在SAP接口编程之 NCo3.0系列(06) : 会话管理 这篇文章中，对会话管理的相关知识点已经说得很详细了，请参考。现在用JCo3.0来实现。

1. JCoContext

如果SAP中多个函数需要在一个session中运行，需要JCoContext来提供保证。如果在同一个线程中，大体模式这样：

JCoContext.begin(sapDestination);

fm1.execute(sapDestination);

fm2.execute(sapDestination);

JCoContext.end(destination);

begin()和end()之间的函数execute之后，SAP不会释放连接，确保同一个session之中。

第二种情况：如果不同的函数不在同一个线程中，需要由开发人员实现SessionReferenceProvider接口，在类中提供session id。逻辑跟nco3.0也是一样的。JCo3.0提供了一个示例代码，但是搞的太复杂，我弄了一个简单的，方便理解。

2. SAP函数

我们要使用的函数是从标准系统函数INCREMENT_COUNTER
，GET_COUNTER拷贝而来的。在SAP系统中INCREMENT_COUNTER
，GET_COUNTER在同一个function group中，共享一个变量count（计数器），每次运行INCREMENT_COUNTER
, count就会加一，GET_COUNTER函数
可以获得这个count。因为这两个函数不能被远程调用，所以我们将这两个函数拷贝出另外两个函数ZINCREMENT_COUNTER和ZGET_COUNTER。

3. 同一线程中执行函数

首先我们把两个函数定义在一个类RfcFunctions中：

package jco3.demo6;

import com.sap.conn.jco.JCoDestination;

import com.sap.conn.jco.JCoException;

import com.sap.conn.jco.JCoFunction;

public class RfcFunctions

{

    public static int runGetCounter(JCoDestination dest) throws JCoException

    {

        JCoFunction counterFM = dest.getRepository().getFunction("ZGET_COUNTER");

        counterFM.execute(dest);

        int counter = (int) counterFM.getExportParameterList().getValue("GET_VALUE");

        return counter;

    }

    public static void runIncrement(JCoDestination dest) throws JCoException

    {

        JCoFunction increment = dest.getRepository().getFunction("ZINCREMENT_COUNTER");

        increment.execute(dest);

    }

}

然后编写测试类进行测试：

package jco3.demo6;

import com.sap.conn.jco.JCoContext;

import com.sap.conn.jco.JCoDestination;

import com.sap.conn.jco.JCoDestinationManager;

import com.sap.conn.jco.JCoException;

public class TestSessionSameThread

{

    public static void main(String[] args) throws JCoException, InterruptedException

    {

        // get JCoDestination object instance

        JCoDestination destination = JCoDestinationManager.getDestination("ECC");

        // make sure the two functions will be executed in the same session

        JCoContext.begin(destination);

        // Before increment

        System.out.println("Before execution of ZINCREMENT_COUNTER:");

        System.out.println("Counter:" + RfcFunctions.runGetCounter(destination));

        // Run incrementCounter five times

        for(int i = 0; i < 5; i++){

            RfcFunctions.runIncrement(destination);

            System.out.println("Add:" + (i + 1));

        }

        // After increment

        System.out.println("After execution of ZINCREMENT_COUNTER:");

        System.out.println("Counter:" + RfcFunctions.runGetCounter(destination));    

        // release the connection

        JCoContext.end(destination);

    }

}

代码很直观，就不多说了。函数执行前，counter的值为0，运行函数5次之后，counter的值为5。如果我们注释掉JCoContext.begin(destination);和JCoContext.end(destination);，可以对比出不同的效果。

4. 不同线程中执行函数

如果在不同的线程中执行不同的函数，需要开发者提供session id。我准备将两个函数放在不同的线程中：

• 在JVM的主线程中调用ZGET_COUNTER，查看counter的结果。
• 在另外一个线程中运行ZINCREMENT_COUNTER，两个线程通过JCoContext，保持在同一个session ID下。

4.1 实现JCoSessionReference接口

JCoSessionRefence实现类的主要作用是提供session ID:

package jco3.session;

import java.util.concurrent.atomic.AtomicInteger;

import com.sap.conn.jco.ext.JCoSessionReference;

public class JCoSessionRefenceImpl implements JCoSessionReference

{

    private AtomicInteger atomInt = new AtomicInteger(0);

    private String id = "session"+String.valueOf(atomInt.addAndGet(1));

    public void contextFinished()

    {

    }

    public void contextStarted()

    {

    }

    @Override

    public String getID()

    {

        /**

         * We need to override getID() method

         */

        return id;

    }

}

4.2 实现SessionReferenceProvider接口

在SessionReferenceProvider接口的实现类中，改写getCurrentSessionReference()方法，获取上面定义的JCoSessionRefence，从而获得session ID。其他方法保持不动。

package jco3.session;

import com.sap.conn.jco.ext.JCoSessionReference;

import com.sap.conn.jco.ext.SessionException;

import com.sap.conn.jco.ext.SessionReferenceProvider;

public class SessionReferencProviderImpl implements SessionReferenceProvider

{

    @Override

    public JCoSessionReference getCurrentSessionReference(String scopeType)

