事务的概念在我看来是指的是1组sql序列，这个序列是1块履行的单位，要末全部履行，要不全部履行，这样可以很好的对数据库进行并发控制。
由于数据库是多个用户都可以同时操作的，如果多个用户同时操作1个数据，就容易造成数据的不1致，所以事务作为并发控制的1个基本单位很有必要。
1.原子性：事务是1个完全的整体，所有的操作和数据都是1个整体。
2.1致性：事务的操作是1致性的。
3.隔离性：事务之间的操作是相互隔离的。
4.持久性：事务的操作是持久的，即便出现了毛病也会完成。
BEGIN TRANSACTION
COMMIT TRANSACTION
ROLLBACK TRANSACTION
public static Statement getStatement(){
Statement st = null;
try {
Class.forName("com.mysql.jdbc.Driver");
Connection conn = (Connection) DriverManager.getConnection("jdbc:mysql://localhost:3306/jsp_dbb", "root", "");
st = (Statement) conn.createStatement();
} catch (Exception e) {
// TODO: handle exception
}
return st;
}
public static void insertUserData(){
try {
String sql = "INSERT INTO tbl_user(id,name,password,email)" +
"VALUES(10,'Tom','123456','tom@qq.com')";
Statement st = getStatement();
int count = st.executeUpdate(sql);
System.out.println("插入了"+count+"行用户数据");
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
public static void insertAddressData(){
try {
String sql = "INSERT INTO tbl_address(id,city,country,user_id)" +
"VALUES(1,'shanghai','china,'10')";
Statement st = getStatement();
int count = st.executeUpdate(sql);
System.out.println("插入了"+count+"行地址数据");
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
public static void main(String[] args) {
insertUserData();
insertAddressData();
}这段代码会报错，由于在tbl_address中已有id = 1的数据了，具体以下图：
插入了1行用户数据
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '10')' at line 1
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:377)
at com.mysql.jdbc.Util.getInstance(Util.java:360)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:978)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3887)
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:2526)
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1618)
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1549)
at liu.peng.jdbc.TransactionTest.insertAddressData(TransactionTest.java:37)
at liu.peng.jdbc.TransactionTest.main(TransactionTest.java:46)检查发现只是插入user表的数据，没有插入address表数据，造成数据不完全。
事务处理的核心代码就是
conn.setAutoCommit(false);
在履行完以后的提交。
conn.commit();
和在捕获异常时候的回滚。
具体代码以下：
public static Connection getConnection(){
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = (Connection) DriverManager.getConnection("jdbc:mysql://localhost:3306/jsp_dbb", "root", "");
} catch (Exception e) {
// TODO: handle exception
}
return conn;
}
public static void insertUserData(Connection conn)throws SQLException{
String sql = "INSERT INTO tbl_user(id,name,password,email)" +
"VALUES(10,'Tom','123456','tom@qq.com')";
Statement st = (Statement) conn.createStatement();
int count = st.executeUpdate(sql);
System.out.println("插入了"+count+"行用户数据");
}
public static void insertAddressData(Connection conn) throws SQLException{
String sql = "INSERT INTO tbl_address(id,city,country,user_id)" +
"VALUES(1,'shanghai','china,'10')";
Statement st = (Statement) conn.createStatement();
int count = st.executeUpdate(sql);
System.out.println("插入了"+count+"行地址数据");
}
public static void main(String[] args) {
Connection conn = null;
try {
conn = getConnection();
conn.setAutoCommit(false);
insertUserData(conn);
insertAddressData(conn);
conn.commit();
} catch (SQLException e) {
System.out.println("==========捕获SQL异常=========");
e.printStackTrace();
try {
conn.rollback();
System.out.println("=======s事务回滚成功=======");
} catch (Exception e2) {
e2.printStackTrace();
}
}finally{
try {
if (conn != null) {
conn.close();
}
} catch (Exception e3) {
e3.printStackTrace();
}
}
}Console界面的报错信息为：
插入了1行用户数据
==========捕获SQL异常=========
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '10')' at line 1
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:377)
at com.mysql.jdbc.Util.getInstance(Util.java:360)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:978)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3887)
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:2526)
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1618)
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1549)
at liu.peng.jdbc.TransactionTest.insertAddressData(TransactionTest.java:31)
at liu.peng.jdbc.TransactionTest.main(TransactionTest.java:40)
=======s事务回滚成功=======
证明两条数据都没有插入进去保证了数据的完全性，而第1次只是插入user表的数据，没有插入address表数据，造成数据不完全。