor());
}
throw sqlException;
} finally {
this.needsPing = this.getReconnectAtTxEnd();
}
}
} 解析：
只允许拿到连接互斥锁的线程进入方法。
检查连接是否被强制关闭，若被强制关闭，则抛出"No operations allowed after connection closed." 异常。
如果autoCommit且relaxAutoCommit为false，则抛出"Can't call commit when autocommit=true"异常。
如果使用本地事务状态以及MySql的版本号至少大于5.0.0并且事务在服务器上。
如果支持事务，则执行。
执行rollback。
com.mysql.jdbc.ConnectionImpl.commit()
public void commit() throws SQLException {
synchronized (getConnectionMutex()) {
checkClosed();
try {
if (this.connectionLifecycleInterceptors != null) {
IterateBlock iter = new IterateBlock(this.connectionLifecycleInterceptors.iterator()) {
@Override
void forEach(Extension each) throws SQLException {
if (!((ConnectionLifecycleInterceptor) each).commit()) {
this.stopIterating = true;
}
}
};
iter.doForAll();
if (!iter.fullIteration()) {
return;
}
}
// no-op if _relaxAutoCommit == true
if (this.autoCommit && !getRelaxAutoCommit()) {
throw SQLError.createSQLException("Can't call commit when autocommit=true", getExceptionInterceptor());
} else if (this.transactionsSupported) {
if (getUseLocalTransactionState() && versionMeetsMinimum(5, 0, 0)) {
if (!this.io.inTransactionOnServer()) {
return; // effectively a no-op
}
}
execSQL(null, "commit", -1, null, DEFAULT_RESULT_SET_TYPE, DEFAULT_RESULT_SET_CONCURRENCY, false, this.database, null, false);
}
} catch (SQLException sqlException) {
if (SQLError.SQL_STATE_COMMUNICATION_LINK_FAILURE.equals(sqlException.getSQLState())) {
throw SQLError.createSQLException("Communications link failure during commit(). Transaction resolution unknown.",
SQLError.SQL_STATE_TRANSACTION_RESOLUTION_UNKNOWN, getExceptionInterceptor());
}
throw sqlException;
} finally {
this.needsPing = this.getReconnectAtTxEnd();
}
}
return;
} 解析：
这段代码与rollback()基本一样，不同之处是commit()方法里执行的是 execSQL(null, "commit", -1, null, DEFAULT_RESULT_SET_TYPE, DEFAULT_RESULT_SET_CONCURRENCY, false, this.database, null, false);
rollback()方法里执行的是 execSQL(null, "rollback", -1, null, DEFAULT_RESULT_SET_TYPE, DEFAULT_RESULT_SET_CONCURRENCY, false, this.database, null, false);
执行事务期间涉及到的sql
/* mysql-connector-java-5.1.34 ( Revision: [email protected] ) */SHOW VARIABLES WHERE Variable_name ='language' OR Variable_name = 'net_write_timeout' OR Variable_name = 'interactive_timeout' OR Variable_name = 'wait_timeout' OR Variable_name = 'character_set_client' OR Variable_name = 'character_set_connection' OR Variable_name = 'character_set' OR Variable_name = 'character_set_server' OR Variable_name = 'tx_isolation' OR Variable_name = 'transaction_isolation' OR Variable_name = 'character_set_results' OR Variable_name = 'timezone' OR Variable_name = 'time_zone' OR Variable_name = 'system_time_zone' OR Variable_name = 'lower_case_table_names' OR Variable_name = 'max_allowed_packet' OR Variable_name = 'net_buffer_length' OR Variable_name = 'sql_mode' OR Variable_name = 'query_cache_type' OR Variable_name = 'query_cache_size' OR Variable_name = 'license' OR Variable_name = 'init_connect'/* mysql-connector-java-5.1.34 ( Revision: [email protected] ) */SELECT @@session.auto_increment_incrementSET character_set_results = NULLSET autocommit=1SET sql_mode='STRICT_TRANS_TABLES'SET autocommit=0select @@session.tx_read_only
以上为不完全统计，jdbc包在执行一个真正的sql语句的时候，实际上会先执行一部分常用sql，把数据库的一些信息给缓存起来。
mysql&oracle区别
oracle的commit详细步骤
SGA中生成undo块
SGA中生成了产生改变的数据块和索引块
SGA中生成前两项的缓存redo信息
依赖于前三项产生的数据量大小以及操作所需要的时间，buffer中的数据可能已经有一部分输出到磁盘
获得所需全部锁
commit
为事务生成一个SCN,SCN是oracle数据库的一种计时信息，用以保证事务的顺序性，同时还用于失败恢复和保证数据库的读一致性和检查点，无论何时何人提交,SCN自动加1
将事务相关的未写入redo log file 中的redo信息从redo log buffer写入到redo log file ，这一步是真正的commit，这一步完成，才叫真正完成commit,事务条目从V$TRANSACTION中“删除
V$LOCK中记录的SESSION关于该事务的锁会释放，其他需要这些锁的事务被唤醒
执行块清理，清理快头保存的事务信息
oracle的rollback详细步骤
撤销已做的所有修改，从undo段读回数据，逆向执行commit中的操作，并将undo条目标记为已用，先前插入，则会删除，先前更新，则会回滚取消更新，先前删除，则回滚再次插入
释放会话中所有的锁，唤醒等待锁。
mysql的commit详细步骤
InnoDB每次提交事务都会刷新日志innodb_log到磁盘，磁盘速度比较慢，不要频繁提交事务
JTA事务
JTA是一种高层，与实现无关，与协议无关的API，应用程序和应用服务器可以使用JTA来访问事务
计划用JTA界定事务，那么需要实现javax.sql.XADataSource、javax.sql.XAConnection、java.sql.XAResource。
容器事务
基于JTA,以及JNDI完成，容器负责事务的管理任务。
三种事务差异
JDBC 事务局限于一个数据库连接，使用简单。
JTA事务功能强大，可以跨多个数据库多个DAO，比较复杂。
容器事务，局限于EJB使用。
补充知识
MySql常用命令
查询隔离级别
select @@tx_isolation;设置手动提交
set autocommit=0 ;查看当前事务自动提交模式
select @@autocommit;设置隔离级别
set tx_isolation = 'READ-COMMITTED';查询表的状态
show table status like 'test1';修改表的存储引擎
alter table test1 engine = INNODB查看是否开启日志
show variables like 'log_bin';查看日志状态
show master status;
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作 者 : @mousycoder
原文出处 : http://mousycoder.com/2016/02/15/explain-transaction-in-simple-language-2/
创作时间：2016-2-15
更新时间：2016-2-15