使用Java開源組件JOTM開發分佈式事務應用

    JOTM（Java Open Transaction Manager）是ObjectWeb的開源事務中間件，支持分佈式事務，實現了JTA規範。下面以jotm-2.0.10爲例說明其在J2EE項目中的用法。

    需要的jar包：carol.jar、commons-logging.jar、connector-1_5.jar、jotm.jar、jotm_iiop_stubs.jar、jotm_jrmp_stubs.jar、jta-spec1_0_1.jar、jts1_0.jar、objectweb-datasource.jar、xapool.jar。

    JOTM默認在classpath下使用名爲carol.properties的配置文件。下面給一個carol.properties的例子，可以根據自己的需要修改：

# JNDI (Protocol Invocation)
carol.protocols=jrmp

# Local RMI Invocation
carol.jvm.rmi.local.call=true

# do not use CAROL JNDI wrapper
carol.start.jndi=false

# do not start a name server
carol.start.ns=false

# Naming Factory
carol.jndi.java.naming.factory.url.pkgs=org.apache.naming

    在context中配置以下資源：

<Resource name="jdbc/db" auth="Container" type="javax.sql.DataSource"
factory="org.objectweb.jndi.DataSourceFactory"
username="db_user_name"
password="db_user_pwd"
driverClassName="oracle.jdbc.driver.OracleDriver"
url="jdbc:oracle:thin:@192.168.0.10:1521:oradb" />

<Resource name="jdbc/db1" auth="Container" type="javax.sql.DataSource"
factory="org.objectweb.jndi.DataSourceFactory"
username="db_user_name"
password="db_user_pwd"
driverClassName="oracle.jdbc.driver.OracleDriver"
url="jdbc:oracle:thin:@192.168.0.11:1521:oradb1" />

<Transaction name="UserTransaction" auth="Container"
type="javax.transaction.UserTransaction"
factory="org.objectweb.jotm.UserTransactionFactory"
jotm.timeout="60"/>

    爲了使用方便，建立一個獲取資源的工具類：

package demo.jotm;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.sql.DataSource;
import javax.transaction.UserTransaction;

public class DBUtil {
private static Context _ctx;

private static Context getContext() throws Exception {
if (_ctx != null) return _ctx;
_ctx = new InitialContext();
return _ctx;
}

public static UserTransaction getUserTransaction() throws Exception {
Context ctx = getContext();
UserTransaction ut = (UserTransaction)ctx.lookup("java:comp/UserTransaction");
return ut;
}

public static DataSource getDataSource() throws Exception {
Context ctx = getContext();
DataSource ds = (DataSource)ctx.lookup("java:comp/env/jdbc/db");
return ds;
}

public static DataSource getDataSource1() throws Exception {
Context ctx = getContext();
DataSource ds = (DataSource)ctx.lookup("java:comp/env/jdbc/db1");
return ds;
}
}

    建立一個jsp文件，完成事務的功能：

<%@page import="java.sql.Statement"%>
<%@page import="java.sql.Connection"%>
<%@page import="javax.transaction.UserTransaction"%>
<%@page import="demo.jotm.DBUtil;"%>

<%
boolean rollback = false;
UserTransaction ut = DBUtil.getUserTransaction();
Connection conn = DBUtil.getDataSource().getConnection();
Connection conn1 = DBUtil.getDataSource1().getConnection();
try {
ut.begin();

Statement stmt = conn.createStatement();
stmt.executeUpdate("insert into t values(1,'1234567890')");
stmt.close();

Statement stmt1 = conn1.createStatement();
stmt1.executeUpdate("insert into t values(2,'abc')");
stmt1.close();
}
catch (Exception e) {
rollback = true;
e.printStackTrace();
}
finally {
if (rollback) ut.rollback();
else ut.commit();

conn.close();
conn1.close();
}

out.print(rollback);
%>