    {

        /**

         *  We need to override getCurrentSessionReference() method

         */

        JCoSessionRefenceImpl sessionRef = new JCoSessionRefenceImpl();

        return sessionRef;

    }

    @Override

    public boolean isSessionAlive(String sessionID)

    {

        return false;

    }

    public void jcoServerSessionContinued(String sessionID) throws SessionException

    {

    }

    public void jcoServerSessionFinished(String sessionID)

    {

    }

    public void jcoServerSessionPassivated(String sessionID) throws SessionException

    {

    }

    public JCoSessionReference jcoServerSessionStarted() throws SessionException

    {

        return null;

    }

}

4.3 注册 SessionReferenceProvider接口

注册SessionReferenceProvider接口的实现类，这样JCoDestination就有状态管理功能了。

package jco3.session;

import com.sap.conn.jco.JCoDestination;

import com.sap.conn.jco.JCoDestinationManager;

import com.sap.conn.jco.JCoException;

import com.sap.conn.jco.ext.Environment;

import com.sap.conn.jco.ext.SessionReferenceProvider;

public class DestinationProvider

{

    public static JCoDestination getDestination() throws JCoException

    {

        // create an instance of SessionReferenceProvider

        // and register in environment

        SessionReferenceProvider provider = new SessionReferencProviderImpl();

        Environment.registerSessionReferenceProvider(provider);

        JCoDestination destination = JCoDestinationManager.getDestination("ECC");

        return destination;

    }

}

4.4 在单独线程中执行ZINCREMENT_COUNTER

定义WorkingThread, 从Thread类继承，在这个线程中执行函数ZINCREMENT_COUNTER 5次。

package jco3.demo6;

import com.sap.conn.jco.JCoDestination;

import com.sap.conn.jco.JCoException;

public class WorkingThread extends Thread

{

    private boolean doneSignal;

    private JCoDestination destination;

    // constructor

    public WorkingThread(JCoDestination destination, boolean doneSignal)

    {

        this.destination = destination;

        this.doneSignal = doneSignal;

    }

    public boolean hasDone()

    {

        return doneSignal;

    }

    @Override

    public void run()

    {

        /**

         * run method of runIncrement() for five times

         */

        for (int i = 0; i < 5; i++){

            try {

                RfcFunctions.runIncrement(this.destination);

                System.out.println("Run " + (i+1) + " times.");

            } catch (JCoException e) {

                e.printStackTrace();

            }

        }

        this.doneSignal = true;

    }

}

doneSignal用于标识该线程是否结束。线程本身结束，是run()方法运行完毕。

4.5 测试多线程函数调用

好了，最后来测试在多线程中函数调用：

package jco3.demo6;

import com.sap.conn.jco.JCoContext;

import com.sap.conn.jco.JCoDestination;

import com.sap.conn.jco.JCoException;

import jco3.session.DestinationProvider;

public class TestSAPSessionMultiThread

{

    public static void main(String[] args) throws JCoException, InterruptedException

    {

        /**

         * Run ZINCREMENT_COUNTER & ZGET_COUNTER functions in

         * different threads in a stateful way.

         *

         * The SAP will keep a session id which was created in

         * JCoSessionReferenceImpl class

         * and used in SessionReferenceProviderImpl class.

         *

         * Before using, SessionReferenceProviderImpl class should be

         * registered using Environment.registerSessionReferenceProvider() method.

         */

        // get JCoDestination object instance

        JCoDestination destination = DestinationProvider.getDestination();

        // make sure the two functions will be executed in the same session

        JCoContext.begin(destination);

        // Before increment

        System.out.println("Before execution of ZINCREMENT_COUNTER:");

        System.out.println("Counter:" + RfcFunctions.runGetCounter(destination));

        // start a new Thread in which function ZINCREMENT_COUNTER

        // will be executed for five times

        WorkingThread workingThread = new WorkingThread(destination, false);

        workingThread.start();

        // wait and switch thread

        Thread.sleep(1000);

        // After increment

        if (workingThread.hasDone() == true){

            System.out.println("After execution of ZINCREMENT_COUNTER:");

            System.out.println("Counter:" + RfcFunctions.runGetCounter(destination));

        }

        // release the connection

        JCoContext.end(destination);

    }

}

与前面同一个线程中代码的主要区别是：
定义一个WorkingThread类的实例，然后启动线程：

WorkingThread workingThread = new WorkingThread(destination, false);

workingThread.start();

然后通过Thread.sleep(), 将线程切换到workingThread中执行，执行完毕再回到主线程显示结果。